Geographical Variation in Pathogenicity of Rhizoctonia solani Isolates from Soybean Plants in Chhattisgarh, India

Rhizoctonia solani Kuhn is a soil-borne pathogen causing diseases such as aerial blight in soybean, it has been recognized as a serious problem in soybean-growing areas resulting in considerable yield losses. The present investigation was conducted to assess the pathogenicity of R. solani isolates collected from naturally infected soybean plants across various geographical locations in Chhattisgarh. A total of ten isolates were obtained and identified based on morphological characteristics. Pathogenicity tests were conducted under controlled conditions using soybean seedlings as hosts. The isolates showed various levels of virulence, ranging from mild to highly aggressive. Pathogenicity tests were tested by the detached leaf method and soil inoculation technique. In the detached leaf method, the symptom appearance was early noticed in RS-1, RS-2, RS-3, RS-5 and RS-10 at 72 hours while delay symptom appeared in RS-4 and RS-9 at 120 hours. In soil inoculation technique, the germination percent and percent mortality were observed and the maximum mortality percent was observed in RS-1 (88.83%) with germination percent (53.33%) whereas minimum in RS-4 (57.50%) with germination percent (80.00%). The fungus spreads close to plant canopy through its mycelia that grow aggressively. Based on pathogenicity test, the fungus caused both leaves to blight by detached leaf assay and soil inoculation method. These results suggest that R. solani could be a destructive pathogen being yield losses, so it must be controlled seriously. These findings underline the need for targeted management strategies to control R. solani in soybean fields, particularly in areas with higher pathogen virulence.