Clonal Testing of Wine Grapes in the San Joaquin Valley

The San Joaquin Valley wine cultivar clonal evaluation study was initiated in 1987. It is an ongoing study to evaluate the most promising, virus disease-free clonal material being held or introduced as potential FPMS source material. French Colombard, Chenin blanc, and Barbera were completed in 1994 and 1995. Trial blocks of 3 clones each of Grenache, Sangiovese, Muscat blanc and Muscat of Alexandria were established in 1993; data collection was initiated at harvest, 1995, in these new trials, except for Muscat blanc which had too much bunch rot for meaningful results. Significant clonal differences were measured in all of the cultivars as follow: Grenache. Clone 3 had heavier berries and a higher yield, but with lower fruit soluble solids, as compared to clone 1. These differences can be attributed to genetic clonal differences, as neither of these selections have indexed positive for virus nor have they been heat-treated. Clone 2 (a heat-treated selection of clone 1A) is not showing any important differences. Thus, there are no apparent effects from heat treatment to date. Sangiovese. This culitvar is showing rather distinct clonal differences, with clone 2 showing the greatest promise due to its smaller berry size, good fruit maturation, lowest fruit pH and bunch rot, while maintaining intermediate yields. Clone 3 had large berries but the lowest yields; clone 4 had the highest fruit pH and bunch rot, although it had the highest yields. Muscat of Alexandria. The California selection A3 out yielded both of its Australian counterparts ? J2 and G5 ? with comparable fruit composition. This data is very preliminary due to the relatively young vine age. More complete data collection, including cluster numbers and weight and berry phenols and anthocyanins, will be taken in 1996.