Avaliação de linhagens de feijão-caupi para resistência a rhizoctonia solani e agroathelia rolfsii

Abstract

Cowpea is susceptible to several pathogens during cultivation, including the fungi Rhizoctonia solani and Agroathelia rolfsii, known to cause root diseases that can significantly reduce crop productivity. The use of resistant cultivars is one of the most effective strategies for managing these pathogens. In this scenario, this study aimed to evaluate cowpea lines for resistance to R. solani and A. rolfsii. Experiments were conducted under laboratory and screenhouse conditions using sterilized soil maintained in pots. To assess the resistance of 21 cowpea genotypes to R. solani, the soil was artificially infested with 0.25 g of inoculum from isolate CMM-2666 prior to sowing. For the evaluation of resistance to A. rolfsii, two sclerotia of isolate SR-01 were placed in contact with the seed of each genotype at sowing. The four most promising genotypes identified in the initial screening were further evaluated in soil infested with three R. solani isolates (CMM-1062, RS-01, and RS-02). Disease severity was assessed 20 days after sowing using pathogen-specific rating scales. Experiments were arranged in a completely randomized design, and evaluations involving the four selected genotypes and three R. solani isolates followed a 3 × 4 factorial design with five replications. Non-infested soil served as the control treatment. Among the 21 genotypes evaluated against R. solani isolate CMM-2666, 13 were classified as moderately resistant, seven as susceptible, and one as highly susceptible. Analysis of variance revealed significant differences among genotypes (P ≤ 0.05), resulting in the formation of three groups, with disease severity ranging from 30.5% to 81.5%. However, genotypes BRS Verdejante, MNC11-1019E-46, MNC11-1026E-19, and MNC11-1018E-17, previously classified as moderately resistant to isolate CMM-2666, were highly susceptible to isolates CMM-1062, RS-01, and RS-02. For A. rolfsii, eight genotypes were classified as susceptible and 13 as highly susceptible. No sources of resistance to either R. solani or A. rolfsii were identified among the germplasm evaluated. These findings highlight the need for continued screening efforts to identify cowpea genotypes with resistance to these economically important pathogens.