CYTOGENETICS OF EURASIAN BLUEBUNCH WHEATGRASS AND THEIR RELATIONSHIP TO NORTH AMERICAN BLUEBUNCH AND THICKSPIKE WHEATGRASSES

Bluebunch wheatgrass, Pseudoroegneria spicata (Pursh.) A. Love, is one of the most important native dryland forage bunchgrasses of the inter mountain West, which often produces depleted stands under moderate to heavy grazing pressure. Tn recent plant collecting trips to the Altai and Tien Shan Mountains of China and Russia, a grazing tolerant bluebu nch wheatgrass complex was obtained. This study was conducted to descr ibe the cytogenetic characteristics and potential for genetic exchange between the Eurasian, bluebunch wheatgrass complex EP. strigosa (M. B ieb.) A. Love, P. geniculata (Trin.) A. Love, Roegneria elytrigioides Yen and Yang, and R. glaberrima Keng et S.L. Chen] and those bIuebunch thickspike wheatgrasses found in North America. Meiotic behavior of t he triploid hybrids between diploid and tetraploid R. glaberrima indic ated that both ploidy levels share the same genome. Almost complete pa iring in hybrids P. strigosa ssp. aegilopoides (Drob.) A. Love x P. sp icata, and R. glaberrima x P. spicata, demonstrated that P. strigosa s sp. aegilopoides and R. glaberrima are comprised of the basic S genome . Triploid hybrids between P. geniculata, and R. elytrigioides with ei ther P. spicata, P. slipifolia (Czern. ex Nevski) A. Love, or P. strig osa ssp. aegilopoides exhibited trivalent frequencies consistent with the hypothesis that tetraploid R. elytrigioides is an autotetraploid ( SSSS) and that P. geniculata is either a segmental autotetraploid ((SS SS2)-S-1-S-1-S-1) or an allotetraploid (SS??). Based on the high level of chromosome pairing in the interspecific hybrids between the Eurasi an and North American bluebunch wheatgrass complex, genetic exchange i s possible. Due to the close genetic and morphological similarity amon g individuals of P. spicata, P. strigosa, P. geniculata, R. elytrigioi des, and R. glaberrima we are likely dealing with a single, polymorphi c, Eurasian-North American species complex.