Antagonistic effect of the newly isolated PGPR Bacillus spp. on Fusarium oxysporum

Soil borne plant pathogens cause annual economic losses in most of the crops. In nature microbial interactions involve competition, hyper parasitism or antibiosis and these phenomena play an important role in striking ecological balance and keeping several plant pathogens in check. It is observed that plant growth promoting rhizobacteria (PGPR) influence the growth and yield of many plants. In this study, isolates of Bacillus, one of the important PGPR, were isolated from different rhizosphere soils. Seven isolates of B. megaterium JUMB1, JUMB2, JUMB3, JUMB4, JUMB5, JUMB6 and JUMB7 were screened in vitro for their plant growth promoting traits like production of indole acetic acid (IAA), ammonia, HCN, phosphate, siderophore and evaluated for the ability to suppress fusarial growth. All the isolates were able to produce IAA, ammonia, HCN and siderophore but none of the isolates solubilized phosphorous. Production of IAA and siderophore was highest in the isolate JUMB3 (127 μg/ml and 124% respectively) and lowest in JUMB7 (35μg/ml and 44% respectively). In-vitro screening for antagonism against F. oxysporum revealed significant inhibitory effects on mycelial radial growth by all the seven isolates. Among seven isolates JUBM5 showed highest inhibition of 3.25, 0.22 and 0.21 cm in well diffusion, streak and point inoculation method respectively.