Impact of agro-ecological areas on the distribution of aspergillus section flavi in maize in Benin

Abstract

Maize is the first cereal grown in the world and adapted as a food crop in sub-Saharan Africa. In Benin,
it is the leading cereal crop with nearly 70% of the cereal area sown. But the post-harvest storage
conditions of these cereals favour the development of moulds and mycotoxins. Previous work has
revealed Aspergillus flavus and aflatoxins in stored maize, naturally occurring substances that are
carcinogenic to humans. The objective of this work is to evaluate the contamination of maize in storage
by agro-ecological area. To do this, the study had collected 50 samples from différents agro-ecological
zones in Benin. On them, evaluated aflatoxin contamination by HPLC-PDA, determined total fungal flora
by direct culture and aflatoxinogenic nature of strains of Aspergillus Flavi by culture in différents media
and thin layer chromatography. At the end of this work, 30.43% of the samples collected are
contaminated by aflatoxins with an average of 6,41µg/kg. Contaminated samples were taken from agroecological zones 1, 3, 5 and 6 with mean aflatoxins levels of 1.88 µg/Kg; 5.81 µg/Kg; 8.38 µg/Kg and 9.59
µg/Kg respectively. Mycological analysis revealed five fungal genre : Aspergillus (53.38%), Fusarium
(23.31%), Penicillium (17.29%), Rhizopus (2.26%) and Mucor (1.50%). By agro-ecological zone, a
similarity is noted with regard to the total fungal flora. Of the 67 strains of Aspergillus Flavi isolated, 65
are aflatoxin-producing and the highest incidence found in agro-ecological zone 6 followed by zone 5.
The contamination of maize stored in Benin by aflatoxins and the various subspecies of the Flavi
section follows a distribution by agro-ecological zone due to different climatic conditions. The
production of a distribution map of pathogenic strains by speculation could help to monitor the
evolution of the quality of agricultural products.