Characterization of Potentially Mycotoxigenic Fungi Associated with Cowpea (Vigna unguiculata L. Walp) Seeds from Ogun West Markets

Cowpea grains stored under sub-optimal conditions are highly susceptible to fungal infection, resulting in significant post-harvest losses, grain quality degradation, and consumer health risks due to mycotoxin contamination. This study performed a morphological identification of seed-borne fungi associated with cowpea grains from major markets in Ogun West Senatorial District, Nigeria, and assessed the occurrence of mycotoxigenic and biocontrol fungal species. Thirty-six cowpea seed samples were randomly collected from retailers across three major Local Government Areas. Fungi were isolated on Czapek Dox Agar and identified by examining morphological characteristics, with emphasis on the known toxigenic nature of the isolates. Eleven fungal species belonging to seven fungal genera were identified. Significantly, the potentially mycotoxigenic species Fusarium verticillioides, F. oxysporium, Aspergillus flavus, and A. niger showed the highest occurrence (100% incidence across locations). Other high-incidence species included Aspergillus tubingensis and Rhizopus stolonifera (91.67%), while the known hyper-parasite and potential biocontrol agent, Trichoderma sp., was also isolated (41.67%). The high prevalence of well-known potential mycotoxin producers (e.g., Aspergillus spp. and Fusarium spp.) in marketed cowpea seeds highlights a critical food safety concern in the region. This characterization establishes a baseline for further genomic and metabolomic analyses of these Nigerian strains, which is essential for developing targeted post-harvest biocontrol strategies utilizing indigenous Trichoderma isolates or engineering crops with enhanced resistance. The specific fungal profiles identified, particularly the high frequency of A. flavus and F. verticillioides, are instrumental for developing cost-effective, high-throughput qPCR assays for early detection. This would enable market regulators in Ogun West to rapidly screen cowpea batches for high-risk contamination before visual symptoms appear.