Common bacterial blight resistance in Phaseolus vulgaris: An examination of the major resistance QTLS of OAC:Rex and HR67

Common bacterial blight (CBB) is a significant pathogen in dry bean (Phaseolus vulgaris) that presents itself as yellow to brown lesions on leaves pods and seeds, and is caused by Xanthomonas axonopodis pv. phaseoli. Recently, CBB-resistant bean genotypes, OAC-Rex and HR67 were developed from crosses between P. vulgaris and CBB-resistant accessions of Phaseolus acutifolius. OAC-Rex represents the first CBB resistant dry bean cultivar released in North America; however the genes responsible for this resistance have not yet been identified. Binary-bacterial artificial chromosome (BiBAC) libraries were created from OAC-Rex and HR67 with library depths of 5.6 and 8.1, respectively. The libraries were screened with CBB resistance-associated molecular markers, identified by previous studies, and the positive clones were analyzed and assembled into contigs, which represent approximately 600Kb in OAC-Rex and 450Kb in HR67. Selected clones from this contig were sequenced using the Roche 454 platform, and analysis of the OAC-Rex contig provided evidence that it is located on bean chromosome 4. The sequence contained approximately 90 ORFs, including NBS-LRR and protein kinase homologues. Synteny between this region and soybean chromosome 19 was also found. To aid in the identification of clones containing CBB-resistance genes, a CBB-infection screen, using Arabidopsis thaliana was developed.