In vitro antagonistic activity and phylogeny of plant growth-promoting bacteria native to Western Ghats of Karnataka, India

Abstract

Isolates from rhizosphere and endorhizosphere niches of Western Ghats, Karnataka were assessed for antagonistic activity against major fungal and bacterial plant pathogens. The isolates exhibited varying potential of cyanogenesis, siderophorogenesis, volatile antimetabolites and indole acetic acid production. Antimetabolites viz., phenazine, phloroglucinol and pyrrolnitrin from endorhizospheric pseudomonads and a Rhizobium sp. were found active against test plant pathogens in vitro; indicating the involvement of multiple mechanisms and crosstalk between the antimetabolite producers. Phylogenetic analysis of isolates revealed polyphyletic separation into 3 major groups: alphaproteobacteria, gammaproteobacteria and bacteroidetus. The study sheds light on the ecology of these isolates with innate broad-spectrum antagonistic activity, thus obviating the need for introducing genetically modified organisms.