Poor seedling vigor is a major factor limiting widespread use of Russian wildrye [Psathyrostachys juncea (Fischer) Nevski] (2n = 2x = 14) as complementary pasture. Induced polyploidy has been shown to increase plant vigor, particularly seeding vigor, of other diploid species. Objectives of this study were to produce autotetraploids in Russian wildrye using the N2O technique and to ascertain meiotic stability and seedling vigor of induced autotetraploids. Spikes were hand emasculated, pollinated, and treated with N2O at 0.5 MPa pressure from 20 to 44 h after pollination. Putative diploid and autotetraploid progeny were identified from measurements of stoma length, stoma frequency, and pollen grain diameter. Ploidy classification was verified by chromosome counts from microsporocytes. Fifty-two progeny were obtained from nine crosses, but only 21 were autotetraploid. One plant was aneuploid, with 29 chromosomes. An average of 0.47 trivalent and 1.96 quadrivalent chromosome configurations were observed per cell at metaphase I, indicating the absence or inactivity of genetic factor(s) conditioning bivalent pairing. Seed set averaged 30 and 27% for diploids and autotetraploids, respectively. Emergence from a 5.0-cm planting depth in a greenhouse test, a measure of seedling vigor, averaged a significant (P less-than-or-equal-to 0.01) 13% higher for autotetraploids than diploids. Nitrous oxide treatment of Russian wildrye resulted in meiotically stable autotetraploid selections with progenies that were superior in seedling emergence to diploid checks.
