Antagonistic activity of cowshed Bacillus sp. bacteria against aflatoxigenic and sclerotic Aspergillus flavus

Abstract

Mycotoxins produced by many food spoilage fungi cause serious damage to human as well as to livestock. Aflatoxins are one such group of mycotoxins produced by Aspergillus flavus in many agricultural and food products including rice. The fungus can virtually grow in any environment and also produces resistive structures such as sclerotia to overcome unfavourable environmental conditions. Hence, the need of the time is to control this toxigenic and sclerotic fungus through an eco-friendly approach. In the current study four biocontrol bacteria belonging to Bacillus species were isolated from Indian cow shed environment and these bacteria could efficiently control not only the mycelia growth of A. flavus but also the germination and growth of sclerotia. Both active bacterial culture broth and cell free culture filtrate could limit the growth of the fungus up to more than 90%. Older culture broth and filtrate lost their inhibition efficiency. Unlike many similar studies the current investigation emphasizes the importance of cowshed environment instead of cow dung and the control of sclerotia instead of fungal spores.

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“…Many Bacillus species isolated from cow dung have also been reported to possess antagonistic activity against many plant pathogens including Fusarium. Subsequently, the cow shed air which is saturated with these useful Bacillus bacteria might also be a selective source for exploration of antagonistic bacteria [18]. However, no study has been conducted elsewhere to explore this possible source for the isolation of antagonistic bacteria against Fusarium pathogens infecting rice and producing fumonisin mycotoxin.…”

“…Sampling was carried out from two sources: from the cowshed air and from rice/paddy stored inside cowshed. Bacteria from cowshed air were isolated following passive air sampling method by exposing Potato Dextrose Nutrient Agar media (PDNA) plates to cattle shed air for one minute and then incubating at 30°C for 24 hours [18,19]. The bacteria associated with seeds or grains were isolated by blotter method [20].…”

“…Various native bacterial species especially belonging to Bacillus species have been found be very effective against both pathogenic and toxigenic Fusarium species [14][15][16][17][18]. These Bacillus species have been isolated from soil and other agro-ecosystems which is a very common source.…”

“…These Bacillus species have been isolated from soil and other agro-ecosystems which is a very common source. Many such Bacillus bacteria have been isolated from cowshed air and from rice seeds stored in cowshed environment which could control the vegetative growth of aflatoxigenic Aspergillus flavus and other pathogenic fungi [18,19]. However, no study has evaluated the antagonistic potential of Bacillus species and other bacteria from cowshed environment for the biological control of toxigenic and pathogenic Fusarium species in rice.…”