Mycotoxin contamination and its impact on the nutritional and germination quality of on-farm stored sorghum grain in Tigray, Ethiopia

Abstract

Mycotoxin contamination of on-farm stored sorghum poses a critical yet often overlooked threat to food safety, nutrition, and seed security in Tigray, northern Ethiopia. This study assessed the occurrence of four major mycotoxins: total aflatoxins (AFT), fumonisins (FUM), deoxynivalenol (DON), and ochratoxin A (OTA), and their relationships with storage conditions, nutritional composition, and germination in 360 sorghum samples from six districts. Aflatoxins, fumonisins, deoxynivalenol, and ochratoxin A were detected in 80.3%, 82.2%, 63.3%, and 77.5% of samples, respectively, with 41.7–63.3% of positive samples exceeding Ethiopian or European regulatory limits. Contamination increased with storage duration, peaking in grain stored for 10–12 months in traditional structures (underground pits, Gombisa, Godo), which were warmer and more humid than polypropylene bags. Melkam, Kodem, Meko, and Dengele varieties accumulated more mycotoxins than Aba'are and Dekeba. Total aflatoxin concentrations varied by location, storage duration, and storage type (p < 0.001), with the highest level recorded in Alamata (19.6 ± 1.3 μg/kg), and followed by Endamehoni and Hintalo Wajirat. The lowest concentrations were found in Ofla, Raya Azebo, and Wukro, with levels statistically similar among these three locations. Higher mycotoxin levels and kernel infection were associated with elevated temperature, relative humidity, and grain moisture, along with declines in protein, fat, and starch contents and significant reductions in germination. By 12 months of storage, sorghum showed marked deterioration in nutritional quality and seed viability, implying that grain retained for both food and planting becomes progressively compromised. These results indicate that multi-mycotoxin contamination in on-farm stored sorghum is widespread in Tigray and warrants integrated mitigation. Based on the findings, safer sorghum storage in Ethiopia should prioritize rapid drying to safe moisture before storage, avoiding high-humidity traditional structures where feasible, using improved storage options, and promoting lower-risk varieties as part of local seed and food safety strategies. • On-farm sorghum often contains aflatoxins, fumonisins, DON, and OTA exceeding Ethiopian and EU limits in 42-63% of samples. • Warm, humid conditions (28.6 °C, 67.7% RH) and 14.5% moisture significantly increase fungal infection and mycotoxin accumulation. • Contamination levels vary by district and variety, indicating strong influences from both environment and genotype. • Higher mycotoxin and mold levels are associated with reduced protein (27%), fat (33%), starch (18%), and germination (36%).