| Accumulation of the potent carcinogen, aflatoxin, in maize poses a significant health risk to humans and animals. Most commercially grown maize lines are susceptible to infection by the fungus that synthesizes aflatoxin, and toxin levels can accumulate to dangerously high levels under the influence of environmental factors---such as drought, heat, and insect damage---that are typical of many corn growing regions. Aflatoxin levels can also be modulated by the type and amount of sugar in the kernels and by the presence of reactive oxygen species (ROS) and antioxidants. How these factors interact to control aflatoxin levels is poorly understood.;The objective of this research was to identify new sources of low aflatoxin maize germplasm and to discover underlying genetic mechanisms leading to low aflatoxin accumulation in maize. Aflatoxin levels were quantified in a large set of diverse maize lines in three locations---Missouri, Georgia, and Mississippi. As expected from previous studies, lines with tropical origins were found to have low aflatoxin levels, but temperate sources of low aflatoxin were also identified. Stiff stalk, popcorn, and sweet corn lines were not good sources of low aflatoxin. Correlations were sought between aflatoxin levels and a suite of previously defined, agronomically important traits for the diversity lines. Significant correlations were found for brace root traits, ear and plant height, and flowering time. A search for associations between aflatoxin levels and DNA sequence polymorphisms for genes involved in various kernel and plant architecture traits revealed significant associations for haplotypes of brittle2, dwarf3, and Dwarf8 (D8). Kernel reactive oxygen species (ROS) levels were not correlated with aflatoxin at 25 days after pollination, but significant correlations were found between aflatoxin and carotenoid levels. Significant associations between aflatoxin levels were identified in genes---anthocyaninless1, colorless2, and white pollen1---encoding antioxidants from the flavonoid pathway. Together, the results of these studies identify new sources of low aflatoxin germplasm and suggest avenues for further investigation of factors that regulate aflatoxin accumulation. |
