ANTAGONISTIC ACTIVITIES OF Bacillus amyloliquefaciens FROM PHYLLOSPHERE OF SUGAR BEET AGAINST Cercospora beticola sacc.

Abstract

Sixteen isolates of Bacillus amyloliquefaciens isolatedfrom phyllosphere of sugar beet leaves were tested for its antagonistic activity against Cercospora beticola the causal agent of sugar beet leaf spot disease. The tested isolates showed a significant antagonistic potential against C. beticola in vitro. The inhibition of the radial growth of the pathogen ranged from 77.8% to 90%. The diffusible metabolites and volatile gases produced by B. amyloliquefaciens dramatically inhibited the pathogen growth. The antifungal proteins (AFP) extracted from culture filtrates showed an antagonistic effect on the pathogen and inhibition zones ranged from 8.17 mm to 16.45 mm. The antifungal metabolites (AFM) produced by the tested B. amyloliquefaciens isolates showed a high thermal stability. The activity of the AFM at pH 3.0 upto 5.0 reduced by 20% and started to increase at pH 6.0 then reached its maximum at pH 7.0. All the tested isolates produced Sidrophores and β1,3,glucanase while only three isolates were able to produce chitinase. In the greenhouse experiments, the AFM and bacterial cells treatments decreased the severity of cercospora leaf spot. It was found that the treatments with AFM or bacterial cells before inoculation with the pathogen was more efficient than the treatments after inoculation with the pathogen. This may be the first report on using B. amyloliquefaciens as a biocontrol agent against C. beticola