Screening and characterization of antibiotic producing bacteria from rhizospheric soil against fungal phytopathogens

Abstract

In this study, antagonistic bacteria were isolated from rhizospheric soil collected from Himachal Pradesh (i.e., Solan and Hamirpur) and Punjab (i.e., Jalandhar and Pathankot). Sixty- eight bacteria were isolated and screened for antifungal activity against Botrytis oryzae, Aspergillus flavus, and Fusarium oxysporum. Three isolates, i.e., S7, S57, and S51, showed maximum inhibition for antifungal activity by using the agar streak method and were further selected for in vitro characterization. In vitro antifungal antibiotic study by using agar diffusion assay of isolates, i.e., S7, S57, and S51 at O.D. 2.0 showed maximum inhibition of 99% against Botyritis oryzae, Fusarium oxysporum, and Aspergillus flavus after seven days of incubation. Antibiotic assays using cell-free supernatant of antagonistic bacterial isolates, i.e., S7 and S57, showed complete inhibition at 10% against Botyritis oryzae and Fusarium oxysporum, whereas isolate S51 showed complete inhibition at 20% against Aspergillus flavus. The bacterial isolates were partially identified based on morphological and biochemical characteristics. The selected antagonistic bacterial isolates S7 and S57 appeared to be similar to Bacillus sp. and S51 to Actinomycete sp. Thus, the present study concludes that these bacterial isolates could serve as proficient biocontrol inoculants in the integrated management of soil-borne diseases in different crops under natural environmental conditions.