BINUCLEATE RHIZOCTONIA ISOLATES CONTROL DAMPING-OFF CAUSED BY PYTHIUM-ULTIMUM VAR SPORANGIIFERUM, AND PROMOTE GROWTH, IN CAPSICUM AND CELOSIA SEEDLINGS IN PASTEURIZED POTTING MEDIUM

Eight isolates of binucleate Rhizoctonia spp, from South Australian plant nurseries and potting mix suppliers, were screened for ability to control damping-off disease caused by Pythium ultimum var. sporangiiferum. The screening was by two bioassays on seedlings of Capsicum annuum grown in a pasteurized potting medium in a glasshouse or controlled environment growth chamber. Three isolates reduced damping-off at least as much as the fungicide propamocarb. The fungicides tolclofos-methyl and benomyl did not reduce disease or increase shoot weights. In other glasshouse experiments, binucleate Rhizoctonia isolates BNR1 and BNR2 reduced damping-off in Capsicum seedlings more as doses of each antagonist were increased. In pasteurized potting medium without added pathogens, isolates BNR1 and BNR2 increased dry weights of Capsicum shoots per punnet by 33 and 24%, respectively, compared with only 13% for the bacterium, Bacillus subtilis A13. Isolates BNR1 and BNR2 completely controlled damping-off in seedlings of Celosia argentea, but propamocarb and B. subtilis did not.