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 (Y 1 ), spikelets/fertile tiller (Y 2 ), florets/spikelet (Y 3 ), seed numbers/spikelet (Y 4 ), and seed weight (Y 5 ) on seed yield (Z) were determined over three successive years. Correlation analysis indicated that fertile tillers (Y 1 ) was the most important seed yield component. And the biggest contribution of those five yield component is fertile tillers (Y 1 ), followed by seed numbers/spikelet (Y 4 ), spikelets/fertile tiller (Y 2 ), florets/spikelet (Y 3 ) and seed weight (Y 5 ), 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.