Pathogenicity, Host Resistance, and Genetic Diversity of Species under Controlled Conditions from Soybean in Canada.

spp. are commonly associated with the root rot complex of soybean (). Previous surveys identified six common species from Manitoba, including , , , , , and . This study aimed to determine their pathogenicity, assess host resistance, and evaluate the genetic diversity of spp. isolated from Canada. The pathogenicity of these species was tested on two soybean cultivars, 'Akras' (moderately resistant) and 'B150Y1' (susceptible), under greenhouse conditions. The aggressiveness of the fungal isolates varied, with root rot severities ranging from 1.5 to 3.3 on a 0-4 scale. Subsequently, the six species were used to screen a panel of 20 Canadian soybean cultivars for resistance in a greenhouse. Cluster and principal component analyses were conducted based on the same traits used in the pathogenicity study. Two cultivars, 'P15T46R2' and 'B150Y1', were consistently found to be tolerant to , , , and . To investigate the incidence and prevalence of spp. in Canada, fungi were isolated from 106 soybean fields surveyed across Manitoba, Saskatchewan, Ontario, and Quebec. Eighty-three isolates were evaluated based on morphology and with multiple PCR primers, and phylogenetic analyses indicated their diversity across the major soybean production regions of Canada. Overall, this study contributes valuable insights into host resistance and the pathogenicity and genetic diversity of spp. in Canadian soybean fields.