Quantitative Trait Loci Influencing Grain Hardness in Hard Red Spring Wheat Breeding Lines MN98550 and MN99394.

Wheat kernel hardness has profound effects on milling and baking quality traits. Flour from hard wheats absorbs more water during baking and results in increased loaf volume. Quantitative trait loci (QTL) affecting kernel hardness were mapped in hard red spring wheat breeding lines adapted to the Upper Midwest region of the United States. Mapping was conducted using a population of 139 recombinant inbred lines (RILs) developed from the MN98550 x MN99394 cross. Lines grown at three Minnesota locations in 2006 were tested for hardness using the single kernel characterization system (SKCS). RILs were genotyped with SSR and DArT markers. The final genetic map was comprised of 536 SSR and DArT markers. The previously known hardness (Ha) locus on chromosome 5DS explained 16 to 22% of the total phenotypic variation in hardness in all three environments. The puroindoline specific markers at the hardness locus were previously reported by several groups and are already in use in breeding programs. In this study, a second QTL, detected on chromosome 5A, explained 6 to 13% of the total phenotypic variation. The 5A QTL also coincided with a grain protein QTL. A QTL on chromosome 1A explained 7 to 17% of the total phenotypic variation. Two more QTL on chromosomes 2A and 5B were only detected in two of the three locations and explained up to 7 and 15% of the variation, respectively. Availability of molecular markers linked to QTL for endosperm texture will be useful in increasing the frequency of desirable alleles and also for selecting increased hardness among hard wheats in early generations of breeding populations.