Submitted to: Crop Science
Publication Type: Peer reviewed journal
Publication Acceptance Date: 9/1/2005
Publication Date: 3/1/2006
Citation: Jensen, K.B., Maughan, K.W., Asay, K.H. 2006. Characterization of amphiploid hybrids between pseudoroegneria spicata (pursh.) a. love and elymus lanceolatus (scribner & smith) gould. Crop Science 46:655-661. Interpretive Summary: Within the wheatgrasses, hyrids are frequently made to combine desirable traits from two different species. This study reports on the chromosome behavior of an amhiploid hybrid with 42 chromosomes derived from a cross between two native grass species bluebunch wheatgrass and thickspike wheatgrass. The original hybrid had 21 chromosomes. The amphiploid population is both self-and cross pollinating. The amphiploid hybrid had a reduction in vegetative vigor, larger guard cells and floral parts, and thicker stems. This amphiploid has successfully combined germplasm from P. spicata and E. lanceolatus into a partially fertile population. Reduced fertility and increased occurrence of plants with unequal chromosome numbers continue to be a problem in the amphiploid breeding population after four cycles of selection. Within this population, those plants with a chromosome number of 2n=6x=42 appear to be as fertile as the two parental species. Selection of hexaploid plants in future cycles may increase fertility levels and the frequency of euploids in the population.
Technical Abstract: 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 charateristics between the triploid F1 hybrids (2n=3x=21) and their colchicine induced hexaploid (2n=6x=42) derivative (Co). 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 amphiloids 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, Co hybrids were less vigorous than the F1 from which they were derived. Through amphiploidy, genetic introgression between the two species is possible.