Genotype by environment interactions influence grain yields of intermediate wheatgrass

Authors: NAFI, EEUSHA - Montana State University; BASCHE, ANDREA - University Of Nebraska; KEENE, CLAIR - North Dakota State University; FRANCO, JOSE - Savanna Institute; Bajgain, Prabin; Larson, Steven; PICASSO, VALENTIN - University Of Wisconsin; JUNGERS, JACOB - University Of Minnesota; DEHAAN, LEE - The Land Institute

Submitted to: Agronomy Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/24/2026
Publication Date: 6/18/2026
Citation: Nafi, E., Basche, A., Keene, C., Franco, J., Bajgain, P., Larson, S.R., Picasso, V., Jungers, J., Dehaan, L. 2026. Genotype by environment interactions influence grain yields of intermediate wheatgrass. Agronomy Journal. Volume 118, Issue 3. https://acsess.onlinelibrary.wiley.com/doi/pdf/10.1002/agj2.70430.
DOI: https://doi.org/10.1002/agj2.70430

Interpretive Summary: Conventional field crops such as wheat require farmers to plant seeds every year and cultivate soil, which often leaves soil exposed to wind or water erosion. Utilization of perennial grain crops, such as intermediate wheatgrass, eliminates the need to replant seeds every year and promotes environmental sustainability with reduced soil cultivation with a continuous living plant cover that survives and produces grain over multiple years. However, the grain yields of new crops like intermediate wheatgrass lag behind wheat, which has been selected and bred over thousands of years. This study investigated the performance of eight intermediate wheatgrass breeding populations across seven diverse locations in the United States over several years. Environmental factors, particularly summer and fall rainfall, had a much greater impact on seed yield than genetic differences among intermediate wheatgrass populations. Two breeding populations, MN-Clearwater and TLI-C5 consistently outperformed the others, particularly under favorable conditions. The forage variety Rush showed low yields across environments, whereas other varieties demonstrated inconsistent performance. Breeding efforts have significantly improved grain yields compared to forage varieties. However, the study found little evidence for the broad adaptation of IWG varieties across diverse environments, emphasizing the need for researchers to breed varieties tailored to specific environmental conditions. These findings also provide useful information for farmers that may be interested to grow perennial crops in different regions of the United States.

Technical Abstract: Crop rotation with perennial grain crops, such as intermediate wheatgrass (IWG; Thinopyrum intermedium), marketed as Kernza®, promotes agroecological intensification and environmental sustainability relative to annual cropping systems. To assess yield performance and adaptability of IWG breeding populations across diverse environments, multi-location field trials were conducted from 2018 to 2022 in Minnesota, Wisconsin, Kansas, Nebraska, North Dakota, and Utah. Eight populations, MN-Clearwater, TLI-C5, TLI-C3, TLI-C4, MN1501, MN1502, MN1503, and the forage cultivar ‘Rush’, were evaluated using a randomized complete block design with four replications. Analysis of variance showed that location (27%) and location × harvest year interactions (44%) explained most seed yield variation, while genotype effects were modest. Yield declined after the second harvest year at most sites, indicating challenges in stand longevity. The Finlay-Wilkinson regression classified populations as high-yielding and responsive (MN-Clearwater, TLI-C5), low-yielding and stable (Rush), or intermediate-yielding but unstable (remaining populations). MN-Clearwater and TLI-C5 exceeded Rush by 78-85%, reflecting breeding progress by the University of Minnesota and The Land Institute. Nonparametric analyses (Lin and Binns superiority index and Huehn’s rank difference) consistently identified MN-Clearwater and TLI-C5 as the top-performing populations across favorable and stressed environments. Although yields declined by 82% and 74% under stress, these populations maintained competitive rankings with minimal rank crossover, indicating broad adaptability. Fall and Summer rainfall was were the primary environmental factors influencing yield across locations. These results highlight increases in grain yield that regional breeding programs have achieved across a broad geographical range, while also demonstrating the possibility to select for location-specific performance in the future.