Profiling and Molecular Identification of Fungi Isolated From Maize Cultivated in Different Agroecological Zones in Nigeria

Abstract

This study investigated the fungal distribution on maize across Nigeria's diverse agroecological zones. A total of 270 maize samples were collected from farms (90), markets (90), and storage facilities (90) from all seven agroecological zones in the country. The fungal strains were identified at the species level using conventional identification techniques, molecular methods, and phylogenetic analysis. The results showed that the highest fungal loads were recorded in the Sahel savanna (SHS), Sudan savanna (SS), and northern Guinea savanna (NGS) zones, with NGS showing peaks above 4 0 × 106 CFU/g, particularly in farm and store samples. Lower fungal loads were observed in the mid altitude, derived savanna (DS), and humid forest (HF) zones, with median values mostly below 5 0 × 105 CFU/g. Notably, the variability and presence of outliers were more pronounced in the SHS, SS, and NGS zones, indicating inconsistent contamination levels. A total of 986 fungal isolates were obtained from across the different agroecological zones. The fungi strains were grouped into 10 fungal genera, namely, Aspergillus sp. (42. 87%), Fusarium sp. (33.50%), Penicillium sp. (18.32%), Rhizopus sp. (3.46%), Absidia sp. (0.5%), Mucor sp. (0.5%), Curvularia sp. (0.3%), Microsporum sp. (0.1%), Alternaria sp. (0.1%), and Cladosporium sp. (0.1%). The molecular-based identification of some of the isolates revealed the presence of new species in the crop, Talaromyces sayulitensis, Aspergillus montevidensis, Epicoccum sorghinum, Aspergillus piperis, Exserohilum rostratum, and Tyrophagus putrescentiae. The studies demonstrated a high prevalence of mycotoxin-producing fungi, particularly from the genera Aspergillus, Fusarium, and Penicillium, which pose serious health risks due to their potential to contaminate food supplies with harmful toxins like aflatoxins and fumonisins.