Genetic mapping of Pierce’s disease resistance in Germplasm collected from the Southwestern US and Mexico

Authors: Riaz, Summaira; Tenscher, Alan; WALKER, MICHAEL - University Of California, Davis

Submitted to: American Journal of Enology and Viticulture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/12/2023
Publication Date: N/A
Citation: N/A

Interpretive Summary: Pierce’s disease (PD) is an important grapevine disease in California and other warmer parts of North America. Farming of new grape cultivars with natural resistance to the bacterium Xylella fastidiosa (Xf), the causal agent of Pierce’s disease, is the only effective approach in regions with high incidence of the pathogen. In this study, natural resistance to Pierce’s disease was identified on chromosome 14 of three grapevine accessions (b40-14, b41-13, and T03-16) collected from Mexico and Texas, USA. Identification of novel sources of Pierce’s disease resistance is important for the development of naturally resistant breeding lines and cultivars.

Technical Abstract: Pierce’s disease (PD) is an important grapevine disease in California and other warmer parts of North America. The combination of warming temperatures and invasive vectors has changed the epidemiology of the disease and more drastic control strategies are needed. Farming of grape cultivars with natural resistance to the disease is the only effective approach in high-pressure PD regions. The grape breeding program at the University of California, Davis is currently utilizing the PdR1 locus, identified from a wild grape species, to develop naturally resistant breeding lines. An important component of the program is the identification of novel sources of resistance to expand the genetic base or resistance. So far ten accessions collected from the southwestern US and Mexico have been identified that have resistance within the genetic window of PdR1 locus on chromosome 14. In this study, we are reporting genetic mapping and QTL analyses results for three additional accessions b40-14, b41-13 and T03-16; the first two collected from Mexico and the latter collected from Texas. Simple sequence repeat (SSR) marker based framework 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. The QTL analyses identified that these three additional accessions also have PD resistance on the chromosome 14 within the genetic window of the PdR1 locus, bringing the total to 13 accessions. The apparent lack of additional genomic regions conferring resistance to PD and the widespread distribution of the PdR1 locus in wild germplasm collected from the Southwestern US and Northern Mexico indicates that wild grapes developed resistance in response to the disease at or very near its center of origin and that gene flow occurring over millennia has spread it to wider regions of southwestern US and Mexico.