Floret site utilization and reproductive tiller number are primary components of yield in intermediate wheatgrass spaced plants

Authors: Altendorf, Kayla; DEHAAN, LEE - The Land Institute; HEINECK, GARETT - Washington State University; ZHANG, XIAOFEI - International Institute For Tropical Agriculture; ANDERSON, JAMES - University Of Minnesota

Submitted to: Crop Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/6/2020
Publication Date: 10/20/2020
Citation: Altendorf, K.R., Dehaan, L.R., Heineck, G.C., Zhang, X., Anderson, J.A. 2020. Floret site utilization and reproductive tiller number are primary components of yield in intermediate wheatgrass spaced plants. Crop Science. 61(2):1073-1088. https://doi.org/10.1002/csc2.20385.
DOI: https://doi.org/10.1002/csc2.20385

Interpretive Summary: Perennial plants provide extensive environmental services and increasing their prevalence on the agricultural landscape is one way to improve sustainability. Direct domestication of intermediate wheatgrass [Thinopyrum intermedium; (Host) Barkworth & D.R. Dewey] as a perennial grain crop is underway, and selection has focused primarily on improving seed size and yield. Breeders lack understanding of seed yield and its relationship with yield component traits in this species. We characterized a large (n = 1,168) spaced plant nursery in St. Paul, MN and Salina, KS in 2017 and 2018 for a series of 13 yield component traits. In year two in St. Paul, yield plant-1 and reproductive tiller number nearly doubled, while other yield components, including yield spike-1, spikelets spike-1, florets spikelet-1, and thousand grain weight, significantly decreased. Correlation analyses between traits highlighted positive associations of seven traits with grain yield. Structural equation modeling (SEM) revealed that when yield was measured on a yield spike-1 basis, floret site utilization was the primary contributor to yield, and when measured on a plant-1 basis, reproductive tiller number was the primary contributor. The indirect effects of biomass and maturity traits on both measures of yield were limited. Future work should assess the predictive ability of reproductive tiller counts in spaced plant and sward environments to inform how breeders assess and select for yield.

Technical Abstract: Perennial cropping systems have the potential to offer more environmental services compared with annual ones. However, there are few crops currently available that fit this system and also provide economical yield. To fill this gap, intermediate wheatgrass (Thinopyrum intermedium) is undergoing direct domestication as a new perennial grain crop. Seed yield is a major target of selection, but breeders are limited by the lack of understanding of the relationship between yield component traits. In the assessment of a series of yield component traits in intermediate wheatgrass spaced plants over two years in two distinct environments, we determined that yield, when measured on a per plant basis, is primarily driven by the number of reproductive tillers. When measured on a per spike basis, it is primarily driven by floret site utilization, or the percentage of florets that are filled with seed. These findings improve our understanding of the relative importance of various yield component traits and provide insight into potential targets for indirect selection on seed yield.