Submitted to: Crop Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/12/2004
Publication Date: 6/27/2005
Citation: Jensen, K.B., Larson, S.R., Waldron, B.L., Johnson, D.A. 2005. Characterization of hybrids from induced x natural tetraploids of Russian wildrye. Crop Science 45:1305-1311. Interpretive Summary: Russian wildrye is a cool-season, dryland bunchgrass that provides excellent forage for livestock and wildlife on rangelands of the Northern Great Plains and the Intermountain Region of North America. However, its relatively slow seedling growth and development has reduced its widespread use as a range grass. Plant collections from Eurasia with chromosome numbers of 28 have exhibited increased seedling growth and development over Russian wildrye cultivars with 14 chromosomes. The 28 chromosome plants are not as drought tolerant as the 14 chromosome cultivars. This paper describes the process used to cross the 14 and 28 chromosome plants. It reports on the meiotic behavior, molecular diversity, forage potential, and seed characteristics of the hybrid population. Meiotically the hybrid is stable, fertile, and increases in forage and seed yield, and seedling vigor are possible through selection.
Technical Abstract: Because of restrictions imposed by hybridization barriers, Russian wildrye [Psathyrostachys juncea (Fisch.) Nevski] breeders have usually limited themselves to selection and hybridization within ploidy levels. Plants of diploid (2n=2x=14) Russian wildrye tend to be shorter, finer stemmed, leafier, and generally higher in forage production than tetraploids (2n=4x=28), which have larger seeds and superior seedling vigor. The principle objectives of the present study were to combine the gene(s) from diploid and tetraploid Russian wildrye into a stable population, and evaluate variability in chromosome behavior, molecular genetic diversity, forage production, seed characteristics, and seedling vigor of the hybrids. Cytologically, the hybrid population behaved as an autotetraploid averaging 0.50 univalents + 9.37 bivalents + 0.24 trivalents + 1.98 quadrivalents per cell. Narrow-sense heritabilities were 31, 63, 17, and 23% for dry matter yield, total seed yield, 100-seed weight, and rate of seedling emergence, respectively. Coefficients of determination (r2) among parent and half-sib family means were 0.12, 0.29, 0.09, and 0.72 for the above traits, respectively. Positive response to selection pressure for improved seed yield, rate of seedling emergence, and dry matter production were achieved and additional gains are expected. Any major improvement in seed mass would be limited without broadening the genetic base of the hybrid.