The Influence of Rootstock on Leaf Water Potential, Yield, and Berry Composition of Ruby Seedless Grapevines

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1 The Influence f Rtstck n Leaf Water Ptential, Yield, and Berry Cmpsitin f Ruby Seedless Grapevines ABDELAZZIZ EZZAHOUANI ~ and LARRY E. WILLIAMS 2. An experiment was cnducted t determine the effect f eight different rtstcks [99 Richter 9R), 110 Richter (110R), Rupestris du Lt (du Lt), 140 Ruggeri (140Ru), SO4, 41B, , and 1103 Paulsen (1103P)] n the prductivity f nn-irrigated Ruby Seedless grapevines grwn in Mrcc. Measurements taken ver a three-year perid included fruit grwth and maturity indices, yield, and pruning weights. Leaf water ptential (~,) was measured at varius times during the secnd year f the study. Results indicated that midday ~F, declined thrughut the seasn fr all rtstcks, averaging -0.9 MPa at fruitset and -1.3 MPa at fruit maturity. The diurnal time curse f ~F, averaged acrss all rtstcks was apprximately -0.4 MPa befre sunrise, -1.2 MPa arund slar nn, fllwed by a recvery t -0.6 MPa shrtly after sunset. An analysis f seasnal, midday ~F, indicated tw extreme grups f rtstcks: du Lt and 11 OR had mre negative leaf water ptentials than 41B and 1103P. The difference between the tw rtstcks with the greatest and the least negative average ~L, du Lt and 1103P, respectively, apprached 0.2 MPa. Berry weight was greatest fr vines n SO4, 99R, and 41 B, and lwest fr and du Lt. At maturity, the lwest fruit sluble slids cncentratin was btained n 99R and 41B while the lwest fruit clratin was btained n 110R, du Lt, 140Ru, and 41B rtstcks. These results demnstrated that rtstck had a significant effect n Ruby Seedless fruit characteristics under nn-irrigated cnditins. KEY WORDS: berry weight, sluble slids cncentratin, fruit clratin, table grapes, drught tlerance Numerus factrs shuld be cnsidered when selecting a rtstck-scin cmbinatin fr a specific site (13). The rtstck St. Gerge has been reprted t be vigrus, resulting in lw bud fruitfulness per unit f grwth (3) and fewer number f berries per cluster (23). In ne study, St. Gerge and SO4 were classified as vigrus stcks, while ll0r was classified the least vigrus (11). Hwever, in anther study, l l0r, SO4, and were classified as higher yielding rtstcks with high cluster number and weight, and berry weight (10). Fruit quality and maturity als were reprted t be affected by the rtstck. Fruit frm vines n St. Gerge had high ptassium and ph, and lw acidity (23). The rtstcks SO4 and ll0r were reprted t delay maturity based upn sluble slids cncentratin (7,10) with fruit n ll0r having lw ph (7). Rtstcks als have been classified with regard t their drught tlerance (5,8,16,17). Galet (8) classified the perfrmance f hybrids f Vitis berlandieri X V. rupestris as the mst satisfactry in very dry sils. The species V. riparia and V. rupestris are thught t be sensitive t sil-water deficits (16). It shuld be pinted ut that the drught resistance classificatin f rt- ~Dept. f Hrticulture, I.A.V. Hassan II, B.P. 6202, Rabat-lnstitutes, Rabat, Mrcc; and 2Dept. f Viticulture and Enlgy, University f Califrnia - Davis and Kearney Ag Center, 9240 S. Riverbend Ave., Parlier, CA *Crrespnding authr. Acknwledgements: The authrs appreciate the cperatin f Prductin Unit Number 1101, S.O.D.E.A. and the helpful cmments f Drs. Wallali and Dkzlian. Partial supprt f this study was prvided by the University f Minnesta, USAID - Mrcc Prject. Manuscript submitted fr publicatin 15 July Cpyright 1995 by the American Sciety fr Enlgy and Viticulture. All rights reserved. 559 Am. J. Enl. Vitic., Vl. 46, N. 4, 1995 stcks may vary frm cuntry t cuntry (5,17). Water is a limiting factr t grapevine prductivity in Mrcc. Mst rainfall ccurs during the drmant prtin f the grwing seasn, and the water hlding capacity f the sils (such as that used in this study) is lw. Average rainfall is apprximately 175 t 225 mm per year. The bjectives f this study were: (1) determine the influence f eight rtstcks n vine water status and vegetative grwth; and (2) determine the effect f rtstcks n yield and fruit quality f Ruby Seedless table grapes. Materials and Methds Vitis vinifera L. (cultivar Ruby Seedless)vines used in this study were grafted nt eight different rtstcks and planted in The vineyard was lcated near Meknes (apprximately 33 N, 6 W), ne f the majr grape prductin regins in Mrcc. The vineyard was perated by the Sciete de Develpement Agricle (S.O.D.E.A), Prductin Unit number 1101, lcated in Agurai. The sil was cmpsed f 74.0% sand, 14.3% silt, and 11.7% clay. The vineyard was flat and nt irrigated. Vine and rw spacings were 1.5 and 3.0 m, respectively. The vines were head trained and pruned t tw canes f six t 10 buds each. The twwire trellis used was cmpsed f a cane wire and fliage wire lcated 0.7 and 1.0 m abve the sil, respectively. The eight rtstcks used in this study were: 99 Richter 9R), 110 Richter (ll0r), Rupestris du Lt [syn, St. Gerge] (du Lt), 140 Ruggeri (140Ru), SO4 (syn. Selectin Oppenheim 4), 41B Millardet et de Grasset (41B), Mgt (101-14), and 1103 Paulsen (l103p). Data were nt cllected in 1990.

2 560 m EZZAHOUANI and WILLIAMS Midday leaf water ptential (~) was measured biweekly thrughut the 1991 seasn and diurnally n 2 August The ~ was measured with a pressure chamber (PMS Instrument C., Crvallis, OR) n six t eight f the mst recent, fully expanded leaves n sunexpsed shts per treatment. T avid evaprative lss, leaves were enclsed in a plastic bag just prir t cutting the petile and left cvered thrughut pressurizatin. At harvest in 1989, 1991, and 1992, crp yield and cluster number per vine were recrded, and samples f 100 berries per replicate were randmly cllected, then analyzed fr berry weight, sluble slids, titratable acidity (determined by titratin with N NaOH using phenlphthalein as indicatr), and ph. Fruit clratin was determined accrding t Kliewer and Weaver (12), n 7-mm diameter discs f berry skin taken frm the apical regin f 20 berries frm each sample. The absrbance f the skin extracts were read at 520 nm with a spectrphtmeter (Perkin-Elmer, Lambda 2). The fruit ph and clr and pruning weights were recrded fr each plt in 1989 and The experimental design was a randmized cmplete blck with each blck replicated three times. Each individual plt (rtstck) cnsisted f three vines. The data were analyzed using analysis f variance and linear regressin. Mean separatins were determined using Duncan's multiple-range test. Means were averaged acrss years. Results Midday ~L declined thrughut the seasn (Fig 1). On the first measurement date, ~L averaged MPa and ranged frm -0.9 fr 99R t -0.8 MPa fr ll0r. On the last measurement date, ~L averaged -1.3 MPa and ranged frm -1.4 fr 140Ru and ll0r t -1.1 MPa fr vines n l103p. The relative psitins f an individual A i, ii, ~" _ -1.1 _ /13 5/23 II All rtstcks ~ "k 1103P! du Lt I [ I I I I I I I 6/3 6/13 6/24 7/4 7/14 7/24 8/3 8/13 Calendar date Fig. 1. Midday leaf water ptential f Ruby Seedless grapevines grafted nt 1103P, du Lt, and the mean f all eight rtstcks frm berry set t harvest. Each data pint represents the mean f 6 t 8 individual leaf measurements fr the single rtstcks. The slid squares are the means f all rtstcks + ne SE n each date. Table 1. The average effect ver three years (1989, 1991, and 1992) f rtstck n yield cmpnents (cllected at harvest, crrespnding t 6, 1, and 11 September fr 1989, 1991, and 1992, respectively), and pruning weights f Ruby Seedless grapevines measured in 1989 and Rt- Yield Clusters Berry Pruning stck per vine wt wt (kg/vine) (number) (g) (kg/vine) dult 3.7 bcy 29 ab 2.86 z 1.14 c 140Ru 4.5 abc 27 abc bc bc 27 abc a 110R 5.1 ab 32 ab bc 41B 6.3 a 35 a c 99R 4.3 bc 25 bc b SO4 4.1 bc 27 abc bc 1103P 2.8 c 19 c c YMeans fllwed by a different letter within a clumn are significantly different at the 5% level using Duncan's multiple range test. zmeans were nt significantly different in this clumn. rtstck's ~L were established early in the seasn and remained such thereafter (Fig. 1). The verall seasnal mean ~L indicated three grups crrespnding t their average midday ~L (Fig. 2). The first grup (cnsisting f du Lt and l l0r) had significantly lwer ~Ls than a secnd grup (cnsisting f l103p and 41B). The remaining fur rtstcks had ~Ls intermediate t the extremes. The diurnal ~L pattern f Ruby Seedless grapevines n all the rtstcks is illustrated in Figure 3. Befre sunrise, ~L averaged -0.4 MPa and ranged frm t-0.45 MPa. By 0900 hurs, ~L had decreased t an average f-1.2 MPa acrss all rtstck/scin cmbinatins. The mean ~L f all rtstcks cntinued t decline up t slar nn. The difference between 1103P and du Lt was 0.3 and 0.25 Mpa at 0900 hurs and t~ -0.3,...,.,im -0.6 NiI m -0.9 _I Rtstcks dult 110R Ru SO4 [ c c bc I I i i J i i i iiiiiiiiiiiiii iii!i!iii!i!il!iii!i!i!!iii ~ iiiiii!i~iiiii iiiiiiiiiii!ii i!ii!!iiii!!ii iiiiiililiiiii iiii~iiii~iiii ~ ilijiiiiiiiii iiiii~iiiiiii~ ~iiiiiiiiiilili iiiiii!iiii!ii iiiiiiiiiiiiiili! iiiiiiii!!iliiiil iiiiii!iiiiii!ii iiii!i!i!iiiiiill iiiiiiiiiiiiiiii iiiiiiiiiiiiiiii ii:ii;:ii~iiiii~ iiiiiiiiii::ii:: iiiiiii iiii!iii!i!iiiiii!!ii!i!i 99R 41B 1103P ab a a Fig. 2. The average midday leaf water ptential f Ruby Seedless grapevines grafted nt eight different rtstcks. Measurements were taken every tw weeks frm 23 May t 31 August Mean separatin by Duncan's multiple range test at the 5% level. Am. J. Enl. Vitic., Vl. 46, N. 4, 1995

3 RUBY SEEDLESS "~'-0.6 =E m.m.!.1 : i._,,i.,i t~ m.j II All rtstcks ~ I I I I I I I Time f day (h) Fig. 3. The diurnal time-curse f leaf water ptential fr Ruby Seedless grapevines grwn in Mrcc. Data were cllected n 2 August Other infrmatin as fund in Figure 1. slar nn, respectively. Leaf water ptential averaged acrss all rtstcks was -0.6 MPa at 1900 hurs. There were significant differences in yield and cluster number per vine amng rtstcks (Table 1). Ruby Seedless grafted nt 41B had the highest yields (an average f 6.3 kg/vine) while thse n l103p had the lwest yield (2.8 kg/vine). The number f clusters per vine was lwest fr l103p (19 clusters/vine), but highest fr 41B (35 clusters/vines). Berry weight did nt differ significantly amng rtstcks (Table 1), while there were significant differences in sluble slids cncentratin at fruit harvest (Table 2). The lwest sluble slids cncentratin was measured n the fruit f 99R and greatest measured n the fruit f and l103p. There was a difference f Table 2. The average effect ver three years (1989, 1991, and 1992) f rtstck n Ruby Seedless berry cmpsitin at harvest (fruit ph and clr were nt recrded n 1992). Rt- Brix TA ph Clr stck (g/100 ml) (A 520 nm) du Lt 18.5 bc z 0.47 e 3.77 ab 0.67 b 140Ru 18.7 bc 0.54 cd 3.75 ab 0.77 b a 0.54 cd 3.82 a 1.32 a 110R 18.8 bc 0.51 de 3.73 ab 0.83 b 41B 18.5 bc 0.58 bc 3.70 b 0.84 b 99R 18.2 c 0.64 a 3.72 ab 1.03 ab SO ab 0.62 ab 3.75 ab 1.08 ab 1103P 19.9 a 0.57 bc 3.72 ab 0.92 ab zmeans fllwed by a different letter within a clumn are significantly different at the 5% level using Duncan's multiple range test. t! 2 Brix between the highest (101-14) and lwest 9R) rtstcks. Titratable acidity was lwest in fruit n du Lt but highest in fruit frm scins n 99R. The ph was lwest in fruit n 41B but highest in fruit n rtstck. Clr absrbance ranged frm 0.67 t Fruit n du Lt, 140Ru, ll0r, and 41B had significantly lwer clr than fruit frm There were significant differences amng treatments with regard t pruning weights (Table 1). The rtstck had significantly greater pruning weights than the rtstcks du Lt, 41B, and l103p. Pruning weights ranged frm 1.14 fr du Lt and 41B t 1.86 kg/vine fr Discussin Averaged acrss all rtstcks, there was a seasnal decline in ~L fr Ruby Seedless grapevines grwn at this lcatin. The decrease f ~L early in the seasn will ccur regardless f whether vines are maintained well watered with irrigatins daily r weekly (21). Hwever, ~L shuld remain relatively stable after veraisn if the vine is given the amunt f water needed t meet vineyard evaptranspiratin (ET) demands ). Therefre, a decline in ~L after this grwth stage wuld be assciated with decreases in sil water cntent r increased evaprative demand. Osmtic adjustment by the leaves may als take place during drught with a resultant decrease in ~L (6). Daily, minr fluctuatins in ~L as the sil water cntent declines wuld be expected due t changes in envirnmental cnditins. The seasnal decrease in midday ~L fund in this study wuld reflect in part the fact that they were nt irrigated. Therefre, water availability in the sil became less as the seasn prgressed. This has been demnstrated fr deficit irrigated Thmpsn Seedless grapevines in Califrnia ). Hwever, in that study, midday ~L f vines irrigated at full ET never became mre negative than-1.0 MPa. Bth seasnal and diurnal patterns f ~L measured in this study indicated differences amng rtstcks. Previusly, a cmparisn f Cabernet Sauvignn grafted nt three different rtstcks (5C, St. Gerge, and A R#1) indicated that rtstck had n effect n ~L (22). Hwever, measurements in that study were made nly n a single date. Research reprted here extended ver a tw and ne-half mnth perid and the relative psitin f an individual rtstck with respect t the thers was generally maintained thrughut that time. The greatest change in ~L frm the first measurement date t the last was 0.6 MPa fr du Lt and 140Ru while the least was 0.2 MPa fr l103p. The midday ~L averaged acrss all measurement dates indicated that there were tw extreme grups f rtstcks. Ruby Seedless vines n du Lt and l l0r had mre negative ~L s than thse n 41B and l103p. In a study with ne-year-ld, ptted Cabernet Sauvignn vines, drught tlerance f rtstcks was determined based upn leaf area develpment and stmatal cnductance measurements (2). The rtstcks , du Lt, and 41B were classified less drught Am. J. Enl. Vitic., Vl. 46, N. 4, 1995

4 EZZAHOUANI and WILLIAMS tlerant than SO4 and 99R. The rtstcks 110R, 140Ru, and l103p were classified as highly drught tlerant in that study. The relative rankings f rtstcks fr drught tlerance using ptted vines (2) had several similarities t the results btained here using field-grwn vines and ~L as a measure f vine water status. Fr example, du Lt and l103p had the greatest and least values f ~L, respectively, in this study and l103p was classified as highly drught-tlerant by Carbnneau (2), while du Lt was ne f the least. SO4 and 99R had intermediate values f ~gl in this study and were classified as intermediate in drught tlerance in the previusly mentined study. Hwever, ther rtstck cmparisns were less clear between the tw studies. This may be due t the fact that ne measure f vine water status (stmatal cnductance) and anther (~L) may nt themselves be related t ne anther. Stmatal cnductance f grape has been shwn t be mre highly crrelated t sil water cntent than t leaf water ptential (19). This may indicate that stmata respnd t signals frm rts as the sil drys ut (4,18) and nt t sme measure f leaf water status. In this study the highest yield was measured n vines grafted nt 41B. This was ne f the rtstcks fund t have the least negative seasnal ~L" A linear relatinship between vine prductivity and midday ~L has previusly been measured n Thmpsn Seedless ). Hwever, averaged acrss all rtstcks there was n significant crrelatin between ~gl and yield per vine in this study. The majr factrs determining vine prductivity in this study were cluster number per vine and t a lesser extent berries per cluster. There was a significant linear crrelatin (r 2 = 0.67) between yield and cluster number per vine. l l0r has previusly been classified as a high yielding rtstck (10,17) under diverse sil and envirnmental cnditins, and its increased yield was assciated with increased cluster number per vine (10). The high yields f 110R and 41B in this study als were assciated with greater cluster number per vine. Vines grafted nt du Lt had a high cluster number per vine but als had the lwest calculated number f berries per cluster. The 41B rtstck had the highest number f clusters per vine and highest number f berries per cluster. Berry set, cluster differentiatin, and cntinued maintenance f the cluster primrdia are sensitive t vine water stress (15). Therefre, vine water stress may explain the differences in cluster number per vine and berries per cluster fund amng the eight rtstcks used in this study. Ruby Seedless grafted nt SO4, 99R, and 41B had the heaviest berries and least negative midday ~gl, cmpared t vines n du Lt and which had the smallest berries and mst negative ~gl- This wuld indicate that vine water status in part affected berry grwth and supprts ther wrk demnstrating the negative effect water deficits have n berry expansive grwth (21). The rtstck had the highest sluble slids cncentratin and fruit clr, but mder- ate yield, du Lt had lw Brix, and lwest titratable acidity and berry clr amng all rtstcks cmpared. This may have been due t the fact that this rtstck als had the mst negative ~L thrughut the grwing seasn. While water stress generally is assciated with an increase in sugar accumulatin (21), severe water deficits actually may delay maturity (20). There was a psitive linear crrelatin (r 2 = 0.59) between titratable acidity and ~gl in this study (1991 data nly). A mderate decrease in titratable acidity has always been bserved when measured water status f the vine has indicated stress (1,21). In this study, rtstcks with mre negative ~gl (du Lt, ll0r, , and 140Ru) had less titratable acidity. Of the tw majr acids fund in grape berries, malic acid is the ne generally affected by water deficits in grapevines. The timing f vine water stress, whether ccurring befre r after veraisn als will affect malic acid cncentratin (14). Cnclusins This is ne f the few studies investigating the effects f rtstcks n vine water status and prductivity in a field situatin. Therefre, this research prvides bth basic knwledge abut rtstcks and applied infrmatin useful t viticulturists. This study als was imprtant because in Mrcc a majrity f the vineyards are either dry-land farmed r the availability f water fr irrigatin is minimal. The results indicate that the eight rtstcks used in this study culd be classified int different grups based upn their seasnal, midday ~L measurements. This classificatin, based upn ne measure f vine water status, was similar in several respects t anther study in which a different measure f vine water status was used t make a classificatin fr drught tlerance. Hwever, the ~gl data indicates that the effect f a rtstck upn the scin's water status was nt the sle factr determining the prductivity f a vine under dryland farming cnditins. Based upn yield data, du Lt shuld nt be cnsidered as a rtstck fr use in Mrcc under dry-land cnditins. Yield data btained frm the rtstck ll0r in this and ther studies has been classified as highly drught tlerant (5,27), wuld indicate that it culd be used in nn-irrigated vineyards in Mrcc and perfrm relatively well. Literature Cited 1. Bravd, B., Y. Hepner, C. Linger, S. Chen, and H. Tabacman. Effect f irrigatin and crp level n grwth, yield and wine quality f Cabernet Sauvignn. Am. J. Enl. Vitic. 36: (1985). 2. Carbnneau, A. The early selectin f grapevine rtstcks fr resistance t drught cnditins. Am. J. Enl. Vitic. 36: (1985). 3. Ck, J. A., and L. A. Lider. Mineral cmpsitin f blmtime grape petile in relatin t rtstck and scin variety behavir. Prc. Am. Sc. Hrtic. Sci. 84: (1964). 4. Davies, W. J., and J. Zhang. Rt signals and the regulatin f grwth and develpment f plants in drying sil. In: Ann. Rev. Plant Physil. Plant Ml. Bil., Vl. 42. W. R. Briggs, R. L. Jnes, and V. Walbt (Eds.). pp Annual Reviews, Inc., Pal Alt (1991 ). Am. J. Enl. Vitic., Vl. 46, N. 4, 1995

5 RUBY SEEDLESS Delas, J. J. Criteria used fr rtstck selectin in France. In: Prc. Rtstck Seminar: A Wrldwide Perspective, J. A. Wlpert, M. A. Walker, and E. Weber (Eds.). pp Am. Sc. Enl. Vitic., Davis, CA. (1992). 6. During, H. Evidence f smtic adjustment t drught in grapevines (Vitis vinifera L.). Vitis 23:1-10 (1984). 7. Ftt, J. H., C. S. Ough, and J. A. Wlpert. Rtstck effects n wine grapes. Calif. Agric. 43:27-29 (1989). 8. Galet, P.A. A Practical Amplegraphy (transl. L. T. Mrtn), 248 pp. Crnell University Press, Ithaca (1979). 9. Grimes, D. W., and L. E. Williams. Irrigatin effects n plant water relatins and prductivity f Thmpsn Seedless grapevines. Crp Sci. 30: (1990). 10. Harris, A. R. Xiphinema index- resistant Vitis rtstcks screened fr cmparative field perfrmance in a Chasselas vineyard replant site. Vitis 27: (1988). 11. Huang, Z., and C. S. Ough. Effects f vineyards lcatins, varieties, and rtstcks n the juice amin acid cmpsitin f several cultivars. Am. J. Enl. Vitic. 40: (1989). 12. Kliewer, W. M., and R. J. Weaver. Effect f crp level and leaf area n grwth, cmpsitin and clratin f 'Tkay' grapes. Am. J. Enl. Vitic. 22: (1971). 13. Lider, L. A., A. N. Kasimatis, and W. M. Kliewer. Effect f pruning severity and rtstck n grwth and yield f tw grafted cane-pruned wine grape cultivars. Am. Sc. Hrtic. Sci. 98:8-12 (1973). 14. Matthews, M. A., and M. M. Andersn. Fruit ripening in Vitis vinifera L.: respnses t seasnal water deficits. Am. J. Enl. Vitic. 39: (1988). 15. Matthews, M. A., and M. M. Andersn. Reprductive develpment in grape (Vitis vinifera L.): respnse t seasnal water deficits. Am. J. Enl. Vitic. 40:52-60 (1989). 16. Pngracz, D. P. Rtstcks fr grape-vines. 150 pp. David Philip, Publisher (Pty) Ltd., Cape Twn, Suth Africa (1983). 17. Suthey, J. M. Grapevine rtstck perfrmance under diverse cnditins in Suth Africa. In: Prc. Rtstck Seminar: A Wrldwide Perspective, J. A. Wlpert, M.A. Walker, and E. Weber (Eds.) pp Am. Sc. Enl. Vitic., Davis, CA (1992). 18. Trej, C. L., and W. J. Davies. Drught-induced clsure f Phaselus vulgaris L. stmata precedes leaf water deficit and any increase in xylem ABA cncentratin. J. Exp. Bt. 42: (1991). 19. Williams, L. E., N. K. Dkzlian, and R. Wample. Grape. In: Handbk f Envirnmental Physilgy f Fruit Crps, Vl. 1 Temperate Crps. B. Schaffer and P. C. Andersn (Eds.). pp CRC Press, Bca Ratn (1994) 20. Williams, L. E., and D. W. Grimes. Mdelling vine grwth-develpment f a data set fr a water balance subrutine. In: Prc. 6 th Austral. Wine Ind. Tech. Cnference. T. H. Lee (Ed.). pp Australian Industrial Publ. Adelaide (1987). 21. Williams, L. E., and M. A. Matthews. Grapevine. In: Irrigatin f Agricultural Crps. B. J. Stewart and D. R. Nielsn (Eds.). pp Agrnmy Mngraphs N. 30, ASA-CSSA-SSSA, Madisn, Wl (1990). 22. Williams, L. E., and R. J. Smith. Partitining f dry weight, nitrgen and ptassium and rt distributin f Cabernet Sauvignn grapevines grafted n three different rtstcks. Am. J. Enl. Vitic. 42: (1991). 23. Zelleke, A., and W. M. Kliewer. Influence f rt temperature and rtstck n budbreak, sht grwth, and fruit cmpsitin f Cabernet Sauvignn grapevines grwn under cntrlled cnditins. Am. J. Enl. Vitic. 30: (1979). Am. J. Enl. Vitic., Vl. 46, N. 4, 1995