Investigating the Role of Microbiologicals (Bacillus Species) in the Biodegradation of Residues of Chemical Fungicides

Abstract

This work investigated the feasibility of finding bacteria able to degrade chemical fungicides and also act as biofungicides. Accordingly, bacterial isolates from samples of plant material from sites where fungicide trials had been carried out with multiple sprays of one fungicide were cultured. Enhanced growth of isolates in the presence of the fungicide was sought in screening tests. This resulted in six isolates from Revysol® sites and 9 from boscalid sites being selected for identification and further characterization. All the strains identified were from the Genus Bacillus (B. megaterium, B. velenzensis, and B. licheniformis) and all were in the lowest risk group. Following the selection of isolates for identification, the growth dynamics of the selected isolates in the absence of any fungicide were examined, and the growth curves obtained were attributed to one of the three typical curves. The isolates segregated into these growth curve types consistent with the species identification. Despite the initial assumption, the degradation ability of the bacterial isolates was not fungicide specific. Furthermore, the enhanced growth of the isolates was restricted to a certain range of fungicide concentrations, with an optimum of 5 ppm for all four fungicides. The selected isolates identified as B. velenzensis functioned particularly well as biofungicides, significantly inhibiting the growth of all three fungal pathogens (Botrytis, Cercospora, and Sclerotinia) tested. Furthermore MBI 600 the commercial biofungicide, in addition to showing biofungicide activity on all three pathogens as expected also demonstrated the capacity to degrade all four of the fungicides used in this study.