REACTION OF COMMON BEAN CULTIVARS TO ROOT ROT CAUSED BY Rhizoctonia solani AND Fusarium solani f. sp. phaseoli

Abstract

Rhizoctonia solani Kuhn is a necrotrophic fungus and soil inhabitant that attacks great number of vegetable species. In bean plants, R. solani can induce different symptoms including toppling, root and colon plant rottenness. Fusarium solani (Mart) Sacc. f. sp. phaseoli (Burcholder) occurs in practically all bean producing areas in Brazil and can cause root rots and death to bean plants. This study evaluated the reaction of commercial common bean cultivars growing in R. solani or F. solani f. sp. phaseoli infested soil, under green house conditions. The experimental design was entirely randomized, with 24 treatments and four replications. A Oxisol was infested with triturated sorghum grains that were previously colonized by R. solani (1.0 g/1.4 L of soil) or F. solani f. sp phaseoli (8.0 g/1.4 L of soil). The disease evaluations were accomplished 21 days after planting. All plants were carefully removed, their root systems were washed in running water and the disease severity was evaluated according to Abawi & Pastor-Corrales (1990) scale for disease severity. The cultivar behavior ranged according to the inoculated pathogen, all cultivars were susceptible with different degrees of susceptibility. Among evaluated common bean cultivars Pérola was less susceptible to R. solani, and Radiante was less susceptible to F. solani f. sp. phaseoli.

KEY-WORDS: Phaseolus vulgaris; resistance, soil pathogen.