Fusarial wilt control and growth promotion of pigeon pea through bioactive metabolites produced by two plant growth promoting rhizobacteria.

The bioactive metabolites produced by two plant growth promoting rhizobacteria strains, a Pseudomonas aeruginosa strain RRLJ 04 and a Bacillus cereus strain BS 03, which showed growth promotion and disease control in pigeon pea against Fusarium udum, were isolated and screened for their efficacy to control fusarial wilt of pigeon pea under gnotobiotic and nursery condition. Bioactive metabolites viz., BM 1 and BM 2 from RRLJ 04 and BM 3 from BS 03 also showed in vitro antibiosis against F. udum. Seeds treated with 50 μl seed⁻¹ of BM 1, 30 μl seed⁻¹ of BM 2 and 70 μl seed⁻¹ of BM 3 and grown in pathogen infested soil showed suppression of wilt disease besides growth enhancement. Per cent disease control was 90 % with BM 2 application as compared to 87 and 83 %, respectively in BM 1 and BM 3 after 90 days of growth. BM 2 treated plants were more resistant to the pathogen as compared to the other fractions tested. Mycelial dry weight was found to be reduced on treatment with the bioactive metabolites. Formation of chlamydospore-like structures was observed in the pathogen mycelium treated with BM 3. The analytical studies confirmed that two of these metabolites are phenazine derivatives.