The effects of climatic variability on the occurrence of Aspergillus species in commercial maize from different agro-climatic regions in South Africa

Abstract

Most African research reports on the frequent aflatoxin contamination of various foodstuffs, with few reports giving details of the Aspergillus species present in these commodities. Numerous research works provide evidence of the ability of fungi to grow, thrive, and interact with other crop species and focus on the fact that these processes are largely affected by climatic variables. As opposed to the attention directed to the above-mentioned themes, information on the biodiversity of Aspergillus species in maize in most African countries, including South Africa, is lacking. This study on Aspergillus species in maize serves to close that gap in that it attempts to establish a comprehensive and most recent picture of the biodiversity of Aspergillus species in South African (SA) commercial maize across the respective climatic regions. Thus, it sets out to predict changes in the distribution of these fungal species, their contamination effects on maize variety as well as to identify and differentiate the aflatoxigenic Aspergillus strains from the non-aflatoxigenic ones under changing climate scenarios across the respective agro-climatic regions of South Africa. By applying molecular methods, a total of 1028 maize samples from six distinct agro-climatic regions, namely, Western Free State (WFS), Eastern Free State (EFS), Northern Free State (NFS), Southern Free State (SFS), North-West (NW), and Gauteng Province (GP) were examined for contamination by the Aspergillus species. About 29.67 % of the maize samples were contaminated by at least one of the eight Aspergillus species that were isolated in this study. Less than 30 % (28.95 %) of the 228 isolates subjected to the aflatoxigenic test was found to possess at least one of the aflatoxin biosynthetic genes. In all, the occurrence of the Aspergillus species (especially Aspergillus fumigatus) in SA commercial maize are significantly influenced (P < 0.0001) by maize variety, year of cultivation as well as the agro-climatic region in which the maize is cultivated.