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Oral: Promising Phenotyping Efforts for Understanding Genetic and Molecular Bases of Plant Disease Resistance


Molecular aspects of host pathogen interactions in common bacterial blight in Phaseolus vulgaris caused by Xanthomonas
K. Pauls (1), K. Pauls (1), W. Xie (1), T. Smith (1), G. Perry (1), E. Castro (1) (1) Department of Plant Agriculture, University of Guelph, Canada

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Common bacterial blight (CBB), caused by Xanthomonas axonopodis pv. phaseoli and its fuscan variant X. fuscans subsp. fuscans, is a damaging disease of common bean throughout the world. Genetic studies have identified a locus associated with the molecular marker SU91 on bean chromosome 8 which confers broad-spectrum resistance to the disease. To examine the genes in the locus in more detail the genomic sequence of the resistant line OAC Rex in the SU91 CBB resistance QTL was compared to the corresponding genome sequence of the susceptible line G19833. This comparison identified a reorganization of a sterol transport gene and the occurrence of additional resistance (R) genes in the OAC Rex genome, which may be associated with resistance. To understand the diversity of the CBB pathogen, single colonies (lines), purified from each of four locally collected bacterial isolates, were tested for symptom development and 7 lines with differential aggressiveness were characterized by genome sequencing. Their genome sizes ranged from 5.32-5.36 Mbp and some genomic rearrangements were observed between the isolates. Differences in candidate virulence factors were identified that may be related to differences in aggressiveness between the bacterial lines through interactions with the promoters of target genes in bean resistance genes in the SU91 QTL region. This information will facilitate breeding bean cultivars with durable CBB resistance.