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CROP BREEDING, GENETICS & CYTOLOGY

Characterization of Amphiploid Hybrids between Bluebunch and Thickspike Wheatgrasses

USDA-ARS, Forage and Range Research Lab., Utah State Univ., Logan, UT 84322-6300

^* Corresponding author (kevin{at}cc.usu.edu)

An amphiploid derivative from hybrids between bluebunch wheatgrass (2n = 2x = 14) [Pseudoroegneria spicata (Pursh) A. Love] and thickspike wheatgrass (2n = 4x = 28) [Elymus lanceolatus (Scribner and Smith) Gould] was developed to compare cytological, morphological, anatomical, and seed characteristics between the triploid F₁ hybrids (2n = 3x = 21) and their colchicine induced hexaploid (2n = 6x = 42) derivative (C₀). The amphiploid population produced an average of 3.1 seeds spikelet^–1 and pollen stainability averaged 85.5%. Seed set under self-pollination in the amphiploids ranged from <1% to >99% with an average of 50%. Fifty-eight of the 103 plants studied were hexaploid (2n = 6x = 42). The remaining plants had chromosomes ranging from 2n = 39 to 2n = 44 and were less fertile than the euploids. Meiosis in the euploid plants was regular and typical of a segmental autoallohexaploid St₁St₁St₂St₂HH. The most common meiotic chromosome configuration was 21 bivalents. A high frequency of bivalents and a low frequency of quadrivalents indicate that the St genomes of the two parental species have diverged. The amphiploids had thicker culms, more leaves per culm, and longer and wider leaves than either parental species. Multivariate analysis demonstrated that the amphiploids, though morphologically similar to the parental species, was distinct. In general, C₀ hybrids were less vigorous than the F₁ from which they were derived. Through amphiploidy, genetic introgression between the two species is possible.