Genetic Characterization of Pierce’s Disease Resistance in a Vitis arizonica/monticola Wild Grapevine

Background and goals Pierce’s disease (PD) is a bacterial disease that threatens vineyards across the United States and Mexico. Genetic resistance against this disease has been achieved using the resistance locus PdR1, which was found in a wild grapevine from Mexico. To broaden the genetic base, we aimed to identify additional unique sources of resistance. The objective of this study was to characterize PD resistance in accession b46-43, a PD-resistant wild grapevine from Texas. The manifestation of PD resistance in b46-43 is different from b43-17, with even cane lignification, minor leaf scorch, and minimum bacterial growth. It was hypothesized that b46-43 possibly carries resistance that differs from the PdR1 locus in b43-17.

Methods and key findings A total of 318 seedlings from population 14399 were evaluated for PD resistance and genotyped. The framework genetic map was developed and a quantitative trait locus (QTL) analysis was carried out. The QTL analysis identified a major locus that explained 55.5% of the phenotypic variation on chromosome 14, at the genomic position where PdR1 was mapped in earlier studies. No minor loci were identified on other chromosomes.

Conclusions and significance The b46-43 PD resistance locus can be used in the breeding program, but further comparative genomic analysis with b43-17 is needed to understand their genetic differences and how the b46-43 locus can be used in the breeding program. Moreover, the rarity of additional loci indicates that PD resistance may have a common origin and is widespread as a result of gene flow.