Seed yield can be explained by altered yield components in field-grown western wheatgrass (Pascopyrum smithii Rydb.)

Western wheatgrass (Pascopyrum smithii Rydb.) is an important cool-season forage and turfgrass. However, due to seed dormancy and poor seedling vigor, it is difficult to develop high seed yield production systems, and assessing these components in response to seed yield. Based on multifactor orthogonally designed field experimental plots under various field management regimes, the effects of numbers of fertile tillers m−2 (Y1), spikelets/fertile tiller (Y2), florets/spikelet (Y3), seed numbers/spikelet (Y4), and seed weight (Y5) on seed yield (Z) were determined over three successive years. Correlation analysis indicated that fertile tillers (Y1) was the most important seed yield component. And the biggest contribution of those five yield component is fertile tillers (Y1), followed by seed numbers/spikelet (Y4), spikelets/fertile tiller (Y2), florets/spikelet (Y3) and seed weight (Y5), respectively. By using ridge regression analysis, we have developed an accurate model of seed yield with its five components. Finally, the results of synergism and antagonism among these yield components on seed yield showed that fertile tillers and seed numbers/spikelet had an antagonistic effect on seed yield. Therefore, selection for high seed yield by direct selection for large values of fertile tillers and seed numbers/spikelet would be the most effective breeding strategy for western wheatgrass.

Merits of native and introduced Triticeae grasses on semiarid rangelands

Experiments were conducted on four semiarid range sites to compare stand establishment, productivity, and persistence of several introduced perennial Triticeae grasses with that of their native counterparts. On Intermountain sites with severe water limitations (< 300 mm), native grasses were more difficult to establish, less productive, and less persistent than the introduced grasses. Stands of native grasses declined most rapidly under defoliation. At locations where moisture conditions were more favorable, particularly where more summer precipitation occurred, native Triticeae grasses established and persisted relatively well compared with the introduced entries. Although difficult to establish, stands of the rhizomatous native, western wheatgrass [Pascopyrum smithii (Rydb.) A. Löve] in creased during the seasons after establishment. Choice of plant materials to be used in range seeding programs should be based on objective criteria. To do otherwise will perpetuate degradation of soil resources, especially on sites that are dominated by weedy annual species such as cheatgrass (Bromus tectorum) and medusahead rye (Taeniatherum asperum). It is proposed that adapted introduced grasses be equally considered along with native grasses as a component of seed mixtures on environmentally harsh sites that have been burned, infested with competitive weedy species, or otherwise degraded. Key words: Grass breeding, revegetation, introduced grasses, Triticeae, cheatgrass, seedling vigor, plant persistence