Effect of nutrient status, temperature and PH on mycelial growth, sclerotial production and germination of Rhizoctonia Solani Isolated from paddy fields

Rhizoctonia solani Kuhn, is one of the most important pathogen of rice causing sheath blight disease, which accounts for heavy yield losses in all the major rice growing areas of the world including India. In the present investigation the effect of different culture media, carbon and nitrogen sources, temperature and pH on mycelial growth, sclerotia production and germination of Rhizoctonia solani (anastomosis groups AG1-IA from rice and AG3 from potato) were studied. Among the five culture media including potato dextrose agar (PDA), malt yeast extract agar (MYA), water agar (WA), oat meal agar (OMA) and soil extract agar (SEA), PDA medium supported maximum mycelial growth and sclerotium yield. The maximum mycelial growth and sclerotia formation was observed in D-glucose as carbon source while the maximum mycelial growth and sclerotia formation was recorded in potassium nitrate as nitrogen source. Different range of temperatures i.e. 10, 15, 20, 25, 30 and 35°C were tested and the maximum hyphal growth was measured at 25°C temperature. Mycelial growth of all isolates occurred between pH 4.0 and 9.0, with an optimum of pH 5.6. Sclerotium germination for all the AG1-IA isolates was optimum between 20 and 30°C on all the media tested, with a pH optimum between pH 5.0 and 6.0.