2018 journal article
Identification of M-Type Gametophyte Factors in Maize Genetic Resources
CROP SCIENCE, 58(2), 719–727.
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Added: August 6, 2018
Maize (Zea mays L.) gametophyte factors are the basis of dent sterile popcorns, where they are used to prevent pollen contamination from dent corns and have been proposed as useful for protection of other specialty types. Current gametophytic systems rely entirely on the strong allele of Gametophyte Factor 1 (Ga1‐s) to impart the selective barrier needed in these hybrids. This allele, however, is naturally overcome by another allele at the same locus (Ga1‐m), which is only detectable by specific evaluation, allowing it to go undetected in breeding lines, thus creating a scenario with substantial risk to Ga1‐s hybrids. Other gametophytic systems exist but have parallel allelic structure with possibly parallel risks, especially from m‐type alleles. By screening a set of maize genetic resources, we assessed the risk posed by the Ga1‐m allele. We identified the allele in several populations readily useful for expanding the genetic base of commercial maize, including several Germplasm Enhancement of Maize lines. To examine the possible distribution of m‐type alleles at other key gametophytic loci, we screened the maize nested association mapping population founder lines for the presence of m‐type gametophytic alleles, identifying 19 previously unreported m‐type gametophytic alleles in these lines. Our results also highlight the frequent concomitancy of gametophytic alleles at different loci, the full interactions of which are ignored by standard phenotyping methods that consider individual loci, confounding allele status determination. We provide a method for determining allele status at multiple gametophytic loci and highlight the implications of concomitant alleles, especially Ga1‐m and Tcb1‐m, on the possible deployment of new barrier systems.