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Title: Diversity of aflatoxin-producing fungi and their impact on food safety in sub-Saharan Africa

Author
item PROBST, CLAUDIA - University Of Arizona
item BANDYOPADHYAY, R - International Institute Of Tropical Agriculture (IITA)
item Cotty, Peter

Submitted to: International Journal of Food Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/3/2013
Publication Date: 3/17/2014
Citation: Probst, C., Bandyopadhyay, R., Cotty, P.J. 2014. Diversity of aflatoxin-producing fungi and their impact on food safety in sub-Saharan Africa. International Journal of Food Microbiology. 174:113-122.

Interpretive Summary: Mycotoxins are toxic fungal metabolites that damage human health and reduce the profitability of agriculture. In order to develop management tools for limiting contamination, it is necessary to identify the fungi that cause the majority of mycotoxin contamination and to determine the regions which require mycotoxin management. Mycotoxin contamination of maize has been a problem in portions of Africa over the past decade. As part of efforts to identify the causal agents of mycotoxin contamination in Africa, we examined the fungi and the mycotoxins contaminating maize in 18 sub-Saharan African nations. The results show that mycotoxins are very common in African maize contaminating almost 50% of maize with unacceptable concentrations. The causal agents varied across the contentment. These results suggest Africa is in great need of mycotoxin management and that different biological control agents may provide the best mycotoxin management in different portions of Africa.

Technical Abstract: Crops frequently contaminated by aflatoxins are important sources of revenue and daily nourishment in many portions of sub-Saharan Africa. In recent years, reports have associated aflatoxins with diminished human health and export opportunities in many African Nations. Aflatoxins are highly carcinogenic metabolites mainly produced by members of Aspergillus sect. Flavi. The current study examined aflatoxin-producing fungi associated with maize grain intended for human consumption in 18 sub-Saharan African countries. The majority (75%) of isolates belonged to the L strain morphotype of A. flavus. Minor percentages were A. tamarii (6%), A. parasiticus (1%), and isolates with S strain morphology (3%). Phylogenetics resolved S strain isolates producing only B aflatoxins into two lineages fully supported by the size of deletions in the gene region spanning the aflatoxin biosynthesis genes cypA and norB aflatoxin biosynthesis genes. One lineage was the A. flavus S strain with either 0.9 or 1.5 kb deletions. The second lineage,recently described from Kenya, has a 2.2kb deletion. Taxa with S strain morphology differed in distribution with strain SBG limited to West Africa. African A. flavus L strain isolates formed a single clade with L strain isolates from other continents. The sampled maize frequently tested positive for fumonisins (81%), aflatoxins (65%), and deoxynivalenol (40%) indicating presence of fungi capable of producing the respective toxins. Percentage of samples exceeding regulatory limits for total fumonisins, aflatoxins, and deoxynivalenol were 49%, 47%, 4%, respectively.