Genetic gains from 60 years of spring wheat breeding in the Northern Plains of the United States

Abstract

Evaluating genetic gains over time is essential for assessing the success of breeding programs and refining strategies for ongoing improvement. Hard red spring (HRS) wheat (Triticum aestivum L.) is an important class of wheat in the United States and is primarily grown in the Northern Great Plains. Despite a long history of breeding efforts in this region, long-term quantification of genetic gains for key traits has remained limited. This study analyzes over 60 years of data from the United States Department of Agriculture-coordinated Hard Red Spring Wheat Uniform Regional Nursery to evaluate genetic improvement in agronomic traits across multiple phases. A significant positive genetic gain of 0.61% per annum was observed for grain yield in HRS wheat released in the Northern plains over the past six decades, which is lower than the expected gains needed to meet future wheat demand. The change was 0.07% for test weight, −0.04% for days to heading, and −0.16% for plant height. Notably, sustained yield improvements have not affected grain protein levels since they were first measured in 1995, indicating that ongoing selection has effectively balanced grain yield and protein despite their negative correlation (r = −0.31). Assessment of genetic gains over 20-year phases suggested slowing rates of genetic gains for grain yield but did not indicate any plateaus. The realized genetic gains were generally higher for individual breeding programs when breeding for target environments, with the public breeding program in Minnesota observing annual gains of approximately 1%. These findings highlight the significant impact of long-term breeding efforts, underscore the importance of regional public breeding programs, and offer valuable insights for refining future breeding strategies.