Fungal infection and mycotoxin contamination of maize in the Humid Forest and the Western Highlands of Cameroon

Fungal incidence and mycotoxin contamination of farm-stored maize were asse ssed and compared in grain samples from three villages each in two agroecol ogical zones over time. Maize samples were collected at 2 and 4 months afte r stocking from 72 farmers' stores in 1996 and 1997 in the Humid Forest (HF ) and Western Highlands (WHL) of Cameroon. Mycological assays of these samp les revealed several fungal species. Nigrospora spp. were the most prevalen t fungi in HF (32%) and WHL (30%) in 1996, Fusarium verticillioides (22%) a nd F. graminearum (27%) were also isolated from these samples. In the WHL i n 1996, no significant difference in fungal incidence was found among villa ges for samples collected 2 months after harvest, but at 4 months incidence was significantly higher (P<0.05). In 1997 the levels of fungal contaminat ion were lower than in 1996. The incidence of Aspergillus spp. was low in g eneral, ranging from 0.0 to 5.9% infected kernels. Analysis with thin layer chromatography detected low levels of aflatoxins in a few samples. f. vert icillioides mycotoxin fumonisin B-1 (300-26,000 ng/g) and F graminearum met abolites deoxynivalenol (<100-1,300 ng/g) and zearalenone (<50-110 ng/g) we re determined by means of polyclonal antibody competitive direct enzyme-lin ked immunosorbent assay. A significant correlation (r=0.72; P=0.0001) was f ound between the incidence of F graminearum and the contamination with deox ynivalenol. Storage time (2 vs 4 months after stocking) had a significant p ositive effect (r=0.39; P=0.013) on the level of fumonisin B-1. This is the first report of the natural occurrence of these mycotoxins in maize in Cam eroon.