Reaction of dry bean cultivars grown in western Canada to root rot inoculation

Root rot is an important disease of dry beans (Phaseolus vulgaris) that is caused by a complex of root pathogens. Cultural and fungicidal controls are available to reduce the adverse impact of this disease on seedling emergence, plant growth and yield, but none of these practices are highly effective. The development of disease-resistant dry bean cultivars is considered to be an important component of an integrated management system for root rot control. A 5-yr field study was conducted to identify potential sources of resistance to seedling blight and root rot in dry bean cultivars that are widely grown in western Canada. A total of 37 dry bean cultivars, representing all the bean classes grown in the region, were tested against the root rot pathogens Rhizoctonia solani, Fusarium solani, F. redolens and F. acuminatum. Partial root rot resistance was detected in the navy bean cultivar Navigator and the black bean cultivars Black Violet and CDC Jet. The greatest root rot resistance occurred in the cranberry bean cultivars Etna and Cran 09. Reductions in root rot severity were not consistently associated with greater seedling emergence, which indicates that resistance to seedling blight and root rot may be independent traits. Inoculation with R. solani had the most adverse effect on seedling emergence, while infection by F. solani f. sp. phaseoli resulted in the most severe root rot ratings.