INVESTIGATION OF FUMONISIN LEVELS IN MAIZE GRAIN COLLECTED FROM AGRO-ECOLOGICAL ZONES OF NIGERIA

Abstract

Fungi cause kernel rots of maize grain in the field and in storage, and Fusariumis the most important genus of the field fungi. Strains of F. moniliforme and F. proliferatum produce toxic metabolites known as fumonisins. F. moniliforme is a frequent contaminant of maize grain in Nigeria, but information on fumonisin in maize grain in West Africa is only available from Benin. This study was undertaken to identify Fusarium spp. and determine the levels of fumonisin in maize grain from farmers’ stores in Nigeria. Maize grain samples from farmers’ stores in three ecological zones of Nigeria were analysed for mould contents using the direct agar plating technique and fumonisin contamination using analytical High-Performance Liquid Chromatography (HPLC) methods with detection limits of 20ng/g. The first sampling involved taking maize grain that was between one and four months in stores, while samples for the second survey were taken when the maize grain had been in stores for not less than six months.  The predominant genera of fungi isolated in all the agro ecological zones were Fusarium, Aspergillus and Penicillium. In the maize grains stored for one to four months, the mean levels of fumonisins were 1.25, 0.91 and 0.78 ppm in the rain forest, Guinea savannah and Sudan savannah respectively. In maize grains that were stored above six months, the mean fumonisin levels were 0.71, 0.73 and 0.65 ppm respectively. These results revealed that maize grain consumers across all the ecological zones of Nigeria are exposed to the risk of fumonisin toxicoses. Furthermore since aflatoxins have been found to be unavoidable contaminants of Nigerian maize grain, this study could show that consumers are likely exposed to multiple mycotoxins, the interactive effect of which is still poorly understood, the synergistic or additive effect of mycotoxin combinations could be applied.