1a. Objectives (from AD-416):
Our contribution to this proposal is in phenotyping powdery mildew resistance and fruit quality traits in 4 breeding populations to develop markers linked with resistance and fruit quality loci.
1b. Approach (from AD-416):
(1) Phenotype the parents and progeny of four powdery mildew resistant families (maintained in Parlier field) for resistance segregation. (2) Phenotype parents and progeny of the same four powdery mildew resistant families for segregation of fruit traits.
3. Progress Report:
The agreement was established in support of Objectives 1B and 2A of the in house project, the goals of which are to evaluate existing table grape populations for powdery mildew (PM) resistance and to select vines for both PM resistance and high fruit quality. This research contributed to the development and validation of single sequence repeat (SSR) markers for PM resistance in segregating grape seedling populations. Seedlings are first screened for reaction to PM in the greenhouse prior to field transplanting. Leaf tissues from these segregating families are then sent to cooperators at Cornell University for DNA extraction and analysis. SSR markers have been identified that are linked to PM resistance. The markers have now been validated, using additional grape families that also are segregating for PM resistance. During the 2012 season, all grape seedling families segregating for PM resistance were field evaluated for reaction to PM on various plant organs (leaf, stem, rachis and fruit). These field evaluations were performed in July (early season) and September-October (late season). Grape seedling families were examined weekly during the 2012 fruiting season to note time of ripening for individual seedlings. As seedlings ripened, fruit was harvested and brought to the lab for evaluation. Fruit evaluations from these seedlings consisted of cluster and berry weights, fruit color, titratable acidity and total soluble solids of the berry juice. Berries also were evaluated for presence of seed or seed traces. Data from both PM field evaluations and fruit quality evaluations were compiled and provided to cooperators at Cornell University. Hybridizations performed during the 2012 bloom period utilized the greenhouse PM screen to identify and rogue PM susceptible seedling progeny. Leaf tissues from approximately 800 PM resistant seedlings were sent to the Cornell University PM Genotyping Center to determine PM allelic constitution of resistant seedlings. The resistant seedlings have been field transplanted to the test vineyard. When results are received from the genotyping center, seedlings bearing different PM resistance alleles and producing high quality fruit will be selected for advanced trials.