Screening Maize Tropical-Derived Lines and NAM Founders for Gametophytic Alleles: Risk Assessment and New Opportunities.

Maize gametophyte factors form the backbone of dent-sterile popcorns, and have recently been employed as a means of preventing genetically modified (GM) pollen from contaminating organic grain. However, the allele system used, Ga1, is overcome by an allele, Ga1-m, at the locus once thought rare, but that has recently been shown to be prevalent in tropical maize. This allele, if present in a US commercial hybrid, would result in a complete failure of the dent-sterile system for popcorn seed production and GM contamination in both popcorn and supposedly protected organic hybrids. To further complicate the problem, Ga1-m is only detectable by specific evaluation resulting in the unintentional release of several lines containing the allele from the NC State Corn Breeding Program. With this in mind, we screened the NAM founder lines, a selected set of Germplasm Enhancement of Maize (GEM) lines, and several popular tropical inbred lines for the presence of the Ga1-m allele to assess the risk posed to current gametophytic systems by use of tropical germplasm. We additionally screened the NAM founders for gametophytic alleles at other loci in an attempt to identify potential candidates for a replacement system without a prevalent “m-type” allele. We identified…