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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

2011 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, 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. This research contributes to development of table grape seedling populations to develop table grape cultivars requiring reduced cultural input with large seedless red, white or black fruit ripening from early to late in the season and with powdery mildew resistance. This project also provides support for evaluation of seedlings and testing of various cultural treatments on advanced selections. 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 35 seedless x seedless and 27 seeded x seedless crosses using a total of 57,373 and 36,313 emasculations respectively, were made. Over 294 mildew resistant table grape seedlings from 26 families screened for powdery mildew-resistance in the greenhouse were planted in the field. The 238 advanced selections in no-spray plots were evaluated in August and September, with 100 selections free of PM. Ninety-eight advanced selections were evaluated in the laboratory and 29 noted for use as parents based on fruit quality and resistance. Eleven new selections were added to the advanced no spray plots for use as parents. One PM resistant table grape selection is fruiting in the 27 vine advanced trial. This mid-season white seedless grape has firm, 5.4 g berries, and small seed traces the size of Thompson Seedless. There is a continued need for improve red, white and black seedless table grape cultivars that ripen early to late in the season. More than 132 table grape in vitro-derived seedlings from 20 seedless x seedless crosses were planted in the field. Thirty-five seedless x seedless crosses were made using a total of 78,307 emasculations. Eight new seedless grape selections (3 red, and 5 white) were propagated into 27 vine advanced trials. Cultural trials were made on 10 advanced selections and 11 cultivars.

4. Accomplishments

Last Modified: 06/24/2017
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