South Asian Journal of Research in Microbiology

Microbial antagonism occurs across a spectrum of interactions, ranging from direct to indirect mechanisms. Direct antagonism involves physical contact and/or highly selective targeting of pathogens by biocontrol agents, whereas indirect antagonism arises from activities that do not require pathogen recognition, such as nutrient competition or production of inhibitory metabolites. The present study explores the antagonistic potential of isolated Fusarium spp. against soil-borne fungus Rhizoctonia solani with a view to recommending these isolates as bio-control agents in agricultural fields which would eventually lead to better production of crops. Laboratory experiments were conducted to explore the antagonistic potential of selected Fusarium spp. against soil-borne phytopathogen Rhizoctonia solani. A total of nine Fusarium isolates belonging to four genera viz., F. equiseti, F. solani, F. oxysporum and F. chlamydosporum were tested for their ability to inhibit the growth of Rhizoctonia sp. in dual culture. The isolates were recovered from different agricultural fields of Murshidabad district and identified by routine morphological studies and molecular analysis. Non-pathogenic nature of the isolates was also proven by increased germination percentage and vigour index in the inoculated chickpea, black gram mustard, cucumber, chilli and paddy seeds. All the isolates tested positive for siderophore production and ammonia production necessary for antagonism against the pathogenic soil fungus. The percentage of inhibition varies from 58 to 85 in dual culture with Rhizoctonia sp. Interestingly, the most potent Fusarium solani SF0204 was found to inhibit the growth of the pathogen under different carbohydrate concentrations.  Maximum antagonism was observed in the absence of dextrose, indicating the Fusarium isolate was more competitive than the fungal pathogen.