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

In separate trials, the yield, yield components, fruit composition, and susceptibility to sour rot of Barbera, and Syrah grapevine selections, and of several generic white wine grape cultivars (French Colombard, Grenache Blanc, Triplett Blanc, and T182­4), were evaluated at the Kearney Agricultural Center, in the central San Joaquin Valley. Barbera clone 6 was the earliest maturing, having similar or higher soluble solids and pH, and similar or lower titratable acidity than the other clones even though it was harvested one week earlier than the others. Barbera clones 2, 3, and 5 produced 25% more fruit, by wt, than clones 4 and 6. Clone 2 always had heavier berries than clones 3, 4, and 5, and those clones had heavier berries, and clusters, than clone 6. Clone 6 had fewer berries per cluster than clones 3 or 5 and had much less sour rot than the other clones, which may make it a desirable selection for the San Joaquin Valley. There was considerable variation among Syrah clones with respect to phenology, fruit composition, and yield. Clone 99 commenced growth soonest, and vines of clone 1 were the last to begin growing. Clone 99 bloomed a few days earlier than clones 1 or 3, but the fruits of clone 1 matured earliest as evidenced by their much greater soluble solids, higher pH, and lower TA than that of most other clones. Fruits of clone 174 matured later than those of clones 1, 100, Shiraz 03, and Shiraz 07, as evidenced by clone 174’s lower soluble solids and pH. Clones 03 and 100 had exceptionally high yields, between 20 and 100% greater, than most other selections. The high yields of clone 03 could be attributed to the fact that it had the most clusters per vine and its clusters were among the heaviest of the selections tested due to its relatively heavy berries. In contrast, the high yield of clone 100 was mostly due to its exceptionally heavy clusters which resulted from it having among the most berries per cluster, and the heaviest berry weights, of the selections tested. Clone 99, whose yield was similar to clone 100, had among the lowest levels of sour rot, and its fruit composition was comparable to that of many other clones. Thus, in this early stage of evaluation, clone 99 is one of the most promising Syrah selection. Grenache Blanc matured much earlier than the other varieties as evidenced by its relatively high soluble solids and earlier harvest date. The other varieties were harvested at soluble solids levels that were comparable to each other, but this required harvesting Triplett Blanc and 182­4 about three weeks after Grenache Blanc and French Colombard. Grenache Blanc and Triplett Blanc had about 40% greater yields than French Colombard or 182­4. The high yields were due to their relatively high number of clusters per vine and average cluster wts. Sour rot incidence varied from 20–30%, but did not differ among varieties. All things considered, Grenache Blanc was superior to the other varieties in having very high yields and relatively early fruit maturity