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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

2010 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, the goal being to perform necessary selection and evaluation steps on breeding populations and advanced selections involved in the 12-15 year cycle of new cultivar development, and the evaluation of existing table grape and raisin populations for powdery mildew resistance and, the selection of vines that combine host-plant resistance with high fruit quality.

This research contributes to development of table grape seedling populations for the goal of developing 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.

Powdery mildew (PM) resistant table grape cultivars will reduce need for chemical control. Modified backcrosses were continued to combine high fruit quality table selections with the best powdery mildew resistant selections. A total of 48 seedless x seedless and 3 seeded x seedless crosses using a total of 78,864 emasculations were made in 2010. Over 102 mildew-resistant table grape seedlings from 19 families screened for powdery mildew resistance in the greenhouse were planted in the field. The 357 advanced selections in no spray plots were evaluated in August and September, with 221 selections free of PM. One hundred thirty-two advanced selections were evaluated in the laboratory and 34 noted for use as parents based on fruit quality and resistance. Nine new selections, representing four different sources of PM resistance, were added to advanced no-spray plots for use as parents. One PM-resistant table grape selection was added to the 27 vine advanced trial. This mid-season white seedless grape has firm, 5.4 g berries, and small seed traces the size of those in 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 759 table grape in vitro-derived seedlings from 29 seedless x seedless crosses were planted in the field. Twenty-seven new seedless x seedless crosses were made in 2010 using a total of 85,490 emasculations. Seven new seedless grape selections (2 red, 1 black, and 4 white) were propagated into 27 vine advanced trials. One early white, and one early black selection show commercial promise. Cultural trials were made on 8 advanced selections and 11 cultivars. The project is monitored by the project leader through active involvement in the day-to-day research activities, and through regular on-site scheduled meetings with the Cooperator and interested stakeholders.


Last Modified: 12/22/2014
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