Genetic architecture of yield-component traits in the new perennial grain crop, intermediate wheatgrass

Abstract

Intermediate wheatgrass [Thinopyrum intermedium (Host) Barkworth & D.R. Dewey] (IWG) is a perennial, cool-season grass species currently undergoing direct domestication as one of the first perennial grain crops. To domesticate and improve this obligately outcrossing allohexaploid (2n = 6x = 42), breeders are using both phenotypic- and genomic-assisted recurrent selection methodologies. Thus far, efforts have focused primarily on improving domestication traits and yield, but breeders are limited by the relatively narrow understanding of the genetic control of these traits. An IWG nested association mapping (NAM) population with 1,168 F1 progeny from 10 families was grown in four unique growing environments (St. Paul, MN, and Salina, KS, in 2017 and 2018) and evaluated for a series of 11 yield-component traits. Using a population-specific genetic map and 8,003 single-nucleotide polymorphism (SNP) markers, we used both linkage mapping (LM) and genome-wide association study (GWAS) to dissect the genetic control of a series of yield-component traits. We identified 20 significant markers in GWAS and 28 in LM that were detected in at least two environments, several of which were shared across traits. The QTL regions on chromosomes 5 and 9 were significant for eight of 11 traits, and many were detected across multiple analysis methods. The results described herein provide additional resources for incorporating QTL as fixed effects in routine genomic selection pipelines to expedite the gains from selection for yield in this new perennial grain crop.