Int. J. Plant Sci. 160(2):371±376. 1999. Copyright is not claimed for this article. MOLECULAR MARKER ANALYSIS OF LEYMUS FLAVESCENS AND CHROMOSOME PAIRING IN LEYMUS FLAVESCENS HYBRIDS (POACEAE: TRITICEAE)1 D. J. Hole,2,* K. B. Jensen,² R. R.-C. Wang,² and S. M. Clawson* *Plants, Soils, and Biometeorology Department, Utah State University, Logan, Utah 84322-4820, U.S.A.; and ²USDA-ARS, Forage and Range Research, Utah State University, Logan, Utah 84322-6300, U.S.A. Leymus ¯avescens (Scribner & Smith) Pilger, yellow wild rye, is a long-lived, strongly rhizomatous, tetraploid (2n54x528) perennial grass of the tribe Triticeae distributed throughout central Washington, eastern Oregon, and the Snake River plains of Idaho. Our objectives were (1) to describe chromosome pairing and fertility in 5 5 F1 hybrids between L. ¯avescens and North American tetraploids (2n 4x 28) L. triticoides and L. cinereus and Eurasian tetraploids L. secalinus, L. racemosus, and L. alaicus subsp. karataviensis and (2) to utilize genome-speci®c random ampli®ed polymorphic DNA (RAPD) markers to verify the genomic composition of L. ¯avescens. The hybrids L. ¯avescens # L. triticoides (NsNsXmXm), L. ¯avescens # L. secalinus (Ns- NsXmXm), L. ¯avescens # L. racemosus (NsNsXmXm), L. ¯avescens # L. cinereus (NsNsXmXm), and L. ¯avescens # L. alaicus subsp. karataviensis (NsNsXmXm) averaged 13.9, 13.8, 13.6, 13.1, and 11.9 bivalents per cell, respectively. Genome-speci®c RAPD assay indicates that L. ¯avescens has the Ns genome but lacks the St genome from the genus Pseudoroegneria and the H genome from the genus Hordeum. On the basis of the bivalent chromosome pairing frequency in the F1 hybrids of L. ¯avescens, the genomic formula of L. ¯avescens is NsNsXmXm. The presence of the Ns genome was veri®ed by molecular characterization. Keywords: Leymus, genome, meiosis, chromosome pairing, interspeci®c hybrids, taxonomy, systematics. Introduction Sections Leymus and Anisopyrum comprise both North Amer- ican and Eurasian taxa. The genus Leymus Hochst. is a relatively old genus erected Species of the genus Leymus are long-lived perennials that by Hochstetter in 1848 only for L. arenarius (L.) Hochst. How- are distributed from the coastal regions of the North Sea (L. ever, Pilger (1947), Tzvelev (1976), Melderis et al. (1980), arenarius) across central Asia (L. angustusÐAltai wild rye) to Barkworth et al. (1983), and Gleason and Cronquist (1991) East Asia (L. chinensis), Alaska (L. mollis), and western North recognized the genus. On the basis of the treatments of Tzvelev America (L. cinereus A .LoÈ veÐGreat Basin wild rye, and L. (1976) and LoÈ ve (1984), Leymus is subdivided into four sec- triticoidesÐbeardless wild rye). Leymus species are character- tions: (1) sect. Leymus Hochst., which is represented by the ized by multiple spikelets per node and are for the most part North American L. mollis (Trin.) Pilger, L. arenarius (L.) rhizomatous (except L. cinereus), long anthered, and variable Hochst., and Eurasian L. racemosus (Lam.) Tzvelev (5Elymus in their degree of self-pollination (Jensen et al. 1990). On the giganteus Vahl.); (2) sect. Aphanoneuron (Nevski) Tzvelev, basis of variation in repeated nucleotide sequences, Dubcovsky which is restricted to Eurasian species typi®ed by L. angustus et al. (1997) reported similar banding patterns for South Amer- (Trin.) Pilger, L. secalinus (Georgi) Tzvelev, and L. alaicus ican Elymus erianthus Phil., and Elymus mendocinus (Parodi) 5 (Korsh.) Tzvelev subsp. karataviensis (Roshev.) Tzvelev ( Ely- A .LoÈ ve and tetraploid Leymus taxa, indicating that the dis- mus karatviensis Roshev.); (3) sect. Anisopyrum (Griseb.) tribution of Leymus taxa may extend into South America. Tzvelev, which is characterized by North American L. ¯aves- Leymus is a polyploid genus that consists of approximately cens (Scribner and Smith) Pilger, L. ambiguus (Vasey and Scrib- 30 species worldwide, all of which had previously been treated  ner) D. Dewey, L. salinus (M. E. Jones) A.LoÈ ve, L. triticoides in the genus Elymus L. (Dewey 1984). More than half of the  (Buckl.) Pilger, L. condenstatus (K. Presl.) A.LoÈ ve, and Eur- Leymus species are allotetraploids (2n528). The higher poly- asian L. chinensis (Trin.) Tzvelev, L. ramosus (Trin.) Tzvelev, ploid species (2n542284) are complex autoallopolyploids. and L. multicaulis (Kar. and Kir.) Tzvelev; and (4) sect. Ma- Multivalents are seen at metaphase I in octaploid L. cinereus lacurus (Nevski) Tzvelev, which is a monotypic section com- and dodecaploid L. angustus (Dewey 1972a), but their fre- prising Eurasian L. lanatus (Korsh.) Tzvelev. Sections Aphan- quency is much less than expected from true autoalloploids, oneuron and Malacurus are restricted to Eurasian species. indicating that gene(s) promoting bivalent pairing appear to be operating (Dewey 1984). 1 Cooperative investigations of the USDA-ARS and the Utah Agri- The genomic constitution of the genus Leymus has tradi- cultural Experiment Station Project 328, Logan, Utah 84322, U.S.A. tionally been based on the Ns genome from Psathyrostachys Approved journal paper 7054. Nevski and the J genome from Thinopyrum A .LoÈ ve (Dewey 2 Author for correspondence and reprints; e-mail dhole@ 1984). However, recent cytogenetic and molecular data (Zhang mendel.usu.edu. and Dvorak 1991; Wang and Jensen 1994) demonstrate the Manuscript received June 1998; revised manuscript received November 1998. absence of the J genome from Thinopyrum in Leymus taxa. 371 This content downloaded from 129.123.124.236 on Wed, 12 Mar 2014 18:05:09 PM All use subject to JSTOR Terms and Conditions 372 INTERNATIONAL JOURNAL OF PLANT SCIENCES Table 1 Plant Materials Used in Crosses Species 2n Genome Accession number Collection origin Leymus ¯avescens ...... 28 Unknown Harris Idaho, U.S.A. L. triticoides ............ 28 NsNsXmXm Dewey E-7-6 Oregon, U.S.A. L. secalinus ............. 28 NsNsXmXm PI210988 Afghanistan L. racemosus ........... 28 NsNsXmXm Jaaska USSR L. cinereus .............. 28 NsNsXmXm J. A. Young Nevada, U.S.A. L. alaicus subsp. karataviensis ......... 28 NsNsXmXm PI314671 USSR On the basis of repeated nucleotide sequence identity between ships between L. ¯avescens and the North American Leymus species and diagnostic hybrid intensities in Southern blots, tetraploid species L. triticoides and L. cinereus. Information Zhang and Dvorak (1991) suggested that Leymus polyploids is also lacking on genomic relationships between L. ¯avescens originated from hybridization of two unidenti®ed Psathyros- and its Eurasian counterparts, L. secalinus, L. racemosus, and tachys species. On the basis of these ®ndings, the genomic L. alaicus subsp. karataviensis. Leymus ¯avescens can be dis- formula for tetraploid Leymus species would be NsiNsiNsjNsj, tinguished morphologically from its close North American rel- where i and j represent modi®ed versions of the Ns genome atives on the basis of its lemmas that are hirsute to densely within the Psathyrostachys genus. On the basis of the low villous with long yellow-whitish hairs. Leymus triticoides, L. frequency of trivalents (0.15±0.40) in eight triploid hybrids cinereus, L. salinus, L. simplex, and L. ambiguus are char- between diploid Psathyrostachys and tetraploid Leymus spe- acterized by glabrous to sparsely strigose lemmas (Holmgren cies (Dewey 1970a, 1972c, 1976; Wang and Hsiao 1984), and Holmgren 1977). The objectives of this study are to de- chromosome pairing does not support the segmental auto- scribe chromosome pairing and fertility in F1 hybrids between tetraploid nature of Leymus tetraploid taxa as proposed by L. ¯avescens and North American tetraploids L. triticoides and Zhang and Dvorak (1991). On the basis of chromosome pair- L. cinereus and Eurasian tetraploids, L. secalinus, L. race- ing data, Wang et al. (1994) proposed that the second genome mosus, and L. alaicus subsp. karataviensis, and to utilize within tetraploid Leymus species be designated Xm, thus giv- genome-speci®c random ampli®ed polymorphic DNA (RAPD) ing Leymus the genomic formula of NsNsXmXm, where Xm markers to understand better the genomic composition of L. is an unidenti®ed genome. However, the actual genomic ¯avescens. makeup of Leymus is still very much in question and open for further investigation. Material and Methods Leymus ¯avescens, yellow wild rye, is a long-lived, strongly rhizomatous, tetraploid (2n54x528) perennial grass of the tribe Triticeae distributed throughout central Washington, Leymus ¯avescens (collection A-6484) was collected from eastern Oregon, and the Snake River plains of Idaho, with sand dunes in the Shelley-Blackfoot region of Idaho by Douglas isolated populations in the black hills of South Dakota (Holm- R. Dewey in the early 1970s. The target and analyzer species gren and Holmgren 1977). The original description of L. ¯a- used are listed in table 1, including their accession and chro- vescens, described as Elymus ¯avescens, was made on the basis mosome numbers, genome designations, and origins. Leymus of material collected on dry sandy soils near Columbus, Klick- cinereus and L. triticoides are North American tetraploids with itat County, Washington, in 1886 (Holmgren and Holmgren the Ns and Xm genomes, the Ns genome originating from the 1977). It was transferred to the genus Leymus in 1947 by genus Psathyrostachys and the Xm from an unidenti®ed dip- Pilger (Homlgren and Holmgren 1977). loid (Dewey 1976; Wang and Jensen 1994). Leymus race- Little is known about the cytogenetic and genomic relation- mosus, L. secalinus, and