Comparison of S1 with open-pollination progenies in selection for yield in crested wheatgrass

Genetic gain from selection for high dry matter yield in most cross-pollinated forage grasses has been an elusive goal, in spite of sustained breeding efforts. This study was conducted to determine the value of one generation of self-pollinating (S-1) before selection for yield in crested wheatgrass (Agropyron spp.). Dry matter yields were compared at two locations near Mandan, ND, for synthetic populations derived from selection among and within S-1 or among and within open-pollination (OP) progenies from three source populations. Within each source population, the 20 parents used to produce S-1 progenies were in common with the 20 maternal parents of the OP progenies. Soil was a Parshall fine sandy loam (coarse-loamy, mixed, superactive, frigid Pachic Haplustolls) at Location 1 and a Wilton silt loam (fine-silty, mixed, superactive, frigid Pachic Haplustolls) at Location 2. In space-plant tests, S-1 family means for dry matter yield averaged 52% of OP family means, indicating high levels of inbreeding depression. In solid-seeded tests, yield differences between S-1- and OP-derived synthetic populations were significant (P less than or equal to 0.05) for only one comparison. On the basis of three distinct source populations, we found that S-1 and OP families were both effective when used as the selection unit to choose high yielding parents for synthetic populations. Additional resources required to produce and evaluate S-1 families over OP families could not be justified in the crested wheatgrass source populations evaluated in this study.