Advancing Germplasm with Improved Agronomics and Pyramided Tolerance to Aflatoxin in Multi-Parent Populations.

Developing resistant germplasm is the ideal way to reduce or eliminate the accumulation of aflatoxins in maize (Zea mays L.). Mycotoxins produced by the fungus Aspergillus flavus, are harmful to humans and animals. Large economic losses are associated with aflatoxin-contaminated maize in upwards of $500 million annually. In order to combat this issue through genetic improvement, many QTL have first been identified in public maize inbreds. Most detected QTL have accounted for less than 5% of total variation with one locus accounting for greater than 15%; this has shown to be repeatable. Using MAS, we can attempt to pyramid these small effect QTL and SNP associations into a single inbred, which could result in a stable tolerant parent. Towards this, eight low-susceptibility parents were crossed in different mating designs to generate progeny for validation and breeding. From LH195 testcrosses of lines pulled from these populations, yield data were collected on first year early generation yield trials of 224 four-way and 132 eight-way hybrid crosses. Current data analysis against commercial checks hybrids compared for yield, maturity, and height characteristics are underway. Concurrently, ongoing evaluation of approximately 280 individual inbreds per se for aflatoxin tolerance and inbred yield per se is also underway. Selection of genotyped individuals with the most beneficial collected QTL and GWAS SNP associations will advance to further evaluation. Many inbred lines were identified that are tolerant in differing environments. All lines contain some amount of tropical germplasm. This germplasm tends to be late, tall, and prone to lodging causing difficulty when introducing into a breeding program. Creation of an early maturing, stable, high yielding, appropriately statured phenotype would offer more opportunities to include tolerant germplasm into established breeding programs, but aflatoxin levels still must be improved.