Date of this Version
Crop Sci. 26:653‑658
Intermediate wheatgrass [Thinopyrum intermedia (Host) Barkworth and D.R. Dewey] is grown over a vast geographical area in North America, but information on the genetic variability for agronomic traits and the stability of these traits over environments is limited. Genotype and genotype X environment interaction effects for forage yield and quality of intermediate wheatgrass were studied using 36 strains (plant introductions, experimental strains, and a released cultivar). They were grown in two central Great Plains environments, Lincoln and Alliance, NE, that differ markedly in climate. Forage yield and forage quality, measured by in vitro dry matter digestibility (IVDMD) and percent protein, were determined in both locations in 1980 and 1981 in spaced-plant nurseries. In the combined analyses over years and locations, there were significant differences among strains or genotypes (G) for first-cut yield and IVDMD, but not for protein. Strain X location (GL) and strain X year (CY) interaction effects were significant for first-cut forage yield but not for IVDMD, a trait that appears to be relatively stable over environments. For forage yield, the variance component for strains (ui) was 300% larger than those for GL (u,:,) and GY (&). These variance components results plus rank correlations of the strains in the two environments of 0.77 for both first-cut IVDMD and yield indicate that the strains ranked similarly for both traits in both environments. Existing genetic variability for forage yield and quality as measured by IVDMD should permit the development of improved intermediate wheatgrass populations. At least in the initial stages of a breeding program, selection for these traits could be done in a single environment. Concurrent selection for both first-cut yield and IVDMD is feasible since the phenotypic correlation coefficients between these traits were positive and significant for both locations.