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 1.B., and 2.A., 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 with the goal of developing raisin types suitable for mechanical harvest 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, powdery mildew resistant raisin grapes that dry before damaging fall rains occur and lend themselves to mechanical harvest are needed. A total of 359 raisin seedlings developed from 13 seedless x seedless crosses for DOV were planted in the field. Fifty-three of the most outstanding DOV selections were added to the advanced natural DOV plot in 2010. Of the 63 natural DOV selections evaluated, 35 were dry by the first week of October. Twelve DOV selections produced more than 4 Kg raisins per vine and four had raisin quality greater than 90% B or better. The best natural DOV selection, fruiting for the third time in the 27 vine plot, was harvested October 7 and averaged 3.97 Tons/acre with 12.9% moisture and raisin grade of >90% B or Better. This selection is an outstanding Muscat flavored raisin with commercial potential. Only 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 requiring 54,065 emasculations were made in 2010. Eight seedless x seedless families from three sources of powdery mildew resistance were screened in the greenhouse and 115 mildew-resistant raisin seedlings were planted in the field. Fourteen new powdery mildew resistant tray dried raisin seedlings were selected. Four selections with high quality raisins were propagated into production trials while the rest were propagated in the no spray plot. Fourteen natural DOV seedlings with powdery mildew resistance had outstanding raisin quality and were propagated into production trials. Six seedless x seedless and two seeded x seedless backcrosses of red flesh selections to raisins were made this year using a total of 17,547 emasculations.