Hydrolytic genes of antagonistic rhizobacteria strains on Fusarium udum causing wilt disease in pigeonpea

Abstract

Pigeaonpea is attacked by various diseases, including the wilt disease of pigeonpea caused by Fusarium udum. This disease is a severe pathogen to this crop. This study aims to identify the potential biocontrol agent against wilt disease as a fungicide alternative. Forty-seven isolates were evaluated for antagonistic activity against F. udum by dual culture method. Interaction of F. udum and antagonistic bacteria was studied in potato dextrose agar (PDA) under in vitro conditions and lysis of fungal hyphae was observed by using Scanning Electron Microscope. Dry weight of F. udum mycelium was recorded after 3 days of co-inoculation with the rhizobacteria in PDB. Potential antagonistic bacterial isolates were further used for enzymatic assay in vitro conditions. Molecular characterization of bacteria was done by using primers based on hydrolytic genes like chitinase and 1,3-glucanase related genes, amplified at 402 and 750 bp, respectively. Out of forty-seven bacterial isolates used to assess their antagonistic activity, only eight isolates, viz., Bacillus amyloliquefaciens CFLB 31, Bacillus velezensis CFLB 24, Bacillus subtilis CFLB 11, Stenotrophomonas rhizophila CFLB 26, S. matalophila CFLB 47, Microbacteria sp. CFLB 28, G.nicotiana CFLB 18 and Pseudoarthrobacter sp. CFLB 36 showed the promising antagonistic activity against F. udum with 70–84% inhibition in a dual culture plate assay. Among them, three Bacillus species (B. amyloliquefaciens, B. velezensis, B. subtilis) and S. maltophilia CFLB 47 were found to be the most effective biocontrol agent against F. udum under in vitro conditions. Lysis of fungal hyphae was also noted during interaction of fungus and bacteria on PDA. These isolates were screened for production of hydrolytic enzymes activities and they showed positive for production of pectinase, protease and cellulase under in vitro conditions. These isolates amplified chitinase and β-1, 3-glucanase-related genes at 402 and 750 bp, respectively. In addition, bacterial strains reduced the mycelium weight of F. udum with the range of 58.42 − 86.84% during co-inoculation in PDB. However, B. amyloliquefaciens had the highest percentage of biomass reduction, up to 86.84%. Bacterial treatments are considered beneficial and nature-friendly. The results propose that the eight potential strains and their hydrolytic enzymatic properties made them promise to manage wilt disease of pigeonpea.