Genome wide analysis of Ga1-s modifiers in maize

A one way reproductive barrier exists between most popcorn varieties and dent corn varieties grown in the United States. This barrier is predominantly controlled by the Ga1 locus. Using data from a diverse population of popcorn accessions pollinated by a dent corn tester, we found that the non-reciprocal pollination barrier conferred by ga1 is more complex than previously described. Individual accessions ranged from 0% to 100% compatible with dent corn pollen. Using conventional genotyping-by-sequencing data from 371 popcorn accessions carrying Ga1-s , seven significant modifiers of dent pollen compatibility were identified on five chromosomes. One locus may either be a nonfunctional ga1 allele present within popcorn, or second necessary gene for the reproductive barrier in genetic linkage with ga1 , while the other modifiers are clearly genetically unlinked. The existence of ga1 modifiers segregating in a popcorn genetic background may indicate selective pressure to allow gene flow between populations, which should be incorporated into future models of the impact of genetic incompatibility loci on gene flow in natural and agricultural plant populations.