Evaluation of commercial maize hybrids for Aspergillus ear rot resistance and aflatoxin accumulation under natural and artificial inoculation conditions.

Aspergillus ear rot (AER) and aflatoxin contamination in maize threaten global food security and public health, with developing countries such as Bangladesh-where maize cultivation is rapidly expanding-being particularly vulnerable. This study evaluated the resistance of 25 commercially available maize hybrids to AER infection and aflatoxin accumulation under natural infection (field exposure without artificial inoculation) and artificial inoculation conditions. Hybrids were artificially inoculated using a toxigenic Aspergillus flavus strain (ES103) via the pin bar inoculation method to ensure uniform infection. Disease severity, kernel infection rates, and aflatoxin levels were assessed using standardized protocols. Significant variation was observed among hybrids, with disease severity ratings ranging from 5 to 7 on a 7-point scale, and no hybrid showed complete resistance. The hybrid 'Mohabeer' exhibited the lowest kernel infection rate (42.59%), the second-lowest total aflatoxin levels (536.31 ng/g total, 115.63 ng/g AFB1), and the lowest disease severity (5). In comparison, 'Uttoron Super' showed the highest infection rate (87.04%), accompanied by high disease severity (7) and aflatoxin accumulation (2,397.43 ng/g total). Artificial inoculation increased aflatoxin levels by over 90% compared to natural infection conditions. Husk tightness is generally considered a physical barrier to natural infection, a strong positive correlation (r = 0.82) was identified between husk tightness index (HTI) and aflatoxin accumulation, suggesting that looser husks (higher HTI) are associated with greater aflatoxin accumulation after infection. In contrast, no correlation existed between aflatoxin levels and yield performance. These findings demonstrate widespread susceptibility among commercial maize hybrids to AER and aflatoxin contamination, emphasizing the critical need for integrated pre- and post-harvest management strategies and informed hybrid selection in high-risk areas.