Identification and Characterization of Common Bacterial Blight Resistance Genes in the Resistant Common Bean (Phaseolus vulgaris) Variety OAC Rex
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Abstract
Common bacterial blight (CBB), caused by the bacterium, Xanthomonas axonopodis pv. phaseoli (Xap), is a major disease of common bean (Phaseolus vulgaris L.). CBB resistance candidate genes (CGs) were identified in the genomic library sequence of resistant variety OAC Rex based on pathogen resistance gene homology. Four CGs (CBB1-4) and other genes in the surrounding sequence were characterized. The CGs had homology to a putative leucine-rich-repeat disease resistance gene in Oryza sativa and retrotransposons. CG expression was not observed in either OAC Rex or OAC Seaforth (susceptible variety) after Xap or water treatment, indicating they are unlikely to be involved in CBB resistance. The other genes encoded ascorbate oxidase, callose synthase and hypothetical proteins. To test Xap susceptibility of Arabidopsis thaliana, detached leaves were inoculated with bacteria. Chlorosis and bacterial growth were observed, suggesting it may be a useful system for testing CGs.