Aspergillus flavus is the most common causal agent of aflatoxin contamination of food and feed. However, aflatoxin-producing potential varies widely among A. flavus genotypes with many producing no aflatoxins. Some non-aflatoxigenic genotypes are used as biocontrol agents to prevent contamination. Aflatoxin biosynthesis genes are tightly clustered in a highly conserved order. Gene deletions and presence of single nucleotide polymorphisms (SNPs) in aflatoxin biosynthesis genes are often associated with A. flavus inability to produce aflatoxins. In order to identify mechanisms of non-aflatoxigenicity in non-aflatoxigenic genotypes of value in aflatoxin biocontrol, complete cluster sequences of 35 A. flavus genotypes from Africa and North America were analyzed. Inability of some genotypes to produce aflatoxin resulted from deletion of biosynthesis genes. In other genotypes, non-aflatoxigenicity originated from SNP formation. The process of degeneration differed across the gene cluster; genes involved in early biosynthesis stages were more likely to be deleted while genes involved in later stages displayed high frequencies of SNPs. Comparative analyses of aflatoxin gene clusters provides insight into the diversity of mechanisms of non-aflatoxigenicity in A. flavus genotypes used as biological control agents. The sequences provide resources for both diagnosis of non-aflatoxigenicity and monitoring of biocontrol genotypes during biopesticide manufacture and in the environment.

This study assessed the mycological and aflatoxin contamination of peanuts collected from Kinshasa, DRC and Pretoria, South Africa. Forty peanut samples were collected randomly at informal markets in the two cities and analysed for mycoflora and aflatoxins (B1, B2, G1 and G2) using standard methods. The results indicated that 95% and 100% of peanut samples collected from Kinshasa and Pretoria, respectively were contaminated with aflatoxigenic fungi with Kinshasa’s samples being the most contaminated (up to 49, 000 CFU/g). Seventy percent (70 %) of Kinshasa-samples and 35% of Pretoria-samples exceeded the maximum allowable limit of aflatoxin B1 set by JECFA (5 ppb). Statistical evidence showed a significant positive correlation between mycoflora and aflatoxin level for Kinshasa-samples (r = 0.4743, p < 0.005) while Pretoria-samples showed no correlation. The study reveals that high level of contamination in Kinshasa-samples could be due to the tropical nature of the climate and poor storage conditions as compared to Pretoria which is sub-tropical and sanitary regulations are enforced. / Life & Consumer Sciences / M. Sc. (Life Sciences)

This study assessed the mycological and aflatoxin contamination of peanuts collected from Kinshasa, DRC and Pretoria, South Africa. Forty peanut samples were collected randomly at informal markets in the two cities and analysed for mycoflora and aflatoxins (B1, B2, G1 and G2) using standard methods. The results indicated that 95% and 100% of peanut samples collected from Kinshasa and Pretoria, respectively were contaminated with aflatoxigenic fungi with Kinshasa’s samples being the most contaminated (up to 49, 000 CFU/g). Seventy percent (70 %) of Kinshasa-samples and 35% of Pretoria-samples exceeded the maximum allowable limit of aflatoxin B1 set by JECFA (5 ppb). Statistical evidence showed a significant positive correlation between mycoflora and aflatoxin level for Kinshasa-samples (r = 0.4743, p < 0.005) while Pretoria-samples showed no correlation. The study reveals that high level of contamination in Kinshasa-samples could be due to the tropical nature of the climate and poor storage conditions as compared to Pretoria which is sub-tropical and sanitary regulations are enforced. / Life and Consumer Sciences / M. Sc. (Life Sciences)