Identification of plant growth promoting Rhizosphere Bacillus sp. WG4 antagonistic to Pythium myriotylum and its enhanced antifungal effect in association with Trichoderma

Among the various rhizospheric bacterial isolates screened from Westren Ghat regions of Kerala, a Bacillus sp. with both antagonistic activity to Pythium myriotylum and plant growth promoting properties was identified. Scanning electron microscopic analysis revealed significant ultrastructural changes of hyphae and spores of P. myriotylum upon treatment with Bacillus sp.WG4. For the structural characterization of antagonistic compound in the crude exract, GC MS analysis was carried out and this has resulted in the identification of presence of pyrrolo [1,2- a] pyrazine-1,4-dione, hexahydro-3-(phenylmethyl) as basis of antifungal activity. The in vivo antifungal activity of Bacillus strain was analysed by pre-inoculation of this to ginger rhizome. Here the presence of Bacillus strain was found to provide effective protection to ginger rhizome upon inoculation with Pythium myriotylum. Very interestingly, when the Bacillus strain was checked for its synergistic antifungal activity with commercially available biocontrol agent Trichoderma, the combination was found to have increased antifungal activity. Due to its antifungal and growth enhancement effects, the isolated strain can be of promising application as antifungal plant probiotic agent alone or in combination with other agents like Trichoderma.