Characterization of Hybrids from Induced × Natural Tetraploids of Russian Wildrye

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 genes 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 (DMY), 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. Essentially all variation among half‐sib families for rate of seedling emergence was associated with environmental effects. Positive responses 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.