Genome-wide association study identifies QTL and candidate genes for grain size and weight in a Triticum turgidum collection.

Wheat breeders are constantly looking for genes and alleles that increase grain yield. One key strategy is finding new genetic resources in the wild and domesticated gene pools of related species with genes affecting grain size. This study explored a natural population of Triticum turgidum (L.) phenotyped for grain weight and size-related traits in three field trials and genotyped with single nucleotide polymorphism markers spread across the entire genome. The genome-wide association study analysis identified 39 quantitative trait loci (QTL) for 1000-kernel weight, grain length, grain width, grain area, and grain aspect consistent in at least two and across environments. Interestingly, 23 QTL for grain-related traits were grouped in nine QTL clusters located on chromosomes 1A, 1B, 2B, 3B, 4B, 5A, and 6B, respectively. Moreover, most of these QTL support findings from previous QTL analyses and are further strengthened by the known functions of the genes (such as BG2, GS5, and SRS3) and their similarity to genes in other cereal species. QTL clusters harbored genes that participate in various metabolic processes potentially involved in seed development, phytohormone signaling, sugar transport, mitogen-activated protein kinases signaling, and transcriptional factors (such as MADS-box and WRKY). Identifying loci controlling grain-related traits will provide information on the genetic resources available to breeders to improve grain yield, as well as the opportunity to develop close gene markers to be used in marker-assisted selection programs.