Efficacy of Antifungal Metabolites of Bacillus spp. for Controlling Tomato Damping-off Caused by Pythium aphanidermatum

A total of 4 strains of bacteria were isolated from the leaf surface of the rambutan using a tissue transplanting technique. They were characterized, by a dual culture test, for their efficacy to inhibit mycelial growth of Pythium aphanidermatum, a causal agent of the damping-off on tomato. All 4 strains significantly inhibited mycelial growth of P. aphanidermatum on potato dextrose agar (PDA) at room temperature (27 °C). B-NST-02 and B-NST-03 gave values of inhibition of 62.0 % and 57.5 %, respectively. All strains were identified as Bacillus spp. Antifungal metabolites extracted from all 4 strains were tested at 1,000 mg/l. Tomato seedlings treated in the laboratory with metabolites from B-NST-03 and B-NST-02 showed germination of 85.5 % and 82.0 %, respectively. Under glasshouse conditions, seedling treated with metabolites from B-NST-03 and B-NST-02 provided seed germination rates were 92.5 % and 92.0 %, respectively, while the controls treated with either sterile water or 2 % methanol had only 28.0 % and 26.5 % seed germination rates, respectively. In P. aphanidermatum viability test, mycelia of P. aphanidermatum treated with antifungal metabolites from 4 strains of Bacillus spp. showed no visible growth, while the control with sterile water or 2 % methanol, mycelia of P. aphanidermatum rapidly grew and covered the whole surface of the PDA in the Petri dish within 5 days