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

Preharvest Sprouting (PHS) is the germination of grain on the mother plant under cool and wet conditions.  Even mild sprouting can cost farmers money, because it causes lower Falling Numbers (FN) due to starch degradation by alpha-amylase.  Low FN grain produces poor quality bread and cakes.  Breeding for good sources of PHS tolerance can help prevent problems with low FN.  This study evaluated PHS-related traits on 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 two PHS-related traits: 1) spike wetting tests and 2) Falling Numbers (FN).  Daily sprouting scores over 7 days and sprouting rates were recorded for the spike wetting test.  A mixed model analysis was used to obtain BLUPs for the spike wetting tests and raw means were calculated for the FN test.  These PHS-related traits were analyzed across four different environments and used to determine loci association.  Association mapping was conducted using the FarmCPU algorithm in R.  Three principal components that were likely made up from end-use class and breeding program of origin were used as covariates.  Five significant QTL were associated with FN on chromosomes 1B, 2B, 3B, 4A, and 5A.  Fifteen significant QTL were associated with the spike wetting test on chromosomes 1B, 2A, 2D, 3A, 3B, 4A, 4B, 5A, 5B, and 6B.  Significant correlations were found between FN environments and between spike wetting test environments.  However, correlations were not as significant or strong when comparing FN to spike wetting tests.  The grain value depends on having low PHS and high FN, and our identification of loci associated with each trait is critical to improving grain quality.