Valley Pearl
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.
Figures
Figure 1 Valley Pearl cluster
Figure 2 Valley Pearl leaf
Origins and History
Valley Pearl resulted from a planned cross of two white seedless grape (Vitis vinifera L.) selections, and embryo rescue technique was employed to develop a seedling from the seedless parents (Ledbetter, 2016). In 1999, a seedling was selected as A85-40 by David Ramming and Ronald Tarailo, and it was subsequently trialed in the San Joaquin and Coachella Valleys of California. A U.S. plant patent (PP23,422) was awarded to Valley Pearl in 2013, and the variety is licensed to the California Table Grape Commission.
Vine Traits
Valley Pearl grape vines were described in detail by Ledbetter (2016). In short, the vines have fruitful basal buds, and cordon-trained, spur-pruned vines are consistently productive, averaging 2 clusters per shoot. Own-rooted Valley Pearl vines are moderately vigorous. Vines are susceptible to powdery mildew (Ramming and Tarailo, 2013). The application of gibberellic acid (GA3) to increase fruit size does not reduce fruitfulness the following year. Vines thinned to 35-40 clusters/vine yielded approximately 49 lbs of fruit.
Vineyard Considerations
Grafting to a rootstock may be expected to affect vigor. Valley Pearl has fruitful basal nodes and is typically trained to quadrilateral cordons and pruned to spurs. Most commercial vineyards use an open-gable trellis (Y) system.
The top half of clusters are naturally looser than the bottom half, which tends to become compact. The bottom half of clusters can be removed after fruit set, to avoid excessive compactness without having to use GA3 as a thinning (bloom) spray (Ledbetter, 2016). The sizing spray recommended by Ledbetter (2016) was 40 ppm GA3 applied just after set. Ledbetter suggested clusters with 50 to 60 berries averaging 9-10 grams were ideal, and berry samples from a commercial vineyard averaged 9.79 g/berry (Fidelibus, unpublished). Some growers have reported that Valley Pearl may be sensitive to touch and suggested using clippers or gloved hands when manipulating clusters for thinning, positioning, or tipping to avoid leaving marks on the fruit.
Quality
Valley Pearl berries have a round shape, with smooth, pale green skin that adheres strongly to the flesh. Skin thickness is medium, with a meaty texture. Average berry weight is 9 g. Flavor is sweet and neutral, though sun-exposed fruit may develop a light muscat flavor. Berries from girdled vines may develop an astringent flavor, so girdling is not recommended (Ledbetter, 2016).
References
Ledbetter, CA. 2016. ‘Valley Pearl’ Table Grape. HortScience 51: 772-774.
Ramming, DW and RE Tarailo. 2013. United States Plant Patent for Grapevine Denominated ‘Valley Pearl’. USPP 23422
Contributor
Ashraf el-Kereamy
Director
Lindcove Research & Extension Center
University of California
Agriculture and Natural Resources
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Tian Tian
Kern County Area Viticulture Advisor
University of California
Agriculture and Natural Resources
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Reviewer
Maha Afifi
Senior Researcher
California Table Grape Commission
