Fine Mapping of the Maize Cross‐Incompatibility Locus Gametophytic Factor 1 (ga1) Using a Homogeneous Population

Abstract

ABSTRACTPhenotyping of a mapping population is usually the bottleneck that limits the size of the mapping population and mapping resolution. A homogeneous population mapping approach was used for mapping maize (Zea mays L.) gametophytic factor 1 (ga1) that could completely eliminate phenotyping during the mapping process. The strong allele of maize ga1 (Ga1‐S), from popcorn inbred line SDGa25, showed a 100% cross‐incompatibility with the majority of Chinese dent and flint maize. A homogeneous mapping population was developed by crossing an (SDGa25/Jing66) F1 male back to an SDGa25 female. During the pollination process, pollen grains of ga1 were completely excluded from fertilization, and a homogeneous BC1F1 (SDGa25//SDGa25/Jing66) population was created in which only the Ga1‐S/Ga1‐S genotype existed, making phenotyping unnecessary. A total of 2245 individuals of this population were genotyped with SD9 and SD12 markers and 20 recombinants were identified. The Ga1‐S locus was quickly delineated to a 100 Kb region between markers dCS1 and insertion deletion ID7 at position 9,491,422 and 9,591,946 bp based on the B73 RefGen_v2 sequence. By marker‐assisted selection, Ga1‐S was introgressed into parental lines of an elite white waxy maize hybrid by six generations of backcrossing and one generation of selfing. The homozygous Ga1‐S/Ga1‐S hybrid showed full cross‐incompatibility to ga1 maize. The Ga1‐S allele could be used as a biological reproductive barrier in reducing cross‐pollination between different types of maize such as waxy and non‐waxy, genetically modified (GM) and non‐GM maize.