Managing aflatoxin – producing fungi using indigenous atoxigenic strains of aspergillus species in groundnut in Mtwara region, Tanzania

A Dissertation Submitted in Partial Fulfillment of the Requirements for the Degree of Master`s in Life Sciences of the Nelson Mandela African Institution of Science and TechnologyThe present study was conducted from January to October 2018 in Mnanje, Mpeta and Naliendele villages to determine aflatoxin levels in dried groundnut kernels, to identify toxigenic and atoxigenic strains of Aspergillus section Flavi from soil samples and to test the effect of atoxigenic strains against aflatoxin-producing fungi in groundnut. Isolation of fungi was done on MRBA and AFPA media and analysis of aflatoxin levels in groundnut was conducted using HPLC. The results showed that, there was significant differences (p < 0.05) in total aflatoxins level between groundnut samples. Eleven (24.4%) out of 45 samples had aflatoxin levels above the Tanzania Food and Drugs Authority’s standard (10 μg/kg). Total aflatoxin contamination levels ranged from higher i.e. 5.86 to 16.81 μg/kg at Mnanje village to lowest at Mpeta village (0.05 to 15.02 μg/kg). The results also indicated that 20.4% of the fungal composition in soil samples were toxigenic strains while 79.5% were atoxigenic implying that these strains can be exploited for biological control to mitigate aflatoxin contamination risks in groundnuts. This was proved through the study that also indicated that total aflatoxin levels in groundnut kernel samples were lower in atoxigenic treated groundnut plots than in controls plots. Thus, there is need to conduct further studies involving a wide geographical location on testing the efficiency of the atoxigenic strains identified in this study for further characterization and formulation of a bio-control against aflatoxin producing- fungi in Tanzania