Effects of Leaf Removal and UV-B on Flavonoids, Amino Acids and Methoxypyrazines Professor Brian Jordan Centre for Viticulture & Oenology, Lincoln University
What are the major factors to be considered that will influence the levels of these compounds? Is the effect on the fruit biochemical composition simply due to the removal of the leaf as the source? And or when you open up the leaf canopy: Is the increased UV-B directly bringing about a change in biochemical composition? What are the other factors that need to be considered-development, temperature, humidity, visible light, change in the grape microbiology- and more!
Experimental Design Vineyard treatments: Control: naturally grow LR: Leaf removal around the fruiting zone UV+: LR + Acrylic UV-: LR + Polycarb UVB-: LR + PETG 1 % Transmission 8 6 4 2 UV-B UV-A 25 275 3 325 35 375 4 425 45 475 5 Wavelength (nm) Acrylic PETG Polycarb
Effects of Leaf Removal and UV-B on Amino Acids Amino acids are a major source of nitrogen and precursors for other important compounds
Aromatic compounds Phenolics Flavonols Anthocyanins Tannins Phe Proline (non-yan) YAN Protein biosynthesis Methoxypyrazines Val Leu Ser Cys Glu Gly Thiols Thr Ser Glu Esters Thr Ser Phe Leu Lys Pro Thr Ser Glu Higher alcohols Acids
Source-sink relationship between leaves and berries. N assimilation NO3- Glutamine Glutamine export Glutamine Glutamate Other amino acids
Leaf removal treatments had no significant effect on berry soluble solids and berry weight through development. 213 - Total Soluble Solids ( Brix) 214 - Total Soluble Solids ( Brix) 2 2 15 15 1 1 5 CONTROL PRE POST 5 CONTROL PRE POST 2.5 213 - Berry Weight (g) 2.5 214 - Berry Weight (g) 2. 2. 1.5 1.5 1..5. CONTROL PRE POST 1..5. CONTROL PRE POST
Leaf removal treatments have a significant effect on total amino acid accumulation through development. 3 213 - Total Amino Acids (μm) 25 2 15 1 5 CONTROL PRE POST
Leaf removal treatments affect a qualitative change in individual amino acids in the grape. 12 1 8 CONTROL PRE POST 213 - Arginine (μm) 45 4 35 3 213 - Arginine (% of Total Amino Acids) 6 25 2 4 2 15 1 5 CONTROL PRE POST 4 35 3 25 2 15 1 5 CONTROL PRE POST 213 - Proline (μm) 18 16 14 12 1 8 6 4 2 213 - Proline (% of Total Amino Acids) CONTROL PRE POST
Leaf removal treatments have a significant effect on amino acids correlated to flavour and aroma in wine. 12 1 8 CONTROL PRE POST 213 - Phenylalanine (μm) 4 35 3 25 213 - Methionine (μm) 6 2 4 2 15 1 5 3 213 - Threonine (μm) 12 213 - Serine (μm) 25 1 2 8 15 6 1 4 5 2
Effects of canopy manipulation on juice amino acids levels Leaf removal at any stage will reduce total amino acid levels The non YAN amino acid proline will increase to highest level at harvest irrespective of canopy treatment The decreased levels of amino acids is not due to UV-B, but loss of import from leaves Does UV-B increase PR proteins, enhancing plant defence, but reducing quality-role of development? It is important to understand amino acid metabolism in leaves and berries- using molecular technology
Effects of Leaf Removal and UV-B on Flavonoids Flavonoids are major components of grape and contribute to a range of attributes from antioxidants to colour
Direct effect of UV-B on grapes Effects on microbiome and biochemistry
LR & UV have no effects on berry development Brix 25 2 15 1 5 Control LR UV + UVB - Season 211 Total soluble solids accumulation during berry development 3 2.5-4 -3-2 -1 1 2 3 4 5 6 Weeks post-veraison Control LR UV + UVB - Season 211 Fresh weight (g) 2 1.5 1.5 Tissue weight at harvest Whole berry Skin Seed Pulp
UV-B increases total UV-absorbing compounds Total Flavonoids (Ab 352nm ) Total Flavonoids (Ab 352nm ) 2 1.5 1.5 8 7 6 5 4 3 2 1 Control LR UV + UVB - -4-3 -1 1 2 4 6 weeks after veraison Control LR UV + UVB - Pulp Seed Skin Juice Season 211 Total flavonoid accumulation in whole berry during berry development Season 211 Total flavonoid accumulation in different tissues at harvest
UV-B stimulates flavonoid biosynthesis 5 Flavonol (µg/g fresh skin) 4 3 2 1 11.7 12.2 13.8 14.7 14.9 15.6 16 16.6 16.8 17.2 Retention time These changes take place in the grape skin; LC-MS identify quercetin-3-o-glucoside (RT 14.9), quercetin-3-o-glucuronide (RT 15.6), kaempferol-3-o-glucoside (RT 16.6).
Implications of UV-B/Light exposure for viticulture management UV-B exposure can have a positive effect to increase the levels of flavonoids Changes in berry skin characteristics, such as permeability, will be induced by UV-B exposure and could influence skin contact application Exposure of the grapes could reduce disease pressure by a direct effect of UV-B on pathogens or enhancing the plants own defence The impact of UV-B on nitrogenous compounds, such as PR proteins (major cause of haze in wine) remains uncertain The canopy management/uv-b balance will have an important effect on grape juice/wine properties (ageing, levels of proteins, antioxidant status, etc)
Effects of Leaf Removal and UV-B on Methoxypyrazines Methoxypyrazines are a major component of Sauvignon blanc wine aroma
Indirect effect canopy management Development, humidity, temperature and visible light
Methoxypyrazine levels between seasons and after leaf removal
Relative expression of O-methyltransferase (VvOMT) genes
Accumulated growing degree days (DD) difference from the long-term average (LTA) DD - difference from long-term average (LTA) 1 Veraison 5 LTA -5 Veraison -1-15 -2 Veraison -25 Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr May Jun 21-211 29-21 211-212 Month
Factors influencing methoxypyrazine juice levels Maximum levels are achieved pre-veraison and will determine levels at harvest The season s climate has a significant effect with cool temperatures giving higher levels Maintaining leaves, particularly pre-veraison and in a cool season, will increase levels; the biology is unclear The region (climate) will influence the levels
Conclusions Exposure to UV-B directly determines the levels of flavonoids (also other antioxidants and microflora) Amino acid levels are determined by leaf removal, but the final composition in the fruit is determined by metabolism within the berry Methoxypyrazine levels can be influenced by leaf removal, although seasonal conditions must be considered
Acknowledgements Scott Gregan Linlin Liu Stephen Stilwell, Jenny Zhao, Jason Breitmeyer and Dr Richard Sedcole Dr Chris Winefield Professor Brian Jordan (Programme Leader) Support From: Foundation for Research, Science & Technology (Sauvignon blanc programme) New Zealand Winegrowers Plant & Food Research Lincoln University Acknowledgement to the population of Christchurch and Lincoln University staff during the recent Earthquakes
Thank You