From Forage to Grain: Structural and Functional Changes Occurred During 10 Generations of Transition of Intermediate Wheatgrass (Thinopyrum intermedium) to Kernza®

Abstract

Thinopyrum intermedium (c.n. intermediate wheatgrass), marketed under the trade nameKernza, is a promising species for perennial grain production based on seed size, easeof threshing, resistance to shattering, and grain quality. Although numerous generationsof breeding for seed yield have been completed, the impact of selection on non-targettraits is unknown. Here, we evaluated structural and functional changes brought aboutby selection for seed yield over a sequence of nine selection cycles (C0 to C9). In twoexperiments under semi-controlled environmental conditions, we compared gas exchange(A, E, gs, and A/Ci curves), leaf and root morphology, and the structure of seedlingsfrom 10 generations. We found that the selection for yield throughout cycles indirectlychanged the leaf structure (leaf size, leaf thickness, and leaf anatomy) and physiology(carbon acquisition and transpiration per unit area), with later cycles showing larger leaveswith higher rates of CO2 assimilation and transpiration. Changes in root structure followedsimilar trends: selection resulted in longer, more branched, and finer roots. These changesin non-target traits are linked to resource-use strategies and to ecosystem services providedby Kernza. Understanding how the domestication of perennial grains impacts non-targettraits will aid in the design of integrated breeding programs for Kernza and other perennialgrain crops.