1a. Objectives (from AD-416):
Develop Pierce's disease (PD) resistant table and raisin grape germplasm/cultivars with fruit quality equivalent to present day standards. Develop molecular map and markers for Xf/PD resistance based on resistance from BD5-117 selection from southeastern United States.
1b. Approach (from AD-416):
1) Backcross the most advanced resistant hybrids (V. arizonica and BD5-117 sources of resistance) to high quality V. vinifera seedless table and raisin grapes. 2) Use embryo rescue to facilitate the hybridization of seedless parents. 3) Use molecular markers to select resistant V. arizonica backcross seedlings. 4) Select seedlings with highest fruit quality in the field and verify resistance by greenhouse inoculation. 5) Field test best resistant selections for PD resistance under natural and inoculated conditions. 6) Establish production and quality trials of selections with commercial potential. 7) Develop molecular map of BD5-117 family to locate PD resistant QTL and associated molecular markers. Documents reimbursable agreement with the University of California Pierce’s Disease Research Grants Program.
3. Progress Report:
Results from this study are in support of objective 4 (Develop and assess strategies to manage diseases caused by Xylella fastidiosa) of the in-house project. Pierce's disease (PD) resistance of over 185 parents and selections from populations of the wild grape, Vitis arizonica were verified in greenhouse tests to ensure molecular markers used to select PD resistance function properly. Two hundred and forty-three seedlings of the BD5-117 mapping family, with PD resistance from a different source, have been greenhouse tested. An additional 42 markers were tested on the 144 original seedlings to increase saturation of the 19 genetic linkage groups compiled for grapes. Data indicated a major quality trait locus on linkage group 2 (LG2). Cuttings of 102 parents and selections from V. arizonica populations also were evaluated in greenhouse tests to ensure resistance co-segregates with markers. Of the 112 markers screened to date, six are located on LG2. These selected markers from linkage LG2 may be useful for selection of PD resistance derived from V. arizonica and BD5-117. This collaborative research between USDA/ARS, Parlier and University of California, Davis has the unique opportunity to develop high quality PD resistant table and raisin grape cultivars for the California grape industry.