Breeding Science 59: 513–518 (2009)

Review

Historical review and prospect of of tribe Dumortier ()

Chi Yen* and Jun Liang Yang

Triticeae Research Institute, Sichuan Agricultural University, Chengdu 611130, Sichuan, The People’s Republic of China

The tribe Triticeae is a taxon in the Poaceae that includes several important cereal crops and forage grasses. All its species, including those that are not used for cereals or forage, are potential sources of genes for crop and forage improvement so they all have high economic value. Taxonomic treatments, including those of the Triticeae, are the basis for identification. They are often designed to reflect phylogenetic relationships and provide a guide for germplasm utilization. Traditional taxonomic treatments of the Triticeae were based on comparative morphology and geography. Morphological characters are phenotypes of an organism, resulting from interactions between or among dominant genes and environmental factors. Morphology cannot reflect recessive inheritance. Similar environmental conditions may result in morphological convergence in distantly related taxa and different environmental conditions in morphological divergence of closely related taxa. Con- sequently, traditional morphological taxonomy may result in misclassification. Cytogenetic and/or molecular genomic analysis may reveal such mistakes. On the basis of recent genomic investigations of the Triticeae, we have recognized 30 genera in this tribe. The taxonomic changes and genomic constitution of these genera are presented in this paper.

Key Words: Triticeae, genera, genomic constitution, phylogenetic relationships.

Introduction Linnaeus (1753) later named them Aegilops ovata and Ae. triuncialis, respectively. These names are, however, al- The tribe Triticeae is a taxon in the Poaceae that includes ways attributed to Linnaeus because, ever since acceptance several important cereal crops and forage grasses. All the of the first edition of the International Code of Botanical tribe’s species are potential sources for genes would im- Nomenclature (1867), it has been agreed that the first edition prove the crop and forage species which makes understand- of Linnaeus’ (1753) ‘Species plantarum’ will be treated as ing and recognizing them of great economic importance. the staring point for botanical nomenclature, earlier works taxonomy, the study and classification of plant diver- being used only to clarify what Linnaeus meant by the sity, provides the basis for circumscribing and naming names he used in ‘Species plantarum’. the units examined and discussed by scientists in other dis- The tribe was first recognized by the Belgian botanist ciplines, including phylogenetics and plant breeders. The Dumortier in 1823 who named it Triticeae. Two years later, economic importance of the Triticeae has resulted in its tax- the German botanist Spenner (1825) named the same tribe onomy being more thoroughly studied than that any other Hordeeae. This name had been used earlier by Kunth (1815) tribe of grasses. and Berchtold and Presl (1820), but the current edition of the International Code of Botanical Nomenclature (McNeill et Historical account al. 2006), like its predecessors, states that the correct name of a taxon at the family level or below is the first name that Taxonomists working before Linnaeus recognized several was correctly published for it at that rank. Unfortunately, taxa in what is now called the Triticeae. For instance, in Dumortier’s use of Triticeae was overlooked by both 1584, Gaspard Bauhin used the name in ‘Pinax Bentham (1882) and Hackel (1887) so many older references theatri botanici’. It was also used by Tournefort (1694), the use the name Hordeeae or Hordeae for the tribe. first botanist to make a clear distinction between what we From the eighteenth to the twentieth century, the taxono- now call genera and species. Similarly, Scheuchzer (1719) my of the Triticeae was based primarily on morphological reported two Triticeae species in his ‘Agrostographia’. and phytogeographic studies. Such studies have made great contributions to our knowledge of the plant kingdom, in- Communicated by H. Tsujimoto cluding the Triticeae. Another important development dur- Received August 5, 2009. Accepted October 23, 2009. ing this period was establishment of the International Code *Corresponding author (e-mail: [email protected]) of Botanical Nomenclature. Its publication helped resolve 514 Yen and Yang

Table 1. Genera included in tribe Triticeae by various morphological taxonomists. Some of the differences reflect differences in the geographic coverage of the works used to develop the table. Names in bold font belong in the tribe; names in plain font are no longer included in the tribe. *Only one of the two species previously treated in belongs in the Triticeae. It is now known as Henradia persica (After Dewey 1984). Melderis et al. Bentham (1882) Hackel (1887) Nevski (1934) Hitchcock (1951) Pilger (1954) Keng (1965) Tzvelev (1976) (1980) Agropyrum Agropyrum Aegilops Aegilops Aegilops Aegilops Aegilops Aegilops Asperella Asperella Agropyron Agropyron Agropyron Agropyron Agropyron Elymus Aneurolepidium Elymus Amblyopyrum Aneurolepidium Amblyopyrum Hordeum Haynaldia Anthosachne Hordeum Crithopsis Asperella Dasypyrum Kralikia Asperella Hystrix Desypyrum Clinelymus Elymus Elymus Lepturus* Hordeum Lolium Elymus Elymus Elytrigis Lolium Jouvea Clinelymus Monerma Eremopyrum Elytrigia Eremopyrum Oropetium Kerinozoma Crithopsis Scribneria Heteranthelium Eremopyrum Henrardia Psilurus Kralikia Hordelymus Hordeum Heteranthelium Hordeum Secale Lepturus* Elymus Sitanion Hordeum Lepturus* Hordelymus Leymus Triticum Lolium Elytrigia Triticum Hystrix Lolium Hordeum Psathyrostachys Monerma Eremopyrum Leymus Parapholis Hystrix Secale Nardus Haynaldia Malacurus Psathyrostachys Leymus Oropetium Heteranthelium Psathyrostachys Roegneria Psathyrostachys Triticum Pariana Hordeum Secale Secale Secale Psilurus Malacurus Sitanion Triticum Taeniatherum Scribneria Psathyrostachys Taeniatherum Triticum Secale Roegneria Triticum Secale Sitanion Taeniatherum Terrella Trachynia Triticum the chaos in plant taxonomy by formally adopting the con- ical characters may lead to mistakes in circumscribing taxa. cept of a hierarchical arrangement of taxonomic entities and For example, the strong epistatic effect of the St genome naming the ranks to be recognized. Table 1 lists a few of the makes distinguishing between Elymus and Roegneria very Triticeae classifications published during this period. difficult, particularly if one wishes to rely on gross features such the number of spikelets per node and the fragility of the Limitation of morphological taxonomy rachis, but only in Elymus sensu stricto, the StH (genome symbols as recommended by the International Triticeae There is no set of rules for determining what makes a group Consortium, http://herbarium.usu.edu/Triticeae/genmsymb. of deserve recognition as a species. Linnaeus and oth- htm) species, can we observe long pointed paleas with er morphological taxonomists described many entities as rather narrow distance between the two densely and finely distinct species that, to them, seemed ’distinctly different‘ scabrous keels similar to those observed in Hordeum. In but later taxonomists have considered to be morphological Rogeneria the paleas have a rounded, truncate, or emarginate variants of little or no taxonomic significance. This is partic- tip and the keels are more widely spaced and have more ularly true of crop plants. One consequence of these chang- sparsely and coarsely scabrous keels (Baum et al. 1991, ing judgments is that the names used to refer to currently Salomon and Lu 1992). These two genera are only separated recognized species have many synonyms, names that were by these morphological characteristics of palea, which are originally thought to refer to different species but that are controlled by a few epistatic genes in the hypostatic ge- now thought to apply to portions of the same species. nomes, H and Y. It is not surprising therefore, that many Morphological characters are phenotypes (P) of an organ- taxonomists include Roegneria in Elymus. The limitations of ism produced by functional interaction(s) between or among morphology are also evident in the inability to distinguish dominant gene(s) (G) and environmental factor(s) (E). between, for example, Roegneria panormitana (StStYY) P = ƒ(G·E) and R. heterophylla (StStStStYY) (Yen et al. 2008) and be- External morphological character cannot reflect internal hy- tween Eremopyrum sinaicum (FsFs) and Er. bonaepartis postatic gene(s). Similar environmental conditions produce (FsFsFF) (Yen et al. 2004) on the basis of morphology. convergent natural selection and different environmental Species is an absolute unit of living organisms in nature. conditions produce divergent natural selection. Therefore, It is a group of individuals that are connected to each other reliance on morphology, particularly easily seen morpholog- by their indispensable relationships of breeding. Species is Taxonomy of tribe Triticeae (Poaceae) 515 an independent gene pool. However, we cannot exactly de- cations and thus E and J haplomes should be changed to fine a species only by morphological characteristics. So, in Ee and Eb, respectively. Therefore, Elytrigia should be a morphological taxonomy, genera and species, like other sys- synonym of Elymus. Those taxa that possess Ee, Eb and St tematic ranks, are subjectively taken for granted. Mistakes haplomes belong to the Trichopyrum. Since E and J can hardly be avoided. haplomes are essentially the same, genus Thinopyrum should be combined with genus Lophopyrum. Löve divided The genetic concept of genus applied in tribe Triticeae the Aegilops-Triticum complex into 16 genera. However, most people continue to recognize two genera, Aegilops and We have a very high opinion of Hitoshi Kihara’s academic Triticum. achievement. He invented genome analysis and proposed Löve (1984) recognized the genus Dasypyrum (Cosson et genome theory in 1930. These contributions led to cytoge- Durieu) T. Durand for the VV and VVXvXv taxa. The valid- netic research in Triticeae and other plant group. He used his ity of this treatment has drawn heated arguments. The dis- methods to refine the classification of and evolutionary rela- pute is focused on whether the type species of Triticum tionships within the Triticum-Aegilops complex. (Kihara section Dasypyrum Cosson et Durieu is invalid. Triticum 1930, 1954, Kihara and Nishiyama 1930). Dewey (1982, hordeaceum Cosson et Durieu, the only species of this sec- 1984) followed Kihara’s lead in his work on the perennial tion, should be the type species without doubt. Unfortunate- species of Triticeae. His work, which built on that of others, ly, this species itself is invalid by principle of priority. provided the information needed for developing a cytotaxo- Triticum hordeaceum (Boiss.) Steudel was applied to another nomic treatment of the tribe. In 1982, Áskell Löve proposed taxon from slightly earlier than to T. hordeaceum adopting a generic taxonomy of tribe Triticeae on the basis Cosson et Durieu. According to principle II of the International of rigorous genomic concept, recommending that each Code of Botanical Nomenclature, “The application of names haplome or unique combination should be used to define a of taxonomic groups is determined by means of nomencla- genus. He regarded the genomic approach as being “crucial tural types”, this genus name, therefore, should be invalid. for studies of the evolution and definition of the basic taxo- So, in 1942, Rann Charles Joseph Ernest Maire named the nomical categories” (Löve 1984). then-invalid genus Dasypyrum using Dasypyrum villosum as Löve (1984) implemented his recommendation in his the type species. Maire’s treatment “Dasypyrum (Cosson et ‘Conspectus of the Triticeae’ which he described as provid- Durieu) Maire in Bell. Soc. Hist.Nat. Afr. Nord, xxxiii 101 ing “a taxonomical and nomenclatural survey of the more (1942) Gramineae” was accepted by Index Kewensis (Index than 500 biological taxa of the Triticeae tribe of grasses in a Kewensis supp. XI 1941–1950). The problem is that the ge- system of 37 genomically defined genera based on twenty- nus name Dasypyrum (Cosson et Duieu) Maire was later three single-haplome taxa as recently validated elsewhere.” than Pseudosecale (Godron) Degen (1936. Fl. Veleb. 1: 574) Löve (1984) recognized 37 perennial and annual genera in by seven years. So, we believe that Hungarian Botanist tribe Triticeae and established 13 new genera, five of which Arpad von Degen’s treatment is the valid one. were status novus based on genomic constitution. Because Douglas R. Dewey basically agreed with Löve’s generic some species on Löve’s list had not been cytogenetically concept about Triticeae. In his paper (Dewey 1984) he quot- studied, he placed them in genera based on their morpho- ed a serial papers of Löve from 1957 to 1984. He recognized logical characteristics. Most of the species involved were some of Löve’s genera, such as Pascopyrum Á. Löve and Asiatic or Oceanic perennial species in what we recognize as Pseudoroegneria (Nevski) Á. Löve and used Löve’s desig- Roegneria, Anthosachne, and Stenostachys. The genomic con- nation about haplome names for those genera. He disagreed stitution of these genera is StStYY, WWStStYY and HHWW, with Löve’s circumscription of Thinopyrum Á. Löve, expand- respectively. Having no evidence to the contrary, he placed ing it to include Lophopyrum Á. Löve. Nevertheless, he did their species in Elymus because they clearly did not belong not use the generic name Lophopyrum proposed by Löve. His to Agropyron sensu stricto, Leymus, Pseudoroegneria, concept of Elymus was somewhat also different from that of Thinopyrum, or Lophopyrum the other perennial genera that Löve. According to Löve (1984), all the species of possessed solitary spikelets. He did not know Elymus californicus only the H and St haplomes. Dewey mentioned that “the (Bolander) Gould, E. coreanus Honda, E. asiatica Á. Löve, greatest information void in Elymus is in those species from E. komarovii (Roshev.) Ohwi, E. japonicus (Hack.) Á. Löve, China, which has more than 50 species of Elymus (including and E. duthiei (Staff) Bor possessed NsXm haplomes Roegneria) (Keng 1965). Many of these species contain a Y- (Zhou et al. 1999, Zhang et al. 2002), which are quite differ- genome of unkown origin” (Dewey, 1984). In 1984, when ent from E. hystrix L. that contains St and H genomes. Dewey visited our Institute, we discussed the recognition of Elytrigia repens L., the type species of Elytrigia contained Roegneria. He said that we should follow Tzvelev in com- StStH haplomes (Assadi and Runemark 1994, Vershinin et bining Roegneria into Elymus. We have never agreed with al. 1994). Löve (1984) thought that Elytrigia combined the him, and but told him that we would not jump to a conclu- E, J and S (St) haplomes and the genus Trichopyrum Á. sion but would wait until the experimental results have been Löve possessed E and S (St) haplomes. Wang (1985) con- obtained. We also showed him some pictures of a diploid cluded that E and J is the same haplome with small modifi- Pseudoroegneria karyotype that had two pairs of satellites 516 Yen and Yang ) has Xp) S , D l , B s ) , B b Xe , C, M, N, U, s , B , B sp l ) T , B ) sp , B, B V m , B c ) ) O A, A D, D L, E ( ( Sitopyros Aegilops Á. Löve ( (Godron) Degen ( (Jaub. et Spach) Eig ( (Ledeb.) Jaub. et Spach) (F, ) O. Seberg, S. Fredrikson et C. Baden ( R C. E. Hubbard ( subg. subg. L. ( , Zc) t International Triticeae Consortium. Thus, Löve’s Amblyopyrum Secale Pseudosecale Eremopyrum Henrardia Triticum Psammopyrum Triticum Xc, X ) ) ) Z B C, D ) ) ) ) O .) ) G, J ) ) D, M, U L ) U ) C C, U D ) B, U A, B A, ) (Jaub. et Spach) ( Á. Löve ( Á. Löve ( Á. Löve ( (Jaub. et Spach) Eig ( Á. Löve ( Á. Löve (Jaub. et Spach) Á. Löve (Ledeb.) Jaub. et Spach) M, U M, A, B, D Á. Löve ( ) Á. Löve ( Á. Löve (Jaub. et Spach) Á. Löve Á. Löve ( Festucopsis (Coss. et Durieu) T.Durand Seidl ( Seidl R are those recommended by the C. E. Hubbard ( Á. Löve ( L. ( L. ( (Jaub. et Spach) Á. Löve ( L. ( ) ) ) ) D, M D, V F M Aegilema Cylindropyrum Aegilopodes Gastropyrum ( Aegilonearum Aegilops Amblyopyrum Triticum Gigachilon Chennapyrum Kiharapyrum Secale Dasypyrum ( Eremopyrum ( Psammopyrum Comopyrum ( Henrardia Orrhopyrum Patropyrum Sitopsis Included in ) b P, P, or E e ) E Xu Xa) ) ) L H) ) ) ) St ours. The genome symbols used A. Löve( W ) P, St, Y ) Durmortier ( ) Xo, Xr) Xo, ) ) ) ) K ) ) H, St, Y I Ns Q ) ( ) Ta Thinopyrum St, H, Ns, Xm P St, W, Y H, W St, Y ) Ns, Xm (Nevski) Á. Löve ( ,) C. Yen, J. L. Yang et B. R. Baum ( Nevski ( Drobov ( Hochst. ( Hordeum Trichostachys (Tzvelev) Á. Löve ( E, St Nevski ( Nevski ( Turcz. ( Steudel ( Á. Löve+ Á. Löve ( (Jessen) Harz. ( Lophopyrum Elymus (C. E. Hubbard) Melderis ( H, St Jun Liang Yang, presented here J. Gaertn. ( Jaub. et Spach ( C. Koch ( C. Yen et J. L. Yang ( L. sect. sect. sect. Marinum (Nevski) Jaaska ( sect. Campestria Andersson ( L. Hochst. ( L. ( ric treatment of the Triticeae with ) Triticum Trichopyrum Pseudoroegneria Elymus Psathyrostachys Leymus Pascopyrum Agropyron Heteranthelium Crithopsis Included in Campeiostachys Roegneria Kengyilia Douglasdeweya Lophopyrum St Taeniatherum Hordeum Hordeum Festucopsis Hordeum Hordeum Hordeum Hordelymus ) ) S W . ) Ns to ) H, T) N ) ) K ) N Q ) G ) ) ) Included in T E S, H, J, N P ) ( J ) ) and his ) A H) J, N (Nevski) Á. Löve ( St E, J, S) Nevski ( ) Hochst. ( (Tzvelev) Á. Löve ( ) E, S Nevski ( I Stenostachys Stenostachys Anthosachne Anthosachne ( Á. Löve ( Á. Löve ( Á. Löve ( (Jessen) Harz. ( (C. E. Hubbard) Melderis H, S Link ( Peridictyon J. Gaertn. ( Jaub. et Spach ( Comparison of Áskell Löve’s gene L. ( Rafin, ( Desv. ( sect. sect. Hochst. ( L. ( 2.

Elymus Psathyrostachys Crithodium Trichopyrum Löve (1984, 1986)Agropyron Chi Yen et been changed to Crithopsis Table Pseudoroegneria Elytrigia Leymus Elymus Pascopyrum Lophopyrum Elymus Thinopyrum Heteranthelium Taeniatherum Hordeum Critesion Australopyrum Festucopsis (including Hordelymus Taxonomy of tribe Triticeae (Poaceae) 517 on fifth and seventh chromosomes, which are very similar to Syst. Evol. 194: 189–205. those karyotype of Y genome. Baum, B., C. Yen and J.L. Yang (1991) Roegneria its generic limits and In our opinion, classification in the Triticeae should justification for its recognition. Can. J. Bot. 69: 282–294. reflect the understanding of relationships that has been Bentham,G. (1882) Notes on Gramineae. Journal of the Linnean obtained from genome analysis and molecular studies. The Society, Botany 18: 14–134. Berchtold, F.G. von and J.S. Presl (1820) O prirozenosti Rostlin. Krala force of habit should also be considered whenever possible Wiljma Endersa, Praha. to avoid adding more chaos. Because speciation in different Dewey, D.R. (1982) Genomic and phylogenetic relationships among species group may follow different pathways; different North American perennial Triticeae. In: Estes, J.R., R.J. Tyri and standards should be applied to their classification to better J.N. Brunken (eds.) Grasses and Grasslands, University of Oklahoma reflect their phylogeny. Following these principles, we recog- Press, Norman, Oklahoma, USA, pp. 51–88. nize 30 genera in the Triticeae. These genera with their Dewey, D.R. (1984) The genomic system of classification as a guide genomic constitutions are listed in Table 2 with a compari- to intergeberic hybridization with the perennial Triticeae. In: son with those recognized by Áskell Löve. Gustafson, J.P. (ed.) Gene Manipulation in Plant improvement, The circumscription of the genomes (or haplomes) used Plenum Publishing, New York, USA, pp. 209–279. by Kihara and Löve differed somewhat. For instance, Kihara Dumortier,B.C.J. (1823) Observations sur les Graminées de la flore B B G Belgique. J. Casterman, Tournay, Belgium. divided the genome into three which he called , and S B Hackel,E. (1887) Gramineae. In: Engler,A. and K.Prantl (eds.) Die . Löve amalgamated them into one genome, the genome. G S Natürlichen Pflanzenfamilien, vol. II, 2. Engelmann, Leipzig, Data from genomic analyses indicates that the and ge- Germany, pp. 70–89. nomes are modified versions of the B genome which has five Hitchcock, A.S. (1951) Tribe 3. Hordeae, in Manial of grasses of sp b s l different versions, they are B, B , B , B , and B (Yen and the United States, U.S.D.A. Misc. Publ. 200, Second edition revised Yang 1999). by Agnes Chase, U.S. Govt. Printing Office, Washington, DC, Finally, we would like to point out that there is no abso- pp.230–280. lute boundary among genera, families and the taxa above. Keng, Y.L. (1965) Tribe 7. Hordeae Benth.am. In: Keng, Y.L. (ed.) Taxonomic treatment above species cannot avoid arbitrari- Flora illustrate plantarum Sinicarum, Sci. Press, Beijing, pp. 340– ness. Taxonomy is a tool for utilization. Philosophically, 451. things will go to their opposite if they are too extreme. Kihara,H. (1930) Genomanalyse bei Triticum und Aegilops. Cytilogia Krause (1898) combined Elymus, Hordeum, Agropyron, 1: 263–284. Kihara, H. and I. Nishiyama (1930) Genomanalyse bei Triticum und Secale and Triticum together and established a giant genus Aegilops. I. Genomaffinitäten in tri-, tetra-, und pentaploiden Frumentum Krause. On the other hand, Áskell Löve recog- Weizenbastarden. Cytologia 1: 270–284. nized 11 monotypic genera in the Aegilops-Triticum group. Kihara, H. (1954) Consideration on the evolution and distribution of Practically, nobody but themselves have accepted these ex- Aegilops species based on the analyzer-method. Cytologia 19: treme treatments no matter how good their reasons. If we 336–357. proposed a giant genus Elymus sensu lato that has St, Y, H, Krause, E.H.L. (1898) Floristische Notizen II. Gräser, Bot. Centralbl. P, W genomes, would include more than 200 species which 73: 337–343. we regard as impractical. Kunth, C.S. (1815) Considérations générales sur les Graminées. Chez G. Dufour, Paris.

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