Alternative Wine Grape Cultivars for the San Joaquin Valley

A San Joaquin Valley wine cultivar trial block was established in 1992 at the UC Kearney Agricultural Center to evaluate potential Italian and Rhone regional cultivars of limited experience to the area A collection of promising selections from Fay Trip left’s wine cultivar breeding program was studied, as well as a collection of Muscat cultivars. The 3-year summary follows: 1. Rhone and Italian Cultivars – Shiraz (Syrah), Nebbiolo, Sangiovese, and Mouvedre showed the most promise of the black cultivars. Cinsaut and Dolcetto were the least promising. Grenache and Barbera served as standard comparisons. Shiraz (Syrah) and Nebbiolo were comparatively early ripening, moderate yielding, small-berried, free of bunch rot, and of good fruit composition. Conversely, Cinsaut had large berries of poor composition (high pH and low TA); Dolcetto had excessive cluster numbers which developed poorly (berry shrivel and drop) with the sparse vine canopy. Delayed fruit maturation with high yielding Sangiovese demonstrates the need to adjust crop load in this large-clustered cultivar. Mouvedre was less promising than Sangiovese due to more bunch rot and poorer fruit composition. Overall, Shiraz (Syrah) was most promising due to its good production of well-colored, small berries of fairly uniform ripening and low rot potential. Clusters were small-medium, loose and have been noted as easy to machine harvest. The very vigorous growth with numerous, loose clusters make it well adapted to non-selective machine pruning systems. Trial wines of Shiraz scored very high, often as high as those from cooler districts. It has potential for regional varietal wine as well as blending. Viognier showed the most promise of the non-standard white cultivars tested, with early ripening small berries, low bunch rot, and satisfactory yields. The vine is moderately vigorous and somewhat open in canopy development. Trial wines had characteristic varietal aromas. Sauvignon blanc performed well except for its higher bunch rot potential. Marsanne had heavy clusters with high rot and the poorest fruit composition. It is not suitable for this warm region. French Colombard, the standard, had the highest yield of the most balanced fruit composition, as might be expected. 2. Muscat Cultivars – Muscat blanc and Orange Muscat were early ripening (mid August-early September). Malvasia Bianca and Aleatico were the highest and lowest yielding, respectively. The opposite was true in 1996, suggesting an ‘alternate bearing’ response. Bunch rot was high in Aleatico, making it the least suitable cultivar. Orange Muscat, Muscat blanc, Malvasia Bianca and Muscat Hamburg show promise but with a need to manage potential bunch rot. 3. Fav Triplett Wine Cultivar Selection – Thirty four selections (8 white and 26 black) remain under study and are being maintained for industry interest. They originated from Mr. Triplett’s wine grape breeding program at Ceres, California, and have been alternately tested at the Kearney Ag Center over a period of 12 years. Six of the most promising selections in the 1996-98 trial block have been targeted as most promising. It is planned to select the most promising 4 to 6 out of the 22 selections from an earlier test. This will limit the final phase of the study to 10 to 12 selections for industry consideration. For blacks, the emphasis will be on productivity, smaller berries and clusters of high color and low bunch rot potential, high acidity and low pH and potential wine aroma characteristics. For whites, high production of sound fruit of high soluble solids and acidity for concentrate is emphasized. Industry evaluation and input will be welcomed for potential release.