ABSTRACT ZINFANDEL PRODUCTIVITY IS MANAGED BY PRUNING SYSTEMS, APPLIED WATER AMOUNTS, AND ROOTSTOCKS IN A HOT CLIMATE

Transcription

1 ABSTRACT ZINFANDEL PRODUCTIVITY IS MANAGED BY PRUNING SYSTEMS, APPLIED WATER AMOUNTS, AND ROOTSTOCKS IN A HOT CLIMATE A field trial was conducted in the hot climate of the southern San Joaquin Valley of California to measure canopy architecture, yield components, yield efficiency, water productivity and phenolic composition of Zinfandel/Freedom in response to three pruning systems and two deficit irrigation regimes. Pruning systems applied were; cane pruned (CP) manually pruned to six, 8-node canes, spur pruned (SP) manually pruned to 22, two node spurs and mechanical pruned (MP) which consisted of hedging to a 100 mm spur height with 55 nodes per meter. Two irrigation treatments were applied: sustained deficit irrigation (SDI) initiated at bud-break and irrigated 80% of the estimated crop evapotranspiration (ET c ) through harvest based on weekly-calculated crop coefficients (K c ). The regulated deficit irrigation (RDI) treatment was applied by altering ET c replacement between bud-break to bloom (80%), fruit-set to veraison (50%) and veraison to harvest (80%). Precipitation was rarely sufficient to fill the soil profile. Lack of precipitation reduced the crop coefficient (K c ), yield and canopy development. Additionally, similar metrics were quantified for Zinfandel 1A in response to two rootstocks and two applied water amount regimes. The rootstocks investigated were both established V. champinii hybrids; Freedom (V. champinii x 1613C) and Salt Creek (V. champinii). This project was successful at identifying management practices which maximized yield, fruit quality and water footprint for Vitis vinifera cv. Zinfandel in a hot climate region as affected by drought. Clinton Craig Nelson May 2015

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3 ZINFANDEL PRODUCTIVITY IS MANAGED BY PRUNING SYSTEMS, APPLIED WATER AMOUNTS, AND ROOTSTOCKS IN A HOT CLIMATE by Clinton Craig Nelson A thesis submitted in partial fulfillment of the requirements for the degree of Master of Science in Viticulture and Enology in the Jordan College of Agriculture and Technology California State University, Fresno May 2015

4 APPROVED For the Department of Viticulture & Enology: We, the undersigned, certify that the thesis of the following student meets the required standards of scholarship, format, and style of the university and the student's graduate degree program for the awarding of the master's degree. Clinton Craig Nelson Thesis Author Kaan Kurtural (Chair) Viticulture & Enology John Bushoven Plant Science Anil Shrestha Plant Science For the University Graduate Committee: Dean, Division of Graduate Studies

5 AUTHORIZATION FOR REPRODUCTION OF MASTER S THESIS X I grant permission for the reproduction of this thesis in part or in its entirety without further authorization from me, on the condition that the person or agency requesting reproduction absorbs the cost and provides proper acknowledgment of authorship. Permission to reproduce this thesis in part or in its entirety must be obtained from me. Signature of thesis author:

6 ACKNOWLEDGMENTS Firstly and most importantly, I must express my sincerest gratitude to Dr. Kaan Kurtural for allowing me to be part of this ambitious project. His support, advice and guidance have been invaluable and have afforded me to tools necessary to succeed as a viticulturist and scientist. Additionally, I would like to thank my committee members Dr. John Bushoven and Dr. Anil Shrestha, as well as Dr. James Kennedy for their guidance and inspiration as professors, advisers and scholars. A special recognition and thanks to my best friend and confidant Jackie Parker for her unwavering support through this process. Also, I want to express love and appreciation to my mother Jaci Nelson, my sisters Jennifer and Tamara, and my resting father Craig Nelson for their inspiration and support. None of this would have been possible without the hard work, dedication and guidance of Geoff Dervishian, assistance from my fellow graduates Mike Cook, Andrew Beebe as well as the diligent labor of Andy Mendez, Tiffany Gunduz and the rest of the Kurtural team. Thank you Bronco Wine Company, West Coast Grape Growing, Michael Blaine and particularly Faustino Valdez for their time and assistance with the application and execution of treatments. Additional acknowledgments are due to the Fellowship Committee and American Vineyard Foundation for the support of my studies.

7 TABLE OF CONTENTS Page LIST OF TABLES... ix LIST OF FIGURES... xi STUDY 1 INTRODUCTION... 1 LITERATURE REVIEW... 5 Climatology... 5 Phenological Development... 6 Source and Sink Physiology... 8 Canopy Architecture... 9 Yield Components Yield Efficiency and Water Footprint Fruit Chemistry Phenolic Composition MATERIALS AND METHODS Site Description and Experimental Site Plant Water Status Determination Pruning Systems Irrigation Treatments Canopy Architecture Yield Components Production Efficiency and Water Footprint Berry Composition Berry Phenolic Composition HPLC Analysis and Procedure... 35

8 vi Page Statistical Analysis RESULTS Climate at Experimental Site Effect of Pruning Systems and Irrigation on Canopy Architecture Effect of Pruning Systems and Irrigation on Yield Components Efficiency and Labor Operations Costs Effect of Pruning Systems and Irrigation on Berry Composition Effects of Pruning Systems and Irrigation on Gallates, Flavonols, Flavan- 3-ol Monomers and Tannins of Seed Tissue Effects of Pruning Systems and Irrigation on Gallates, Flavonols, Flavan- 3-ol Monomers and Tannins of Skin Tissue Effects of Pruning Systems and Irrigation on Anthocyanins DISCUSSION Climatology and Irrigation Canopy Architecture Yield Components Berry Constituents Yield Efficiency Berry Composition Gallates, Flavonols, Flavan-3-ol Monomers and Total Tannins of Seed Tissue Gallates, Flavonols, Flavan-3-ol Monomers and Total Tannins of Skin Tissue Anthocyanin-Glucosides of Skin Tissue Anthocyanin-Glucoside Acetates of Skin Tissue Anthocyanin-Glucoside Coumarates of Skin Tissue CONCLUSION... 70

9 vii Page REFERENCES APPENDIX A: FIGURES APPENDIX B: TABLES STUDY 2 INTRODUCTION LiTERATURE REVIEW Rootstock Background Drought Tolerance Canopy Architecture Yield Components Yield Efficiency and Water Footprint Fruit Chemistry Phenolic Composition MATERIALS AND METHODS Preface Experimental Design Rootstock Parentage RESULTS Effect of Rootstock Selection and Irrigation on Canopy Architecture Effect of Rootstock Selection and Irrigation on Yield Components Effect of Rootstock Selection and Irrigation on Berry Composition Effect of Rootstock Selection and Irrigation on Gallates, Flavonols, Flavan-3-ols Monomers and Tannins of Seed Tissue Effect of Rootstock Selection and Irrigation Regime on Gallates, Flavonols, Flavan-3-ols Monomers and Tannins of Skin Tissue Effect of Rootstock Selection and Irrigation Regime on Anthocyanin Glucosides, Acetates and Coumarates of Skin Tissue DISCUSSION

10 viii Page Canopy Architecture Yield Components Berry Constituents Yield Efficiency and Water Footprint Berry Composition Gallates, Flavonols, Flavan-3-ols and Tannins of Seed Tissue Gallates, Flavonols, Flavan-3-ols and Tannins of Skin Tissue Anthocyanin-Glucosides of Skin Tissue Acylated-Anthocyanins of Skin Tissue CONCLUSION REFERENCES APPENDIX C: TABLES

11 LIST OF TABLES Page Table B.1. Phenological progression of Zinfandel clone 1A/Freedom' in 2013 and 2014, in the southern San Joaquin Valley of California (n = 4) Table B.2. Effects of pruning systems and deficit irrigation methods on canopy architecture and microclimate of Zinfandel clone 1A/Freedom in the southern San Joaquin Valley of California in 2013 and 2014 (n = 4) Table B.3. Effects of pruning systems and deficit irrigation methods on yield components, pruning weight, yield efficiency and water foot print of Zinfandel clone 1A/Freedom in the southern San Joaquin Valley of California in 2013 and 2014 (n = 4) Table B.4. Effect of pruning system and deficit irrigation on chemical compositions of Zinfandel clone 1A/Freedom in the southern San Joaquin valley of California in 2013 and 2014 (n = 4) Table B.5. Effects of pruning systems and deficit irrigation on exhaustively extracted gallates, flavan-3-ols, flavonols, and total tannins (mg/kg) of Zinfandel clone 1A/Freedom from seed tissue in the southern San Joaquin Valley of California in 2013 and 2014 (n = 4) Table B.6. Effects pruning systems and deficit irrigation methods on exhaustively extracted gallates, flavan-3-ols, flavonols, and total tannins (mg/kg) of Zinfandel clone 1A/Freedom skin tissue in the southern San Joaquin Valley of California in 2013 and 2014 (n = 4) Table B.7. Effects pruning systems and deficit irrigation methods on exhaustively extracted of anthocyanins (mg/kg) of Zinfandel clone 1A/Freedom from skin tissue in the southern San Joaquin Valley of California in 2013 and 2014 (n = 4) Table C.1. Effects of rootstock selection and deficit irrigation methods on canopy architecture and microclimate of MP z Zinfandel 1A in the southern San Joaquin Valley of California in 2013 and 2014 (n = 4) Table C.2. Effects of rootstock selection and deficit irrigation methods on yield components, pruning weight, yield efficiency and water foot print of MP Zinfandel 1A in the southern San Joaquin Valley of California in 2013 and 2014 (n = 4) Table C.3. Effect of rootstock selection and deficit irrigation on chemical compositions of MP Zinfandel 1A in the southern San Joaquin valley of California in 2013 and 2014 (n = 4)

12 x Page Table C.4. Effects of rootstock selection and deficit irrigation on exhaustively extracted gallates, flavonols, flavan-3-ols and total tannins (mg/kg) of MP Zinfandel 1A from seed tissue in the southern San Joaquin Valley of California in 2013 and 2014 (n = 4) Table C.5. Effects rootstock selection and deficit irrigation methods on exhaustively extracted gallates, flavonols, flavan-3-ols and total tannins (mg/kg) of MP Zinfandel 1A skin tissue in the southern San Joaquin Valley of California in 2013 and 2014 (n = 4) Table C.6. Effects rootstock selection and deficit irrigation methods on exhaustively extracted of anthocyanins (mg/kg) of MP Zinfandel 1A from skin tissue in the southern San Joaquin Valley of California in 2013 and 2014 (n = 4)

13 LIST OF FIGURES Page Figure 1. Seasonal summation (March-Feb.) of temperature and precipitation from California Irrigation Management Information System (CIMIS weather station #125) Figure 2. Development of crop coefficient (K c ) in 2013 and 2014, K c calculated from weekly shade estimated of canopy shade development Figure 3. Cumulative winter precipitation (mm), weekly precipitation during growing season (mm/meek), irrigation applied (L/vine) and weekly ET c (A) 2013 (B) Sustained deficit irrigation (SDI) = initiated at (Ѱ) of -1.2MPa, irrigated to 80% of crop evapotranspiration (ET c ) from budbreak until harvest. Regulated deficit irrigation (RDI) = 80% of ET c from budbreak to fruit set, where after 50% ET c was replaced to maintain (Ѱ) at -1.4MPa until veraison, but not thereafter Figure 4. (A) Application of (MP): mechanically box-pruned to 100 mm spur height, (B) architecture of pruning system at canopy closure Figure 5. (A) SP: Spur-pruned to 22 buds, (B) architecture of pruning system at canopy closure Figure 6. (A) CP: cane-pruned to six, eight node long canes with canopy separation (B) architecture of pruning system at canopy closure

14 STUDY 1 INTRODUCTION The southern San Joaquin Valley (SJV) of California is classified as Region V growing area (Amerine and Winkler 1944). The region receives 198 mm of green water (10 year average of annual precipitation Fig. 1) and despite minimal precipitation this area is responsible for a considerable proportion of California s wine grape production. As of 2013, 82% of Zinfandel (Vitis vinifera L) grapevine in California was grown in the SJV with growers receiving a gross return of $ per ton (CDFA 2013). Since green water (precipitation) received in the region is not enough to sustain production, blue water (irrigation) has to be supplemented three weeks prior to bud-break to fill soil profile (Kurtural et al. 2013, Wessner and Kurtural 2013). However, in the presence of anthropogenic climate change, water has become a limited resource (Chaves et al. 2010, Morison et al. 2008, Teixeira et al. 2013). Water footprint (blue water + green water applied per ton of grapes harvested) of wine grape production in the region has not been investigated. In fact, research reports from the region have dismissed utilizing deficit irrigation as too limiting to growers due to reduction in yield for wine grape vineyards in the SJV (Cook et al. 2015, Terry and Kurtural 2011, Williams 2012). Most viticulture research in the region has investigated production efficiency since lack of water for growers has not been a concern, and its use under limited availability has not been a research demand. There is lack of knowledge on water productivity of traditional and mechanical pruning systems under limited water availability. Most vineyards in the SJV are planted to a modified California Sprawl trellis. This trellis forms a single plane, non-shoot positioned canopy. Benefits of this trellis system include pronounced yields, low input cost and ease of adapting

15 2 to mechanical pruning (Dokoozlian 2009). However, the combination of this trellis and pruning system in a hot climate area results in excess vigor, congested fruiting zone, poor microclimate and increased incidence of sour-rot (Dokoozlian and Kliewer 1995, Fidelibus et al. 2005, Terry and Kurtural 2011). The problems associated with spur-pruning a California sprawl can be partially remedied with altering applied water amounts with deficit irrigation, low vigor rootstock and canopy management methods (Dokoozlian 2009). However, these practices may decrease yield. Mechanically box-pruning vineyards is an option for SJV growers due to increased labor costs and small profit margins (Dokoozlian 2009, Zabadal 2002). In addition to reduced labor costs, advantages of mechanical pruning may include; improved fruiting zone microclimate, increased photosynthetically active radiation (PAR) transmittance, decreased berry size, increased nodes per shoot, increased clusters at harvest and increased flavonoid accumulation (Clingeleffer 2009, Dokoozlian 2009, Wessner and Kurtural 2013, Zabadal 2002). Over-cropping in initial years of implementation of MP treatments has been reported, but tend to decrease as vines compensate over time (Dokoozlian 2009). In contrast to the single plane canopy created by the California Sprawl which is spur pruned and mechanical hedge pruned, the horizontally divided training system creates a split canopy with dual planes of light interception. Early development of this training system was described by Gladwin (1919) where the Munson was implemented on Concord grapevines. The Munson was applied to vines approximately 1.8 m in height with four canes tied in opposite directions, with less than 1 meter spread between trained canes (Gladwin 1919, Reynolds and Vanden Heuvel 2009). In the presence of readily available water, this training system is known to increase yields, and enhance node fruitfulness and flavonoid

16 3 accumulation as a result of increased light exposure into the canopy (Gladstone and Dokoozlian 2003, Reynolds and Vanden Heuvel 2009, Wessner and Kurtural 2013). However as surface and ground water becomes increasingly limited, the increased water demand from a larger canopy may make this training/pruning system combination effectively obsolete in the hot climate of the southern SJV (Williams 2012). In an area that is moisture limited such as the southern SJV, optimization of vineyard practices is necessary. Thus, impetus is upon development and identification of a pruning and training system that can maximize water productivity. Williams (2014) reported that by applying fractions of vineyard crop evapotranspiration (ET c ), calculated as a product of reference evapotranspiration (ET o ) and seasonal crop coefficients (K c ) (Allen et al. 1998), it is possible to increase water use efficiency. Williams (2012) reported that divided canopies may not be suitable for hot climate areas due to increased water demand associated with divided canopies. This increased water demand is partly due to increased leaf surface area exposure to the southern SJV s intense photoperiods and prolonged heat. There is some agreement on the impact of water stress on the flavonoid pathway where slight water stress, applied pre-veraison has the potential to increase anthocyanin, flavonol and flavan-3-ol accumulation (Castellarin et al. 2007, Cortell and Kennedy 2006, Teixeira et al. 2013). There have been numerous studies on pruning systems and irrigation regimes, few have looked at the interactions between them and none have quantified phenolic composition and water productivity in the southern SJV. The specific objectives of this study were to investigate the interactive effects of pruning methods and applied water amounts on canopy architecture, yield

17 4 components, yield efficiency and flavonoid accumulation with Vitis vinifera cv. Zinfandel in the hot climate.

18 LITERATURE REVIEW Climatology It is known that climate has an effect on a grapevine s reproductive and vegetative growth and development (Smart 1985). Primarily, temperature and rainfall contribute to the suitability of a growing region. The southern SJV is considered a hot and dry climate (Region V) by Amerine and Winkler (1944). Hot days in this region range from C during the growing season. The high evaporative demand of this area necessitates irrigation to sustain crop production and provides an opportunity to manipulate grapevine and berry attributes through irrigation management (Keller et al. 2008, Winkler et al. 1975). A region s base-line annual and seasonal climate, along with climatic variability, largely determines a crops suitability, productivity, and quality (Jones and Davis 2010). It is known that anthropogenic climate change is affecting areas of agriculture worldwide (Chaves et al. 2010). Water may soon become a limiting factor for grape growers and winemakers, as many of the world s wine grape regions experience predicted increases in aridity according to the Intergovernmental Panel of Climate Change (IPCC) model (Chaves et al. 2010). Mendez-Costabel et al. (2013) found that winter rainfall exclusion severely hindered reproductive and vegetative growth, regardless of in-season irrigation applied. Additionally, climate change has been predicted to affect the phenology of grapevines. It has been projected that bud-break in red cultivars will, on average, occur four to eight days earlier by Furthermore, the growing season (bud-break to harvest) is projected to be shortened across all studies with harvest occurring 45 days early by 2050 (Jones and Davis 2000). The enhanced pressure

19 6 on water resources has amplified the global perception of the urgency to reduce the water footprint of irrigated crops (Chaves et al. 2010, Williams 2014). Phenological Development The grapevine system is composed of the above ground parts consisting of trunk, cordon, shoots, leaves and fruit; as well as a below ground part, the roots (Smart and Robinson 1991). A grapevine system s development can be defined by its phenological actions. Considering the phenology of a plant system is important in defining the ability of a cultivar to produce a crop within the limits of its climatic regime. Vitis vinifera grapevines are a phenologically distinct crop, with the most important developmental stages being debourrement (budburst), florasion (flowering), veraison (color change and maturations) and harvest (full maturation). The difference between phenological stages is dependent upon location, climate, soil and other factors commonly termed the terroir of a certain area, as well as the cultivar (Smart and Robinson 1991). The grapevine berry growth follows a double sigmoid curve and can be separated into two distinct growth phases, stages I and III, divided by a lag phase, stage II (Castellarin et al. 2007, Coombe 1976, Dokoozlian and Kliewer 1996). During stage I, berry pericarp cells rapidly divide and expand while organic acids accumulate (Dokoozlian and Kliewer 1996). Stage II is known as the lag phase and development is delayed. Once cell growth is resumed, stage III has begun and initiates rapid cell enlargement and berry maturation. Color and sugars quickly increase, while organic acid concentrations decline (Dokoozlian and Kliewer 1996). Additionally, climate has been reported to affect phenological development where time between phenological stages is known to shorten in a hot climate areas

20 7 (Jones and Davis 2000), compared to cooler regions. Furthermore, Tomasi et al. (2011) reported increases in relative heat during specific phenological stages can compress the time between stages or shift the entire growing season, dependent upon timing of increased temperatures. A relatively warm summer compressed the growing season, while a warm spring shifted the growing season (Tomasi et al. 2011). Considering plant development does not necessarily follow a calendar year, it would appear appropriate to develop a baseline schedule upon phenological stages and not calendar days (Jones and Davis 2000). The effect of water stress on berry growth and composition is dependent upon the phenological stage at which irrigation is withheld (Basile et al. 2011). Regulated deficit irrigation (RDI) aims to utilize this principle by applying a limited water deficit after fruit-set. Earlier deficit is generally avoided due to the risk of poor fruit-set (Hardie and Cosidine 1976, Keller et al. 2008). During application of RDI treatments, irrigation is cut off and the soil is allowed to dry in order to control plant growth (Keller et al. 2008). Water stress can be applied during both pre- and post-veraison and has been shown to improve wine color intensity and concentrations of phenols and anthocyanins compared to grapevines irrigated at 100% ET c (Ferreyra et al. 2004). In addition, it was reported that preveraison deficit produced smaller berries than post-veraison deficit (McCarthy 1997). Irrigation is commonly applied after harvest to refill the soil water profile and allow the vine to recuperate from damages incurred during harvest. Timing of pruning application has been shown to effect the on-set of budbreak (Loomis 1939). Yield components of Vitis vinifera cv. Merlot where affected by pruning date where delayed pruning of vines increased yields over a three year study (Friend and Trought 2007). However, it should be noted that this was partly due to frost protection. Pruning system and node retention may directly

21 8 affect phenological progression due increased node retention increasing yield (Howell 2001, Iland et al. 2011). However, direct reports on pruning system influence on grapevine phenology are lacking. Source and Sink Physiology The relationship between source and sink is a fundamental concept in plant physiology and can be considered the foundation of canopy management. The term source is used to indicate organs that export solutes (leaves, shoots, roots), while the term sink indicates where the solute is moved to (growth, fruit or reserve). This movement of photosynthates and solutes accumulated by a source to a sink is termed translocation (Taiz and Zeiger 2010). Photosynthates are actively loaded into the phloem and translocated throughout the plant system. Studies have looked at the pattern of translocation of leaf photosynthates in grapevines and can be broken down into four phenological periods with distinct movements of sugars and solutes related to leaf regions on the shoot. Iland et al. (2011) defines these stages (1) budburst to fruit-set, the previous year s stored energy (sugar, starch) are moved from the roots to emerging shoots and leaves and are utilized for growth and expansion. As the leaf develops it gradually switches from a sink to a source and begins contributing photosynthates to increase shoot elongation and eventually fruit production. During this stage of development the apical tip of the shoot is a strong sink and developing inflorescences are weak sinks, leaf removal at this stage can have both positive and negative effects on berry quality dependent upon leaf region removed. From (2) fruitset to veraison, apical leaves are the primary contributor to shoot elongation, translocation from middle and basal leaves in mainly to the lower leaves, developing fruit and trunk. From (3) veraison to harvest, shoot expansion typically ceases and translocation is

22 9 shifted entirely towards lower leaves, fruit and trunk. Petrie et al. (2003) reported that removal of basal and bunch leaves at this stage caused a significant decrease in whole-vine photosynthesis. Finally (4) post-harvest translocation shifts towards storage of carbohydrates (Iland et al. 2011). Pruning is a means by which sink strength can be altered. Relationships between node retention and cluster counts, bunch weight and yield and have been mixed (Howell et al. 1978, O Daniel et al. 2012, Reynolds and Vanden Heuvel 2009), theoretically an increase in node retention should lead to an increase in cluster counts and subsequent decrease in berry size (Iland et al. 2011). Therefore, a lighter pruning method, such as mechanical-box pruning, which retains a greater amount of nodes would be expected to have decreased shoot length, increased clusters and smaller bunches. Petrie et al. (2003) reported that differences in pruning and node retention affected maturity where vines with increased node counts had delayed percentage of total soluble solids (TSS) and anthocyanin accumulation. It should be noted that pruning system and node retention has shown to have inconsistent effects on yield, berry weight and wine sensory attributes and seem to be dependent upon cultivar, desired yield and climate (Iland et al. 2011). Canopy Architecture Training a grapevine is intended to accomplish four specific objectives as defined by Reynolds and Vanden Heuvel (2009); (1) perennial wood and canes can be disposed in such a way as to optimize intercepted light, leading to greater yields, increased fruitfulness and berry quality, and decreased incidence of disease, (2) bearing units are appropriately distributed on a trellis to facilitate movement of equipment through the vineyard, (3) vines and canes are distributed

23 10 appropriately to avoid competition and shading, (4) training provides a proper renewal zone which ensures consistent year to year form and yield are maintained. Additionally, dormant pruning may be used as the sole means of crop control over a season, thus making it the most important means of regulating canopy architecture. One of the most important factors that pruning and training systems can affect is intercepted light (Gladstone and Dokoozlian 2003). Reynolds and Vanden Huevel (2009) state that alteration of leaf distribution and total area by pruning and training systems can affect the canopies microclimate as well as intercepted light quality and quantity. Gladstone and Dokoozlian (2003) further separate light quality and intensity by looking at light attenuation as impacted by trellis design. In addition to looking at varying trellis designs, Gladstone and Dokoozlian (2003) compared single and horizontally and vertically divided canopy architectures and related that to light attenuation, canopy volume and leaf density. They reported that metrics such as leaf layer number, leaf area per vine and canopy volume were affected by canopy division where the vertically-divided canopy architecture had the highest amount of light attenuation from the top of the canopy to the bottom fruiting zone as a result of layered fruiting areas. In concert with Gladstone and Dokoozlian (2003), Reynolds and Vanden Heuvel (2009) also reported effects of canopy manipulation on canopy sun exposure. They state that the amount of leaf area that can be consistently exposed to the sun is a primary consideration when choosing a training system; it is affected by the disposition of the bearing units, the trellis height, and the associated type of pruning. Furthermore, it is stated that the principle component of training and pruning systems effects on grapevine physiology is dependent upon the ability of total leaf area of these systems to maximize PAR transmittance

24 11 (Reynolds and Vanden Heuvel 2009). It is of common thought that by decreasing canopy density one can impact fruitfulness, yield, and berry quality (described later), hence the development of divided canopies and positioned shoot training systems (Reynolds and Vanden Heuvel 2009). Moreover and of equal importance is the ability of a training or pruning system to utilize diffused light, such as sun flecks or light which has passed through adjacent leaves (Reynolds and Vanden Heuvel 2009), thus increasing the amount of diffused radiation intercepted by interior leaves. This notion is paramount to canopy management practices in the southern SJV due to the intensity of sunlight that grapevines are subjected to during the growing season. It is known that the impact of light intensity and quality is of upmost concern the southern SJV where light rarely doesn t exceed the saturation point of grapevine leaf photosynthesis ( E m -2 s -1 ) and routinely exceeds 2000 E m -2 s -1 (Howell 2001). Howell (2001) reported that the second leaf layer of grapevine canopies exposed to 2000 E m -2 s -1 could potentially exceed 200 E m -2 s -1. This is in agreement with Smart (1985) who reported that 8-10% of PAR transmittance passes through a leaf. The ability of shaded leaves to intercept diffused light may be attributed to the grapevine leaves ability to increase photosynthetic capacity in a shaded environment (Reynolds and Vanden Heuvel 2009). The high intensity of light in the southern SJV creates a quandary for growers who must find the ideal balance between adequate vegetation to protect fruit, while allowing enough light absorbance to achieve optimal photosynthetic capacity. Improper utilization of the modified California Sprawl is known to increase canopy shading and affect the microclimate in the fruiting zone. The light environment within grapevine canopies is strongly affected by the training and

25 12 trellis systems employed (Gladstone and Dokoozlian 2003, Howell 2001, Reynolds and Vanden Heuvel 2009). It should be noted that the strongest effects of light on berry growth have been observed when shading is excessive in hot environments (Reynolds and Vanden Heuvel 2009). This creates a particular dilemma for growers in the southern SJV who tend to irrigate at 100% ET c to increase or maintain yields. This increase in irrigation leads to increased canopy congestion and shade. Shade coupled with increased temperatures is a major problems for growers within the southern SJV that deal with vigorous vines as well as hot days and nights during the growing season. Canopy Architecture and Pruning Systems In addition to pruning systems a grapevine training system can modify exposed leaf area and leaf layers which directly affect canopy shading and microclimate. Gladstone and Dokoozlian (2003) reported differences in light attenuation in response to different trellis and training systems. They compared single curtain (SC), double curtain (DC), vertical shoot position (VSP), Smart- Dyson (SD), Smart Henry (SH) and Lyre and found that light attenuation was minimized with the VSP and Lyre trellis designs. The VSP design being a shoot position, non-divided trellis system and the Lyre being a horizontally divided, shoot positioned trellis system. Furthermore, Gladstone and Dokoozlian (2003) reported that canopy division reduced leaf area density and improved sunlight exposure within the canopy interior by means of increasing canopy volume or the amount of space available for foliage distribution. The amount of leaf area exposed to the sunlight plays a considerable role when selecting an appropriate training system. Training systems regardless of their complexity (divided or non-divided) can be categorized to four basic combinations

26 13 (Reynolds and Vanden Heuvel 2009); (1) head/spur, consisting of a short trunk and multiple two-node bearing spurs; (2) head/cane, comprised of a short trunk with one or more longer bearing units; (3) cordon/spur, with horizontal extension of the trunk with several two-node spurs; and (4) cordon/cane, similar to head/spur but with longer bearing canes (Reynolds and Vanden Heuvel 2009). It is known that pruning level largely determines shoot count based on the retention of increased nodes (Iland et al. 2011). Pruning methods which retain more nodes typically results in shorter shoots compared to methods which retain fewer nodes. This increase in shoot count can delay harvest compared to more severely pruned vines, but is not always the case (Iland et al. 2011). The majority of wine grapes within the SJV are grown on a two or three wire single curtain, non-shoot positioned trellis (Geller and Kurtural 2013, Gladstone and Dokoozlian 2003) otherwise termed the modified California Sprawl. This trellis design utilizes the grapevine s tendency to grow upward and eventually flop over from its own wait as the shoots elongate (Iland et al. 2011). The modified California Sprawl is commonly cordon trained and spur pruned. Spur pruning for vigorous cultivars can reduce pruning costs, compared to cane pruned vines, with its greatest disadvantage being the cost of establishing a cordon. Benefits of spur pruning include decreased labor costs and necessity for less skilled labor (Kasimatis et al. 1985). In regards to microclimate, spur pruned vines are generally known to have increased leaf layer number (LLN) relative to other pruning systems which can inhibit photosynthetic capabilities, due to increased amount of interior leaves (Reynolds and Vanden Heuvel 2009). Additionally, the modified California Sprawl is advantageous to growers because it allows flexibility of pruning systems implemented. This flexibility of the

27 14 modified California Sprawl trellis permits growers to easily convert pruning systems from spur pruned to mechanically pruned vines (Dokoozlian 2009). Mechanical pruning of grapevine canopy can retain a desired spur height depending on production goals. The problems associated with the modified California Sprawl s excessive vigor and non-shoot positioning can be exacerbated by mechanical pruning due a higher retention of dormant nodes and subsequent increase in shoot counts (Iland et al. 2011). However, it has been shown that this pruning is cost effective and maybe able to improve light interception in the fruiting zone. Wessner and Kurtural (2013) reported mechanically pruned vines had increased PAR transmittance levels when compared to spur pruned and cane pruned vines. Furthermore, mechanical pruning decreased LLN comparatively. Compared to single plane, non-shoot positioned canopies generated by spur or mechanically pruned systems, growers may implement a horizontally divided training system. Development of divided canopies involves the modification of the vine where two or more canopies are created from the initial single canopy or curtain (Reynolds and Vanden Heuvel 2009). Gladstone and Dokoozlian (2009) reported that divided canopied (horizontally or vertically) increased canopy surface area and volume. This increased canopy surface area and volume may lead to an increase in water demand (Williams 2012). The overall effects, when irrigation stress is limited, include; increased yields, enhanced node fruitfulness and increased fruit composition as a result of reduced canopy shade (Reynolds and Vanden Heuvel 2009). The ability of a training system to incorporate two planes of light interception can be advantageous in vigorous areas. Wessner and Kurtural (2013) reported divided canopies that were cane pruned had increased LLN after first year of study, relative to spur and mechanically pruned vines.

28 15 However, canopies trained to produce a divided or split canopy may not be a sustainable training system due to increased canopy volume, leaf area, water demand and limited profit margins in a resource limited area such as the southern SJV (Wessner and Kurtural 2013, Williams 2012). Additionally, the cane pruning associated with this training system requires increased labor skill and time. Cane pruning is considered to be the most costly and challenging training system used in California. Cane pruned system s primary disadvantages include; a need for experienced judgment in choosing the fruiting unit canes with characteristics of good fruiting potential and the additional cost of tying these canes to trellis wires (Kasimatis et al. 1985). Canopy Architecture and Applied Water Amounts Excessive uptake of water can lead to an increase in canopy vigor (Iland et al. 2011). Differences in vine water status can be accomplished through natural means such as; soil type and climate or imposed by applying different amounts of irrigation (Iland et al. 2011). There seems to be agreement that regulated deficit irrigation (RDI) reduces vegetative growth (Shellie and Bowen 2014, Terry and Kurtural 2011). Shellie (2006) reported that PAR transmittance increased, while trunk growth decreased as irrigation stress increased. Similarly, Shellie and Bowen (2014) reported the effects of RDI treatment were increased PAR transmittance and alteration cluster microclimate. Terry and Kurtural (2011) reported RDI treatment applied from fruit set to veraison optimized canopy architecture. Reductions in growth can be contributed to decreased photosynthetic rates caused from stomatal closure induced by irrigation deficit (Cifre et al. 2005). This regulation of stomatal conductance is determined partially by hydraulic

29 16 conductance variations, as well as synthesis of abscisic acid (ABA) in the roots, which is translocated to leaves (Lovisolo et al. 2002). The grapevine benefits from stomatal closure by limiting the loss of water due to reductions in transpiration. However under severe to moderate stress, this equally limits photosynthesis and thus inhibits growth (Keller 2010). It should be noted that even mild stress, that would not hinder photosynthesis, may reduce shoot growth via limited cell expansion. This limitation arises because reduction in growth usually occurs well before stomata begin to close (Hsiao 1973, Keller 2010). This combination of decreased photosynthesis and leaf area can cause a reduction in daily assimilation of carbon. Furthermore, root growth of deficit irrigated vines may decline, but less so than shoot growth, this can be contributed to the roots ability to grow at a lower water potential than shoots, partly because increased action of expansion proteins may increase cell wall extensibility in the root tips (Keller 2010). Yield Components Yield Components and Pruning Systems Training and pruning systems have a significant impact on yield. This impact is partly attributed to the strong association between cluster numbers per vine and cluster weight where an increase in cluster count has been linked to a decrease in cluster weight (Gladstone and Dokoozlian 2003, Reynolds and Vanden Heuvel 2009). A training system, along with pruning application, has the strongest effect on yield due to the source/sink relationship associated with the number of buds retained during pruning (Howell 2001). The relationship between the

30 17 grapevine source and sink is a fundamental concept in plant physiology (previously discussed). In opposition to (Howell 2001, Reynolds and Vanden Heuvel 2009) studies conducted with Traminette and Concord reported both pruning severity and the subsequent cluster count had no effect on cluster weight and mixed effects on yield (Howell et al. 1978, O Daniel et al. 2012). A study on balanced pruning conducted by Howell et al. (1978) reported no differences in cluster weight, TSS or yield between two balanced pruning methods. Howell et al. (1978) attributed lack of pruning severity effect on yield to the Concord vines reaching equilibrium. The balanced pruning methods consisted of a 30+10, otherwise stated 30 buds left for the first 454 g of dormant wood removed and 10 more for each additional 454 g, and a lighter pruned treatment. It should be noted that this study was conducted on Concord grapevine in Michigan, over one year with an emphasis on pruning severities effects on cold hardiness. A similar study was conducted on Traminette by O Daniel et al. (2012) over two years in Kentucky. O Daniel et al. (2012) implemented three pruning severities which included a 20+10, and a In the first year of study cluster count per vine was significantly affected by pruning severity, but yield was not different at a p = 0.05 level falling just short at where the treatments with increased node retention had increased cluster counts and yields. In the second year of study, cluster count per vine was affected by pruning severity where the increased node retention lead to increased cluster counts and yield. Minimal pruning and mechanical pruning have been compared due to retention of increased nodes (Iland et al. 2011). The retention of increased shoots generally results in an increase in cluster counts leading to increased reproductive points. This increase in fruit sinks directly hinders shoot elongation. This was

31 18 reported by Howell (2001) where shoots with increased clusters had a highly significant decrease in shoot length at harvest. As previously stated, an increase in node retention often leads to an increase in cluster counts and subsequent decrease in berry size (Iland et al. 2011) Additionally, increases in cluster counts typically lead to increased yield (Reynolds and Vanden Heuvel 2009). It should be noted that mechanical pruning effects on yield and yield components have been mixed. Wessner and Kurtural (2013) reported declining yields in the southern SJV. However, Howell (2001) reported that increase node retention typically increased yields. Similarly, Poni et al. (2004) reported that mechanical short-cane hedging increased yields compared to the control spur pruned Vitis vinifera cv. Croatina. Growers that implement mechanical pruning have shown concern of over-cropping because of increased node counts leading to alternate bearing, reduction in fruit quality, delayed cane maturation and eventual vine decline (Reynolds 1988). Conversely, it was reported that mechanical pruning increased yields and cluster counts, while decreasing canopy shading, berry weight and cluster weight (De Toda and Sancha 1999, Reynolds 1988). In general, grapevines trained in divided canopies produce increased yields compared to those on non-divided canopies. This increase in yield can be attributed to an increase in exposed leaf area to direct sunlight and increased canopy surface area (Reynolds and Vanden Heuvel 2009). The increase in canopy surface area exposed to direct sunlight has the ability to increase photosynthate accumulation and thus increase yields (Iland et al. 2011). However, in areas of increased light intensity, such as the southern SJV, a lack of LLN can be detrimental to fruit quality due to increased fruit temperature. This issue is compounded when factors like irrigation stress and drought hinder canopy development (Williams 2012). However, when irrigation level is near 100 % ET c,

32 19 implementation of a divided canopy can be recommended over more cost efficient pruning systems due to potential increases in flavonoid accumulation and yield (Wessner and Kurtural 2013). Yield Components and Applied Water Amounts Generally, yield decreases as water availability decreases (Hardie and Considine 1976). Reductions in yield of Vitis vinifera cv. Cabernet franc were further increased when water stress was applied early in the growing season due to reduced fruit-set (Hardie and Considine 1976). Similarly, Shellie and Bowen (2014) reported a positive linear relationship between water applied and yield. However, recent advances in timing of applied water stress have opened the possibility of decreasing yield loss, conserving water and reducing the water footprint. As stated, Hardie and Considine (1976) reported the greatest effect of water stress on yield was observed when fruit-set was disrupted. Furthermore, reductions in yield can partially be alleviated by minimizing post-veraison water stress (Shellie 2006). Hardie and Considine (1976) state that berry development is distinguished by two distinct phases separated by a lag phase. It would appear that the greatest decreases in yield are associated to application of water stress in either of the major growth phases. Recent reports on potential disadvantages of irrigation stress have been mixed. Studies have reported that water stress applied from fruit-set to veraison, veraison to harvest, or fruit-set to harvest did not detrimentally affect yield (Keller et al. 2008). The outcomes of deficit irrigation treatment are a result of the changes in sensitivity of both vegetative and reproductive tissues to water stress during developmental stages (Keller at al. 2008, Shellie and Bowen 2014).

33 20 However, investigations into the effects of irrigation stress have been highly variable in regards to yield. Deficit irrigation effects have ranged from no distinguishable differences (Cook et al. 2015) to slight decrease (Keller et al. 2008) to severe decrease (Shellie and Bowen 2014). It is obvious that deficit irrigation effects on yield components are dependent upon more than just applied water and variables such as soil type, cultivar and precipitation must be taken into account. Yield Efficiency and Water Footprint A vine is considered over-cropped when it bears more reproductive sinks than the vegetative growth can mature and this can be caused by pruning to high numbers of buds per vine (Nuzzo and Matthews 2006). Vegetative and reproductive developments occur simultaneously in woody perennials. Competition between the two processes begins when resources are not sufficient to support growth at potential rates. This competition is the basis for the partitioning of resources to reproductive and vegetative organs. Several cultural practices can affect the partitioning between vegetative and reproductive growth. These can include management of sinks, water and nutrient status and rootstockscion combinations (Nuzzo and Matthews 2006). These factors contribute to the regulation of a grapevines yield capacity, vigor and subsequent crop load. Moreover, vine capacity is proportional to total growth otherwise stated; older, larger vines can produce a greater capacity of fruit, until grapevines express detrimental signs of aging (Keller 2010). Pruning can control vine capacity due to the reduction in shoot number and leaves, this decrease in canopy area can hinder development of leaf area. Production of fruit can depress vine capacity by reducing reserves that are allocated to leaf area, thus

34 21 decreasing carbohydrate stores which can decrease the following years yield capacity (Keller 2010). Furthermore, shoot vigor is inversely proportional to the shoots per vine and to crop load, as shoot numbers and crop load increase; vigor will decrease. This decrease in vigor could lead to over-cropping and subsequent reductions in fruit maturity and quality (Keller 2010). It has been reported that excessive crop loads can delay harvest and possibly reduce fruit quality (Keller et al. 2008). One common metric used to define a balanced grapevine is the leaf area: fruit ratio (Howell 2001, Kliewer and Dokoozlian 2005, Reynolds and Vanden Heuvel 2009). Ideal leaf area: fruit ratios have been proposed to avoid the detriments of excessive crop loads (Kliewer and Dokoozlian 2005, Reynolds and Vanden Heuvel 2009). However, these ratios are highly dependent upon cultivar, region and desired maturity (Kliewer and Dokoozlian 2005). Recommendations for leaf area: fruit ratios are lacking in the southern SJV. Howell (2001) reported that an increase in the period of time where the grapevine was foliated and functional post-harvest could effectively decrease the required leaf area: fruit ratio needed to mature the fruit. This is achieved when the extended period post-harvest allows the re-accumulation of carbohydrates which are allocated to the final stages of bud and inflorescence differentiation in the following spring (Howell 2001). This is of relevance to the southern SJV, due to the significant amount of time post-harvest where vines retain leaves. As California deals with a record drought and anthropogenic climate change, greater emphasis is being placed upon water footprint efficiency (Chaves et al. 2010, Williams 2014). The amount of water needed to produce a distinct product has been labeled the water footprint. The general agricultural water footprint has also been divided into categories to include blue, green and grey

35 22 water footprints (Williams 2014). The blue water footprint is the amount of irrigation applied to a crop while the green water footprint is the amount of additional precipitation that contributes to production. Finally, the grey water footprint refers to the amount of fresh water required to assimilate pollutants generated in the crop production (Williams 2014). It should be noted that consumptive water use for applied treatments should be attributed to both green and blue water. In addition to Williams (2014), this study did not quantify grey water footprint efficiencies due to their limited impact on consumptive water usage. Global water footprints for wine grapes have been estimated at 608 m 3 per ton with the majority of that footprint consisting of green water followed by blue water (Williams 2014). Contrary to other growing regions, where precipitation is generally sufficient to fill the soil profile (Williams 2014), the southern SJV rarely has enough precipitation to fill the soil profile. Thus, the majority of consumptive water usage was associated with blue water or applied irrigation. Additionally, the ratio of consumptive green water decreases as applied irrigation increases (Williams 2014), therefore increasing the percentage of blue water expended from limited resources such as ground wells and aqueducts. Yield Efficiency and Water Footprint and Pruning System Vegetative growth and reproductive growth compete for resources (Keller et al. 2008). Thus, it is important to have balanced vines with adequate leaf area to mature fruit and replenish woody material (Keller et al. 2008). Winter pruning of grapevines is a time consuming and labor intensive operation that requires equipment and skilled labor (an increasingly limited commodity) (Gatti et al. 2011). Mechanization of canopy and crop load management in vineyards has been

36 23 shown to maintain yield and quality, while reducing labor costs (Geller and Kurtural 2013). De Toda and Sancha (1999) reported mechanical pruning produced a consistently more balanced vine when compared to traditional hand pruning methods. It is known that mechanically pruned vines increase the amount of retained nodes compared to spur pruned grapevines. This retention of a large number of nodes functions as a yield self-regulator and has been reported to keep vines more in balance (Gatti et al. 2011). Gatti et al. (2011) reported that year to year consistency is dependent upon mechanically pruned vines having reduced bud-break rates, berry set, cluster and berry weight and even self-pruning due to abscission of immature wood. It should be noted that mechanical pruning is not as successful with cultivars that produce high fruitfulness of basal and base buds like Sangiovese (Gatti et al. 2011). Furthermore, Gatti et al. (2011) reported similar leaf area: fruit ratios between spur and mechanically pruned vines. The threshold leaf area: fruit weight ratio is significantly impacted by the ratio of exposed versus non-exposed leaves, which is directly affected by training system (Dokoozlian and Kliewer 1995). Research on the effects of pruning systems on water footprint is lacking. However, inferences can be made where training systems that have increased water demand may suffer a decline in water footprint efficiency. Therefore, the increased water demand associated with divided canopies (Reynolds and Vanden Heuvel 2009) may decrease the viability of divided canopies in a hot climate area, known to be subjected to limited precipitation and increased evapotranspiration demands (Williams 2012).

37 Yield Efficiency and Water Footprint and Applied Water Amounts Recent research emphasis has focused on the concept of water use efficiency and deficit irrigation (Shellie and Bowen 2014, Williams 2014). Shellie and Bowen (2014) reported that an increase in water productivity is generally accompanied with a decrease in yield. Williams (2014) reported increased water footprint efficiencies with decreased irrigation as yield was not affected by irrigation treatments in a four year study looking at Chardonnay grapevines exposed to varying deficits of irrigation ranging from 25% ET c, 50% ET c, 75%ET c, 100% ET c and 125% ET c. The 25% ET c treatments were the most efficient irrigation treatments. Furthermore, increases in water footprint efficiency, associated with decreased application of irrigation, followed a curvilinear and linear trend dependent upon treatment year. The main advantage of water stress treatments for growers include improved fruit: leaf ratios, water footprint and water use efficiencies (Williams 2014). However, more severe water deficit regimes, such as RDI, have been exposed as punitive amounts of water stress in hot climate regions (Cook et al. 2015, Terry and Kurtural 2011). 24 Fruit Chemistry It is known that increased amount of diffused light can hasten berry maturation, thus increasing TSS and ph while decreasing TA. However, the environmental extremes of the southern SJV increases the difficulty in balancing intercepted light with canopy cover. Excessive temperature is known to inhibit and degrade TSS and flavonoid accumulation (Spayd et al. 2002).

38 25 Fruit Chemistry and Pruning System Canopy architecture and light regulation of grape berry composition has received significant attention in recent decades. A major reason for this increased study is and was to characterize light quantity and quality within the canopy and potential interaction with architecture and pruning system (Dokoozlian and Kliewer 1995, Gladstone and Dokoozlian 2003). Efficient grapevine photosynthesis primarily depends upon the pruning system and subsequent light interception of the vine leaves. High shoot density and poor light penetration have been linked to decreased fruit quality and diminished net carbon assimilation rate (Reynolds and Vanden Heuvel 2009). Additionally, pruning systems have been reported to influence TSS, ph and TA (De Toda and Sancha 1999, Reynolds 1988). De Toda and Sancha (1999) reported that mechanical pruning reduced TSS and ph relative to hand pruned systems. Fruit Chemistry and Applied Water Amounts Shellie (2006) reported irrigation stress has been shown to increase TSS and decrease TA. However, there is contradicting information on the sensitivity of berry composition to early-season water stress in a warm climate area. Hardie and Considine (1976) reported that water stress applied in the second phase of berry development hinder TSS, but reported no differences in TSS between the control and early deficit treatments. Water deficit has been reported to be beneficial for fruit quality and color in red cultivars (Keller et al. 2008), whether due to an increased TSS, skin: pulp ratio or up-regulation of certain maturation genes. Furthermore, Cook et al. (2015) and Terry and Kurtural (2011) reported minimal effects of deficit irrigation on fruit chemistry in a hot climate area.

39 26 Phenolic Composition The grapevine berry is a non-climacteric fruit with distinct stages of berry growth separated by a lag phase (Coombe 1976, Hardie and Considine 1976). Tannins, flavan-3-ols, proanthocyanidins and flavonols are synthesized during the first stage of growth, while anthocyanins are synthesized during berry maturation (Castellarin et al 2007, Cortell and Kennedy 2006, Kennedy et al. 2002). Flavonoids comprise a significant portion of the phenolic material in grapes (Teixeira et al. 2013). The majority of flavonoids are contained within the seed and skin tissue of grape berries. Flavan-3-ols and proanthocyandins are the major compound within seed tissue. While skin tissue, in most red cultivars, contains a multitude of flavonoid compound classes including anthocyanins, flavonols, flavan-3-ol monomers and proanthocyanidins (Kennedy et al. 2002). Flavonoids consist of a similar C 6 -C 3 -C 6 backbone in which two hydroxylated benzene rings A and B are joined by three-carbon chain that is part of a heterocyclic C ring (Teixeira et al. 2013). The synthesis of flavonoids begins with phenylalanine that enters the flavonoid biosynthetic pathway (Castellarin et al. 2007, Cortell and Kennedy 2006, Teixeira et al. 2013). Flavonoid concentrations are thought to be one of the principal determining metrics for red wine as well as grape quality. Color and taste of red cultivars have shown a strong association between concentrations of anthocyanins, flavonols and proanthocyanidins with wine scores where wines with increased flavonoid content higher wine scores (Castellarin et al. 2007). Anthocyanins, generally reported in skin tissue, are responsible for the color of red wines, while flavonols are efficient as cofactors of co-pigmentation (Kennedy et al. 2002). Several aspects can alter the rate of accumulation of color constituents such as; temperature, exposure to light, water status, soil type and cultural practices (Pastor del Rio and Kennedy

40 , Kennedy et al. 2002). It has been reported that flavonol content is highly responsive to light exposure and functions as a UV protectant and free radical scavenger (Cortell and Kennedy 2006). In agreement, Price et al. (1995) reported that quercetin was particularly responsive to enhancement of fruiting zone microclimate. Additionally, vine vigor, canopy shading and UV absorption have been shown to affect flavan-3-ol and anthocyanin content and composition where shaded clusters had increased tannin content in seed tissue and decreased anthocyanin content in skin tissue (Cortell and Kennedy 2006). Astringency is a significant characteristic for red cultivars and proanthocyanidins are responsible for this quality (Pastor del Rio and Kennedy 2006). Proanthocyanidins reported in seed and skin tissues are responsible for bitter and astringent properties of red cultivar wines (Kennedy et al. 2002) and are composed of polymeric flavan-3-ol subunits, which are extracted during maceration of skins, seeds and stems (Pastor del Rio and Kennedy 2006). Cortell et al. (2005) reported mean degree of polymerization (mdp) of skin proanthocyanidins increased during fruit ripening. Cortell et al. (2005) state that as mdp of proanthocyanidins increase, sensory perception shifts from bitter to astringent. Chira et al. (2009) confirmed a positive correlation between astringency intensity and mdp content in skin tannin extracts. Otherwise stated, sensory perceptions of monomers are usually more bitter than astringent, whereas the opposite is observed for greater molecular weight derivatives. Grape derived proanthocyanidins contain the flavan-3-ol subunits (+)-catechin and (-)- epicatechin (Chira et al. 2009).

41 Phenolic Composition and Pruning System As stated, light is known to influence the growth and composition of fruit. Additionally it has been reported that grapes exposed to more sunlight are generally higher in sugars, color and phenolics, while being lower in organic acids (Dokoozlian and Kliewer 1996). Light is considered a benefit to grape composition. However, heat is not and it can be difficult to separate the effects of light and temperature on fruit development (Dokoozlian and Kliewer 1996). Additionally, excessive light in hot climate regions can decrease fruit quality. This decrease in fruit quality is due to the concomitant effects of light and temperature within hot climate regions (>35 o C). Moreover, excessive sun exposure in the fruiting zone has been shown to decrease fruit quality by inhibition of the anthocyanin synthesis pathway (Reynolds and Vanden Heuvel 2009). Berry quality can be optimized, within a hot climate area, by reducing berry temperature in concert with moderate light exposure in the fruiting zone (Bergqvist et al. 2001, Reynolds and Vanden Heuvel 2009). Wessner and Kurtural (2013) reported no significant difference between berry skin phenolics and pruning treatments. Gatti et al. (2011) compared the phenolic composition of spur pruned, mechanically hedged and severe pruned treatments and reported minor differences. However, hand-simulated mechanical pruned treatments exhibited a slight decrease in anthocyanin content compared to spur pruned (Gatti et al. 2011). This observation was attributed to the excessive shading for the mechanically pruned vines. 28 Phenolic Composition and Applied Water Amounts It is known that regulation of vine water status can affect flavonoid concentration and be used as a means of increasing fruit quality for red cultivars

42 29 (Castellarin et al. 2007, Kennedy et al. 2002). Castellarin et al. (2007) reported a concentration increase in flavonoids of fruit and subsequent wine samples when exposed to pre-veraison water stress. In concert with pre-veraison water stress studies, research has identified specific flavonoid development that was considered independent of berry growth inhibition (Castellarin et al. 2007, Roby et al. 2004). Roby et al. (2004) reported seed tannins increased as berry size increased due to vine water status differences that were directly affected by irrigation treatments. The increase in seed tannins can be attributed to a linear function of both seeds number and seed mass per berry. Similarly, Roby et al. (2004) reported an increase in skin tannins with an increase in berry size. These finding would suggest tannin concentration is dependent upon mass of material present and not necessarily concentration differences. Conversely, Kennedy et al. (2002) reported a significant increase in proanthocyanidins when vines were exposed to deficit irrigation regimes. However, Kennedy et al. (2002) states that the attribute increases cannot solely be attributed to a concentration effect. It was reported that the main mechanism by which water deficits increased the concentrations of skin tannin and anthocyanin is likely the differential growth responses of skin and inner mesocarp tissue to water deficits. The differences in skin mass between irrigation regimes were primarily attributed to growth sensitivity and increased skinlocalized solutes, without invoking any other mechanisms (Roby et al. 2004). It is known that deficit irrigation treatments decrease berry size. The increased skin: pulp ratio associated with smaller berries has long been considered a beneficial characteristic for wine makers due to their increased tannins, anthocyanins and flavor compounds (Kennedy et al. 2002). Shellie and Bowen (2014) reported that the RDI treatments decreased berry size and increased

43 30 anthocyanin concentration. Additionally, Shellie and Bowen (2014) reported that total anthocyanins per berry were greater in sustained deficit irrigation (SDI) treatments relative to RDI treatments; regardless of decrease in anthocyanin concentration due to increase skin tissue mass. Furthermore, the effects of RDI treatments compared to 100% ET c irrigation treatments are analogous to the effects of intercepted light on berry quality (Williams 2012). It would appear that both sample tissue mass and concentration should be considered when analyzing flavonoid content. It has been reported that water stress applied during both pre- and postveraison, can improve wine color intensity and concentrations of flavonoids compared to less stressed vines (Ferreyra et al. 2004). Roby et al. (2004) reported deficit irrigation effects on flavonoid concentrations per berry as well as concentrations in skin tissue. Water deficit can up-regulate the gene that encodes the enzyme F3 5 H which can alter the anthocyanin composition the grape berry. This enzyme stimulates the synthesis of delphinidin, petunidin and malvidinglucosides (Berdeja et al. 2014, Kennedy et al. 2002). Castellarin et al. (2007) confirmed that water deficits have consistently promoted increased concentrations of anthocyanins in several key red cultivars. Furthermore, Castellarin et al. (2007), reported that early deficit irrigation promoted sugar accumulation, increased anthocyanin concentration, and accelerated the shift of anthocyanin biosynthesis by up-regulation of certain color and maturation genes like flavonone-3- hydroxylase (F3 H), dihydroflavonol reductase (DFR), UDP-glucose:Flavonoid 3- O-glucosyltransferase (UFGT) and glutathione S-transferase (GST). However, it should be noted that these studies were conducted in cool climate areas where temperature was not a major concern in regards to flavonoid production.

44 MATERIALS AND METHODS Site Description and Experimental Site This study was conducted at a commercial vineyard in Kern County, CA (latitude N, longitude W; elevation 137 m, 0-2 percent slope). The vineyard, planted to Zinfandel 1A/Freedom (Vitis solonis x ((Vitis vinifera x (Vitis labrusca x Vitis riparia)) x Vitis champinii)) at 2.3 m 3.35 m (vine row) spacing in North to South orientation on a bilateral cordon trained at 1.4 m with two support wires at 1.70 m and a 20 cm T-top. The soil type was Premier sandyloam soil, a coarse-loamy, mixed, superactive, calcareous thermic Xeric Torriorthent derived from granitoid parent material ( The vineyard was drip-irrigated with pressure-compensating emitters spaced at 1.1 m with two emitters per vine delivering 1.89 L/h each. Vineyard crop evapotranspiration (ET c ) was estimated as the product of reference evapotranspiration (ET o ) and seasonal crop coefficients (K c ) (Allen et al. 1998). The reference ET o was obtained from the California Irrigation Management Information System (CIMIS) weather station (#125) in Arvin, CA. The amount of precipitation received (green water), and the additional irrigation amounts (blue water) were recorded weekly. The seasonal K c used to schedule irrigation at this site was developed by measuring the shade cast on the vineyard floor beneath the canopy of vines irrigated at 0.8 ET c (SDI) amount treatments at solar noon weekly. The shaded area beneath the canopy was determined by counting the number of equi-distant 0.01 m 2 cells on an 18 m 2 grid. The growing degree days (GDD) were calculated using the sine method with a threshold of 10 o C with data obtained from the CIMIS station #125. All other cultural practices were carried out according to commercial industry standards for that area.

45 32 Plant Water Status Determination The water status of the grapevines throughout the growing season was monitored weekly by measuring the l. One fully expanded leaf, exposed to the sun showing no sign of disease or damage was selected. A zip-top plastic bag was placed over the single leaf and sealed before the petiole was excised in order to suppress transpiration. l was then directly determined with the use of a pressure chamber (Model 610 Pressure Chamber Instrument., PMS Instrument Co., Corvallis, OR). Pruning Systems Three pruning system were applied: cane pruning (CP) (Fig. 6.A), spur pruning (SP) (Fig. 5.A) and mechanical pruning (MP) (Fig. 4.A). The grapevines that received the CP treatment were manually pruned to six, 8-node canes and trained in opposing directions (North to South orientation). Three canes trained in each direction were attached to canopy catch wires and separated 25 cm horizontally at 170 cm above vineyard floor. This canopy design created a horizontally split-canopy with dual planes of light interception. The SP treatment consisted of manually pruning to 22, two node spurs for a total of 44 nodes. The MP treatment consisted of hedging to a 100 mm spur height with a 600 mm sprawl pruner to a node density of 5.5 nodes per 10 cm of row. Irrigation Treatments There were two irrigation treatments applied. A control treatment of sustained deficit irrigation (SDI) at 0.8 of estimated ET c was applied from anthesis until harvest (EL Stage 38) with a mid-day leaf water potential ( l ) threshold of MPa. A RDI treatment was applied at 0.8 ET c from anthesis to fruit set (EL stage 28) with a l threshold of -1.2 MPa, 0.5 ET c from fruit set to veraison (EL

46 33 stage 35) with a l threshold of -1.4 MPa and at 0.8 ET c from veraison until harvest with a l at -1.2 MPa. Irrigation treatments in each year were not initiated until mid-day leaf water potential ( l ) reached -1.0 MPa for vines in the 0.8 ET c treatments. Canopy Architecture The following canopy architecture variables were quantified by measuring exterior and interior leaf contact numbers, cluster contact numbers, and percentage canopy gaps in fruiting zone with ten insertions per data vine at 15 cm intervals at 150 cm above vineyard floor at fruit-set in each year of the study. Leaf layer numbers and the ratio of cluster to leaf number ratios were calculated based on the methodology described by Smart (1991). A ceptometer (AccuPAR-80, Decagon Devices, Pullman, WA) was placed directly above cordon, within the fruiting zone parallel to the vine row at the head of each vine oriented due-south. Ambient readings were taken 60 cm above the canopy surface. The remaining three measurements were taken within the fruiting zone at the head of the vine. Measurements were taken at 1000 GDD at mid-day with PAR values ranging approximately mol m 2 s -1. The fruiting zone PAR measurements were combined and expressed as the percentage of total ambient PAR for the daylight period. Leaf area was measured destructively at stage 35 by defoliating a one meter section of canopy. The number of total shoots per meter was measured. Leaf area of one meter section of canopy was measured with the Li-Cor 3100 Leaf Area Meter (Li-Cor. Environmental, Lincoln, NE). Yield Components Harvest commenced when berry total soluble solids TSS (measured as TSS) reached 20%, the commercial benchmark for Zinfandel in the SJV. Each

47 34 treatment replicate was harvested manually, clusters harvested per vine counted and weighed with a top-loading scale. Cluster mass was calculated by dividing weight of clusters harvested by the number clusters. One hundred berries were randomly collected and weighed on an analytical top-loading digital scale (model: Mettler Toledo ML-104). The number of berries per cluster were calculated by dividing the cluster mass by berry mass. The pruning weights were collected in January of the following year. Production Efficiency and Water Footprint Leaf area to fruit ratio was calculated by dividing the leaf area vine -1 by the yield vine -1 (m 2 kg -1 ). Labor operations cost was calculated based on 2013 and 2014 harvest crush report value for Zinfandel in CA crush district 14 (CDFA 2013, 2014) based on established methods for traditional and mechanically managed single and dual plane canopies (Geller and Kurtural 2013, Kurtural et al. 2012). The water footprint was calculated based on methods reported by Williams (2014). Briefly in 2013, green water accounted for 23% and 27% of water supplied for the SDI and RDI treatments, respectively. In 2014, green water accounted for 18% and 22% of water supplied for the SDI and RDI treatments, respectively. The remainder derived from blue water or irrigation in both treatment years. Berry Composition The berry total soluble solids percentage TSS (measured as Brix), juice ph, and titratable acidity (TA, g/l of tartaric acid) were analyzed from a one-hundred, random berry sample collected at harvest from each treatment replicate. The TSS were measured using a (Atago PR-32 Palette digital refractometer; ATAGO USA, Bellevue, Washington). The juice ph was determined with a glass electrode and a

48 35 ph meter (model: Accumet A AB15; Fisher Scientific, Pittsburgh, PA). The TA was quantified by titrating to and end point ph of 8.2 with 0.1 N sodium hydroxide and expressed as grams per liter. Berry Phenolic Composition The phenolic composition of the berry was determined with an exhaustive extraction method modified from Pastor del Rio and Kennedy (2006). At harvest 20 random berry samples were collected, weighed and stored at -80 o C until analyzed. Berry skins and seed were removed from the pulp by hand, rinsed with tap water followed by distilled water, and blotted dry with paper towels and freeze-dried (model: Triad Freeze Dry System; Labconco, Kansas City, MO) mass was measured. The skins and seeds were then extracted in 30 ml 67% (v/v) acetone solution in darkness for 24 h. The acetone in samples was then evaporated under vacuum in a centrivap (model: ; Labconco, Kansas City, MO) attached to -103 o C cold trap (model: ; Labconco, Kansas City, MO). The samples were then filtered through a Whatman #1 90 mm filter under vacuum. Solution volume was measured in a type A graduated cylinder. 5 ml of sample were then centrifuged for five minutes at 1400 g. The supernatant was then poured off from the precipitate. 1.5 ml samples were then Pasteur pipetted into 2 ml HPLC vials and was subjected to HPLC-DAD analysis. HPLC Analysis and Procedure Phenolic composition was measured with a reversed-phase high performance liquid chromatography (HPLC) using an Agilent 1100 (Santa Clara, CA) modular system. The system was equipped with a G1313A injector, G1311A HPLC quaternary pump, on-line G1379A degasser, G1316A thermostatted column holder, G1315B photodiode array detector and Agilent Chemstation software

49 36 (version B03). A LiChrosphere 100 RP-18 reverse-phase column (5mm packing, 250 x 4 mm) was used, protected with a guard column of the same material, thermostatted at 40 o C. The procedure used three mobile phases for analysis. The solvents were (A) 50mM ammonium di-hydrogen phosphate adjusted to a ph of 2.6, (B) 20% Mobile A + 80 % Acetonitrile (v/v), (C 0.2 M ortho-phosphoric acid) and mobile phase D (50% Water + 50% Acetonitrile (v/v)) Solvents established the following gradient: isocratic 100% A in 5 min, from 100 to 92% A and from 0 to 8% B in 3 min, from 92 to 0% A, from 8 to 14% B and from 0 to 86% C in 12 min, from 0 to 1.5% A, from 14 to 16.5% B and from 86 to 82% C in 5 min, from 1.5 to 0% A, 16.5 to 21.5% B and 82 to 78.5% C in 10 min, from 21.5 to 50% B and from 78.5 to 50% C in 35 min, from 0 to 100% A, 50 to 0%B and 50 to 0% C in 15 min at a flow rate of 0.5 ml/min. Analytical grade water was purified with (Siemens Labostar Ultrapure Water Systems) 0.2 µm charged sterile filter before use. Acetonitrile of HPLC-gradient grade, o-phosphoric acid of analytical grade and analytical grade ammonium phosphate were purchased from (Fischer Scientific, Waltham, MA). Spectra were recorded from 250 to 600 nm. Quantification of phenolic compounds was carried out by peak area measurements at 280 nm for gallates and flavan-3-ols, 365 nm for flavonols and 520 nm for anthocyanins. The commercial standards used were gallic acid, catechin, rutin and malvidin-3-glucoside (Extrasynthése, Genay, France). Individual phenolic compounds were tentatively identified according to their order of elution, retention times of pure compound, and previous research conducted by Ritchey and Waterhouse (1999). Total tannin for seeds and skins were measured based on a procedure described by Kurtural et al. (2013). Briefly, total tannins were quantified spectrophotometrically (Lambda 25 UV/VIS; PerkinElmer,

50 37 Waltham, MA). Tannin content was assayed using protein precipitation (bovine serum albumin, Sigma-Aldrich, St. Louis, MO) ferric chloride reagent (Fisher Scientific, Pittsburg, PA), buffer solutions and quantified from a standard curve for catechin (catechin hydrate, Sigma-Aldrich). Statistical Analysis Data for all parameters were tested to verify if the assumptions of analysis of variance (ANOVA) were met using Shapiro-Wilk s test. Data which failed to meet the assumptions of ANOVA were log10 transformed and analyzed using generalized linear model (GLM) procedure in SAS (version 9.3; SAS Institute Inc., Cary, NC). The significance level was set at = 0.05 and means were separated using Tukey s honestly significant difference test. For the transformed data, when the ANOVA showed significant differences, the mean separation test was conducted on the transformed data but non-transformed means were presented for ease in discussion. Interactions between year and treatments were tested and whenever these interactions were significant (P<0.05) analysis was conducted separately for each year.

51 RESULTS Climate at Experimental Site Growing degree days (GDD) accumulation was calculated from March 15 th through harvest. The GDD accumulation was 1908 and 1814 in 2013 and 2014, respectively. Precipitation was 50.0 mm (Fig. 3.A) and 9.9 mm (Fig. 3.B) between March 15 th through harvest in 2013 and 2014, respectively. In 2013, the experiment site received mm between November to bud-break, 23.0 mm bud-break to veraison, 0.0 mm veraison to harvest. Compared to the 10-year average the amount of precipitation received at the experimental site was 84% the annual sum, 87% of dormant season and 70% of the growing season average. In 2014, the experiment site received 53.7 mm between November to bud-break, 9.9 mm bud-break to veraison, 0.0 mm veraison to harvest. Compared to the 10-year average the amount of precipitation received at the experimental site was 32% the annual sum, 30% of dormant season and 30% of the growing season average. The estimated crop coefficient (K c ) in the study varied considerably by year (Fig. 2). In 2013, the K c reached maximum of 0.84 after 618 GDD. Conversely in 2014, the K c reached a maximum of 0.54 at 550 GDD. The K c hence affected the estimated vineyard water use as a percentage of the seasonal estimated ET c from bud-break onwards. The l of Zinfandel vines in both years responded to respective irrigation treatments during application. The l was maintained at -1.2 MPa from bud-break through harvest for the SDI treatment and irrigation scheduling was based on a weekly crop coefficient K c calculations and weekly evapotranspiration measurements. The l was -1.2 MPa from bud-break to fruit set, and veraison to

52 harvest; while l was maintained at -1.4 MPa between fruit set to veraison for the RDI treatment. 39 Effect of Pruning Systems and Irrigation on Canopy Architecture There was an effect of experimental year on leaf layer number, number of cluster contacts, percent canopy gaps and PAR transmittance in the fruiting zone (Table B.2). Leaf layer number and PAR transmittance increased from 2013 to Percent canopy gaps and cluster contacts decreased from 2013 to In 2013, there was an interaction of year and pruning systems where the SP treatment had the greatest percent cluster contacts. In 2014, there was an interaction between year and irrigation treatments where the RDI treatment had the lowest percent of cluster contacts. The canopy gap percentage was not affected by pruning systems or irrigation treatments. In 2013, the SP treatment had the greatest number of cluster contacts. In 2014, the SDI treatment had the greatest number of cluster contacts. In 2014, there was an interaction between year and pruning systems where the SP treatment had the greatest PAR transmittance. In 2013, there was an interaction between year and irrigation treatments where the SDI treatment had the greatest PAR transmittance. In 2013, there was an interaction of pruning systems and irrigation treatments where a combination of the MP and SDI treatments had the greatest PAR transmittance. However, no such interaction was present in In 2013, PAR transmittance was greatest for the MP treatment. Similar results were not evident in 2014 where the SP and CP systems had the greatest PAR transmittance, compared to the MP treatment.

53 Effect of Pruning Systems and Irrigation on Yield Components The experimental year had an effect on berry weight, clusters harvested per vine, yield per vine, seed mass, total anthocyanin per hectare and the water footprint of Zinfandel (Table B.3). Berry weight, clusters harvested per vine, yield per vine, total anthocyanin per hectare and the water footprint decreased from 2013 to 2014, while seed mass increased. The MP treatments displayed the smallest decrease in yield per year followed by the SP and CP treatments, respectively. Pruning systems had no effect on berry weight in either year. The RDI treatment decreased berry weight by 18% and 11% in 2013 and 2014, respectively. There were no interactions between pruning systems and irrigation treatments on berry weight. In both years, the numbers of clusters harvested per vine were affected by pruning systems and by irrigation treatments in In 2013, the MP treatment had 16% fewer clusters per vine when compared to SP and CP treatments. Conversely, the MP treatment had 24% more clusters per vine when compared to the SP and CP treatments in In 2014, the SDI treatment had 14% more clusters harvested per vine. There were no interactions for clusters harvested per vine between irrigation treatments and pruning systems in Similar results were not evident in 2014, where a combination of the MP and SDI treatments yielded the most clusters harvested per vine. In 2013, the SP and CP treatments increased yield per vine by 17% compared to the MP treatment, while irrigation treatments had no effect on yield. In 2014, pruning systems and irrigation regimes interacted where the MP and SDI treatments had the greatest yield per vine. In 2014, there was an interaction between year and irrigation methods where the RDI treatment had the lightest berry skin mass. There was an effect of experimental year on berry skin mass where skin mass decreased from 2013 to 40

54 across all treatments. In 2014, the RDI treatment decreased berry skin mass by 24%. There was an effect of experimental year on berry seed mass where it increased from 2013 to 2014 across all treatments. In 2014, there was an interaction between year and berry seed mass where the SDI treatment had the greatest seed mass. In 2014, the RDI treatment decreased berry seed mass by 12%. In 2013, pruning systems affected the pruning weights where the CP treatment had a 31% decrease in pruning weight per vine compared to SP and MP treatments. The irrigation treatments had no effect on pruning weights. Efficiency and Labor Operations Costs There was an interaction between experimental year and pruning treatments on leaf area to fruit ratio where the CP treatment in 2013 had the lowest leaf area to fruit ratio. In 2013, there was an interaction between pruning systems and irrigation treatments on leaf area to fruit ratio where a combination of the MP and SDI treatments yielded the greatest leaf area to fruit ratio, while the CP and RDI treatment combination yielded the smallest leaf area to fruit ratio. The same interaction was not evident in The experimental year had an effect on total anthocyanin produced per hectare where it decreased from 2013 to In 2013, total anthocyanin produced per hectare was not affected by pruning systems or irrigation treatments. However in 2014, pruning systems and irrigation treatments interacted to affect it. A combination of the MP and SDI treatments yielded the greatest total anthocyanin produced per hectare, while the CP and RDI treatment combination yielded the least. The experimental year had an effect on the water footprint of Zinfandel grapevines where it decreased from 2013 to 2014 across all treatments. There was

55 42 an interaction between year and pruning systems with the water footprint being the greatest for the MP treatment in 2013 and lowest for the MP treatment in 2014, compared to other treatment combinations. In 2013, the MP treatment had a water footprint that was 19% higher than the CP and SP treatments. There was an interaction between year and irrigation treatments where the RDI treatment in 2014 had the lowest water footprint. Effect of Pruning Systems and Irrigation on Berry Composition Generally, the TSS was higher in 2014 across all treatments when compared to There was an interaction between experimental year and pruning systems where the SP treatment in 2013 had the lowest TSS. In 2013, the MP treatment increased TSS by 5% compared to the SP treatment (Table B.4). However, the same result was not evident in In both years, there was no effect of irrigation on TSS. Experimental year had an effect on juice ph where values increased from 2013 to There was an interaction between year and irrigation treatments where the RDI treatment in 2014 had the highest juice ph. The juice ph was affected by the irrigation treatments in both years. The SDI treatment reduced juice ph by 4% in both 2013 and 2014 compared to the RDI treatment. In 2013, pruning systems affected juice ph where the CP and MP treatments had higher juice ph than the SP treatment. There was an interaction between year and pruning systems where the SP treatment in 2013 yielded the greatest TA values. In 2013, TA was greatest for the SP treatment compared to the CP and MP treatments. In 2013, there was a pruning systems and irrigation treatments interaction where the CP and RDI combination had the lowest TA compared to other treatment combinations. In both years, SDI treatments had greater TA values than RDI treatments.

56 Effects of Pruning Systems and Irrigation on Gallates, Flavonols, Flavan-3-ol Monomers and Tannins of Seed Tissue There was an interaction between experimental year and irrigation treatments where gallic acid was greatest in 2014 under the RDI treatment (Table B.5). In 2013, there was an interaction between pruning systems and irrigation methods where the combination of SP and SDI treatments yielded the most gallic acid. In 2014, the RDI treatment yielded 82% more gallic acid compared to the SDI treatment. There was a strong effect of experimental year on the levels of (+)- catechin, where it increased across all treatments from 2013 to There was a year by irrigation interaction where the combination of the RDI treatment in 2013 produced the lowest (+)-catechin compared to other treatment year combinations. In 2013, the SDI treatment increased (+)-catechin by 22% compared to the RDI treatment. Experimental year had an effect on (-)-epicatechin in seed tissue where it increased across all treatments from 2013 to In 2014, there was an interaction of year by pruning systems by irrigation treatments where the combination of MP and RDI treatments yielded the greatest amount of (-)- epicatechin. In 2013, there was no effect of pruning systems or irrigation methods on (-)-epicatechin. In 2014, there was a year by irrigation interaction where the RDI treatment yielded the greatest (-)-epicatechin. In 2014, the RDI treatment increased (-)-epicatechin by 11% compared to the SDI treatment. There was a strong effect of experimental year on quercetin within seed tissue where it increased across all treatments from 2013 to In 2013, the CP treatment yielded 31% more quercetin compared to the SP treatment. In 2014, there was a year by irrigation interaction on quercetin where the RDI treatment had yielded the greatest amount of quercetin. There was an effect of experimental year on 43

57 44 myricetin where it increased across all treatments from 2013 to In 2013, there was an interaction between pruning systems and irrigation treatments where the SP and RDI treatments yielded the lowest amount of myricetin and the MP and SDI yielded the highest. In 2014, the RDI treatment increased myricetin by 12% compared to the SDI treatments. There was a strong effect of year on total tannins where total seed tannins decreased across all treatments from 2013 to There was a year by irrigation interaction where the SDI treatment in 2013 yielded the greatest amount of total seed tannins. In 2013, the SDI treatment increased total seed tannins by 26% compared to the RDI treatments. In 2014, there was no effect of pruning systems or irrigation methods on total seed tannins. Effects of Pruning Systems and Irrigation on Gallates, Flavonols, Flavan-3-ol Monomers and Tannins of Skin Tissue In 2013, pruning systems and irrigation treatments had no effect on gallic acid. In 2014, the MP treatment increased gallic acid by 62% compared to the CP treatment (Table B.6). There was an effect of experimental year on (+)-catechin where (+)-catechin increased across all treatments from 2013 to There was a year by pruning interaction MP in 2014 and SP in 2013 yielded the greatest (+)- catechin. In 2014, there was an interaction between pruning systems and irrigation treatments, where a combination of the MP and RDI yielded the greatest (+)- catechin compared to other treatment combinations. In both years, (+)-catechin was affected by pruning systems. In 2014, the MP treatment increased (+)- catechin by 28% compared to the SP and CP treatments and the RDI treatment increased (+)-catechin by 38%. The same results were not evident in 2013 where the SP treatment increased (+)-catechin by 95% compared to CP and MP treatments. There was a strong effect of experimental year where (-)-epicatechin

58 45 increased across all treatments from 2013 to In 2013, (-)-epicatechin was affected by pruning systems with the SP treatment yielding 88% more (-)- epicatechin compared to CP. There was an effect of experimental year on quercetin where it decreased across all treatments from 2013 to In both years, quercetin was not affected by irrigation method. In 2014, the MP treatment increased quercetin by 47% compared to the CP and SP treatments. There was an effect of experimental year and a year by pruning systems interaction where myricetin decreased across each treatment from 2013 to 2014 and the SP treatment in 2013 yielded the greatest amount of myricetin in skin tissue. In both years, myricetin was affected by pruning systems. In 2013, the SP treatment increased myricetin by 83% compared to the CP and MP treatments. The same results were not evident in 2014 where the MP treatment increased myricetin by 36% compared to the SP and CP treatments. There was an effect of experimental year on total skin tannins where total tannins generally decreased from 2013 to There was a year by pruning systems interaction where the SP treatment in 2013 yielded the most total skin tannins compared to other treatment combinations. In both years, total skin tannins were affected by pruning systems. In 2013, the SP treatment yielded 347% more total skin tannins compared to the CP and MP treatments. In 2014, both the MP and SP treatments yielded 30% more total skin tannins compared to the CP treatment. Effects of Pruning Systems and Irrigation on Anthocyanins There was a general effect of year for anthocyanin-glucosides where they increased from 2013 to 2014 across all treatments (Table B.7). There was an experimental year by pruning interaction where the MP treatment in 2013 yielded the greatest amount delphinidin-3-glucoside. In both years, delphinidin-3-

59 46 glucoside was affected by pruning systems. In 2013, the SP treatment yielded 110% more delphinidin-3-glucoside compared to the CP and MP treatments. The same results were not evident in 2014 where the MP treatment yielded 37% more delphinidin-3-glucoside compared to the CP and SP treatments. In 2014, pruning systems affected cyanidin-3-glucoside where the MP treatment yielded 35% more cyanidin-3-glucoside compared to the CP treatment. There was a year by pruning systems interaction where the MP treatment in 2014 yielded the greatest amount of petunidin-3-glucoside. In both years, petunidin-3-glucoside was affected by pruning systems. In 2013, the SP treatment yielded 61% more petunidin-3- glucoside, compared to the CP and MP treatments and the SDI treatment yielded 20% more petunidin-3-glucoside compared to the RDI treatment. In 2014, the MP treatment yielded 35% more petunidin-3-glucoside compared to the CP and SP treatments. In 2014, peonidin-3-glucoside was affected by pruning systems where the MP treatment yielded 27% more peonidin-3-glucoside compared to the SP and CP treatments. In 2014, malvidin-3-glucoside was affected by pruning systems and irrigation methods. The MP treatment yielded 23% more malvidin-3-glucoside compared to the CP and SP treatments, while the RDI treatment yielded 16% more malvidin-3-glucoside compared to the SDI treatment. In 2014, total anthocyaninglucosides were affected by pruning systems and irrigation methods. The MP treatment yielded 21% more total anthocyanin-glucosides compared to the CP and SP treatments, while the RDI treatment yielded 15% more total anthocyaninglucosides compared to the SDI treatment. In general, anthocyanin-acetates were affected by experimental year where anthocyanin-acetates decreased from 2013 to In 2014, cyanidin-3-glucosideacetate responded to both pruning systems and irrigation methods. The MP treatment yielded 36% more cyanidin-3-glucoside-acetate, while the RDI

60 47 treatment increased cyanidin-3-glucoside-acetate by 10%. In 2014, petunidin-3- glucoside-acetate was affected by both pruning systems and irrigation methods. The MP treatment yielded the greatest amount of petunidin-3-glucoside-acetate followed by the SP and CP treatments, respectively. The RDI treatment yielded 18% more petunidin-3-glucoside-acetate compared to the SDI treatment. In both years, peonidin-3-glucoside-acetate was affected by pruning systems. In 2013, the SP treatment yielded 118% less peonidin-3-glucoside-acetate compared to the CP and MP treatments. In 2014, the MP treatment yielded 25% more peonidin-3- glucoside-acetate compared to the CP treatment. The RDI treatment yielded 18% more peonidin-3-glucoside-acetate compared to the SDI treatment. In both years, malvidin-3-glucoside-acetate was affected by pruning systems. In 2013, the SP treatment yielded the greatest amount malvidin-3-glucoside-acetate, followed by the CP then MP treatments, respectively. These results were not evident in 2014 where the MP treatment yielded 38% more malvidin-3-glucoside-acetate compared to the CP and SP treatments. There was an experimental year by pruning systems interaction for petunidin-3-glucoside-coumarate and malvidin-3-glucoside-coumarate where the MP treatment in 2014 yielded the greatest amount of anthocyanin-coumarates. There was also a strong effect of experimental year on malvidin-3-glucosidecoumarate where malvidin-3-glucoside-coumarate decreased from 2013 to 2014 across all treatments. In both years, anthocyanin-coumarates were affected by pruning systems. In 2013, the SP treatment yielded the most malvidin-3-glucosidecoumarate and petunidin-3-glucoside-coumarate compared to the CP and MP treatments, respectively. In 2014, the MP treatment yielded 32% more malvidin-3- glucoside-coumarate and 68% more petunidin-3-glucoside-coumarate compared to

61 48 the CP and SP treatments. There was no effect of irrigation methods on anthocyanin-coumarates.

62 DISCUSSION Climatology and Irrigation As the results indicated, both years of the study received less than the ten year average of precipitation, while the second year of the study received only 30% of that average. Irrigation amounts were determined by calculating crop evapotranspiration (ET c ) by the product of the estimated crop coefficient (K c ) and reference evapotranspiration (ET o ) (Allen et al. 1998, Williams and Ayars 2005). Williams and Ayars (2005) reported an R 2 value of (0.95) between the relationship of the K c and ground cover cast by the canopy. This relation allows one to use canopy shade estimates to calculate the K c (Allen et al. 1998, Williams 2012). The maximum K c in this study was 0.85 and 0.58 in 2013 and 2014, respectively (Fig. 2). It has been recommended that maximum K c for a 3.35 m row be 0.70 by Allen et al. (1998). However, Williams et al. (2003) reported a maximum K c of 0.98 for a 3.35 m row within the San Joaquin Valley s hot climate area. Recommended K c is dependent upon trellis, pruning system and row spacing where a common maximum K c cannot be appropriate for all circumstances (Williams 2012). Therefore region V, which accumulates significantly greater GDD, can support increased K c values in the presence of sufficient irrigation as well as proper vine and row spacing. Reduced precipitation at bud-break, affected the crop coefficient (K c ) where it reached a maximum that was 38% less in 2014 compared to Winter precipitation exclusion has been shown to severely restrict shoot growth and canopy development, regardless of in-season irrigation (Mendez-Costabel et al. 2013). In 2014, a lack of canopy development reduced ground cover and reduced estimated K c which led to a decrease of in-season irrigation. This affected the

63 50 canopy architecture, yield components, efficiency and flavonoid accumulation where year effects and interactions were ubiquitous. Global weather projections have recently predicted shifts in phenological stages and increased occurrences of drought and heat waves (Chaves et al. 2010). Phenology was affected by untoward drought conditions and was similar to phenological shifts predicted by warming projections (Chaves et al. 2010, Jones and Davis 2000). In addition to decreased precipitation, there was a marked increase in temperature during the second year of study, where the average temperature increased by 0.8 C over the growing season. Furthermore, there was an 11% increase in days which recorded a maximum temperature over 32.2 C in 2014 compared to 2013 ( Canopy Architecture A general observation is that vine vigor is inversely proportional to shoot number per grapevine, which is determined by node count per grapevine during winter pruning (Clingeleffer 2010). However, in a warm climate area when resources are not limited, high levels of canopy development and growth have been observed regardless of dormant pruning application (Wessner and Kurtural 2013). It was not surprising to see a strong effect of year on canopy development due to the lack of winter precipitation which is known to decrease fruitfulness and canopy architecture (Lakso et al. 1999, Mendez-Costabel et al. 2014). In addition, Lakso et al. (1999) reported reduction of leaf photosynthesis, reduced berry growth and partial defoliation in sites that experienced dry winter conditions in Concord grapevines. The cluster contacts appeared to be more affected by deficit irrigation following an arid winter where the RDI treatment had fewer cluster contacts

64 51 compared to the SDI treatment in A deficit irrigation carry-over effect has been reported where a lack of soil moisture can hinder subsequent seasons reproductive and vegetative development that may not have been present in the initial year of study (Petrie et al. 2004). There were year by irrigation methods and year by pruning systems interactions for cluster contacts and PAR transmittance. The MP and SDI treatments in 2013 had the least congested canopy architecture with lower cluster contacts and increased PAR transmittance, similar to that reported by Wessner and Kurtural (2013). However, these results were upturned after an arid winter where the MP and SDI treatments had the densest canopy with increased cluster contacts and decreased PAR transmittance compared to other treatments. The interactive effects of the SDI and MP treatments were similar to (Bindon et al. 2008, Intrieri et al. 2001) where PAR transmittance decreased due to retaining increased nodes and adequate irrigation. The relative difference between the MP treatment compared to the CP and SP treatments suggest that the latter pruning systems were more affected by irrigation treatment carry over effects. In addition, initial canopy congestion and PAR transmittance have been reported to effect the following year s canopy production and may have contributed to the CP and SP treatment s decreased canopy size similar to reports by (Geller and Kurtural 2012, Gladstone and Dokoozlian 2005). Gladstone and Dokoozlian (2005) reported increased bud fruitfulness succeeding a season in which the canopy was mechanically thinned to produce a less congested architecture; similarly Geller and Kurtural (2012) reported increased fruitfulness for MP treatments due to a less dense canopy in the previous year.

65 52 Yield Components In general, there was a strong effect of year on yield components. It has been reported that reproductive growth is affected more by winter pruning than vegetative growth (Nuzzo and Matthews 2006), while vegetative growth is more affected by irrigation regimes than reproductive (Keller et al. 2008, Shellie and Bowen 2014). These two statements held true in the presence of adequate resources where the soil profile was filled before the growing season with irrigation marginally affecting yield components. However after receiving minimal precipitation during dormant and growing season, treatments that affected water usage became limiting factors. Similar differences in year effects were reported by (Lakso et al. 1999, Mendez-Costabel et al. 2014, Petrie et al. 2004) and can be attributed to a combination of the deficit irrigation carry-over effect and exclusion of winter precipitation. Biennial alternate bearing has been proposed as an explanation for the drastic decrease yield from year to year. As reported by Intrieri et al. (2001), yield was affected by pruning treatments where a significant reduction in the second year of study followed by a marked increase in the third year of study. Intrieri et al. (2001) suggests that grapevines can exhibit an alternate bearing tendency that is dependent upon said grapevines experiencing relatively high yields in the initial year of study, as was reported in this experiment. A third year of study is needed to confirm the alternate bearing hypothesis in this study. If confirmed, this would suggest that the MP treatment is a more suitable pruning system for the southern San Joaquin Valley, due to the ability to compensate for the off-year and minimize annual yield variability. It should be noted that Olmstead (2006) refuted the alternate bearing hypothesis in grapevines and attributed seasonal variability in yield to weather related events or physiological imbalances.

66 53 Initial differences in yield were primarily affected by pruning systems where the CP and SP treatments yielded the most clusters per vine at harvest and subsequent yield compared to the MP treatment. The CP and SP treatments increased yield by 17% compared to the MP treatment. In addition to producing the highest yield compared to treatments in this study, the CP and SP treatments had nearly a 30% increase in yield compared to similar studies on Zinfandel 1A in the San Joaquin Valley (Fidelibus et al. 2005) and over 60% increase compared to Zinfandel 1A in the northern San Joaquin Valley (Wolpert 1996). It should be noted that (Fidelibus et al. 2005, Wolpert 1996) did not incorporate deficit irrigation practices and likely had lower water productivity in comparison to vines in this study (discussed later). In addition, the initial year of study showed no reduction in yield from deficit irrigation similar to (Bindon et al. 2008, Chaves et al. 2010, Williams 2014) but contrary to reports by (Shellie and Bowen Williams 2012). In both years, yield was strongly associated to number of clusters per vine at harvest. These results follow reports by (Bindon et al. 2008, Petrie et al. 2004) where greater canopy size had an association to increased fruit production. However, there was an effect of year and the same results were not evident in The treatment with the largest canopy still produced the greatest yield and in addition there was an interaction with irrigation treatments. The interaction between pruning systems and irrigation treatments where the combinations of the MP and SDI treatments produced the greatest yields and were similar to (De Toda and Sancha 1999, Shellie and Bowen 2014, Williams 2012) whom reported increased yield from the combination of less water stress and mechanical pruning application. The combination of the MP and SDI produced tonnage similar to a

67 54 Zinfandel study by Fidelibus et al. (2005), little information is available on the performance of grapevines in the San Joaquin Valley after an arid winter. Yields were affected by the RDI treatment in the second year of study and were similar to reports by (Chaves et al. 2010, Shellie and Bowen 2014, Williams 2012). Chaves et al. (2010) reported reductions in yield in response to deficit irrigation only after an unseasonably dry growing season, which was confirmed by this study. Overall, reductions in yields can be attributed to several factors such as previously stated; lack of winter precipitation (Lakso et al. 1999, Mendez-Costabel 2014), deficit irrigation carry-over effect (Bindon et al. 2008, Lakso et al. 1999, Petrie et al. 2004), initial PAR transmittance and canopy congestion (Geller and Kurtural 2012, Gladstone and Dokoozlian 2005) or possibly the alternate bearing hypothesis proposed by (Intrieri et al. 2001). However, it should be noted that the effect of a dry winter was the most likely culprit for the differences in yield from year to year due to similar experiments being able to sustain pronounced yields on a yearly basis (Fidelibus et al. 2005, Wessner and Kurtural 2013). The reductions in yield were exacerbated when the previously stated conditions were coupled with pruning systems that promoted canopy development and water consumption similar to (Petrie et al. 2004, Williams 2012). Reports have shown that the CP treatment, when coupled with sufficient winter precipitation and in-season irrigation can consistently produce pronounced yields (Wessner and Kurtural 2013). However, as competition for water increases, pruning systems that generate a split canopy may become economically unsuitable and effectively obsolete for commercial viticulture in the southern San Joaquin Valley. The MP treatment experienced the smallest decrease in yield from year to year and would appear to have the highest sustainability of the three pruning systems due its interactions with irrigation treatments. The MP treatment s

68 55 consistent yields have been previously reported (Geller and Kurtural 2012, Terry and Kurtural 2011). It should be noted that Zinfandel 1A has a propensity to develop thin skinned, tight clusters and when combined promote sour rot (Fidelibus et al. 2005). Therefore, a pruning strategy that promotes fewer, larger clusters should be avoided with this cultivar, thus giving more credence to the application of the MP treatment in the southern San Joaquin Valley, because of the promotion of increased number of smaller clusters relative to the CP and SP treatments. Berry Constituents It is well known that deficit irrigation can reduce berry size and increase the skin to pulp ratio (Keller et al. 2008, Kennedy et al. 2002, Shellie and Bowen 2014, Terry and Kurtural 2011, Williams 2014). The increase in skin: pulp ratio is considered a valued aspect in determining berry quality, thus giving credence to the benefits of deficit irrigation. The effects of winter precipitation were considerable with up to 24% reduction in berry size from 2013 to The decrease in berry size from year to year was greater than the decrease in berry size seen between in-year irrigation treatments, the significant reductions in berry size caused by lack of winter precipitation were similar to results reported in other studies (Lakso et al. 1999, Mendez-Costabel et al. 2014). Skin tissue weight was not affected by pruning systems in either year. However, there was strong influence of year on skin weights where they decreased across all treatments from 2013 to In addition, skin tissue weight was affected by irrigation treatment in the second year of study. These results parallel the reductions observed in berry weights. The combination of winter drought and

69 56 deficit irrigation carry-over effect are likely responsible for the irrigation effect on skin weights in the second year of the study. Conversely to berry weight and skin tissue weight, seed tissue weight increased from year to year of the study. There were irrigation effects in both years, hinting at the susceptibility of seeds being affected by irrigation deficit regimes. The effect of irrigation should be expected due to the phenological timing of irrigation stress coinciding with seed development and parallel reports by Genebra et al. (2014). These authors reported a relation between seed weight and applied irrigation where the seed weight increased as irrigation stress between fruit set and veraison was alleviated. The strong effect of year on seed tissue weight where seed tissue weights per berry increased across all treatments from 2013 to 2014 was similar to results were reported by Wien et al. (1979) with Cowpeas Vigna unguiculata and Soybean Glycine max under seasonal drought conditions. The authors reported increased seed weight after the incidence of a drought, possibly due to a biological shift in carbohydrate allocation due to stress signals. While in grapes, Cortell et al. (2005) reported an association between increased seed mass per berry as vigor decreased by means of increased seeds per berry due to effects of drought stress. Yield Efficiency Pruning systems had a strong effect on the majority of yield efficiency parameters reported in this trial. Perhaps a more interesting finding in this experiment was the strong effect year had on yield efficiency and furthermore an adjustment of recommendations for crop load and leaf area to fruit ratios in the southern SJV. According to Kliewer and Dokoozlian (2005) a single-canopy training systems, the leaf area to fruit ratio required for maximum maturity at

70 57 harvest ranged from 0.8 to 1.2 m 2 /kg, whereas for split canopies, this ratio was reduced to 0.5 to 0.8 m 2 /kg. However in 2013, this trial was successful at maturing Zinfandel 1A fruit to a commercial standard of approximately 20 TSS (Fidelibus et al. 2005, Wolpert 1996) at leaf area to fruit ratios well below the recommended values for grapevines in the northern SJV, Sacramento Valley and North Coast. It is obvious that the southern SJV should have revised recommendations for yield efficiency variables, but little research has focused on this viticultural area (Williams 2012). Therefore, we are able to synthesize recommendations for the southern SJV based on the results from this project for Zinfandel grapevines. The two single canopy pruning systems (SP and MP) had a leaf area to fruit ratio of 0.59 and 0.70, respectively. The MP treatment reached the commercial standard for maturity (Fidelibus et al. 2005, Wolpert 1996). However, the SP treatment suffered from excessive sour rot (data not shown) compared to the MP and CP treatments, indicating that a leaf area to fruit ratio below 0.60 may not be sufficient to mature Zinfandel in the southern SJV for single canopy architecture. Fidelibus et al. (2005) reported excessive sour rot between 30 and 63 percent in all four years of study suggesting that Zinfandel may be a problematic cultivar in this region. However, this experiment reported excessive incidence of sour rot in just one year 2013 with one pruning system (SP). The CP treatment reached commercial maturity at a leaf area to fruit ratio of 0.38 which was below the Kliewer and Dokoozlian (2005) recommendation of 0.50 for divided canopies. These ratios in combination with Ravaz indices provide novel recommendations for yield efficiencies metrics for the southern SJV. Furthermore, Howell (2001) attributed decreased leaf area: fruit ratios, in regions which experienced extended

71 58 periods of foliated vines post-harvest, to the re-accumulation of carbohydrates which are allocated to the bud and inflorescence stages in the following spring. Ravaz index (data not shown) was strongly affected by pruning systems and all treatments were considered to be over-cropped with Ravaz indices > 10 by traditional North Coast and Sacramento Valley standards. The CP treatment had the highest Ravaz index at This would suggest that the CP treatment was the most over-cropped pruning treatment of the three systems. It is difficult to deduce if the decrease in yield was primarily affected by the over-cropped Ravaz indices or previously mentioned climate and cultural practice effects (Bindon et al. 2008, Geller and Kurtural 2012, Gladstone and Dokoozlian 2005, Intrieri et al. 2001, Mendez-Costabel et al. 2014, Petrie et al. 2004, Williams 2012). It should be noted that the CP treatment suffered the greatest decrease in yield (-13.6 kg/vine), followed by the SP (-12.7 kg/vine) and MP (-5.5 kg/vine), respectively. A reasonable conclusion would suggest that a Ravaz index comparable to the MP treatment < 20 would be an adequate recommendation, since this pruning system suffered the smallest decrease in yield and still out produced tonnage from similar projects in the northern SJV (Wolpert 1996). Williams (2012) reported balanced vines at a Ravaz index of up to 18 in a warm climate environment. This may indicate that the previous recommended ratio suggested may not apply to all grapevines in the southern SJV. In the second year of study all pruning systems reached commercial maturity and incidence of sour rot was minimal to none (data not shown). The leaf area to fruit ratio was at or above the previously mentioned thresholds > 0.60 for single canopy architecture and > 0.38 for divided canopy architecture. Total anthocyanin per hectare decreased from year to year of this study as a direct result of decreased yields, even though anthocyanin content per berry increased. In 2014,

72 59 there was an interaction with total anthocyanin per hectare where the MP treatment with SDI irrigation combined to produce the most anthocyanin per hectare. These results contribute to the sustainability and productivity of the MP treatment compared to the CP and SP treatments where berry quality and yield were greatest for the MP treatment in a challenging environment. Increased anthropogenic climate change will intensify present water shortages, as well as increase incidence of drought in Mediterranean climates (Chaves et al. 2010, Morison et al. 2008, Teixeira et al. 2013). The sustainability of agriculture in warm climate areas has recently been brought into question (Morison et al. 2008, Williams 2012). As competition for water increases, the urgency for conservation is amplified. It has been stated that irrigated agriculture in hot, dry environments should be reduced because these environments produced the least yield per unit of water (Morison et al. 2008). Similarly, it has been reported that deficit irrigation in warm environments is not economically stable, because of decreased yields (Williams 2012). To the contrary, this project reported increased water crop productivity and subsequent decrease in blue water footprint (Williams 2014) with limited reductions in yields for deficit irrigated vines. It should be noted that yield reductions were only seen following an unseasonably dry winter as reported elsewhere (Chaves et al. 2010). Water productivity increased as applied water decreased and yields increased, similar to other reports (Chaves et al. 2010, Shellie and Bowen 2014, Williams 2012, Williams 2014). Initially the CP and SP treatments, as well as the RDI treatment had the most efficient water footprint. In addition, water footprint efficacy was strongly affected by year (Williams 2014). In contrast to the first year, the MP treatment had the most efficient water footprint. In opposition to reports by (Williams 2012, Williams 2014) the water

73 60 footprint efficiency was comparable and even exceeded grapevines in a cool climate environment, while productivity increased after the incidence of a challenging, arid winter. The strong differences in blue water footprints (Williams 2014) between irrigation treatments were contributed to the minor reduction in yield as applied water decreased. This study suggests that the interactive effects of deficit irrigation in combination with mechanical pruning have the ability to enhance viticultural water efficiency and subsequent blue water footprint within the southern SJV. Berry Composition In general berry composition was strongly affected by year and irrigation where effects of pruning systems were reported in the initial year of study, but not the second. The discrepancies in pruning system effects can be contributed in part to the lack of maturity and sour rot experienced by the SP treatment in the first year of study. As previously mentioned, a low leaf area to fruit ratio may have contributed decreased ripening coupled with the cultivars propensity to develop sour rot due to thin skin and tight clusters, created a compound problem for the SP treatment in the initial year of study (Fidelibus et al. 2005, Kliewer and Dokoozlian 2005). Therefore it is not surprising that the SP treatment had reduced TSS, ph and increased TA. Effects of pruning systems on berry composition were not present in the second year of study as each pruning system reached full commercial maturity for Zinfandel as reported by (Fidelibus et al. 2005, Wolpert 1996). Irrigation method s effects on berry composition have been widely reported and tend to be in agreement with our findings. The more stressed RDI treatment decreased TA and increased ph compared to the SDI treatment as reported in

74 61 some studies (Esteban et al. 1999, Keller et al. 2008, Shellie 2010). These differences in composition have been mostly attributed to the accelerated ripening associated with the RDI treatment or irrigation stress. It should be noted that TSS was slightly higher for the RDI treatment, but not significantly different in both years of study. Of greater interest are the observed effects of experimental year on grape maturity. There was a significant increase in maturation from 2013 to This coupled with the fact that harvest occurred two weeks earlier in 2014 compared to 2013 give credence to the shortening of seasons and phenological shifts predicted by (Chaves et al. 2010, Jones and Davis 2000). Gallates, Flavonols, Flavan-3-ol Monomers and Total Tannins of Seed Tissue There is a general consensus that temperature and diffuse light can affect berry skin and seed composition and content (Cortell and Kennedy 2006, Downey et al. 2004, Shellie and Bowen 2014, Spayd et al. 2002). There was a general lack of in-season effects on phenolic composition of seed tissue. However, there were strong effects of experimental year observed for the majority of seed tissue flavonoids. The trend associated with seed phenolic composition was consistent with other reports (Cortell et al. 2005, Cortell and Kennedy 2006, Downey et al. 2004) where shade and heat influenced flavan-3-ols, flavonols and total tannins composition. Some researchers (Cortell et al. 2005, Cortell and Kennedy 2006, Downey et al. 2004) conducted experiments where clusters were artificially shaded to simulate the effects of light exclusion on flavonoid accumulation and composition. Their in-season results parallel the year effects observed in this experiment due to the significant reduction in canopy architecture and subsequent cluster shading from year to year attributed to the incidence of drought. Cortell and Kennedy (2006) reported that under low water availability plants can reduce

75 62 growth and shift carbon assimilation towards secondary plant metabolites, thus increasing flavonoid content. In addition, it has been reported that diffuse light exposure and water stress are known to affect the flavonoid pathway. It has been reported that flavonols are highly responsive to decreased vine water status and increased light exposure. Cortell and Kennedy (2006) reported an eightfold increase in flavonols in exposed treatments versus shaded treatments. However, temperature was not an included variable. Temperature has been reported to inhibit the flavonoid synthesis pathway and thus inhibit accumulation of flavonol (Spayd et al. 2002, Tarara 2008). In addition to influencing flavonol content, vine vigor, intercepted light and temperature have been shown to decrease flavanols and tannin composition and accumulation (Cortell et al. 2005, Spayd et al. 2002, Tarara 2008). In general, seed phenolic content increased from 2013 to There was a marked year by irrigation interaction for the flavan-3-ol monomers and flavonols suggesting that the vines were more susceptible to irrigation stress in the second year of study do to the deficit irrigation carry-over effect (Bindon et al. 2008, Lakso et al. 1999, Petrie et al. 2004). The proportion of (-)-epicatechin to (+)- catechin increased as the canopy shading decreased from 2013 to These results were similar to other reports (Cortell et al. 2005, Cortell and Kennedy 2006) where the proportion of (-)-epicatechin to (+)-catechin increased in a shaded environment. Previous literature treatments applied opaque boxes around cluster bunches of Shiraz and Pinot noir to simulate shaded environments (Cortell and Kennedy Downey et al. 2004). In this study, we considered a shaded environment as a canopy which intercepted less than 8.0% PAR transmittance. Consistent with the decrease in K c observed from 2013 to 2014, the canopy created less ground cover and exposed fruit to more intercepted light in 2014

76 63 where PAR transmittance increased across all treatments from year to year of study. Contrary to results reported by Cortell and Kennedy (2006), who found an overall increase in flavan-3-ol monomers in a shaded environment. There was an overall increase in flavan-3-ol content from 2013 to 2014, as canopy shading decreased. These results were also different than Cortell et al. (2005) who found no effects of shade or irrigation on flavan-3-ols content. These discrepancies were attributed to an increase in seed mass combined with a decrease in yield leading to an increase in seed flavonoid concentration. The two pruning systems that reported the smallest flavan-3-ol content had the lowest PAR transmittance, the SP treatment in 2013 and the MP treatment in However, total tannins decreased from year to year. These findings contradict reports by Cortell et al. (2005) where total tannins were not affected by environmental factors. The differences between total tannins within this experiment were likely contributed to differences between maturation where the grapes reached a higher maturity in 2014 compared to 2013 where maturation has been shown to decrease total seed tannin content (Cortell and Kennedy 2006). Consistent with the Cortell and Kennedy (2006) report, the SDI treatment had increased total tannins compared to the RDI treatment in Separating the effects of light and temperature on berry quality and composition can be difficult, many of the biochemical pathways are both light and temperature sensitive (Spayd et al. 2002). However, temperatures were higher in the growing season from compared to with 130 days above 32.2 C compared to 116, respectively. This increase in extreme temperatures can effect flavan-3-ol accumulation, regardless of increased light interception (Spayd et al. 2002, Tarara 2008). In general, it can be deduced that seed composition was altered and seed

77 64 content increased from 2013 to This increase in seed flavonoid accumulation can be directly linked to an increase in seed mass and seed count per berry as a result of redirection of energetic resources and carbohydrate partitioning in response to extended drought conditions (Cortell et al. 2005, Gauthier et al. 2014). Gallates, Flavonols, Flavan-3-ol Monomers and Total Tannins of Skin Tissue As previously stated, flavan-3-ol composition and content is known to be affected by shade, temperature and berry maturity. It is known that quantification of berry skin flavan-3-ol monomers can be difficult due to low content (Cortell et al. 2005, Cortell and Kennedy 2006, Downey et al. 2004, Spayd et al. 2002). In addition, flavan-3-ol content is less in skin tissue compared to seed (Cortell et al. 2005, Cortell and Kennedy 2006, Downey et al. 2004, Monagas et al. 2003) as was observed in this experiment. The composition and content of flavan-3-ol, flavonols and anthocyanins is dependent upon cultivar and terroir (Cortell and Kennedy 2006, Downey et al. 2006, Monagas et al. 2003). Cortell and Kennedy (2006) reported a lower proportion of malvidin-3-glucoside in Pinot noir compared to the Zinfandel in this study. In addition, an increase in flavonoid accumulation relative to this a hot climate region is expected in the cooler climate area, as flavonoid synthesis is negatively affected by increased temperatures (Spayd et al. 2002, Tarara 2008). In 2013, the SP treatment yielded the greatest amounts of flavan-3-ols and total tannins compared to the CP and MP treatments. Skin and seed tannin content has been shown to decrease with berry maturation (Cortell and Kennedy 2006). The SP treatments yielded the greatest total tannin and flavan-3-ol content and can be attributed to the lack of maturation seen with this pruning system. In 2013, the

78 65 SP treatment failed to reach an acceptable leaf area to fruit ratio, had increased incidence of sour rot and did not make it to the commercial maturity standard for Zinfandel 1A in the southern SJV (Fidelibus et al. 2005). Research is lacking on the effects of sour rot on flavonoid content, but it can be deduced that the SP treatment flavonoid content and composition was affected by lack of maturation and incidence of infection. The following year s data as well as the strong influence of year are better representatives of treatment results. In 2014, there was a general trend where the MP treatment yielded greater amounts of gallates, flavonols, flavan-3-ols and total tannins compared to the SP and CP treatments. There was a strong effect of year where the SP treatment yielded less (+)- catechin from 2013 to 2014, while the CP and MP treatments yielded more. There was a marked decrease in canopy development from 2013 to 2014 and results parallel light exclusion studies reported by Cortell and Kennedy (2006) and Price et al. (1995). There have been conflicting reports on the effects of shade and (+)- catechin content. The CP and MP treatments follow results reported by Cortell and Kennedy (2006) where the exposed cluster had increased flavan-3-ols compared to shaded clusters. The SP treatment followed results reported by Price et al. (1995) where shaded treatments yielded greater amounts of (+)-catechin. These differences in results can be attributed to reduction in yield and increase in temperature experienced from 2013 to There monomeric (+)-catechin to (-)- epicatechin ratio seen with skin tissue paralleled Monagas et al. (2003) where there was a higher percentage of (-)-epicatechin relative to (+)-catechin in skin tissue. Flavan-3-ol skin composition and content is highly cultivar and terroir dependent as stated earlier and further research is needed to gain a greater perspective on the effects of light, temperature and irrigation within a warm climate area.

79 66 Generally, there was a lack of irrigation treatment effect on gallates, flavan- 3-ols and flavonols in skin tissue. Similar results were reported by Goto- Yamamoto et al. (2009). The accumulation of flavonols is an important defense against UV damage for sunlight (Price et al. 1995). Flavonols were strongly affected by year and pruning systems. In 2013, the SP treatment yielded the greatest amount of myricetin compared to the CP the SP treatments. However, the same results were not evident in 2014 where the MP treatment yielded the greatest amounts of flavonols. Quercetin and myricetin decreased from 2013 to 2014 which was contrary to Cortell and Kennedy (2006), where cluster exposure to more intercepted light increased flavonol content. However, it should be noted that the Cortell and Kennedy (2006) experiment was conducted in cool climate region which may contribute to differing results. In contrast to Cortell and Kennedy (2006) inhibitory effects of high temperature on flavonols were reported by Goto- Yamamoto et al. (2009) and Spayd et al. (2002). Thus, decreases in flavonol content can be attributed to increased temperatures from one season to the next. Effects of winter drought on following season flavonoid synthesis and composition are lacking. Anthocyanin-Glucosides of Skin Tissue Anthocyanin synthesis in grapes is controlled genetically, but it can be manipulated by environmental conditions and viticulture practices (Guan et al. 2014). Skin anthocyanins require two additional enzymes encoded by VvLDOX and VvUFGT beyond that of flavan-3-ol synthesis. The VvUFGT enzyme is restricted to mostly red cultivars (Castellarin et al. 2011, Cortell and Kennedy 2006). It has been reported that tight clusters are associated with increased berry temperature. Commercial clones of Zinfandel are notorious for having tight, large,

80 67 rot prone clusters (Wolpert 1996). Thus, commercial Zinfandel clones are more susceptible to the detriments of increased berry temperature. Additionally, the detrimental effects of temperature on berry quality are amplified when associated with shading (Spayd et al. 2002). These authors reported that elevated temperature increased the degradation as well as inhibited synthesis of anthocyanins. Delphinidin-3-glucoside and petunidin-3-glucoside experienced the greatest increase from 2013 to 2014, while cyanidin-3-glucoside, peonidin-3-gluocide and malvidin-3-glusoside experienced less of an increase. These results can be attributed the year to year decrease in K c and cluster shading. These results paralleled the report by Cortell and Kennedy (2006), except peonidin-3-glucoside which decreased in the presence of light. However, effects of shading on anthocyanin content have been dependent upon cultivar and phenological stage at which light is withheld (Cortell and Kennedy 2006, Guan et al. 2014). The enzymes encoded by VvUFGT, VvMybA1, VvMybA2 and VvMyc1 were lower in shaded treatments and strongly correlated to decreased anthocyanin content. The VvF3 H/F3 5 H enzyme ratio correlated to cyanidin- and delphinidin-based anthocyanin content. Sunlight exclusion decreased expression of VvF3 5 H, but not VvF3 H. Thus it can be concluded, that delphinidin-based anthocyanins (petunidin- and malvidin-3-glucoside) were more affected by shade than cyanidinbased anthocyanins (peonidin-3-glucoside) (Cortell and Kennedy 2006, Guan et al. 2014). In 2014, irrigation treatments affected total anthocyanin and malvidin-3- glucoside. While not significantly different, other tri-hydroxylated anthocyanins petunidin-3-glucoside and delphinidin-3-glucoside experienced slight increases, while the di-hydroxylated anthocyanins experienced slight decreases in the presence of water stress. These results are in concert with reports by Castellarin et

81 68 al. (2007). It can be concluded that up-regulation of biosynthetic genes that encode for anthocyanins, specifically tri-hydroxylated anthocyanins aka delphinidin-based anthocyanin, is the cause of increased color due to irrigation stress as a secondary effect of increased light exposure and not solely a result of reduced berry growth concentration effect (Castellarin et al. 2007). Anthocyanin-Glucoside Acetates of Skin Tissue In general anthocyanin-acetates decreased from 2013 to The lack of canopy development, general increased PAR transmittance and hindered K c created a less shaded canopy in The SP and MP treatments had increased malvidin-3-glucoside acetates in 2013 and 2014, respectively. Both the SP in 2013 and the MP in 2014 treatments had decreased PAR transmittance, increased yields and increased leaf area to fruit ratios relative to other pruning system by year combinations. These results are similar to what Spayd et al. (2002) found where malvidin-3-glucoside acetate levels increased in the presence of shade and heat. In addition to malvidin-3-glucoside acetate, the MP treatment yielded the greatest amount of cyanidin-3-glucoside acetate, petunidin-3-glucoside acetate and peonidin-3-glucoside acetate. Anthocyanin-Glucoside Coumarates of Skin Tissue Irrigation method did not affect anthocyanin-coumarates. However, there was strong effect of year with malvidin-glucoside coumarate decreasing from 2013 to Petunidin-3-glucoside coumarate was not affected by year. These results parallel what Spayd et al. (2002) found in regards to the effects of shading on berry anthocyanin content where shaded clusters coupled with increased heat experienced an increase in malvidin-3-glucoside coumarate and no effect on petunidin-3-glucoside coumarate. In 2013, the SP treatment had the greatest

82 69 amount of coumarates. However in 2014, this result was not evident where the MP treatment yielded the greatest amount of coumarates. This is attributed to the SP and MP treatments having the greatest yield, leaf area to fruit ratio and PAR transmittance in 2013 and 2014, respectively. The increased leaf area to fruit ratio and decrease PAR transmittance increased cluster shading and thus increased malvidin-3-glucoside coumarate synthesis. These results would indicate an inherent decrease in anthocyanin constituents as canopy development and yield decrease, due in part to increased temperatures.

83 CONCLUSION The treatment results reported here were successful in developing pruning and irrigation guidelines for Zinfandel grapevines in a hot climate under prolonged drought conditions. Recommendations were altered based on highly significant differences between years. The strong influence of experimental year gives weight to the second year of the study being more representative of the interactive effects of pruning systems and irrigation regimes in a resource limited environment, as anthropogenic activity continues to effect climate. After severe winter precipitation exclusion, the MP treatment increased accumulation of anthocyanins, flavonols, flavan-3-ols, and total tannins compared to traditional hand pruned methods. In addition to increasing berry quality, the MP treatment increased yield and exhibited the lowest variability from year to year. In agreement with previous studies, the RDI treatment increased skin to pulp ratio and water footprint efficiency in both years of the study. However, the RDI treatment invoked a decrease in yield in the second year of study and was exposed as a punitive amount of water stress after an arid winter, due to a phenomenon known as RDI carry-over effect. The increase in skin to pulp ratio and water footprint efficiency was not enough to outweigh the loss of yield at harvest. The combination of MP and SDI treatments are recommended for growers within the hot climate region of the southern SJV as a sustainable alternative that can increase fruit quality, optimize yield and increase water footprint efficiency compared to industry standards.

84 REFERENCES

85 REFERENCES Allen, R.A., L.S. Pereira, D. Raes, and M. Smith Crop evapotranspiration: Guidelines for computing crop water requirements. FAO Irrigation and Drainage Paper. 56. FAO, Rome. Amerine, M.A. and A.T. Winkler Composition and quality of musts and wines of California grapes. Hilgardia, University of California. 15: Basile, B., J. Marsal, M. Mata, X. Vallverdú, J. Bellvert, and J. Girona Phenological sensitivity of Cabernet Sauvignon to water stress: Vine physiology and berry composition. Am. J. Enol. Vitic. 62: Bates, T Pruning level affects growth and yield of New York Concord on two training systems. Am. J. Enol. Vitic. 59: Berdeja, M., G. Hilbert, Z. Dai, M. Lafontaine, M. Stoll, H. Schultz and S. Delrot Effect of water stress and rootstock genotype on Pinot Noir berry composition. Aust. J. of Grape and Wine Res. 20:1-13. Bergqvist, J., N. Dokoozlian, and N. Ebisuda Sunlight exposure and temperature effects on berry growth and composition of Cabernet Sauvignon and Grenache in the central San Joaquin Valley of California. Am. J. Enol. Vitic. 52:1 7. Bindon, K., P. Dry, and B. Loveys Influence of partial rootzone drying on the composition and accumulation of anthocyanins in grape berries (Vitis vinifera cv. Cabernet Sauvignon). Aust. J. Grape Wine Res. 14: Castellarin, S.D., G.A. Gambetta, H Wada, K.A. Shackel, and M.A. Matthews Fruit ripening in Vitis vinifera: Spatiotemporal relationships among turgor, sugar accumulation, and anthocyanin biosynthesis. J. Exp. Bot. 62: Castellarin, S.D., M.A. Matthews, G.D. Gaspero, and G.A. Gambetta Water deficits accelerate ripening and induce changes in gene expression regulating flavonoid biosynthesis in grape berries. Planta. 227: Chaves, M.M., O. Zarrouk, R. Francisco, J.M. Costa, T. Santos, A.P. Regalado, M.L. Rodrigues, and C.M. Lopes Grapevine under deficit irrigation: Hints from physiological and molecular data. Annals of Botany. 105:

86 Chira, K., G. Schmauch, C. Saucier, S. Fabre, and P.L. Teissedre Grape variety effect on proanthocyanidin composition and sensory perception of skin and seed tannin extracts from Bordeaux wine grapes (Cabernet Sauvignon and Merlot) for two consecutive vintages (2006 and 2007). J. Agric. Food Chem. 57: Cifre, J., J. Bota, J.M. Escalona, H. Medrano, and J. Flexas Physiological tools for irrigation scheduling in grapevine (Vitis vinifera L.). An open gate to improve water use efficiency? Agric. Ecosyst. Environ. 106: Clingeleffer, P.R Influence of canopy Management systems on vine productivity and fruit composition. Recent advances in grapevine canopy management. pp UC Davis Review. Clingeleffer, P.R Influence of canopy management systems on vine productivity and fruit composition: In a low-input context. Aust. and New Zea. Grape. Wine. 50: Cook, M., C. Nelson, G. Gambetta, J. Kennedy and S.K. Kurtural Concentration, proportion and hydroxylation of Merlot grapevine anthocyanins are ameliorated by interaction of light microclimate and applied water amounts in the San Joaquin Valley of California. Thesis, Fresno State University. Fresno, California. Coombe, B Development of fleshy fruits. Ann. Rev. of Plant Phys. and Plant Mol. Bio. 27: Cortell, J.M., M. Halbleib, A.V. Gallagher, T.L. Righetti, and J.A. Kennedy Influence of vine vigor on grape (Vitis vinifera L. Cv. Pinot Noir) and wine proanthocyanidins. J. Ag. Food Chem. 53: Cortell, J.M., and J.A. Kennedy Effect of shading on accumulation of flavonoid compounds in (Vitis vinifera L.) Pinot Noir fruit and extraction in a model system. J. Ag. Food Chem. 54: De Toda, F.M., and J.C. Sancha Long-term effects of simulated mechanical pruning on Grenache vines under drought conditions. Am. J. Enol. Vitic. 50: Dokoozlian, N.K. and W.M. Kliewer The light environment within grapevine canopies. Description and seasonal changes during fruit development. Am. J. Enol. Vitic. 46:

87 Dokoozlian N.K Intergrated Canopy Management: A twenty year evolution in California. Recent advances in grapevine canopy management. pp UC Davis Review. Downey, M.O., J.S. Harvey, and S.P. Robinson The effect of bunch shading on berry development and flavonoid accumulation in Shiraz grapes. Aust. J. of Grape and Wine Res. 10: Esteban, M.A., M.J. Villanueva, and J.R. Lissarrague Effect of irrigation on changes in berry composition of Tempranillo during maturation. Sugars, organic acids, and mineral elements. Am. J. Enol. Vitic. 50: Ferreyra, R.E., G.V. Selles, J.A. Peralta, and J.B. Valenzuela Effect of water stress applied at different development periods of Cabernet Sauvignon grapevine on production and wine quality. Acta Hortic. 646: Fidelibus, M.W., L.P. Christensen, D.G. Katayama, and P.T. Verdenal Performance of Zinfandel and Primitivo grapevine selections in the central San Joaquin Valley, California. Am. J. Enol. Vitic. 56: Friend, A.P., and M.C.T. Trought Delayed winter spur-pruning in New Zealand can alter yield components of Merlot grapevines. Aust. J. Grape Wine Res. 13: Gatti, M., S. Civardi, F. Bernizzoni, and S. Poni Long-term effects of mechanical winter pruning on growth, yield, and grape composition of Barbera grapevines. Am. J. Enol. Vitic. 62: Gauthier, N.W., S. Fox, K. Wimberley How dry seasons affect woody plants. UK Ag. Ext. 89:1-7. Geller, J.P., and S.K. Kurtural Mechanical canopy and crop-load management of Pinot gris in a warm climate. Am. J. Enol. Vitic 64: Genebra, T., R. Santos, R., Francisco, M. Pinto-Marijuan, R. Brossa, A.T. Serra and O. Zarrouk Proanthocyanidin accumulation and biosynthesis are modulated by the irrigation regime in Tempranillo seeds. Int. J. of Mol. Sci. 15: Gladstone, E.A. and N.K. Dokoozlian Influence of leaf area density and trellis/training systems on the microclimate within grapevine canopies. Vitis. 42:

88 Gladwin, F.E A test of methods in pruning the Concord grape in the Chautauqua grape belt. New York State Agric. Exp. Sta. Bull. 464: Guan, L., J.H. Li, P.G. Fan, S.H. Li, J.B. Fang, Z.W. Dai, S. Delrot, L.J. Wang, and B.H. Wu Regulation of anthocyanin biosynthesis in tissues of a teinturier grape cultivar under sunlight exclusion. Am. J. Enol. Vitic. 65: Goodhue R.E., D.M. Heien, H. Lee, D.A. Sumner Contracts and quality in the California winegrape industry. Review of industrial organization 23: Goto-Yamamoto, N., K. Hashizume, and M. Esaka Expression of multicopy flavonoid pathway genes coincides with anthocyanin, flavonol and flavan-3-ol accumulation of grapevine. Vitis. 47: Goto-Yamamoto N.K. Mori, M. Numata, K. Koyama, M. Kitayama Effects of temperature and water regimes on flavonoid contents and composition in the skin of red-wine grapes. J. Int. Sci. Vigne Vin. 50: Hardie, W.J., and J.A. Considine Response of grapes to water-deficit stress in particular stages of development. Am. J. Enol. Vitic. 27: Heien, D. and P. Martin California's wine industry enters new era. Cal. Ag. 57: Howell, G.S Sustainable grape productivity and the growth-yield relationship: A review. Am. J. Enol. Vitic. 52: Howell, G.S., B.G. Stergios, and S.S. Stackhouse Interrelation of productivity and cold hardiness of Concord grapevines. Am. J. Enol. Vitic. 29: Hsiao, T.C Plant responses to water stress. Ann. Rev. Plant Physiol. 24: Iland, P., P. Dry, T. Proffitt, L. Rolley, E. Wilkes The Grapevine: From the Science to the Practice of Growing Vines for Wine. 1st ed. Patrick Iland Wine Promotions, Adelaide, AU. Intrieri, C., S. Poni, G. Lia, and M. Gomez del Campo Vine performance and leaf physiology of conventionally and minimally pruned Sangiovese grapevines. Vitis. 40:

89 Jones, G.V., and R.E. Davis Climate influences on grapevine phenology, grape composition, and wine production and quality for Bordeaux, France. Am. J. Enol. Vitic. 51: Kasimatis, A.N., E.P. Vilas, Jr., F.H. Swanson, and P.P. Baranek A study of the variability of Thompson Seedless berries for soluble solids and weight. Am. J. Enol. Vitic. 26: Keller, M Managing grapevines to optimise fruit development in a challenging environment: A climate change primer for viticulturists. Aust. J. Grape Wine Res. 16: Keller, M., R.P. Smithyman, and L.J. Mills Interactive effects of deficit irrigation and crop load on Cabernet Sauvignon in an arid climate. Am. J. Enol. Vitic. 59: Kennedy, J.A., M.A. Matthews, and A.L. Waterhouse Changes in grape seed polyphenols during fruit ripening. Phytochemistry 55: Kennedy, J.A., M.A. Matthews, and A.L. Waterhouse Effect of maturity and vine water status on grape skin and wine flavonoids. Am. J. Enol. Vitic. 53: Kliewer, W.M., and N.K. Dokoozlian Leaf area/crop weight ratios of grapevines: Influence on fruit composition and wine quality. Am. J. Enol. Vitic. 56: Kurtural, S.K., G.G. Dervishian, and R.L. Wample Mechanical canopy management reduces labor costs and maintains fruit composition in Cabernet Sauvignon grape production. Hort. Tech. 22: Kurtural, S.K., L.F. Wessner, G. Dervishian Vegetative compensation response of a procumbent grapevine (Vitis vinifera cv. Syrah) cultivar under mechanical canopy management. Hortsci. 48: Lakso, A.N., R.M. Dunst. A. Fendinger Responses to drought of balancepruned and minimally-pruned Concord grapevines. Acta Hort. 493: Loomis, N. H. Note on grape foliation as affected by time of pruning Proc. Am. Soc. Hortic. Soc. 37:

90 Lovisolo, C., W. Hartung, and A. Schubert Whole-plant hydraulic conductance and root-to-shoot flow of abscisic acid are independently affected by water stress in grapevines. Funct. Plant Biol. 29: McCarthy, M.G The effect of transient water deficit on berry development of cv. Shiraz (Vitis vinifera L.). Aust. J. Grape Wine Res. 3:2 8. Mendez-Costabel, M.P., K.L. Wilkinson, S.P. Bastian, C. Jordans, M. McCarthy, C.M. Ford, and N.K. Dokoozlian Effect of winter rainfall on yield components and fruit green aromas of Vitis vinifera L. cv. Merlot in California. Aust. J. of Grape and Wine Res. 20: Monagas, M., V. Núñez, B. Bartolomé, and C. Gómez-Cordovés Anthocyanin derived pigments in Graciano, Tempranillo and Cabernet Sauvignon wines produced in Spain. Am. J. Enol. Vitic. 54: Morison, J.L., N.R. Baker, P.M. Mullineaux, and W. J. Davies Improving water use in crop production. Philo. Trans. of the Royal Soc. B: Biol. Sci. 363: Nuzzo, V. and M.A. Matthews Response of fruit growth and ripening to crop level in dry-farmed Cabernet Sauvignon on four rootstocks. Am. J. Enol. Vitic. 57: O Daniel, S.B., D.D. Archbold, and S.K. Kurtural Effects of balanced pruning severity on Traminette (Vitis spp.) in a warm climate. Am. J. Enol. Vitic. 63: Olmstead, M Cover crops and a floor management strategy for Pacific Northwest vineyards. extension bulletin College of Agriculture, Human, and Natural Resource Sciences, Washington State University, Pullman, Washington. Pastor del Rio, J.L., and J.A. Kennedy Development of proanthocyanidins in Vitis vinifera L. cv. Pinot noir grapes and extraction into wine. Am. J. Enol. Vitic. 57: Petrie, P.R., G.M. Dunn, S.R. Martin, M.P. Krstic, and P.R. Clingeleffer Crop stabilisation. In Grapegrowing at the Edge. Australian Society of Viticulture and Oenology Seminar. S.M. Bell et al. (Eds.), pp ASVO, Adelaide.

91 Petrie, P.R., N.M. Cooley, and P.R. Clingeleffer The effect of post veraison water deficit on yield components and maturation of irrigated Shiraz (Vitis vinifera L.) in the current and following season. Aust. J. Grape Wine Res. 10: Poni, S., F. Bernizzoni, P. Presutto, and B. Rebucci Performance of Croatina under short-cane mechanical hedging: A successful case of adaptation. Am. J. Enol. Vitic. 55: Price, S.F., P.J. Breen, M. Valladao, and B.T. Watson Cluster sun exposure and quercetin in Pinot noir grapes and wine. Am. J. Enol. Vitic. 46: Reynolds, A.G Response of Okanagan Riesling vines to training system and simulated mechanical pruning. Am. J. Enol. Vitic. 39: Reynolds, A.G. and J.E. Vanden Heuvel Influence of grapevine training systems on vine growth and fruit composition: A review. Am. J. Enol. Vitic. 60: Roby, G., J.F. Harbertson, D.A. Adams, and M.A. Matthews Berry size and vine water deficits as factors in winegrape composition: Anthocyanins and tannins. Aust. J. Grape Wine Res. 10: Shellie, K.C Vine and berry response of Merlot (Vitis vinifera L.) to differential water stress. Am. J. Enol. Vitic. 57: Shellie, K.C Water deficit effect on ratio of seed to berry fresh weight and berry weight uniformity in winegrape cv. Merlot. Am. J. Enol. Vitic. 61: Shellie, K.C. and P. Bowen Isohydrodynamic behavior in deficit-irrigated Cabernet Sauvignon and Malbec and its relationship between yield and berry composition. Irrig. Sci. 32: Smart, R.E Principles of grapevine canopy microclimate manipulation with implications for yield and quality. A review. Am. J. Enol. Vitic. 36: Smart, R.E., and M. Robinson Sunlight into wine: A handbook for winegrape canopy management. Winetitles, Underdale, Australia. Smart, R.E., S.M. Smith, and R.V. Winchester Light quality and quantity effects on fruit ripening for Cabernet Sauvignon. Am. J. Enol. Vitic. 39:

92 Spayd, S.E., J.M. Tarara, D.L. Mee, and J.C. Ferguson Separation of sunlight and temperature effects on the composition of Vitis vinifera cv. Merlot berries. Am. J. Enol. Vitic. 53: Taiz, L., and E. Zeiger Plant Physiology. 5th ed. Sinauer Associates, Sunderland, MA. Tarara, J.M., J. Lee, S.E. Spayd, and C.F. Scagel Berry temperature and solar radiation alter acylation, proportion, and concentration of anthocyanin in Merlot grapes. Am. J. Enol. Vitic. 59: Teixeira, A., J. Eiras-Dias, S.D. Castellarin, H. Gerós Berry phenolics of grapevine under challenging environments. Int. J. of Mol. Sci. 14: Terry, D.B., and S.K. Kurtural Achieving vine balance of Syrah with mechanical canopy management and regulated deficit irrigation. Am. J. Enol. Vitic. 62: Tomasi, D., G.V. Jones, M. Giust, L. Lovat, and F. Gaiotti Grapevine phenology and climate change: Relationships and trends in the Veneto region of Italy for Am. J. Enol. and Vitic. 62: Wessner, L.F., and S.K. Kurtural Pruning systems and canopy management practice interact on the yield and fruit composition of Syrah. Am. J. Enol. Vitic. 64: Wien, H.C., E.J. Littleton, A. Ayanaba Drought stress of cowpea and soybean under tropical conditions. Stress Phys. in Crop Plants. pp A Wiley-Interscience Publication, New York. Williams, L.E Potential Vineyard evapotranspiration (ET) due to global warming: Comparison of vineyard ET at three locations in California differing in mean seasonal temperatures. Acta Hort. 50: Williams, L.E Effect of applied water amounts at various fractions of evapotranspiration on productivity and water footprint of Chardonnay grapevines. Am. J. Enol. Vitic. 65: Williams, L.E., C.J. Phene, D.W. Grimes, and T.J. Trout Water use of mature Thompson Seedless grapevines in California. Irr. Sci. 22:11 18.

93 Williams, L.E., and J.E. Ayars Grapevine water use and the crop coefficient are linear functions of the shaded area measured beneath the canopy. Ag. Forest Met. 132: Winkler, A.J., J.A. Cook, W.M. Kliewer, and L.A. Lider General Viticulture. Soil Science pp 462. University of California Press. London, England. Wolpert, J.A Performance of Zinfandel and Primitivo clones in a warm climate. Am. J. Enol. Vitic. 47: Zabadal, T.J., G.R. Vanee, T.W. Dittmer, and R.L. Ledebuhr Evaluation of strategies for pruning and crop control of Concord grapevines in southwest Michigan. Am. J. Enol. Vitic. 53:

94 APPENDIX A: FIGURES

95 Precipitation (mm) Temperature (C) Year vs Precipitation Seasonal Year Year vs Temperature Figure 1. Seasonal summation (March-Feb.) of temperature and precipitation from California Irrigation Management Information System (CIMIS weather station #125).

96 R 2 = Crop coefficient (K c ) R 2 = Degree days (>10 C from 15 March) Figure 2. Development of crop coefficient (K c ) in 2013 and 2014, K c calculated from weekly shade estimated of canopy shade development.

97 Winter precip. Bud-break to fruit set Fruit set to veraison Veraison to harvest 300 ET c or precipitation in mm/week Liters of irrigation applied/vine/week A Julian days (2013) ET c or precipitation in mm/week Winter precip. Bud-break to fruit set Fruit set to veraison Julian days 2014 Veraison to harvest B Liters of irrigatioin applied/vine/week Precipiation mm/week SDI L/vine RDI L/vine SDI ET c mm/week RDI ET c mm/week Figure 3. Cumulative winter precipitation (mm), weekly precipitation during growing season (mm/meek), irrigation applied (L/vine) and weekly ET c (A) 2013 (B) Sustained deficit irrigation (SDI) = initiated at (Ѱ) of - 1.2MPa, irrigated to 80% of crop evapotranspiration (ET c ) from budbreak until harvest. Regulated deficit irrigation (RDI) = 80% of ET c from budbreak to fruit set, where after 50% ET c was replaced to maintain (Ѱ) at -1.4MPa until veraison, but not thereafter.

98 85 A B Figure 4. (A) Application of (MP): mechanically box-pruned to 100 mm spur height, (B) architecture of pruning system at canopy closure.

99 86 A B Figure 5. (A) SP: Spur-pruned to 22 buds, (B) architecture of pruning system at canopy closure.

100 87 A B Figure 6. (A) CP: cane-pruned to six, eight node long canes with canopy separation (B) architecture of pruning system at canopy closure.