Occurrence of aflatoxins and fumonisins in preharvest maize from south-western Nigeria

A survey was conducted on the incidence of fungi, and the natural occurrence of aflatoxins and fumonisins in preharvest maize from fields in south-western Nigeria. Mycological examinations revealed the predominance of F. verticillioides ( Zea mays ) (syn. F. moniliforme ), occurring in 89.3% of samples with a mean kernel infection of 49.4%, while Aspergillus flavus was isolated from 65% of samples having a mean kernel infection of 6.8%. Aflatoxin B-1 was detected in 18.4% of samples with a mean of 22 mug kg(-1) , while aflatoxins B-2 , G(1) and G(2) were present in 7.8, 2.9 and 1% of the samples with mean levels of 10, 8 and 7 mug kg(-1) , respectively, in contaminated samples. Total aflatoxins ranged from 3 to 138 mug kg(-1) in positive samples, with a mean of 28 mug kg(-1) . Fumonsin B-1 was the predominant toxin detected in terms of frequency (78.6% of samples) and quantity (concentration range 70-1780 mug kg(-1) , mean = 495 mug kg(-1)). Fumonisin B-2 was detected in 68 samples (66%) with a mean of 114 mug kg(-1) . Fifteen samples were contaminated with both aflatoxins and fumonisins.