Genomic Selection of an Index Trait to Develop Winter Malting Barley

Genomic selection (GS) takes advantage of genome-wide marker data and may accelerate gain from selection because it allows breeders to evaluate lines in earlier generations and at multiple times per year. For three breeding cycles, we selected lines that were predicted by marker data to have the best value for an index trait combining winter survival, malt extract, plant height, heading date, and grain yield. The lines were evaluated for these traits as well as Fusarium head blight severity, beta-glucan, and free amino nitrogen (not under selection) in three to six locations in 2014 and 2015. Genome-wide markers used to generate genomic predictions also allowed us to assess changes in genotypic variation across selection cycles. The objectives of this study were to 1) assess accuracy of predictions based on progeny performance, 2) assess rate of gain from GS, and 3) evaluate changes in the genetic variance of the population over cycles of selection based on principal components analysis (PCA). Progeny-based prediction accuracy was high for winter survival, plant height, and malt extract (>0.50) and was low for heading date and yield (<0.25). Winter survival was the only trait that improved significantly after two cycles of GS. Based on PCA, we observed that the genetic variance of the population decreased over cycles of selection and that the population shifted toward similarity with the winter parents used to create the population. This empirical evaluation of GS will inform plant breeders who are considering whether to adopt this breeding strategy.