Genome-wide Association Mapping of Preharvest Sprouting Traits in PNW White Winter Wheat

Preharvest sprouting (PHS), the germination of grain on the mother plant under cool and wet conditions, is a reoccurring problem for wheat farmers worldwide.  PHS susceptibility can lead to degradation of starch granules which results in low Falling Numbers (FN).  Low FN grain produces poor quality bread and cakes.  PHS susceptibility is also associated with lower seed dormancy.  Too much seed dormancy can result in poor seedling emergence of winter wheat when grain is planted approximately 8 weeks after harvest.  Association mapping can help increase breeding efforts towards PHS tolerance by identifying genetic loci contributing to PHS-related traits in PNW germplasm.  This study evaluated a panel of 469 white winter wheat cultivars and elite breeding lines.  The panel was genotyped using the 90k SNP Illumina iSelect array and 25,968 polymorphic markers were identified.  PHS tolerance was examined using three PHS-related traits: 1) spike wetting tests, 2) falling numbers, and 3) emergence.  A mixed model analysis was used to obtain BLUPs for all of the PHS-related traits over 2-3 environments in Washington State and also to determine loci association.  Association mapping was conducted using the GAPIT R package.  In order to account for the presence of population structure, principal component and kinship matrix analyses were conducted and incorporated. The panel had three kinship groups based on the end-use class and breeding program of origin.  Novel loci identified in this study can improve PHS tolerance in a breeding program through marker assisted selection.