Isolation and Molecular Characterization of Fungi Associated with Maize from Five Farms in Osogbo, Osun State, Nigeria

Abstract

Maize (Zea mays L.) is a vital staple in Nigeria, yet tropical conditions frequently promote fungal contamination in stored grains. This study isolated and characterized fungi from 15 maize samples across five farms in Osogbo, Osun State, Nigeria, using phenotypic and molecular techniques. Morphological characterization of isolates, particularly the predominant Aspergillus spp., revealed rapid to moderate growth with colors ranging from olive-green to black and textures varying from granular and powdery to velvety or cottony. These surface variations reflect the specific arrangement and abundance of conidial structures. To achieve definitive taxonomic resolution, the concentration and purity of extracted genomic DNA were assessed using a NanoDrop spectrophotometer, ensuring samples were contaminant-free (A260/A280 ≈ 1.8) for downstream PCR amplification. Molecular analysis of the Internal Transcribed Spacer (ITS) region confirmed eleven distinct species, including Aspergillus flavus, A. niger, and Fusarium solani, with 100% homology to NCBI sequences. Fungal growth rates ranged from 1.3 ± 0.06 to 4.5 ± 0.21 cm/week, with the highest contamination observed at Ejigbo Farm. The study highlights significant food safety concerns due to widespread contamination by fungi in the region and underscores an urgent need for improved post-harvest handling, enhanced storage infrastructure, and regular surveillance programs to safeguard public health.