The Influence of Benomyl on Penicillin Production and Rhizosphere Organisms

Aims: To evaluate the antimicrobial effects of benomyl (a systemic fungicide) on penicillin production and rhizosphere organisms of cowpea plant. Study Design: 3 factor factorial experiment. Place and Duration of Study: Department of Microbiology, Federal University of Technology, Akure, Nigeria, 2006. Methodology: Complementary plate and pot experiments were designed to achieve these objectives. Bioassay methods such as the agar cup plate and the agar plug techniques were used to examine the metabolic fitness of Penicillium italicum and Penicillium oxalicum for penicillin production when cultured in agar medium with varying concentrations of benomyl. The pot experiment was also carried out to determine the effect of 0.8g of benomyl on the microbial load of 1.5kg of rhizosphere soil of cowpea. Results: Biological assay predominantly shows that benomyl at different concentration has the ability to impair the metabolic and mitotic activity of Penicillium species mentioned above. This development resulted in the inhibition of penicillin and other allied metabolites. It was discovered that there was a reduction in the microbial load of rhizosphere soil containing benomyl and the fungicide was incriminated to be responsible for it. Conclusion: Certain species of bacteria and fungi that predominated in the rhizosphere soil sample without benomyl were either few or absent in the sample with benomyl.