Evaluation of Wine Grape Clones and Cultivars for the San Joaquin Valley

The performance of ten recently introduced selections of Syrah from Australia and France were evaluated at the Kearney Agricultural Center, Parlier, California. Variables measured included yield, yield components, fruit composition, and susceptibility to sour rot. There was considerable variation between some of the Australian and French Syrah selections. The Australian Shiraz selections 01, 03, and 07 have generally had higher soluble solids, higher pH, smaller berries, smaller clusters, and less sour rot than the French Syrah selections. Shiraz 1 is particularly early, and thus has the highest soluble solids, and among the highest pH and lowest titratable acidity, of the clones tested. Of the French selections, Syrah 525 was notable in having relatively low yields of small, compact, clusters which were highly susceptible to rot. Though production of grapes for high quality table wines is increasingly important in the San Joaquin Valley, there remains a market for generic white wine grapes, for concentrate, brandy, and generic wines and blends. To insure profitability of this commodity, growers must develop vineyards capable of producing high yields of fruit at low cost. To aid these efforts, four white winegrape varieties having high yield potential, Colombard, Grenache blanc, Triplett blanc, and 182-4 were compared when subjected to standard hand pruning, and simulated mechanical box pruning. The fruits of hand pruned Grenache blanc have generally attained 21 Brix in late August, one to two weeks ahead of the other varieties. Machine pruning delayed maturation of most varieties by at least one to two weeks, depending on the variety and year. Hand pruned vines, regardless of variety, averaged about 31.5kg fruit/vine; machine pruning increased yields by 20% to 40%, depending on the year and variety. Machine pruning greatly increased the number of clusters per vine, but the clusters on machine pruned vines had fewer and smaller berries, and thus were far less susceptible to sour rot than the clusters of hand pruned vines. Thus, machine pruning increased yield and improved fruit quality compared to hand pruning, but it also delayed harvest, sometimes by several weeks, which may be undesirable.