1a. Objectives (from AD-416)
Develop Pierce’s disease (PD) resistant table and raisin grape germplasm/cultivars with fruit quality equivalent to standards of present day cultivars. Develop molecular markers for Xf/PD resistance in a family from southeastern United States (SEUS).
1b. Approach (from AD-416)
1) Backcross BC1, BC2, BC3 hybrids (F8909-08 V. arizonica source of resistance) that have been selected for Pierce’s Disease (PD) resistance to high quality V. vinifera seedless table and raisin grapes. 2) Backcross F1 and BC1 resistant bunch grapes from native SEUS source of PD resistance as identified by greenhouse tests with high quality V. vinifera seedless table and raisin grapes. 3) Use embryo rescue to facilitate the hybridization of seedless parents. 4) Use molecular markers to select resistant F8909-08 backcross seedlings. 5) Select seedlings with highest fruit quality and test in the greenhouse to determine resistance. 6) Field test best resistant selections for PD resistance under natural conditions. 7) Perform production and quality trials of selections that have commercial potential. 8) Develop rough framework map of V. vinifera table grape X BD5-117 family to locate PD resistant QTL and develop molecular markers for marker assisted selection. Documents Trust with the Consolidated Central Valley Table Grape Pest and Disease Control District. Log 35507.
3. Progress Report
Pierce’s disease (PD) resistant table and raisin grape varieties are needed to overcome the increased incidence of PD as a result of the introduction of the glassy-winged sharpshooter. Fruit quality of the resistant varieties needs to be equivalent to varieties currently grown so they are commercially acceptable. Progress in making additional backcross generations to combine high quality table and raisin grapes with Pierce’s disease (PD) is continuing. Fifty-one seedless x seedless crosses to develop additional BC1 to BC4 V. arizonica and BC1 Southeast United States (SEUS) BD5-117 families were made. The crosses consist of 55,606 emasculations from which 12,216 ovules were cultured. With continued backcrossing, fruit quality and seedlessness is being increased while keeping PD resistance. Powdery mildew resistance was included in eight of the crosses. Molecular markers were successfully used to detect PD resistant individuals at a young seedling stage in the greenhouse for two BC2 and 12 BC3 families (V. arizonica source of resistance) consisting of 1,191 individuals from 2007 crosses. 363 seedlings were rated resistant and planted in the field. In November, 2008, seedlings in test tubes from 12 crosses made in 2008 were tested with molecular markers and 134 resistant plants identified from 360 individuals. Greenhouse screening for Xf resistance was completed on 150 selections and 63 of the 64 resistant individuals were from V. arizonica. Twelve resistant selections have been planted in the field at Weslaco, Texas to determine field resistance. The BD5-117 F1 family for development of additional molecular markers associated with PD resistance has been increased to over 500 plants this year. This meets our goal for the population size. BD5-117 has given the highest number of resistant offspring of any of the SEUS resistant selections to date and makes an excellent choice for study to develop molecular markers. Fruit of these seedlings was evaluated for cluster size, berry size, percent soluble solids and seed/aborted seed size. Cuttings of all 154 F1 BD5-117 seedlings were made for evaluation of PD resistance in the greenhouse. Testing of 125 individuals is complete, with 25 being resistant. 105 polymorphic primers for Simple Sequence Repeat DNA markers have been identified and 75 were labeled with fluorescent tags to analyze all 154 individuals. The project is monitored through active involvement in the day-to-day research activities, and through discussions with the Cooperator and interested stakeholders at the California Department of Food and Agriculture’s Annual Pierce’s Disease Research Symposium.