Identification of New Sources of Root Rot Resistance in Manitoba Grown Dry Bean Cultivars

Manitoba dry bean cultivars and select dry bean germplasm lines were evaluated for their reactions to Fusarium solani and Rhizoctonia solani. Certain cultivars were resistant to the root rot pathogens as the moderately resistant check cultivars; however, most of the dry bean cultivars were susceptible to the root rot pathogens. Partial resistance to the root rot pathogens was not always associated with high rates of seedling emergence. High rates of seedling emergence were observed in dry bean belonging to a number of different bean classes, which indicated that those cultivars were resistant to seedling blight caused by the root pathogens. However, only two cranberry bean cultivars, a navy bean cultivar and two black bean cultivars had significantly lower root rot ratings than the mean of the seven partially resistant check cultivars.  Significant differences in root rot severity were observed among the four bean cultivars and the four root pathogens. Root rot severity was lowest in the moderately resistant cultivars Etna and greatest in the Envoy, while the other two cultivars had intermediate ratings. The yields of Etna, Envoy and Maverick were not affected by inoculation treatment. In the root rot resistance and the root rot yield experiments, the pathogens were shown to differ in their effects on seedling emergence and root rot severity. Generally inoculation with R. solani had the most adverse effect on seedling emergence, while inoculation with F. solani consistently resulted in the greatest root rot ratings.