In vitro activity of neem oil [Azadirachta indica A. Juss (Meliaceae)] on Aspergillus flavus growth, sporulation, viability of spores, morphology and Aflatoxins B1 and B2 production

The effectiveness of neem (Azadiracta indica) oil on the growth, morphology, sporulation, viability of spores, aflatoxin B1 and B2 production by A. flavus on Yeast Extract-Sucrose medium was determined. Neem oil inhibited the fungal growth (i.e. mycelia dry weight, diameter of colony and growth rate) on solid media at concentrations from 0.5 to 5.0% v/v, although it significantly increased sporulation in the same conditions. Spores obtained from cultures grown without neem oil reduced germination when incubated in a neem oil supplemented medium. Colonies grown on solid media and in submerged cultures in the presence of neem oil exhibited morphological alterations, including granular cytoplasm, atypical hyphae branching pattern, abnormal and undifferentiated conidiophores. High Performance Liquid Chromatography was used to measure aflatoxins. In submerged cultures, neem oil at concentrations from 0.5 to 4.0% v/v caused approximately 95% inhibition in Aflatoxin B1 and B2. On other hand, these conditions failed to suppress fungal growth. Current research emphasized that neem oil was not fungistatic or fungicidal, but exhibited anti-aflatoxigenic activity.