Genetic characterization of trait architecture in multi‑population half-sib families of the perennial crop intermediate wheatgrass

The cool-season perennial species Thinopyrum intermedium (intermediate wheatgrass [IWG]) is a forage grass recognized for its extensive root structure, high biomass, and promising grain yield potential. The University of Minnesota has been domesticating IWG as a food crop since 2011. While most breeding work is carried out in spaced-planted selection nurseries, these do not represent how the plants are grown in fields for commercial grain production. Therefore, this research evaluated half-sib families (HSFs) established in sward plots over multiple locations and years to study trends in grain production as the plant stands aged. A total of 208 HSFs were assessed for plant height, grain yield, and seed size. Principal component analysis using genetic data detected a weak but visible population structure as genotypes clustered into two groups. Across the field environments, that is, 3 years and two locations in Minnesota, substantial variation in trait performance was observed. Thirty-two HSFs exhibited stable grain yield across 3 years and both locations with no decline in grain production, a crucial finding as IWG yield typically declines after the first 2 years of cultivation. Trait heritability estimates were the lowest for grain yield (0.36) and highest for the plant height (0.51). A scan of the genome for marker-trait associations identified 42 genomic loci associated with the three traits. These findings suggest that HSFs can be a valuable resource in IWG breeding programs to identify maternal genotypes and sib families with stable yield performance and should be evaluated on a regular basis.