Evaluation of Selected Local and Exotic Common Bean Germplasm for Genetic Resistance to Rust Pathogen Uromyces appendiculatus (Pers.)

Common bean rust caused by Uromyces appendiculatus is one of the major biotic constraints in the production of common bean (Phaseolus vulgaris L.) in Sri Lanka. The present study was conducted to identify potential sources for rust resistance by phenotypical and molecular screening of 20 local and exotic common bean germplasm lines. Six characterized rust pathogen races (15-3, 22-6, 31-1, 31-7, 5-0, and 22-52) were obtained from ARS-USDA and four rust spore samples (63-21, 23-5, 31-1, 31-11) collected from different bean growing areas in Sri Lanka were screened against selected germplasm in a protected house. In addition to phenotypic screening, Sequences Characterized Amplified Region (SCAR) markers SK 14, SI 19, and GT-2 closely associated with Ur-3, Ur-5 and Ur-11 were used for molecular analysis. Local bean varieties, Bandarawela green, Bandarawela Kalu (Capri type 1), and Galpalama Kalu (Capri type 2) showed resistance to rust races 15-3, 22-6, and two local isolates of rust pathogen, based on phenotypic screening. All tested local varieties were susceptible to local rust race 31-11. Molecular markers tested with local genotypes revealed none of the tested local genotypes had Ur-3, Ur-5, or Ur-11 genes. Tested SCAR markers were reproducible with germplasm including relevant resistance genes, revealing their specificity. Bean germplasm enriched with Ur-3, Ur-5, and Ur-11 resistance genes were identified as the much-needed resistant genes for bean rust disease resistance and pyramiding of those genes is important in bean crop improvement in Sri Lanka.