Evaluating Parental Genotypes in the Maize Nested Association Mapping (NAM) Population for Reduced Aflatoxin and Fumonisin Contamination

Aspergillus flavus and Fusarium verticillioides produce highly carcinogenic mycotoxins including aflatoxins and fumonisins resulting in significant losses to the US maize industry each year. Genetic mapping studies have struggled to identify markers associated with reduced mycotoxin traits in maize across multiple environments. To address this and increase mapping resolution beyond traditional biparental populations, we examined the parental founder lines used for the USDA Nested Association Mapping (NAM) population for reduced mycotoxin contamination. In 2022-2024, these parental lines were grown alongside resistant checks in Georgia and Mississippi. The lines were inoculated with A. flavus in both locations and inoculated with F. verticillioides only in Mississippi while natural infections were used in evaluations in Georgia. Aflatoxin results significantly differed by genotype and year, ranging from 0 to 12,000 ppb. Fumonisin results ranged from 0 to 110 ppm, but significant differences were only seen in Georgia. B73, the common parent in the NAM, was very susceptible to contamination by both mycotoxins. Among the unique founders, many were poorly adapted to the Southern US and had poor agronomic performance. However, CML322, CML247, and NC358 accumulated significantly less aflatoxin and fumonisin in both locations and years with levels comparable to resistant checks. Members of NAM families derived from these founders will be selected as a “Mini-NAM” to be examined in both locations for fine mapping of aflatoxin and fumonisin resistance-associated markers and genes.