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.
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 and select vines that combine host-plant resistance with high fruit quality. This research contributes to development of raisin grape seedling populations to develop 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 trait combined with high raisin quality. Early ripening powdery mildew resistant raisin grapes that dry before damaging fall rains occur and lend themselves to mechanical harvest are needed. Of the 41 natural DOV selections evaluated, 17 were dry by the third week of October. The best natural DOV selection, fruiting for the fourth time in the 27 vine plot, was harvested October 19-21 and the best treatment averaged 4.49 Tons/acre with 13.7% moisture and raisin grade of 77.6% 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 25 seedless x seedless crosses using 54,631 emasculations were made. Twelve seedless x seedless families were screened in the greenhouse and 82 mildew resistant raisin seedlings were planted in the field. One DOV raisin seedling and 13 tray-dried raisin seedlings with powdery mildew resistance were selected. Four tray-dried selections and one DOV selection with high quality raisins were propagated into production trials, while the rest were propagated in the no-spray plot. Three seedless x seedless and three seeded x seedless backcrosses of red flesh selections to raisins were made using a total of 14,474 emasculations. Five seedless raisin types with red flesh were selected for propagation to determine production and raisin quality.