In vitro studies on the potential for biological control of Fusarium verticillioides by Bacillus subtilis

LILIA CAVAGLIERI Y MIRIAM ETCHEVERRY

San Pablo (Brasil)

Congreso; X International IUPAC Symposium on mycotoxins and mycotoxins; 2000

Instituto Adolfo Lutz

The purposse of this work was to obtain a strain of Bacillus able to exert antagonistic activity on fumonisin producing fungi isolated from soil pre-harvested maize. Ten strains of Bacillus subtilis were characterized to determine their ecophysiology behaviour under water eand thermal stress. In order to estimate niche similarity between these strains of B. subtilis and Fusarium verticillioides in an ecologically significan resource dimension, in vitro carbon source utilization profiles were compared and niche overlap indices (NOI) were derived. Following these experiments a strain of B. subtilis with capacity of competition in the same niche overlap of F. verticillioides was selected. The effect on germination, growth and fumonisin B1 production in culture medium was determined. Ten stains of B. subtilis had growth at all water activities (0.93, 0.95, 0.98, 0.99) and temperatures (20, 25, 30°C) assayed. Only one strain utilized the patterns of carbon/nitrogen sources found in maize, showing that this strain of B. subtilis and F. verticillioides have ecological similarity. B. subtilis demonstrated competition to the same ecological niche. When the ten strains were assayed to determine the influence over lineal growth of F. verticillioides on corn meal agar, 50% of the strains demonstrated inhibition in relation to fumonisin B1 production, it was observed that when water activity decreased, the number of strains that inhibited the fumonisin B1 production was greater. On the basis of the behaviour on growth and fumonisin production, a strains of B. subtilis was selected to assay the effect on germination. A decrease of germination was observed at high water activity. On the basis of these experiments, this strain of B. subtilis will be studied to determine the antifungal metabolite and the potential use of the compound as fungicide.