Genetic Characterization and Molecular Mapping Pse-2 Gene for Resistance to Halo Blight in Common Bean

Pseudomonas syringae pv. phaseolicola (Burkholder) Young et al. (Psp) causes halo blight, which is a serious bacterial disease of common bean (Phaseolus vulgaris L.). Several resistance (R) genes have been discovered in host differential cultivar ZAA 12. Our objectives were to further characterize and enable marker-assisted selection (MAS) of the Pse-2 gene in ZAA 12 purported to have broad effect against multiple Psp races. A recombinant inbred population, ZAA 12 × ‘Canadian Wonder’, was challenged by the halo blight pathogen differential set consisting of nine Psp races. The resistance conferred by Pse-2 to races 2, 3, 4, 5, 7, 8, and 9 expanded the effect known for this gene from three to seven races. Segregation in F 2 populations confi rmed dominant inheritance for Pse-2 against all races except Race 8. Resistance to Race 8 was recessively inherited and most closely fi t a 7 resistant to 9 susceptible segregation ratio in the F 2 generation. Perhaps other genes are segregating that modify the effect of Pse-2 against Race 8. A sequence characterized amplifi ed region (SCAR) marker tightly linked with Pse-2 was generated. The marker was used to integrate Pse-2 to chromosome 10. A survey of lines and cultivars revealed the SCAR will have broad utility for MAS of Pse-2.