Rootstock effects on wine grapes John H. Foott o Cornelius S. Ough 0 James A. Wolpert Chardonnayand Cabernet Sauvi- gnon varieties were grafted onto phylloxera-resistant rootstocks in a vineyard not yet infested with the insect in the south central coastal region. Rootstocks influenced growth and yield, as well as compo- sition and quality of juice and wine, but a major consideration would be phylloxera resistance. For more than 100 years, California grape growers have been using rootstocks for resistance to grape phylloxera, an aphidlike insect that forms galls on vine roots. Nu- merous rootstock evaluations over the last 35 years by University of California viticul- turists at Davis have resulted in the identi- fication of AxR#l (Aramon x rupestris Ganzin 1) as a useful rootstock for the north- ern coastal valley vineyards. None of these studies, however, was conducted in the south central coastal region-San Luis Obispo and Santa Barbara counties. About 20,000 acres of new vineyards for wine grape production have been planted in the last 20 years in San Luis Obispo and Santa Barbara counties. Nearly all of the Rootstock 1202C (left) shows excellent compatibility with Chardonnay scions. It was a vigorous, plantings have been own-rooted, that is, not high-yielding stock. Union of rootstock 110R with Chardonnay (right) is conspicuous because of on phylloxera-resistant rootstocks. Al- scion overgrowth. Wine sensory scores showed relatively little difference among rootstocks. though phylloxera was not present at the time of the plantings, it is a potentially seri- ous problem as vineyards age and as the vertical trellis and pruned to four canes per pressed. Sulfur dioxide (35 to50 milligrams probability increases for a chance introduc- vine. The vineyard, on a Ballard clay loam per liter [mg/L]) was added to each lot be- tion of the pest. soil, was cultivated between rows, and a fore addition of yeast, Saccharomyces cerevis- We therefore established six rootstock herbicide strip down the vine row was iue strain Montrachet (UCD Enology No. evaluation experiments, three in San Luis maintained by preemergence herbicides. 522). The Chardonnay was settled over- Obispo County and three in Santa Barbara. Irrigation was by permanent-set overhead night, racked, and fermented at 60°F. The This report presents results from two of the sprinklers. Yield and pruning weights from Cabernet Sauvignon was fermented at 70°F trials, one with Chardonnay scions and the each vine, and juice and wine composition with caps punched down twice daily. The other with Cabernet Sauvignon, both in the and wine sensory analysis for quality were "Brix reading was taken as necessary to fol- Vina de Santa Ynez Vineyard, just west of obtained from four replications of five ex- low the fermentation. When the wines were Santa Ynez in Santa Barbara County. perimental vine units each for 4 years for dry, they were taken to the cellar for clarifi- Cabernet Sauvignon and 3 years for Char- cation and cold stabilization. All samples Methods donnay. were held in glass. Small amounts of sulfur Rootstocks were grafted and grown by After harvesting, grapes were trans- dioxide were added at the time of filtration. the UC Department of Viticulture and Enol- ported to Davis and crushed the next day. Storage was at 52°F. ogy at Davis. The eight rootstocks and own- Chardonnay was pressed immediately in a For the first 3 years (1984-86),samples of rooted vines were established in 1976, with basket press (equivalent to winery free-run the field replicates were fermented sepa- replanting in 1978, at a density of 605 vines juice). Cabernet Sauvignon was fermented rately, and analyses of the juice and wines per acre. Vines were trained to a two-wire on the skins to about 5"Brix then lightly were averaged. In 1987, field samples were CALIFORNIA AGRICULTURE. JULY-AUGUST 1989 27 crushed separately and juice samples ana- TABLE 1. Rootstock effect on cane pruning weight and fruit yield, Cabernet Sauvignon, 1984-87 lyzed, then combined and fermented in Aver- treatment lots. Rootstock 1984 1985 1986 1987 age* The juice samples were taken after the lots ...... ............... Pruning weight (/b/vine) ......... ........................................ were pressed and analyzed for "Brix, total 1202c 6.1 7.2 6.7 5.8 6.5 a acidity, and pH. The wine samples were 5A 4.2 4.7 4.9 4.3 4.5 b analyzed after cold stabilization for total St. George 3.4 5.1 4.8 4.1 4.4 bc acidity, pH, ethanol, potassium, total phe- SO4 3.9 4.4 4.2 4.3 4.2 bc Own 3.0 5.0 4.1 4.2 4.1 bc nols, and color. 3309C 4.0 4.1 4.5 3.3 4.0 bc The sensory analysis was done using the AxR#1 3.9 4.0 3.7 3.9 3.9 bc 20-point scoring system of M. A. Amerine 110R 2.9 3.3 3.4 3.0 3.2 bc and E. B. Roessler, of UC Davis, which al- Harmony 3.1 2.9 3.2 2.9 3.0 c lows wines to be rated for appearance, ........ ........ Fruit yield @/vine) ....... .............. aroma, flavor, balance, and other quality AxR#1 16.6 19.0 13.7 13.8 15.8a SO4 13.6 15.6 15.0 13.4 14.4 ab parameters. The tastings were presented in 1202c 12.3 19.1 14.0 10.8 14.1 ab blocks of nine per day. Each taster received Own 11.8 18.4 12.4 11.5 13.5 ab nine different rootstock treatments at a sit- 5A 13.9 14.0 14.3 11.8 13.5ab ting, and each made eight replications to 3309C 13.0 11.3 15.3 10.7 12.6ab 110R 14.0 17.1 12.0 7.0 12.5b ensure that significant variations would be St. George 11.6 14.9 11.8 11.4 12.4b detected. We performed statistical analysis Harmony 11.7 9.4 9.6 5.5 9.1 c of each year's sensory scores. Seven to ten tasters participated each year. *Averages followed by the same letter are not significantly different by Duncan's Multiple Range Test, p=0.05 Results TABLE 2. Cabernet Sauvignon juice and wine analysis, data averaged, 1984-87 Cabernet Sauvignon. Growth was de- termined by pruning weight measurements Juice analysis Wine analysis fromeachvineover a4-year period (table 1). Total Total Potas- Total Color 0.0.' Scion growth was significantly greater on Rootstock "Brix acidity pH acidity pH Ethanol sium phenol 420nm 520nm 1202C than on all the other rootstocks each 9 H, Td 9 H, Jd %v/v mg/L mg/L year. It was followed by 5A, which was IOOml lOOrnl Harmony 23 6 071 366 071 379 133 1596 1754 3 24 5 19 significantly greater than the others for the St. George 22 9 074 362 071 380 129 1663 1591 2 87 4 57 4-year average only. The six remaining AxR#I 22 3 073 352 072 361 127 1316 1486 2 66 4 93 5A 23 3 080 356 073 370 132 1543 1541 2 90 4 85 rootstocks showed very small differences, Own 23 1 073 361 070 373 132 1584 1560 2 66 4 41 although Harmony was consistently low SO4 23 4 075 361 071 378 135 1599 1604 2 76 4 62 each year. 1202c 23 2 076 358 072 373 132 1608 1511 2 71 4 49 IIOR 22 9 076 357 073 367 129 1440 1594 2 88 5 01 Yield comparisons resulted in a different 3309C 23 2 078 358 073 371 13 1 1544 1568 2 71 4 54 grouping, with AxR#l, S04, 1202C, own- NOTE: All juice analyses performed as described by M.A. Amerine and C. S. Ough, MethodsofAnalysfs of Musts and Wines, J rootstocks, 5A, and 3309C all in the top Wileyand Sons, NewYork, 1980. group over the 4-year period (table 1). * O.D. =optical density. Harmony was the lowest producing stock. The juices varied considerably from year TABLE 3. Cabernet Sauvignon sensory evaluations, average sensory scores, 1984-87 to year, but treatment differences (table 2) were quite small. AxR#l had the lowest Score' soluble solids at an average 22.3"Brix, and Rootstock 1984 1985 1986 1987 Harmony the highest at 23.6"Brix. In total Harmony 13.63 a 13.56ab 14.07 ab 13.75 ab acidity, 5A was highest and Harmony low- St. George 13.58 a 13.50 b 13.71 cde 13.62 ab est, witha range of 0.71 to 0.80 gram tartaric AxR#1 13.55ab 13.83 a 14.00 abc 13.57 ab acid per 100 milliliters of juice (H,Ta/100 5A 13.53 ab 13.77 ab 13.59 def 13.20 c Own 13.40 ab 13.58 ab 13.80 bcd 13.68 ab ml). The pH reflected the "Brix and acidity SO4 13.40 ab 13.60 ab 12.91 g 13.48 bc measurements; Harmony had the highest 1202c 13.30 abc 13.75 ab 13.46 ef 13.71 ab pH and AxR#l the lowest. These differ- 110R 13.18bc 13.79 ab 14.21 a 13.84 a ences may be partially due to differences in 33090 12.93 c 13.69 ab 13.38 f 13.70 ab cropping level, vigor, or both. LSD .05 0.38 0.29 0.29 0.32 The total acidity of the wine showed a NOTE: Sensory analysis was by the 20-point scoring system of M.