Genetic Mapping of Pierce’s Disease Resistance in Germplasm Collected from the Southwestern United States and Mexico

Background and goals Pierce’s disease (PD) is an important grapevine disease in California and other warm grapegrowing areas in North America. Farming grape cultivars with natural resistance to the disease that have broader genetic base is an effective approach in high-pressure PD regions. The goal of this study was to genetically characterize PD resistance in three new accessions, b40-14 and b41-14, both collected from Mexico, and T03-16, collected from Texas.

Methods and key findings Simple sequence repeat (SSR) marker-based genetic maps that cover all 19 grape chromosomes were developed for b40-14 and b41-14, while the genetic map for T03-16 was developed only for chromosome 14. Quantitative trait locus (QTL) analysis was carried out by interval mapping, using parental and consensus maps for all three backgrounds. The QTL analysis identified a major locus in the three accessions on chromosome 14, within the genetic window of the previously-identified PD resistance locus PdR1. This increases the total to 13 known accessions with a major QTL for PD resistance in a similar genomic region.

Conclusions and significance All three accessions have major, but not complete, effect QTL for PD resistance on chromosome 14, indicating that other minor QTLs may be present in other genomic regions. Larger populations and map resolution are required to identify all minor QTLs.