BREEDING PIERCE’S DISEASE RESISTANT TABLE AND RAISIN GRAPES AND THE DEVELOPMENT OF MARKERS FOR ADDITIONAL SOURCES OF RESISTANCE Project Leaders:

This year six crosses for Pierce’s disease (PD) resistant table and raisin grapes using seedless parents were made, resulting in 2,398 ovules and 747 embryos. These crosses were based on Muscadinia and V. tiliifolia sources of resistance. Nineteen seeded crosses consisting of 3,950 emasculations and 49 bagged clusters were made. These crosses were based on V. arizonica, Muscadinia, and southeastern United States (SEUS) sources of resistance. Over 120 selections have been made based on fruit quality and are ready for greenhouse screening for resistance to PD. Two BC2 families from 89-0908 V. arizonica source of resistance segregated in a 1:1 ration for resistance:susceptibility, based on molecular markers associated with the PdR1 locus. A smaller family from the same source of resistance had an unexpectedly small number of resistant seedlings. DNA samples have been collected from 154 seedlings from the C33-30 x BD5-117 family and are ready for SSR marker analysis. Additional seedlings are being produced to increase probability of identifying markers associated with this source of resistance. INTRODUCTION Pierce’s disease (PD) has existed in California at least since the late 1800s when it caused an epidemic in Anaheim. A number of vectors for PD already exist in California causing its spread. The introduction of the glassy-winged sharpshooter (GWSS) to California in the 1990’s increased the spread and damage caused by PD. Other vectors exist outside California and are always a threat. All of California’s table and raisin grape cultivars grown commercially are susceptible to PD. An effective way to combat PD and its vectors is to develop PD resistant varieties so that PD epidemics or new vectors can be easily dealt with. PD resistance exists in a number of Vitis species and in Muscadinia. PD resistance has been introgressed into grape varieties in the southeastern United States, but fruit quality does not match the Vitis vinifera table and raisin grape cultivars grown in California. Greenhouse screening techniques have been improved to expedite the selection of resistant individuals (Krivanek et al. 2005, Krivanek and Walker 2005). Molecular markers have also been identified that make selection of PD resistant individuals from V. arizonica in these families even quicker (Krivanek et al. 2006). The USDA, ARS grape breeding program at Parlier, CA has developed elite table and raisin grape cultivars and germplasm with high fruit quality. This collaborative research gives the unique opportunity to develop high quality PD resistant table and raisin grape cultivars for the California grape industry. OBJECTIVES 1. Develop PD resistant table and raisin grape germplasm/cultivars with fruit quality equivalent to standards of present day cultivars. 2. Develop molecular markers for Xylella fastidiosa (Xf)/PD resistance in a family (SEUS) other than those from V. arizonica. RESULTS Objective 1 This year the seedless embryo culture crosses concentrated on using the Muscadinia source of resistance and a unique source of resistance from V. tiliifolia. Six crosses were made for a total of 2,398 ovules cultured (Table 1). A total of 748 (31%) embryos were extracted and transplanted on fresh medium for growth into plants. Nineteen seeded crosses were made for PD resistance (Table 2). For five of the crosses, 3,950 emasculations were made and 49 clusters were bagged for 14 additional crosses which had female flowered parents. Fruit has been harvested and seeds are being extracted for germination in January. The number of seeds produced from each resistant source was: 1,881 from V. arizonica; 1,643 from Muscadinia, and 2,071 from SEUS with an additional 184 from BD5-117 BC1. Over 120 selections have been made based on fruit quality from populations made for PD resistance. These families are from resistant sources different than the V. arizonica source of resistance. These selections are in line for PD testing in the greenhouse. Three families (89-0908 V. arizonica source of resistance) produced in 2005 were tested for molecular markers associated with PdR1 locus on chromosome 14