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Induced and natural tetraploids have been proposed as promising sources of germplasm in breeding programs to improve Russian wildrye [Psathyrostachys juncea (Fisch.) Nevski]. Studies were conducted under semiarid conditions to evaluate the potential of tetraploid (2n=4x=28) Russian wildrye germplasm recently obtained from Kazakhstan. The teraploids had significantly heavier seeds, greater seedling vigor, and they were significantly taller, and had longer and wider leaves than standard diploid (2n=2x=14) cultivars. Carbon isotope discrimination, which has been negatively correlated with water-use efficiency in cool-season grasses, was significantly lower in the tetraploid accessions than the diploid cultivars. Dry matter and seed yield of these unselected tetraploid accessions were superior to the diploid cultivar Vinall and equivalent to more recently developed diploid cultivars, Bozoisky-Select and Syn-A. In general, relative phenological development and forage quality of the tetraploid populations did not differ significantly from the diploid cultivars; however, water content, which has been associated with greater succulence, was significantly higher in the tetraploid accessions. Significant variation was found among entries within ploidy levels for most characters indicating that genetic variability is available for additional improvement through selection. Results indicate that these tetraploid accessions can be used in the development of promising breeding populations and support earlier conclusions that tetraploid germplasm should receive emphasis in future Russian wildrye breeding programs. The Journal of Range Management archives are made available by the Society for Range Management and the University of Arizona Libraries. Contact lbry-journals@email.arizona.edu for further information. Migrated from OJS platform August 2020