Resistance to bacterial brown spot in Adzuki bean

Adzuki bean [Vigna angularis (Willd.) Ohwi & Ohashi] is cultivated on approximately 18,000 acres across Ontario, mostly for export to Japan. Bacterial brown spot caused by Pseudomonas syringae pv. syringae van Hall (Pss) can result in yield losses of up to 40 % in Adzuki bean but there is currently no resistant commercial adzuki variety. The objectives of the current research are to (a) characterize differences between highly virulent and less virulent strains of Pss, (b) develop a screening methodology for bacterial brown spot in adzuki bean, and (c) identify single nucleotide polymorphisms associated with quantitative trait loci (QTL) for resistance to bacterial brown spot using a population of adzuki recombinant inbred lines (RILs). To date, putative cultures of Pss have been isolated from adzuki seed lots from various locations in Ontario. Their identity will be confirmed by 16S rRNA sequencing and whole genome sequencing will be used to identify virulence factor genes. A method for screening the RILs for resistance/susceptibility to bacterial brown spot was developed using a Pss isolate from AAFC (Harrow). A screen of a subset of the RILs indicated that the population is segregating for resistance to bacterial brown spot. The parents of the RIL population have been sequenced by PacBio to 40x coverage. Assemblies of the genomes using HiFiASM show 534 Mb and 562 Mb of contig sequences in the resistant and susceptible parents respectively.