Vol. 7, Issue 11, Part B (2025)

Sheath blight of rice, caused by Rhizoctonia solani Kühn, poses a major threat to rice cultivation worldwide. This soil-borne fungus exhibits strong saprophytic growth and infects a wide range of host plants. Under favorable environmental conditions and with a high inoculum load, the disease severity increases significantly. Among the tested media, Potato Dextrose Agar, Czapek’s Dox Agar, and modified Czapek’s Agar were found to best support R. solani growth, each promoting maximum mycelial development (90 mm) and abundant sclerotia formation. Among the various carbon and nitrogen sources tested, sucrose, dextrose, and mannitol, along with ammonium nitrate and sodium nitrate, proved to be the most effective in promoting the growth and sclerotial formation of Rhizoctonia solani compared to other supplemented sources. Although the fungus was able to grow across a broad pH range, the highest mycelial growth and sclerotial production occurred at pH 5. Optimal growth and sclerotia formation were recorded at temperatures between 25 °C and 30 °C on Potato Dextrose Agar under in vitro conditions. These findings indicate that suitable nutrient sources, temperature, and pH serve as key edaphic factors influencing the growth and sclerotial development of R. solani.