Occurrence of toxigenic Aspergillus and Fusarium species and associated mycotoxins in at-harvest and post-harvest maize (Zea mays L.) from selected districts of Ethiopia

Abstract

Maize ( Zea mays L.) contamination by mycotoxins represents a major threat to food safety and economic stability in Ethiopia. This study investigated the occurrence of toxigenic fungi and multi-mycotoxin contamination in 180 maize samples collected across three critical value chain stages (at-harvest, three-month storage, and six-month market) from four districts: Bako Tibe, Ilu Galan, Boricha, and Halaba Special. Mycological analysis revealed Fusarium and Aspergillus as the dominant genera, with Fusarium verticillioides prevailing at harvest (42.8% mean incidence) and Aspergillus flavus dominating during storage (53.6% mean incidence) as moisture content declined from 21.5 to 13.5%. LC-MS/MS analysis detected Fusarium toxins in 73.9% of samples, with fumonisin B 1 (FB 1 ) reaching 6,570  μ g/kg at harvest before declining during storage. In contrast, deoxynivalenol (DON) and zearalenone (ZEN) levels increased progressively from harvest to market, with ZEN prevalence rising from 21.7 to 93.3% and a mean concentration of 100 ± 317  μ g/kg. Maximum ZEN (3,140  μ g/kg) surpassed the EU regulatory limit of 100  μ g/kg, while aflatoxin B 1 remained below detectable risk thresholds (max 0.72  μ g/kg). Spatial variation was evident across districts: Boricha exhibited the highest pre-harvest FB 1 contamination (80%), whereas Bako Tibe showed a pronounced post-harvest ZEN escalation (13.3 to 100%). Halaba Special recorded a toxic cocktail of 100% ZEN and 86.7% DON prevalence at the market stage. Widespread occurrence of CIT was observed, reaching 60% in Boricha and 53.3% in Bako Tibe market samples. The co-occurrence of multiple mycotoxins was common across all stages. Therefore, mycotoxin mitigation strategies both under field conditions and post-harvest stages, including improved storage technologies and drying practices, require urgent intervention to address food safety concerns in the studied areas and at the national level.