Field evaluation of maize genotypes for resistance to pre-harvest Aspergillus ear rot and aflatoxin contamination under natural inoculation in Eastern and Northern Tanzania

Résumé

Maize, a staple for billions of people, is highly vulnerable to aflatoxin contamination caused by Aspergillus flavus . Aflatoxins pose serious threats and risks to food safety, public health, and trade. This study aimed to evaluate and identify superior maize genotypes as potential sources of resistance for sustainable breeding programmes focused on high yield and aflatoxin resistance, ultimately reducing aflatoxin exposure. Twelve (12) genotypes were evaluated under natural aflatoxin-prone conditions using a 4 × 3 alpha lattice design across three locations: Ilonga-Kilosa, SUA-Morogoro, and Kirusix-Babati. Phenological, agronomic, and yield-related data were collected, and harvested ears were visually scored for Aspergillus ear rot (AER). Aflatoxin levels in kernels were analysed using Ultra High-Performance Liquid Chromatography (UHPLC). Genotype (G) and environment (E) significantly influenced ear rot (ER), grain moisture (GM), and field weight (FW) (p < 0.05). G × E interactions were significant for ER and GM but not FW. Grain yield ranged from 1.63 to 5.54 t/ha (mean: 3.59 t/ha), with SUA recording the highest yield and lowest aflatoxin levels. Aflatoxin contamination varied from 0.16 to 14.34 µg/kg (mean: 4.225 µg/kg), with 50% of samples exceeding the EU safety limit of 4 µg/kg. Correlations between aflatoxin levels and agronomic traits/parameters related to aflatoxin contamination differed across environments, highlighting strong genotype and environmental effects. Principal Component Analysis (PCA) identified plant height, ear height, and flowering time as key contributors to aflatoxin contamination. These findings emphasise the need for breeding high-yielding, AER-resistant genotypes with reduced aflatoxin levels to enhance maize productivity and food safety.

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