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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 Research

2012 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. Documents Trust with CAL Table Grape Commission. Log 38313.

3. Progress Report:
The agreement was established in support of Objectives 1B and 2A, of the in-house project, to select and evaluate breeding populations and advanced selections involved in the 12-15 year cycle of new cultivar development, evaluate existing table grape and raisin populations for powdery mildew resistance and select vines that combine host-plant resistance with high fruit quality. We developed table grape seedling populations for use in the development of table grape cultivars with the following characteristics; reduced cultural input, large seedless red, white or black fruit ripening in a sequence from early to late in the season, and powdery mildew resistance. Powdery mildew (PM) resistant table grape cultivars will reduce the need for chemical control. Modified backcrosses were continued to combine high fruit quality table selections with the best powdery mildew (PM) resistant selections. A total of 27 seedless x seedless crosses were made using a total of 49,714 emasculations. Twenty-six families representing five sources of resistance were screened in the greenhouse and only resistant seedlings planted in the field. The 252 advanced selections in no-spray plots were evaluated in August. Eighty-six selections remained free of PM after three years. Twenty new selections based on fruit quality and resistance were added to the advanced no spray plots for use as parents. One PM resistant table grape selection with mid to late-season red seedless fruit was added to the 27 vine advanced trial. There is a continued need for a series of improved red, white and black seedless table grape cultivars that ripen from early to late in the season. More than 748 table grape in vitro-derived seedlings from 35 seedless x seedless crosses were planted in the field. Thirteen seedless x seedless crosses were made using a total of 36,237 emasculations. Nine new seedless grape selections (4 red, 2 white and 1 black) were propagated into 27 vine advanced trials. Cultural trials were conducted on 15 advanced selections to determine commercial potential in comparison with 8 commercial cultivars.

4. Accomplishments

Last Modified: 10/16/2017
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