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).
Early ripening raisin grapes that dry before damaging fall rains occur and lend themselves to mechanical harvest are needed. A total of 150 raisin seedlings developed from 10 seedless x seedless crosses for dried-on-the-vine (DOV) were planted in the field. Fourteen new seedless x seedless crosses were made in 2009, consisting of 36,091 emasculations, from which 3,876 ovules have been cultured. A total of 336 raisin selections were evaluated in the laboratory. Fifteen of the most outstanding DOV selections were added to the advanced natural DOV plot. A total of 54 advanced DOV selections fruited for the first time in two vine plots and 47 selections fruited for the 2nd time. Of the 101 natural DOV selections evaluated, 33 had good drying and raisin quality. Sixty-seven were discarded for various reasons. The best natural DOV selection fruiting for the second time in the 27 vine plot was harvested September 30 and averaged 4.14 tons/acre with 14.7% moisture and >90% BorB. It is an outstanding Muscat flavored raisin with commercial potential.
Modified backcrosses were continued to combine high fruit quality from raisin selections with the best powdery mildew resistant selections. Fifteen families from four sources of powdery mildew resistance were screened in the greenhouse and 170 mildew resistant raisin seedlings were planted in the field. Eight seedless x seedless crosses were accomplished in 2009 from which 1,973 ovules have been cultured. Ninety-nine raisin samples from new and advanced powdery mildew resistant selections were evaluated in the laboratory. Thirty-six had traces smaller than Fiesta or exhibited natural DOV ability. Four were good enough to propagate into a production test. The highest rated of these also has natural DOV ability. C88-43 and Rubired were shown to have the highest antioxidant activity of the red flesh selections tested. The antioxidant activity appeared to be related to total phenolics but not to anthocyanin content. Even one white grape selection had antioxidant activity similar to one selection with black skin and white flesh. Five backcrosses of red flesh selections to raisins were made this year and 1,589 ovules recovered from 8,263 emasculations. This project is monitored through active involvement in the day-to-day research activities, and through regular on-site scheduled meetings with the Cooperator and interested stakeholders.