Identification of bacterial pathogens and races of Pseudomonas syringae pv. Phaseolicola from dry bean fields in Western Canada

Several bacterial diseases can significantly impact dry bean production in western Canada. The objectives of this study were to assess the incidence of multiple bacterial diseases on dry bean in southern Alberta and to determine the prevalent races causing halo blight (HB) in western Canadian dry bean fields. Field surveys combined with a pathogen isolation component were conducted in 2012-2014 to determine relative frequency of bacterial pathogens. Bacterial pathogens causing HB and brown spot were most commonly isolated from symptomatic tissues, whereas the pathogens causing common blight (CBB) and bacterial wilt were infrequently detected. In order to screen bean breeding lines for resistance to HB, the races of Pseudomonas syringae pv. Phaseolicola (Pph) present in western Canada needed to be determined. A total of 114 Pph isolates were recovered from dry bean samples from Alberta, Saskatchewan and Manitoba in 2010-2013. Virulence testing of these isolates on the halo blight dry bean differential set indicated that only races 2 and 6 were present. These races were equally predominant in Manitoba, race 2 comprised 81% of Alberta isolates, and only race 2 occurred in Saskatchewan. Screening of select CBB-resistant breeding lines indicated that all were susceptible to a race 2 isolate of Pph. However, several commercial cultivars either currently grown, or recently registered for commercial production in Alberta, showed reduced susceptibility to HB. These results should be applicable to dry bean breeding programmes attempting to incorporate halo blight resistance into Canadian-adapted dry bean lines.