CULTURE OF RHIZOCTONIA-SOLANI AND BINUCLEATE RHIZOCTONIA SPP ON ORGANIC SUBSTRATES FOR INOCULATION OF SEEDLINGS IN CONTAINERS

New culture and inoculation techniques were developed for use in experiments requiring incorporation of Rhizoctonia solani Kuhn AG 4, AG 8 and binucleate Rhizoctonia spp into small volumes of soil in seedling containers. Three organic substrates with small particles (millet seed, wheat bran and pulverized rice hulls) were sieved, washed, sterilized and inoculated with Rhizoctonia. After about 2 weeks, colonized substrates were air-dried and frozen for later use as inoculum. The inocula were mixed with pasteurized potting medium, and the mixes were placed in punnets for bioassay with seedlings of Capsicum annuum L. Rice hulls and wheat bran were deemed to be suitable substrates for culture and delivery of R. solani and binucleate Rhizoctonia spp because particles became thoroughly colonized, small doses could be uniformly incorporated into a potting medium, and the fungal colonists subsequently infected seedlings. Small increases in dose of R. solani inoculum caused large increases in disease; therefore millet seeds inoculated with R. solani were considered too large to obtain even distribution and acceptable disease levels in small seedling containers.