A field-based analysis of genetic improvement for grain yield in winter wheat cultivars developed in the US central plains from 1992 to 2014

Progress in plant breeding programs is the result of creating and selecting new lines with novel allele combinations that perform better than their parents. This year-on-year improvement is known as genetic gain and is a function of genetic diversity, selection accuracy, selection intensity, and selection cycle time. To estimate the gain in wheat (Triticum aestivum L.) breeding in the US Central Plains, lines that were submitted to the collaborative Southern Regional Performance Nursery (SRPN) between 1992 and 2014 were grown in a common nursery for 3 yr at two locations in a single-replicate augmented block design. Moderate to high broad-sense heritability was observed for plant height (H2 = 0.88), heading date (H2 = 0.79), and grain yield (H2 = 0.41). From the common grow-out, genetic gain for yield over the time period was estimated at 1.1% yr-1, whereas individual breeding program genetic gain varied between 0.3 and 1.9% yr-1. Increases in Kansas state on-farm yields during the same period showed a nonsignificant trend of 0.13% yr-1 with large year-to-year variation. These results suggest that although progress is being made in US Central Plains breeding programs, a yield gap remains that could be attributable to genetic progress not being realized in on-farm production.