Study of Antimicrobial Compounds of Bacillus subtilis (PSB5) and its Interaction with Fungicides against Fusarium oxysporum f. sp. gerberae

Objectives: To study the antifungal activity of Bacillus spp. against Fusarium oxysporum f. sp. gerberae (FOG) and studies of interaction between Bacillus subtilis (PSB5) and commercially active fungicides against FOG. Methods: Extraction of crude antibiotics (PSB5, BSD5, BmTNAU1) was done by continuous precipitation and acidification to pH 2.0 using solvent ethyl acetate and further subjected to GC/MS analysis (PSB5). Bioassay of these extract against the pathogen (FOG) was done by Agar Diffusion method. The control employed was ethyl acetate alone in the media. Further the compatibility test was done by Poisoned food technique. Findings: The crude antibiotic extracts (PSB5, BSD5, BmTNAU1) were highly effective against the FOG probably due to the presence of antimicrobial compounds in strain PSB5 detected through GC/MS. Moreover, the test of compatibility of PSB5 with fungicides revealed the growth promotion of the bacteria at lower dosages of fungicides alone. The most effective fungicide, tebuconazole 250 EC(Score) against FOG showed compatibility at moderate dosage (250 ppm) with the highly efficient strain of bacteria, PSB5. Application: In our present study, we tried to emphasize on the efficacy of antifungal activity of Bacillus spp. and compatibility interactions of antagonistic bacteria and fungicides which could be utilized for further field experiments against FOG.