Diversity of fumonisin-producing Aspergillus and Fusarium species in maize collected in South Africa

Abstract

Maize(Zea mays L.) is a major crop grown all over the world, and it is a staple in the diets of millions of people, particularly in Africa. Fusarium and Aspergillus fungal species are reported to be associated with maize ear rot in South Africa. The most common and frequently isolated maize ear rot pathogen is Fusarium verticillioides, which can produce fumonisins that can be harmful to humans and animals. Aspergillus niger has recently been reported to cause maize ear rot and it can produce fumonisin B2 which can have adverse health implications on humans and animals. Maize samples were collected from subsistence farmers in five provinces namely Eastern Cape, KwaZulu-Natal, Limpopo, Mpumalanga, and North-West in South Africa. The morphological characterization, Sanger DNA sequencing, and phylogenetic analysis of Fusarium and Aspergillus were investigated in this study. Fumonisin levels were quantified using Enzyme-Linked Immunosorbent Assay (ELISA). The production of fumonisin B2 by Aspergillus spp. Isolates was analyse using Ultra-High-Performance Liquid Chromatography (UHPLC) and Quadrupole Time-Of-Flight (QTOF) -High Resolution Mass Spectrometry (HRMS). The results indicate F. verticillioides is major species isolated in maize. Based on morphological and molecular identification, Six Aspergillus species were identified belonging to section Nigri (A. niger; A. tubingensis; A. brasiliensis and A. welwitschiae) and section Flavi (A. flavus and A. parasiticus). Sample from KwaZulu-natal had high concentration of fumonisin that exceeded maximum allowable of 2000 µg/kg set by the department of health in South Africa. Five strains of A. niger appear to produce fumonisin B2 in Yeast Extract Sucrose Agar. The production of fumonisins by Fusarium and Aspergillus spp., serious health implications on small-scale farmers and their community because of the high-level exposure to fumonisins. The study has addressed understanding of maize ear rot associated with Fusarium and Aspergillus spp., and fumonisin contamination levels from subsistence farmers in South Africa.