Genetic improvement of winter wheat (Triticum aestivum L.) grain yield in the Northern Great Plains of North America, 1959-2021

Plant breeding progress is often based on assessments of genetic gain, a measure of year-on-year improvement of newly developed varieties for important traits of interest. Herein, we present data from the USDA-coordinated hard winter wheat (Triticum aestivum L.) Northern Regional Performance Nursery (NRPN) collected from 1959 to 2021 for grain yield, grain volume weight, days-to-heading, and plant height and use it to estimate absolute and relative rates of genetic gain (loss) of the control cultivar Kharkof for winter wheats adapted to the Northern Great Plains of North America. Regression analyses revealed significant relative grain yield increases of 0.67% Kharkof year(-1) or 39.2 kg ha(-1) year(-1) for the NRPN over the 63-year period. From 2008 to 2021, however, negative linear relationships were observed for relative grain yield for all NRPN entries and the five highest yielding NRPN lines each year, with genetic grain yield losses estimated at -0.95 and -0.79% Kharkof year(-1), respectively. Surprisingly, genetic progress for grain yield in the NRPN was limited to just 8.9 kg ha(-1) year(-1) over the past 13 years. Moreover, linear-plateau models significantly (p < 0.0001) fit all relative and absolute yield datasets from 1959 to 2021, with yield plateaus beginning by 2008 for all groups. These results support that winter wheats adapted to the Northern Great Plains have reached an upper yield plateau and could be nearing a yield potential ceiling due to global warming or other combined abiotic and biotic environmental stressors that are straining the biophysical limits of the crop.

Automated summary

This study analyzed the genetic gains of winter wheat adapted to the Northern Great Plains of North America using long-term data. The results showed a decline in relative grain yield in recent years and limited genetic progress. The study suggests that winter wheat in this region has reached its yield potential and may be limited by environmental factors such as global warming.