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 pl ant nurseries and potting mix suppliers, were screened for ability to control damping-off disease caused by Pythium ultimum var. sporangiife rum. The screening was by two bioassays on seedlings of Capsicum annuu m grown in a pasteurized potting medium in a glasshouse or controlled environment growth chamber. Three isolates reduced damping-off at leas t as much as the fungicide propamocarb. The fungicides tolclofos-methy l and benomyl did not reduce disease or increase shoot weights. In oth er glasshouse experiments, binucleate Rhizoctonia isolates BNR1 and BN R2 reduced damping-off in Capsicum seedlings more as doses of each ant agonist were increased. In pasteurized potting medium without added pa thogens, isolates BNR1 and BNR2 increased dry weights of Capsicum shoo ts per punnet by 33 and 24%, respectively, compared with only 13% for the bacterium, Bacillus subtilis A13. Isolates BNR1 and BNR2 completel y controlled damping-off in seedlings of Celosia argentea, but propamo carb and B. subtilis did not.