Characterization and pathogenicity of Rhizoctonia spp. from field crops in Canada

Abstract

A survey for the presence of Rhizoctonia species on barley, bean, canola, corn, pea, soybean and wheat in 170 fields in Canada was completed during 2009–2011. Rhizoctonia solani was recovered from 52 (31%) of the 170 fields surveyed. A total of 191 isolates of R. solani belonging to anastomosis groups (AG) AG 2-1, AG 2-2, AG 4, AG 5, AG 9 and AG 11 were recovered. Fifty-two binucleate isolates of Rhizoctonia spp. were also recovered from 35 (21%) of the crops surveyed. In growth room pathogenicity studies, isolates belonging to AG 2-1 were pathogenic primarily on canola while isolates of other anastomosis groups tended to have wider host ranges. Symptoms included pre- and post-emergence damping off, crown rot and, to a lesser extent, root rot. The majority of binucleate isolates were not pathogenic or only had low aggressiveness on the hosts tested. There was considerable variation in host range among isolates of R. solani within individual AGs, and isolates recovered from asymptomatic seedlings of some hosts were pathogenic to other hosts often used in the same rotation. Collectively, the results are important for documenting the widespread occurrence of R. solani in seedlings of field crops in Canada, for characterizing variation in AGs and host range, and for identifying effective crop sequences used in crop rotations.