Czech J. Genet. Breed., 41, 2005 (Special Issue)

Twenty-one Years Later: The Impact of Löve and Dewey’s Genomic Classification Proposal

M. E. B��������1 and R. ��� B������2

1Intermountain Herbarium, Department of Biology, Utah State University, Logan, Utah, U.S.A. 84322-5305; 2Department of Crop Science, Swedish University of Agricultural Sciences, SE-230 53 Alnarp, Sweden, e-mail: [email protected]

Abstract: The Fifth International Symposium was held 21 years after Drs. A���� L��� and D������ R. D���� independently proposed that generic classification in the Triticeae be based on genomic constitution, spe- cies containing the same genomes being placed in the same . This was a startling proposal, particularly for taxonomists in North America where the existing treatments of the tribe still reflected the proposals made a century earlier by Bentham and Hackel. Although few taxonomists endorsed the principle of genomic circumscription, current generic treatments of the Triticeae have been strongly influenced by the wealth of genomic data available. The challenge that faces taxonomists is to determine which, if any, morphological characters or character sets can be used to identify the genomic composition of species in the tribe. The challenges for those engaged in molecu- lar research include elucidating the mechanism that underlies the formation of genomes and understanding the causal relationship of genomic constitution and morphology.

Keywords: Triticeae; ; generic delimitation; genomic classification

In 1984, Löve and Dewey independently proposed constitution of a species from its customary taxo- that generic classification in the Triticeae should be nomic treatment. One may not agree with Löve’s based on genomic constitution (L��� 1984; D���� taxonomic treatment (i.e. his decisions as to which 1984), in other words, that species with the same names represent good taxa and which should be genomic constitution be placed in the same genus. synonyms), but his synopsis is a phenomenal sum- The Fifth International Triticeae Symposium was mary of nomenclatural information for the Triticeae held 21 years after publication of their papers. This and is the obvious starting point for an electronic makes the papers “adults” according to the law in nomenclatural catalogue of the tribe, one of the some countries. It seemed appropriate to start this necessities for development of information on the symposium with a review of the impact of their Triticeae in the Global Biodiversity Information recommendation on research in the tribe. Facility (GBIF; http://www.gbif.org). The frequent- The two papers differed in their focus and taxo- ly heard statement that the tribe includes about nomic scope. Löve provided a checklist of the 350 specific or subspecific taxa is based, in large whole tribe that included all the names of which part, on Löve’s treatment. he was aware, together with their place of publi- Löve also provided short descriptions of the cation. As he stated in the introduction, many of genera and subgenera, including their chromosome Löve’s decisions were based on existing treatments number and genomic constitution. The descriptions rather than personal knowledge of the in- were not intended to be comprehensive, nor to serve volved and in some cases he inferred the genomic as the basis for writing keys. K������ (1989) used

Proc. 5th International Triticeae Symposium, Prague, June 6–10, 2005 3 Czech J. Genet. Plant Breed., 41, 2005 (Special Issue) them as the starting point for a cladistic analysis Both Löve and Dewey stated that future work of the tribe, but added information from other might lead to the necessity of recognizing additional sources in order to develop an almost complete genera. In 1986, L��� published two additional data matrix. A more serious problem arises from genera: Trichopyrum for species having a genomic Löve’s failure to cite sources for the cytological constitution of EeSt or EeEeSt and Psammopyrum information included. Such an omission is quite for species with a LEe, LLEe, or LLEeEe constitu- common in floras and checklists. Unfortunately, tion (using designations of Wang et al. (1994) that in at least one case, Löve’s omission conceals a are equivalent to the JS, JJS, GJ, GGJ, and GGJJ, lack of supporting evidence: his statement that respectively, used by Löve). Dewey, although aware Leymus has an NsJ genomic constitution (genomic that , as he and Löve treated it, contained symbols used in accordance with recommenda- species with at least three different genomic con- tions of the International Triticeae Consortium, stitutions, was not prepared to publish additional see W��� et al. (1994); http://herbarium.usu.edu/ generic names to reflect the different genomic Triticeae/genmsymb.htm) was based on instinct groups. Since he did not accept Lophopyrum as dis- rather than cytological study (L���, pers. comm. tinct from Thinopyrum, it is unlikely that he would to D����, circa 1986). His statement was accepted have accepted Trichopyrum and Psammopyrum. by several individuals, including B�������� et Although Löve and Dewey worked completely al. (1983) and D���� (1984). Subsequent work independently, Löve was well aware of Dewey’s (Z���� & D����� 1991; W��� & J����� 1994; work and used it in formulating his ideas. Dewey A���������-J������ & B������������ 2001; became aware of Löve’s interest after circulating Ø������ & H�����-H������� 1994a, b) provides the manuscript of a paper he had presented at a no evidence for the presence of the J genome; the conference held in 1979 (see D���� 1982) in which second genome appears to be a modification of the he proposed a more timid version of his later clas- Ns genome. A well-documented online database sification. Löve wrote to Dewey, urging him to of cytological information needs to be developed be more courageous and telling Dewey about his so that, in future, it will be easy to determine for work on the Conspectus. Thus, although the two which species the genomic constitution has been worked independently of each other, they were determined and by what means. aware of each other’s work when they prepared D���� (1984) in paper, The genomic system of clas- their manuscripts. sificationas a guide to intergeneric hybridization with The immediate response of taxonomists to the the perennial Triticeae, was restricted to the peren- proposal made by Löve and Dewey that generic nial genera, among which he included Hordeum. circumscription in the Triticeae be based on ge- In it he stated that, because genomic constitution nomic constitution was negative. To understand was the best guide to biological and phylogenetic the response, it is useful to consider the generic relationships within the Triticeae, it should be used treatments in use in 1984. For this purpose, we for generic delimitation. He discussed the relation- review the treatment of the tribe in the major floras ships of the genera he recognized based on wide that were in existence at that time. hybridizations and classical analyses of meiosis and cited the papers documenting his statements. Perceptions of the Triticeae in 1984 He listed the species he knew to be included in each genus, but did not attempt to include species Americas: In 1984, the majority of North Ameri- with which he was not familiar. He did not provide can floras based their treatment of the Triticeae morphological descriptions for the genera, nor a (which many still called Hordeae) on the treatment complete list of synonyms. in H�������� (1951) which was, in turn, based on The only difference between Dewey and Löve B������ (1882) or H����� (1887). In other words, in their treatment of the perennial Triticeae was included annual and perennial species Löve’s recognition of Lophopyrum, a genus whose with a tough rachis and a single at each members Dewey included in Thinopyrum. This node, species with tough rachises and more than difference reflected a difference in opinion as to one spikelet at a node being placed in Elymus. The whether the genome of T. elongatum [≡ L. elongatum] one departure from Bentham’s treatment involved should be designated JE or E (W��� 1985; W��� & recognition of the North American genus Sitanion, H���� 1989; J����� 1990; W��� et al. 1994). which differs from other species of Elymus in hav-

4 Proc. 5th International Triticeae Symposium, Prague, June 6–10, 2005 Czech J. Genet. Plant Breed., 41, 2005 (Special Issue) ing disarticulating rachises. In 1956, S������� com- Immediate Response mented that, genetically speaking, the whole tribe could be treated as a single genus. Despite this, The immediate response of most systematists American floras continued to adopt the traditional was negative. Almost all objected to the concept of generic treatment of the tribe (e.g. R��������� et basing generic delimitation on what was seen as a al. 1970; S������ 1978; B����� 1983). single character, pairing behavior of chromosomes. Eurasia: The former Soviet Union followed This objection reflects a long history of discovering T������ (1976), whose treatment differed from that new characters or approaches, despite their that of B������ (1882) and H����� (1887) in re- initial promise, have never lived up to their early cognizing several additional genera, both annual promise for solving taxonomic problems; exceptions and perennial, e.g. Eremopyrum, Taeniatherum, to a generalization are soon discovered. Why should Elytrigia, and Leymus. Agropyron was restricted to looking at meiotic pairing be different? Löve and A. cristatum and its allies (the crested wheat- Dewey argued that pairing behavior reflected the grasses), the other species Bentham included in genetic similarity along the chromosomes and was, Agropyron being placed in Elymus or Elytrigia. therefore, a summary of multiple characters. They The treatment in Flora Europea (M������� 1980) knew that, in some instances, pairing is overridden was similar to that in T������ (1976) except that by genes that control pairing but considered such Elytrigia was included in Elymus. Chinese tax- instances exceptional, at least in the Triticeae. onomists (K��� 1965; G�� & W��� 1981) adhered Another objection was that, if adopted, the ge- more closely to the treatment advocated by N����� neric affiliation, and hence the name of a species, (1934) than that adopted by T������ (1976), plac- could not be determined until its genomic consti- ing Agropyron species that Tsvelev included in tution had been determined. L��� (1984) made it Elymus into Roegneria. clear that he considered that morphological simi- Where the authors of all the treatments cited did larity was usually a reliable indicator of genomic not differ was in basing their generic circumscrip- constitution, relying on it to place the many species tion primarily on morphological similarity and of which he had no personal knowledge. Indeed, the relative frequency with which hybrids were in 1986 he stated (L��� 1986, p. 44), “Therefore, formed. Cytological data were considered but not the methods of genome analysis based on studies given priority (see, e.g. N����� 1934; M������� 1953, of meiosis in hybrids may be augmented or even 1978), let alone used to define genera as Löve and replaced by several other more or less subjective Dewey advocated. procedures. Utilizing either or both herbarium It is worth noting that Dewey and Löve were or live material, comparison of descriptions and working in the region where the generic treat- specimens are sometimes enhanced by a variation ment had changed least in the century following of methods …”. Dewey would point out to those publication of the global synopses by Bentham and who asked the morphological similarity among Hackel. In 1978, Dewey circulated a preliminary the taxa that had similar genome constitutions. draft of his generic concepts to several taxonomists Both were aware of examples where the correlation in North America (including Barkworth); with few between morphology and genomic constitution exceptions the response was negative (Dewey, pers. breaks down. For instance, Hystrix is a genus comm. to Barkworth, 1979). The most frequent that is distinguished by its lack of glumes. Its comment was that the new generic concepts would type species, Elymus hystrix, is an StH species be difficult to apply in the field. Other comments (C����� 1967) but other species examined ap- were that treatments used in other regions of the pear to be autoploids based on the Ns genome world were not necessarily better than those in use and either a modification of that genome or a in North America and that the change would be different genome (J����� & W��� 1997; Z���� difficult for people to learn. Taxonomists can be et al. 2002). According to genomic classification, very conservative when it comes to names. Löve’s such species belong in Leymus. When confronted response was one of very few that was positive. It with such discrepancies between the genomic and was against this background that the two prepared morphological data, both Löve and Dewey placed their papers advocating that genomic constitution the species concerned on the basis of their genomic should be used to determine generic limits in the constitution. Even if genomic data were only avail- Triticeae. able for one of a recognized group of species, as

Proc. 5th International Triticeae Symposium, Prague, June 6–10, 2005 5 Czech J. Genet. Plant Breed., 41, 2005 (Special Issue) was the case with Hystrix in 1984, they treated all repens, there may be more genomic diversity within species of the group in the same way. a species than can be detected via traditional mei- Dewey was not always consistent. He knew in otic analyses. 1984 that Elymus as he treated it included species What was the reaction of geneticists and plant with at least three different genomic constitutions, breeders? In general, such individuals readily but he considered it premature to name additional adopted Dewey’s treatment of the perennials; a genera. Recently, Y�� et al. (2005) published one of few followed Löve. Basing generic delimitation on the additional names needed to accommodate the genomic constitution was appealing for its logical known variation and indicated their intention of consistency and simplicity. The fact that the new publishing another. These names, combined with generic boundaries were based on information Roegneria (StY), Kengylia (StYP), Austrolapyrum (W), relevant to breeding undoubtedly added to their and Stenostachys (HW), will permit recognition appeal. Although it is still not understood how at the generic level of all varied genomic groups genomic identity is determined, all subsequent that Löve and Dewey included in Elymus. What no methodologies (e.g. DNA sequencing, fluorescent one has provided so far are good morphological in situ hybridization, genomic in situ hybridiza- characterizations of the genomically circumscribed tion) have supported their reality. Moreover, many taxa and a reliable key to their identification. geneticists and plant breeders are only minimally In addition to objecting to reliance on a single concerned with morphological circumscriptions character for classification, many systematists and field identification of genera. disagreed with Dewey’s statement that genomic Within the annual species, Löve’s splitting of constitution was a guide to phylogenetic relation- Aegilops was generally rejected, the genus continu- ships within the tribe. The objection stems, at least ing to be interpreted as treated by Linnaeus. It is in part, from failure to appreciate that Dewey worth noting that the opposite recommendation, and Löve used the term phylogeny in the sense that Triticum and Aegilops be combined into a single that it had had in their academic youth, one that large genus, has also failed to find acceptance encompassed groups giving rise to groups as well despite the strong arguments for such an expan- as species to species. One could draw phyloge- sion and its support by some of the major names netic relationships using bubbles, not lines. In that in taxonomy (e.g. B������ 1882; H����� 1887; sense, the StH species arose from two bubbles, one G������ & R�������� 1967) and endorsed in this containing St species, the other H species. Dewey symposium (D� B����� and J���� this volume) did not mean to imply that one could tell which as well as by Y�� et al. (2005). This is a reminder St species was ancestral to other St species, nor that the value of names lies in large part in their to suggest that one could use genomic analysis to stability. So far, the general conclusion seems to determine which St and which H species had given be that it is easier for each generation to learn that rise to a particular StH. Around 1984, however, the all polyploid species of Triticum include genomes term “phylogeny” was morphing into its current, from Aegilops than to start referring to the Aegilops narrower interpretation that is reflected in the use as members of Triticum. of lines derived from cladistic analyses, preferably analyses of molecular data, to show phylogenetic Later responses relationships. There is no question that genomic constitution is To see more clearly whether taxonomic proposals not, in itself, a guide to phylogenetic relationships are broadly accepted by taxonomists, one needs in the current sense. Nevertheless, phylogenetic to consider floristic treatments, for it is through analyses of single genes have consistently shown such treatments that most people acquire taxo- that diploid species with the same genomic con- nomic knowledge and identify plant materials. stitution are part of the same lineage or clade; in Table 1 summarizes the treatment of the perennial a few instances, trees based on chloroplast trees Triticeae in various floras that have been published have differed from those based on nuclear genes since 1984, either in print or on the Web. As can be (K������ et al. 1996). Interestingly, the species in seen, there is still considerable disagreement even question have also been regarded as taxonomically among the genera that are widely distributed. Even puzzling. M����-G���� (2004; this volume) has greater variability would be evident if the floras also demonstrated that, at least in Elymus (Elytrigia) of other regions (e.g. H������� & X������ 1986,

6 Proc. 5th International Triticeae Symposium, Prague, June 6–10, 2005 Czech J. Genet. Plant Breed., 41, 2005 (Special Issue)

Table 1. Treatment of the perennial Triticeae in various floras published since 1984

Flora of New () Grasses of the Flora of China Flora of North Zealand in Australia New World (Dra�) America (Dra�) E����, C����� W������ et al. S����� et al. C��� & Z�� B�������� et al. (2000) (1995) (2003) (2005) (in prep.) Agropyron NA NA √ √ √ Australopyrum √ √ NA NA NA Critesion √ X X X X Elymus √ √ √ √ √ Elytrigia √ √ X √ X Hordeum NA √ √ √ √ Hystrix NA NA X √ X Kengyilia NA NA NA √ NA Leymus √ NA √ √ √ Pascopyrum NA NA √ NA √ Pseudoroegneria NA √ √ √ √ Roegneria NA NA NA X NA Sitanion NA NA X NA X Stenostachys √ X NA NA NA Thinopyrum √ √ √ X √

√ – accepted in publication; NA – not applicable to the region; X – applicable but included in another genus

2000; W���� et al. 2003) and the generic proposals would be a significant achievement in itself, one of others (e.g. S����� & L����-L������ 1996; Y�� that would be welcomed by individuals in many et al. 2005) were included. different disciplines. Despite rejecting the idea that genomic constitu- And now? tion should be used to define genera in the Triticeae, almost all papers in systematic, cytological, and The papers by Dewey and Löve have lead to plant breeding research routinely provide informa- increased agreement on generic limits within the tion about the genomic constitution of the species tribe. The agreement is not complete, but the differ- involved. Moreover, determination of the genomic ences are smaller than they were in 1984. Before the constitution is, as Dewey claimed, an important next Symposium in 2011, the taxonomists among us step in evaluating the breeding potential of any need to focus on developing a species-level treat- species combination. There have been enormous ment of the tribe, because the ability to accurately advances in many fields of research since Dewey identify species is critical to all other work. One and Löve published their papers. A wide array of approach to such a project would be to develop molecular techniques has permitted considerable illustrated, multi-entry identification keys using progress to be made in understanding the genetic program such as DELTA (D������� 1980; D������� bases for salinity tolerance, root development, and et al. 1993, 1995, 2000) or Lucid ID (Centre for other agronomically important traits. Molecu- Bioinformation Technology 2004). Adopting such lar techniques also make it possible to determine an approach would develop the data required to the distribution of genes on the chromosomes determine which, if any, characters, either singly or in different genomes. We can hope that, eventu- in combination, are reliable indicators of genomic ally, this ability will also enable us to understand constitution in the Triticeae. Even if no such char- the causative difference between genomes and acters are found, a reliable, illustrated multi-entry why differences in the location and sequences of key for the identification of species of the Triticeae homeologous gene sequences result in different

Proc. 5th International Triticeae Symposium, Prague, June 6–10, 2005 7 Czech J. Genet. Plant Breed., 41, 2005 (Special Issue) morphologies, even among species with the same G������ W., R�������� K.H. (1967): Chloris kythereia. genomic constitution. Boissiera, 13: 22–196. G�� P.-C., W��� S.-J. (1981): Research on the evolution References of the inflorescence and the generic relationships of the Triticeae in China. Acta Botanica Boreali-Oc- A���������-J������ K., B������������ S.K. (2001): cidentalia Sinica, 1: 12–19. Genomic and genetic relationships among species H����� E. (1887): Gramineae. In: E����� A., P����� of Leymus (Poaceae: Triticeae) inferred from 18S- K. (eds.): Die Natürlichen Pflanzenfamilien, Vol. II, 26S ribosomal genes. American Journal of Botany, 2. Engelmann, Leipzig, Germany: 1–97. 88: 553–559. H�������� A.S. (1951): Manual of Grasses of the United B�������� M.E., D���� D.R., A����� R.J. (1983): New States, ed. 2, rev. A. Chase. U.S. Department of Agri- generic concepts in the Triticeae of the Intermountain culture Miscellaneous Publication No. 200. U.S. Gov- Region: Key and comments. Great Basin Naturalist, ernment Printing Office, Washington, D.C., U.S.A. 43: 561–572. H������� J.H., X������ C.C. (1986): Notas criticas sobre B����� A.A. (1983): Las Gramíneas de México. Secretaría Elytrigia (Gramineae). Darwiniana, 27: 561–564. de Agricultura y Recursos Hidráulicos, COTECOCA, H������� J.H., X������ C.C. (2000): Observations on México D.F., México. the taxonomy of South American Elymus (Poaceae). B������ G. (1882): Notes on Gramineae. Journal of Kurtziana, 28: 287–295. the Linnean Society, Botany, 18: 14–134. J����� P.P. (1990): Multidisciplinary approach to ge- Centre for Bioinformation Technology (2004): Lucid ID. nome analysis in the diploid species, Thinopyrum University of Queensland, Brisbane, Australia. bessarabicum and Th. elongatum (Lophopyrum elongatum) C��� S.-L., Z�� G.-H. (2005): Tribe 14, Triticeae. In: of the Triticeae. Theoretical and Applied Genetic, 80: F���� �� C���� E�������� C�������� (eds.): Flora 523–536. of China, Vol. 22 (Poaceae), dra� version. h�p://flora. J����� K.B., W��� R.R.-C. (1997): Cytogene- huh.harvard.edu/china/mss/volume22/Poaceae-MO_ tic and molecular evidence for transferring Ely- Triticeae_original.htm. Accessed 5 May 2005. mus coreanus from the genus Elymus to Leymus C����� G.L. (1967): Taxonomic and genetic relation- and molecular evidence for Elymus californicus. In- ships of eastern North American species of Elymus ternational Journal of Plant Science, 158: 872–877. with setaceous glumes. Rhodora, 69: 121–162. K������ E.A. (1989): Comments on genomic genera in D������� M.J. (1980): A general system for coding the Triticeae (Poaceae). American Journal of Botany, taxonomic descriptions. Taxon, 29: 41–46. 76: 796–805. D������� M.J., P���� T.A., Z������ E.J. (1993): User’s K������ E.A., A����� R., M����-G���� R.J. (1996): guide to the DELTA system: A general system for When gene trees tell different stories: The diploid processing taxonomic descriptions, 4th ed. h�p:// genera of the Triticeae (Gramineae). Systematic delta-intkey.com. Botany, 21: 321–347. D������� M.J., P���� T.A., Z������ E.J. (1995): User’s K��� Y.-L. (1965): Tribus 7, Hordeae Bentham. In: K��� guide to Intkey: A program for interactive identification Y.-L. (ed.): Flora Illustrata Plantarum Primarum and information retrieval. h�p://delta-intkey.com. Sinicarum: Gramineae. 2nd Ed. Scientific Publishing, D������� M.J., P���� T.A., Z������ E.J. (2000): Prin- Beijing, China: 340–351. ciples of interactive keys. h�p://delta-intkey.com. L��� Á. (1984): Conspectus of the Triticeae. Feddes D���� D.R. (1982): Genomic and phylogenetic relation- Repertorium, 95: 425–521. ships among North American perennial Triticeae. In: L��� Á. (1986): Some taxonomical adjustments in eur- E���� J.R., T��� R.J., B������ J.N. (eds.): Grasses and asiatic wheatgrasses. Veröffentlichungen des Geobo- Grasslands. University of Oklahoma Press, Norman, tanis�en Institutes des Eidg[enössis�e] Te�n[is�e] Oklahoma, U.S.A.: 51–88. Ho�s�ule, Sti�ung Rübel in Züri�, 87: 43–52. D���� D.R. (1984): The genomic system of classifica- M����-G���� R.J. (2004): Reticulate evolution, intro- tion as a guide to intergeneric hybridization with gression, and intertribal gene capture in an allohexa- the perennial Triticeae. In: G�������� J.P. (ed.): Gene ploid grass. Systematic Botany, 53: 25–37. Manipulation in Plant Improvement. Plenum Pub- M������� A. (1953): Generic problems within the lishing, New York, U.S.A.: 209–279. tribe Hordeeae. In: O����� H., A���� E. (eds). Proc. E���� E., C����� H.E. (2000): Flora of New Zealand, Vol. 7th Int. Botanical Congr., Stockholm, July 12–20, 5. ManaakiWhenua Press, Lincoln, New Zealand. 1950. Almqvist & Wiksell, Stockholm, Sweden, and

8 Proc. 5th International Triticeae Symposium, Prague, June 6–10, 2005 Czech J. Genet. Plant Breed., 41, 2005 (Special Issue)

Chronica Botanica, Waltham, Massachuse�s, U.S.A.: S������� G.L. Jr. (1956): Taxonomy and evolution of 853–854. genera, with special reference to the family Gra- M������� A. (1978): Taxonomic notes on the tribe Triti- mineae. Evolution, 10: 235–245. ceae (Gramineae) with special reference to the genera T������ N.N. (1976): Zlaki SSSR (Grasses of the Soviet Elymus L. sensu lato and Agropyron Gaertner sensu Union). Nauka, Leningrad, U.S.S.R. lato. Botanical Journal of the Linnean Society, 76: W��� R.R.-C. (1985): Genome analysis of Thinopyrum 369–384. bessarabicum and T. elongatum. Canadian Journal of M������� A. (1980): Tribe Triticeae. In: T���� T.G., Genetics and Cytology, 27: 722–728. H������ V.H., B����� N.A., M���� D.M., V�������� W��� R.R.-C., B������ R., D����� J., F���� G., L����- D.H., W������ S.M., W��� D.A. (eds.): Flora Europaea, L������ I., M�������� M. (1994): Genome symbols Vol. 5. Cambridge University Press, Cambridge, in the Triticeae (Poaceae). In: W��� R. R.-C., J����� U.K.: 190–206. K.B., J����� C. (eds). Proc. 2nd Int. Triticeae Symp. N����� S.A. (1934): Tribe XIV. Hordeae Benth. In: R����- Forage and Range Research Laboratory, U.S.D.A., ���� R.Y., S������� B.K. (eds.): Flora of the U.S.S.R., Logan, Utah, U.S.A., 29–34. Vol. II (transleted by N. Landau). Israel Program for W��� R.R.-C., H���� C. (1989): Genome relationships Scientific Translations, Jerusalem, Israel: 469–579. between Thinopyrum bessarabicum and T. elongatum Ø������ M., H�����-H������� J.S. (1994a): Investiga- revisited. Genome, 32: 802–809. tions of genome relationships in Leymus, Psathyro- W��� R.R.-C., J����� K.B. (1994): Absence of the J stachys and Hordeum by genomic DNA:DNA in situ genome in Leymus species (Poaceae: Triticeae). Ge- hybridization. Annals of Botany, 73: 195–203. nome, 37: 231–235. Ø������ M., H�����-H������� J.S. (1994b): Relation- W������ C.M., H������ M.J., L��� J., W����� L. (1995): ships between species of Leymus, Psathyrostachys and Pooideae (Poaceae) in Australia – Descriptions and Hordeum (Poaceae, Triticeae) inferred from Southern illustrations. h�p://www.biodiversity.uno.edu/delta/ hybridization of genomic DNA and cloned DNA pooid/www/. Accessed 21 Aug 2005. probes. Plant Systematics and Evolution, 189: 217– W���� S.L., A����� N.D., G������� S., H������ L.C. 231. (2003): A Utah Flora, 3rd ed., revised. Brigham Young R��������� B., A�������� �� M����� B.R., I�������� �� University, Provo, Utah, U.S.A. A������ P. (1970): Gramíneas Uruguayas. Universidad Y�� C., Y��� J.-L., Y�� Y. (2005): Hitochi Kihara, Áskell de la República, Montevideo, Uruguay. Löve and the modern genetic concept of the genera in S������ H.J. (1978): Flora of Canada, pt. 2. National the tribe Triticeae (Poaceae). Acta Phytotaxonomica Museum of Natural Sciences Publications in Botany Sinica, 43: 82–93. No. 7(2). National Museum of Natural Sciences, Na- Z���� H.-B., D����� J. (1991): The genome origin tional Museums of Canada, O�awa, Canada. of tetraploid species of Leymus (Poaceae: Triticeae) S����� O., L����-L������ I. (1996): Eremium, a new inferred from variation in repeated nucleotide se- genus of the Triticeae (Poaceae) from Argentina. quences. American Journal of Botany, 78: 871–884. Systematic Botany, 21: 3–15. Z���� H.-Q., Z��� Y.-H., Z���� Y.-L., Y��� R.-W., D��� S����� R.J., P������� P.M., D������ G., J��������� C.-B. (2002): Morphology and cytology of intergeneric E.J., Z������ F.O., F��������� T.S., M������ O. hybrids between Hystrix duthiei ssp. longearistata and (2003): Catalogue of New World Grasses (Poaceae): Psathyrostachys huashanica (Poaceae: Triticeae). Acta IV. Subfamily Pooideae. Contributions from the United Phytotaxonomica Sinica, 40: 421–427. States National Herbarium, 48: 1–730.

Proc. 5th International Triticeae Symposium, Prague, June 6–10, 2005 9