Twenty-one rice samples from field (ten), store (six) and market (five) from the traditional rice-growing areas of Niger State, Nigeria were analysed for aflatoxins (AFs), ochratoxin A (OTA), zearalenone (ZEA), deoxynivalenol (DON), fumonisin B1 (FB1) and B2 (FB2), and patulin (PAT) by thin-layer chromatography (TLC) and high-performance liquid chromatography (HPLC) respectively. T-2 toxin was determined using TLC only. AFs were detected in all samples, at total AF concentrations of 28–372 μg/kg. OTA was found in 66.7% of the samples, also at high concentrations (134–341 μg/kg) that have to be considered as critical levels in aspects of nephrotoxicity. ZEA (53.4%), DON (23.8), FB1 (14.3%) and FB2 (4.8%) were also found in rice, although at relatively low levels. T-2 toxin was qualitatively detected by TLC in only one sample. Co-contamination with AFs, OTA, and ZEA was very common, and up to five mycotoxins were detected in a single sample. The high AF and OTA levels as found in rice in this study are regarded as unsafe, and multi-occurrences of mycotoxins in the rice samples with possible additive or synergistic toxic effects in consumers raise concern with respect to public health.

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The study reports on the natural occurrence of fungi in 21 samples of field (10), stored (6) and marketed (5) rice (Oryza sativa L.) collected from Niger State, Nigeria. Fungal isolates were primarily identified based on morphological characteristics, while representative isolates were characterized genetically. An evolutionary tree was constructed from the resulting sequences of the isolated fungi. The toxigenic potentials of some of the isolated fungi were also determined. A total of 357 fungal isolates of nine genera including Aspergillus, Fusarium, Sarocladium, Acremonium, Curvularia Botryosphaeria, Penicillium Alternaria and Ascomycota in decreasing order of predominance were identified. The most frequent fungal contaminants of the rice samples were A. flavus, A. fumigates, A. niger, A. parasiticus and F. proliferatum. All strains of A. flavus (aflatoxins B1 and B2), A. parasiticus (aflatoxins B1, B2, G1 and G2), A. ochraceus (ochratoxin A), F. proliferatum and F. verticillioides (fumonisins B1 and B2) tested, were excellent producers of their respective mycotoxins. Patulin was produced by A. terreus, whereas deoxynivalenol, zearalenone and T‐2 toxin were produced by F. chlamydosporum and other Fusarium spp. The increased prevalence of toxigenic fungi in rice, a highly consumed food grain in Nigeria, poses serious health concerns to the general public. PRACTICAL APPLICATIONS This study investigated the natural fungal occurrence of rice grown in Nigeria using polymerase chain reaction‐based techniques as well as the toxigenic potentials of some of the identified fungi. The resultant fungal profile of rice, gene sequences of the fungi detected in the survey, which were deposited in the GenBank and the constructed evolutionary tree, will serve as reference data for the incidence of fungal species in rice and will help to evaluate the safety of Nigerian rice. It could be used in developing and predicting the degree of mycotoxin contamination in rice from Nigeria for effective mycotoxin control. The toxigenic fungi acquired from the work will be excellent microbial sources for production of mycotoxin standards namely aflatoxins BI, B2, G1 and G2, ochratoxin A and fumonisin B1 and B2.