1a. Objectives (from AD-416):
Develop new raisin grape cultivars for mechanical harvest and evaluate existing raisin selections in the breeding program to determine their commercial potential.
1b. Approach (from AD-416):
Standard sexual hybridization will be used to combine traits between seedless raisins and in some instances seeded parents will be used for traits not found in seedless germplasm. Embryo rescue will be used to recover plants from seedless parents. Plants will be evaluated in the field for fruit and vine characteristics. Selected individuals will be put in six vine plots to test production and raisin quality. Cultivars with good raisin quality that ripen early and that can be mechanical harvested will be released to the industry. Documents Trust Agreement with California Raisin Marketing Board. Log 35739. Formerly 5302-21220-004-20T (08/08).
3. Progress Report:
The agreement was established in support of Objective 1B, and 2A, 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 to evaluate existing table grape and raisin populations for powdery mildew resistance, select vines PM resistance and high fruit quality. Developed raisin grape seedling populations to identify raisin types suitable for mechanical harvesting and powdery mildew resistance. This project also provides support for evaluation of seedlings and advanced selections for the natural Dry-On-The-Vine (DOV) trait combined with high raisin quality. Early ripening raisin grapes that dry before damaging fall rains occur and can be mechanically harvested are needed. Of the 63 natural DOV selections evaluated, 15 were dry by the first week of October. The best natural DOV selection, fruiting for the fifth time in the 27 vine plot, was harvested October 19 and the best treatment averaged 5.3 Tons/acre with 12.3% moisture and raisin grade of 91.0% B or Better. This selection is an outstanding Muscat flavored raisin with commercial potential. Modified backcrosses to combine high fruit quality from raisin selections with the best powdery mildew resistant selections were made. A total of 18 seedless x seedless crosses using 42,793 emasculations were made. Eighteen seedless x seedless families were screened in the greenhouse. The 135 advanced selections in no-spray plots were evaluated in August, with 43 selections free of PM after three years testing. Three DOV and 15 tray-dried new raisin selections based on fruit quality and resistance were added to the advanced no spray plots for use as parents. Five tray-dried selections with high quality raisins were propagated into production trials. Seven seedless x seedless backcrosses of red flesh selections to raisins were made using a total of 10,088 emasculations. Five seedless DOV raisins with red flesh from mBC1 family for red flesh were selected for propagation to determine production levels and raisin quality.