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United States Department of Agriculture

Agricultural Research Service

Research Project: Develop Seedless Grapes for the Fresh Market Including Types Resistant to Powdery Mildew

Location: Crop Diseases, Pests and Genetics

2013 Annual Report


1a.Objectives (from AD-416):
Develop a series of seedless table grapes that ripen from early to late with white, black & red fruit. Fruit must meet shipping & storage requirements with high quality fruit. Emphasis will be placed on the development of early-ripening white grapes with large berry size, reduced hand thinning in the cluster, good sugar development & attractive appearance. Develop new table grape cultivars resistant to powdery mildew.


1b.Approach (from AD-416):
Standard breeding methods are being used. This consists of selecting varieties having the most desirable characteristics, hybridizing those varieties, selecting the best offspring and testing them as potential varieties. Tissue culture methods will be used to recover hybrids from seedless by seedless crosses. Advanced selections are tested in demonstration plots to determine commercial potential. Major areas of effort are for the development of seedless types to replace seeded varieties and varieties requiring high production costs. Powdery mildew resistance will also be incorporated into the table grapes from resistance germplasm. Selection for resistance will be done in the greenhouse and field where no fungicide applications are made.


3.Progress Report:

The agreement was established in support of Objectives 1B and 2A of the in house project, the goals of which are to identify advanced table grape selections with powdery mildew (PM) resistance and high fruit quality.

In 2012, over 550 seedlings and advanced table grape selections were fully evaluated for fruit and crop quality in the field. However, no new grape selections were determined to be sufficiently promising to warrant addition to 27-vine evaluation plots. Over 80 specific cultural treatments were administered to the 16 advanced selections and 10 cultivars in the experimental evaluation field plot. Selections H20, K2 and K15 show commercial potential.

Numerous hybridizations were performed during the 2012 bloom. Fourteen specific crosses (36,000 emasculations) involved high fruit quality seedless parents. Another 28 crosses were performed (48,000 emasculations) among PM resistant parents. Seedlings arising from PM resistant parent(s) were challenged with PM in the greenhouse to identify susceptible seedlings. Only PM resistant seedlings were transplanted to the field.

All previously planted PM resistant table grape selections were re-evaluated in the field for resistance. One particular selection, with Vitis romanetii-based PM resistance, warranted propagation into a 27-vine production trial. This red-skinned selection has high fruit production of average-sized conical clusters of 10/16” berries. Advanced selection O8, the first PM resistant selection to fruit in 27-vine production plots, did not perform well in post-harvest storage tests.


Last Modified: 4/23/2014
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