IMPACT OF DIFFERENT CULTURE MEDIA, TEMPERATURE AND PH ON GROWTH OF Rhizoctonia Solani Kühn CAUSES BLACK SCURF OF POTATO

Among fungal, bacterial, viral and nematode diseases, black scurf of potato (Solanum tuberosum) is one of the most destructive soil and seed born fungal disease, caused by Rhizoctonia solani Kuhn AG3 (telomorph Thanatephorus cucumeris). Factors like culture media, temperature and pH made impact on the growth of black scurf fungus. During in-vitro study, among six culture media Potato Dextrose Agar supported the best redial growth of the tested fungus 90 mm at 10 days after inoculation, followed by Carrot Meal Agar (76.73mm). The colony colour varied whitish to brownish white and growth of R. solani maximum and collective, supported by Potato dextrose agar. Maximum biomass was also harvested from Potato Dextrose Broth (26.75mg) while minimum biomass was obtained from Sterilized tap Water (3.15mg). Among seven different temperatures, 25ºC has given maximum colony diameter (88.40mm) at 7 days after inoculation and minimum (5.10mm) at 10ºC. Between 5.5 to 7 pH range is the best for Rhizoctonia solani growth, optimum growth was found at 6 pH.