Antimicrobial peptides producing native Bacillus spp. for the management of root-knot nematode Meloidogyne incognita infecting okra (Abelmoschus esculentus L. Moench)

Abstract

In the present study, native strains of Bacillus species were isolated, characterized and evaluated for their biocontrol efficacy in laboratory, pot and field conditions to combat Meloidogyne incognita incidence in okra (Abelmoschus esculentus L. Moench). Based on the laboratory results, two Bacillus spp., Bacillus marisflavi CRB2 and Bacillus subtilis CRB7 were found most effective against M. incognita. We also profiled antimicrobial peptide (AMP) genes associated with this two Bacillus spp. Bacillus marisflavi CRB2 was found to harbour 10 AMP genes whereas, B. subtilis CRB7 had 8 AMP genes with the expression of 3 and 4 genes, respectively at the RNA level. Talc based formulation of B. marisflavi CRB2 and B. subtilis CRB7 were evaluated under pot and field conditions for the management of M. incognita in okra. Bacillus marisflavi CRB2 and B. subtilis CRB7 at dose of 5 g plant−1 were found most effective against M. incognita by reducing the nematode incidence in okra under pot conditions. Further, field application of either Bacillus marisflavi CRB2 and B. subtilis CRB7 as a combination of seed treatment 20 g kg−1 seed + soil application (5 kg ha−1) of enriched vermicompost (2 t ha−1) + soil drenching @ 1% at 30 days interval showed a significant reduction of M. incognita incidence in okra and also increased yield as compared to untreated control. Their bioefficacy was comparable with carbofuran 3G (1 kg a.i. ha−1) treatments. Thus, the native strains B. marisflavi CRB2 and B. subtilis CRB7 having diverse antimicrobial peptide genes can be used as one of the components in the integrated nematode management strategy to combat M. incognita incidence in okra.