Valley Pearl is an early-season white-skinned table grape (Vitis vinifera L.), typically ripening in mid to late July in the San Joaquin Valley of California. This variety produces 1.3 lb conical-shaped clusters that are medium to well-filled. Berries are spherical in shape, with smooth pale green skin. Optimal berry size, 9 g, can be achieved with one application of GA3. Berries are large and sweet, with a neutral to slightly muscat flavor. Growers may expect >1,100 19-lb boxes of fruit per acre annually. Valley Pearl is patented and licensed exclusively to the California Table Grape Commission.
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Autumn King is a late-season white-skinned table grape (Vitis vinifera L.), typically ripening in late October in the San Joaquin Valley. It is notable for its very large berries (>9 g natural berry weight), and high yield potential. Head-training and cane-pruning is recommended. Preliminary reports suggested Autumn King vineyards will yield 700-800 22 lb boxes of fruit per acre each year (Hashim-Buckey and Ramming), but more recently it was suggested the variety could produce 1,800 19 lb boxes/acre annually (Fidelibus et al., 2018). The difference in yield estimates depends, in part, on berry size, as original yield estimates were based on natural berry size of approximately 10 g, but optimal cultural practices can substantially increase berry size. Autumn King is patented and licensed exclusively to the California Table Grape Commission.
Thompson Seedless is a white seedless grape of ancient origin and suitable for a variety of uses, including table, raisin, wine, concentrate, and canning. Its leaves are also edible and used as a wrap around fillings, in types of dolma known as sarma. In California, most Thompson Seedless grapes are grown for raisins, dried on trays placed on the vineyard floor, or in dehydrators; the grapes of this variety ripen too late to dry on vine (DOV). Tray-dried raisins develop a dark brown color and are known as ‘naturals’. Some Thompson Seedless grapes are picked fresh and taken to a dehydrating facility for pretreatments, drying, and treatment with sulfur dioxide, to preserve color. Such raisins are known as “goldens,” or “golden raisins.”. Other types of raisins, including “Sultanas” and “dipped” raisins, are also made from Thompson Seedless grapes dried in a dehydrator.
Selma Pete is a white seedless “Thompson-type” raisin grape from the USDA-ARS, selected by Ramming and Tarailo (Okie, 2002) and named after former UC Davis viticulture specialist L. Peter Christensen. Selma Pete was selected for its early maturity, ripening approximately 14 to 21 days earlier than ‘Thompson Seedless’, making it suitable for dry-on-vine (DOV) (Fidelibus, 2021; Petrucci, 2002). Selma Pete is currently the earliest-ripening Thompson-type raisin grape grown in California. It is less productive than Fiesta, but ripens sooner, dries faster, and usually produces a higher proportion of ‘B and better’ raisins (Fidelibus et al., 2008; Fidelibus, 2021). Selma Pete berries have the highest titratable acidity of Thompson-type raisin grape varieties, and the raisins are tarter as a result (Parpinello et al., 2012).
Fiesta is a white seedless “Thompson-type” raisin grape from the USDA-ARS, selected by Weinberger and Loomis (1974). Selected for its early maturity, Fiesta ripens approximately 10 to 14 days earlier than ‘Thompson Seedless’, making it less susceptible to rain damage and more suitable for dry-on-vine (DOV) raisins (Fidelibus, 2021). Raisin varieties that ripen earlier than Fiesta have since been released, but Fiesta remains popular because it is among the most productive raisin grapes available, and ripens early enough to DOV. However, Fiesta’s large crops tend to limit soluble solids accumulation, and thus result in lower raisin quality compared to other Thompson-type DOV raisin grapes (Fidelibus et al., 2008; Fidelibus, 2021). Therefore, the need to balance acceptable soluble solids accumulation, which is critical for raisin yield and quality, against timely cane severance, which is critical to ensure adequate drying, is more difficult for Fiesta than it is for varieties such as Selma Pete or DOVine, which ripen sooner than Fiesta (Fidelibus, 2021). Fiesta is also particularly susceptible to powdery mildew, and the fruit may have fewer but larger seed traces than Thompson Seedless (Christensen et al., 1983).
Marsanne is a white wine grape cultivar native to the Rhône Valley region of France where it is found growing with other white wine grapes including Roussanne, Grenache Blanc, Viognier, Picpoul blanc, Clairette, Picardin and Muscat blanc. In California, it is productive, vigorous and well suited to warm regions (especially Winkler Region III), though it performed poorly in Parlier, a hot region (Winkler Region V). It is not widely grown in the United States. Under the best growing conditions and with skilled wine making, it can be made into long lived and interesting wines, especially when blended with other members of the Rhône wine grape family. It is susceptible to powdery mildew and bunch rot and requires careful attention in the vineyard to show its greatest potential in the wine bottle.
Fiano, an ancient variety from Campania, in southern Italy, “may well be Italy’s greatest native white grape” (D’Agata, 2014). It is versatile and fit for a variety of wine styles, “from light to full-bodied, dry to sweet, easygoing to very ageworth” (D’Agata, 2014). Fiano’s origin in southern Italy, and its reputation for producing high quality fruit and wine, contributed to its selection for a warm-climate wine grape variety trial at the UC Kearney Agricultural Center, in Parlier, California, which has a hot (Winkler region V) climate. In Parlier, Fiano produced moderate yields of fruit from which excellent quality white wines were consistently produced. Desirable traits included the retention of good acidity, and excellent flavor. Currently (2021) there are four selections available at Foundation Plant Services, although two of the four were selected from the same vineyard in Hopland, CA. The selection tested in the San Joaquin Valley was FPS 03.
Sunpreme is a white seedless raisin grape bred by David Ramming, USDA-ARS. It is the first raisin variety to spontaneously dry-on-vine, without cutting canes or otherwise separating the fruit from the vine. It has fruitful basal nodes and may be spur-pruned. The combination of spontaneous drying and fruitful basal nodes should make it possible to harvest and prune Sunpreme with machines, a degree of mechanization that is not possible with other raisin varieties. However, Sunpreme is also prone to preharvest fruit drop caused by the abscission of cluster branches. Compared to other Thompson-type raisin grapes, Sunpreme has larger, rounder, berries, and heavier raisins that are lighter in color. Sunpreme grapes and raisins also have a pleasant, mild, Muscat flavor.