Karyotype analysis in some Vernonia species (Asteraceae) from South America*:

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1 CARYOLOGIA Vol. 51, n. 3-4: ,1998 Karyotype analysis in some Vernonia species (Asteraceae) from South America*: MASSIMILIANO DEMATTEIS Instituto de Botanica del Nordeste (UNNE-CONICET), Casilla de Correo 209, 3400 Corrientes, Argentina. SUMMARY - The somatic chromosomes of eight Vernonza species (Asteraceae) from Brazil, Paraguay and Argentina were analyzed. First chromosome counts are presented for V coriacea Less. (2n=32 = 20m + 10sm + 2st), V dura Mart. ex DC:. (2n=32 = 22m + 10sm), V eriolepis Gardn. (2n=32 = 22m + 8sm + 2st), V grandiflora Less (2n=64 = 50m + 14sm) and V onopordioides Baker (2n=32 = 18m + 2m-sm + 10sm + 2st) Besides, the chromosome numbers of V brevifolia Less. ((2n=32 = 22m + 10sm) and V sellowii Less. (2n=62 = 40m + 20sm + 2st) are also confirmed. The number found in V saltensis, Hieron (2n=64 = 48m + 16sm) support the occurrence of two cytotypes within the species, one diploid (2n=32) and the other tetraploid (2n=64). The eight species revealed certain differences between their karyotypes principally in formula, total length and asymmetry level, which coincides with earlier studies for South American taxa. Satellites were commonly found on submetacentric or subtelocentric pairs, being also variable in morphology and location. Chromosomal data here reported and the already available for the genus indicate that the evolution of Vermonia have been followed for a decrease in number and size of the chromosomes. Key words: chromosomes, karyotypes, Vernonia, taxonomy, evolution. INTRODUCTION The genus Vernonia sensu lato, includes more than 1000 species distributed in the tropical regions of the New and Old World, having two major centers of diversification, one in southern Brazil and the other in tropical Africa (JONES 1977). During several years, many researchers have attempted to resolve the complex taxonomy of the genus. Some authors grouped related species in sections, subsections and series (CABRERA 1944; KEELEY 1978; JONES 1979a, 1981; STUTTS 1988); while others as ROBINSON (1988, 1989, 1990, 1992a, *, Part of a thesis that will be presented to the Facultad Ciencias Exactas, Fisicas y Naturales of the Universidad Nacional de Cordoba (Argentina) in partial fulfillment of the requirements for the Doctoral degree.

2 280 DEMATTEIS 1992b) have segregated several groups to new genera. However, the status and position of many species are still doubtful, due to the lack of information on important areas, such as chemistry, palinology and cytology. From a cytological viewpoint, the genus Vernonia has been poorly understood. In particular, relatively little is known about the cytology of the South American species. T o date only the karyotypes of about 25 species have been described (RUAS et al., 1991; DEMATTEIS 1996,1997,1998; DEMATTEIS and FERNANDEZ 1998). Even chromosome numbers are unknown for most of the approximately 250 Brazilian species. Previous chromosome studies for the genus indicate some differences between Old and New World species. The first present basic chromosome numbers x=9 and x=10 UONES 1979b), while the American species have a large variation that ranges fromx=10 tox=19 (KEELEY and TURNER 1990; RUAS e tal. 1991). In this paper chromosomal data on eight South American species of Vernonia are reported. Five chromosome numbers and seven karyotypes are notified for the first time. The results are discussed in relation to the taxonomic position of the species and the evolution of the genus. MATERIALS AND METHODS Voucher specimens have been deposited at the herbaria of Instituto de Botanica del Nordeste (CTES) and the Prefeitura Municipal de Curitiba (MBM). The sources of the studied materials are the following: V. brevifolia Less.: Argentina. Corrientes. Dept. Capital: 1 km SE from Riachuelo. Dematteis and Cristobal 673 (CTES). V. coriacea Less.: Brazil. Mato Grosso. Chapada dos Guimaràes: Agua Fria'. Hatschbach et al (CTES, MBM). V. dura Mart. ex DC.: Brazil. Mato Grosso. Chapada dos Guimaràes: Campo Verde. Hatschbach et al (CTES, MBM). V. eriolepis Gardn.: Brazil. Mato Grosso. Chapada dos Guimaràes: Salgadeira. Hatschbach et a! (CTES, MBM). V. grandiflora Less.: Paraguay. Dept. Amambay: Chirihuelo. Dematteis & Schinini 861 (CTES). V. onopordioides Baker: Brazil. Mato Grosso. Chapada dos Guimaràes: Salgadeira. Hatschbach et a! (CTES, MBM). V. saltensis Hieron.: Argentina. Jujuy. Dept. Ledesma: Fraile Pintado. Dematteis et a!. 520 (CTES). V. sellowii Less.: Argentina. Misiones. Dept. Candelaria: Route 15,21 km E from Santa Ana. Dematteis 588 (CTES). Mitotic chromosome preparations were obtained from root-tips of germinating seeds. The material was pretreated for about 4 hours in 8-hydroxyquinoline M solution, fixed in lactic acid-ethanol (1:5) and then stained using the Feulgen's technique.

3 KARYOTYPES IN VERNONIA SPECIES 281 Nomenclature utilized for the karyotype description is that proposed by LEV AN et al. ( 1964). Chromosome morphology was determined using the centromeric index (ci = short arm x l00/total chromosome length). Accordingly, the chromosomes were classified in metacentrics (m): , submetacentrics (sm): and subtelocentrics (st): The idiograms and chromosome measures were estimated from ten metaphase plates of 7-10 individuals per species. Karyotype asymmetry has been determined using the intrachromosomal (A1) and interchromosomal (A2) index suggested by ROMERO ZARCO (1986). RESULTS The somatic chromosome numbers, karyotype formulae and satellite positions of the eight Vernonia species are detailed in T able 1. Chromosome sizes in!-tm and asymmetry index are summarized in Table 2. TABLE 1 - Chromosome number, karyotype formula and satellite position of the eight Vernonia species. TABLE 2 - Total chromosome length in µm (TCL), average chromosome length (X), total form percentage (T.F%), and intra (Al) and interchromosomal (A2) asymmetry index in Vernonia species

4 282 DEMATTEIS The cytological study revealed two different basic chromosome numbers, x=16 and x=31. V. brevifolia, V. coriacea, V. dura, v. eriolepis and v. onopordioides were diploids based on x=16, while V. grandiflora and v. saltensis resulted tetraploids with this same basic number (Figs. 1-6). The remainder species, V. sellowii, was found to be diploid with base number x=31. All karyotypes are presented for the first time, with exception of that belonging to V. brevifolia. They were mostly composed of metacentric and submetacentric chromosomes (Figs. 7-14). However, four species also presented a small subtelocentric pair, that commonly constituted the lesser chromosome pair of the complement. Total chromosome length ranged from µm in V. eriolepis to µm in V. saltensis. The total form percentage (TF% ) was around 40-41% in all species, which was slightly lower in V. onopordioides (39.82 % ). In spite that some species presented a subtelocentric pair, the karyotype asymmetry was in general of moderate level, due to the presence of a greater proportion of metacentric chromosomes. The relationships between the intrachromosomal (Al) and interchromosomal (A2) asymmetry index of the eight species are represented in Fig. 15. The intrachromosomal index (A1) showed few differences between the length of the chromosome arms from the eight species. Meanwhile, the interchromosomal index (A2) indicated a distinctive variation among size of the chromosomes of v. coriacea, V. grandiflora and v. sellowii respect to the remainder species. Satellites commonly located in the short arm of some small submetacentric or subtelocentric pair were found in almost all the species (Figs. 7-14). The presence of satellites was a relatively constant feature, since they were observed in 80%) or 90% of the metaphase plates. In five over a total of seven plants sampled of v. sellowii were found between 1 and 6 B chromosomes. The accessory chromosome was characterized as a small subtelocentric element with an average length of 1.02 ~m (Fig. 14). Its was observed to have mitotic instability in 3 plants analyzed, which showed a variable number of Bs between different cells. DISCUSSION The results obtained in V. saltensis (2n=64) clearly differ from a previous study that reported 2n=32 for a population of Cordoba, Argentina (BERNARDELLO 1986). However, it agrees with a recent analysis made on material Fig Somatic chromosomes of Vernonia 1. V coriacea,2n=32 2. V dura, 2n= V eriolepis, 2n= V grandiflora, 2n= V onopordioide.l; 2n=32 6. V saltensis, 2n=64. Scale = 5 µm

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6 Figs Idiograms of Vernonia 7. V brevifolia, 22m + 10sm. 8. V coriacea, 20m + 10sm + 2st. 9. V dura, 22m + 10sm. 10. V eriolepis, 22m + 8sm + 2st. 11. V grandiflora, 50m + 14sm. 12. V onopordioides, 18m + 2m-sm + 10sm + 2st. Scale = 2 µm.

7 KARYOTYPES IN VERNONIA SPECIES 285 Figs ldiograms of Vernonia 13. V,salten.sis, 48m + 16 sm. 14. V sellowii, 40m + 20sm + 2st. Scale = 2 µm. from northwestern Argentina (DEMATTEIS 1998). These records confirm the occurrence of two different cytotypes within V. saltensis, one diploid (2n=32) and other tetraploid (2n=64) based on x=16. The chromosome number found in V. brevifolia and V. sellowii coincide with the determined in an earlier study for both species (DEMATTEIS 1997). The occurrence of B chromosomes has been previously reported for many Vernonia species (JONES 1979b; GALIANO and HUNZIKER 1987; DEMATTEIS 1997), but they are noticed for the first time in V. sellowii. Although there is some dispute concerning the chromosome evolution of Vernonia, most authors consider x=9 the ancestral basic number of the genus (JONES 1979b; KEELEY and TURNER 1990; RUAS et al. 1991). Higher chromosome numbers, such as x=17, x=16 or x=15, has been considered to be result of polyploid increase from x=9 to 18 followed by aneuploid loss (JONES 1979b). Regarding this hypothesis and the morphological affinities, it is possible to suppose that the base number x=31 found in V. sellowii has been derived by aneuploidy from a tetraploid species based on x=16. Nevertheless, owing to the existence of Vernonia species with basic number x= 15, an alternative to the first hypothesis would be certainly the hybridization between two species based on x=16 and x=15 respectively.

8 286 DEMATTEIS Fig Dispersion diagram showing the relation between intra (Al) and interchromosomal (A2) asymmetry index. The comparative karyotype analysis showed up certain differences among the species, particularly in formula, total length and asymmetry level. Like other New World species (RUAS et al. 1991; DEMATTEIS 1997), the karyotypes were composed of a variable number of metacentric and submetacentric chromosomes, completed occasionally by a subtelocentric pair. The presence of subtelocentric chromosomes seem to be rare in the genus Vernonia, taking into account the number of species in which its have been reported. At the present, subtelocentric chromosomes are only known for V. polyphylla Sch. Bip. (RUAS et al. 1991) and V. cincta Griseb. (DEMATTEIS 1998). Furthermore of the aneuploid reduction cited above, the evolution of the South American Vernonias appears to have been accompanied of a considerable decrease in chromosome size. The karyological data available indicate that the primitive species (x=10, x=17) have a comparatively higher chromosome size than the more advanced taxa (RUAS et al. 1991; DEMATTEIS 1996, 1997; DEMATTEIS and FERNANDEZ 1998). The species with basic number x=17 present a mean chromosome size of ~m (DEMATTEIS and FERNANDEZ 1998), while the species based on x=14 or x=15 commonly have an average length of ~m (DEMATTEIS 1996, 1998). The taxonomic position of the species analyzed has been in dispute for several time. JONES (1979a) based upon the inflorescence type included these taxa within two different subsections named 5corpioides and Nudiflorae. Mean-

9 KARYOTYPES IN VERNONIA SPECIES 287 while ROBINSON ( 1988) on the basis of the pollen type, has placed all the species in a different genus called Lessingianthus. Although the generic status of this species group may be discussed, the cytological and morphological data su port the taxonomic treatment of ROBINSON ( 1988), since they constitute a fairly distinct assemblage. In addition to the species examined here, all other members belonging to the Lesstngianthus group like V. mollissima, V. oxyodonta, V. polyphylla, V. rubricaulis and V. squarrosa, have been reported to have basic chromosome number x=16 (RUAS etal. 1991; DEMATTEIS 1996,1997). From a morphological viewpoint, the species present also a close similarity, being easily distinguished from another American members of Vernonieae using current vegetative features. The group consists of perennial herbs and shrubs with xylopodia, having seriate-cymose inflorescences and pollen grains "B" type. Most genera of the tribe Vernonieae genera exhibit a close relationship between basic chromosome number and pollen morphology (ROBINSON 1992a). Particularly in Vernonia, the base numbers show a high correlation with the inflorescence type, in addition to the pollen structure (DEMATTEIS and FERNANDEZ 1998). Species having thyrsoid or paniculiform inflorescences and type " A " pollen always have basic number x=17. The taxa with small heads arranged in seriate-cymose inflorescences and pollen types "C", "D" or "G" possess x=14 and x=15. While, the entities with median or large sized heads in seriate-cymose inflorescences and "B" type pollen mainly present base number x=16. The cytological knowledge of Vernonia is still limited and additional chromosome counts are necessary. More karyotype studies should provide essential information in understanding the systematic and evolution of the genus. Acknowledgements - I wish specially thank to Dr. Gert Hatschbach (Curitiba) and Mr. Aurelio Schinini (Corrientes) for collecting plant material. The assistance of Ing. Aveliano Fernandez and Dr. Carmen L. Crist6bal is gratefully acknowledged. This work was supported by grants from the Secretaria General de Ciencia y Tecnica of the Universidad Nacional del Nordeste. REFERENCES BERNARDELLO L.M., Numeros cromosomicos en Asteraceae de Cordoba Darwiniana, CABRERA A.L., Vernonieas Argentinas (Compositae). Darwiniana, 6: DEMATTEIS M., Estudios cromosomicos en especies argentinas de Vernonia (Asteraceae). Bonplandia, 9: , Numeros cromosomicos y cariotipos de algunas especies de Vernonia (Asteraceae). BoI. Soc. Argent. Bot., 33: , Chromosome studies of some Vernonia species (Asteraceae). Genet. Molec. BioI., 21:

10 288 DEMATTEIS DEMATTEIS M. and FERNANDEZ A., Karyotypes of seven South American species of Vernonia (Asteraceaej Cytologia; GALIANO N.G. and HUNZIKER ].H., E,tudios cariologicos en Compositae IV Vernonieae y Eupatorieae Darwiniana, ]ONES S.B., Vernonieae - systematic review In: Heywood V.H., Harborne].B. and Turner B.L. (Eds), "The Biology and Chemistry of the Compositae", 1: Academic Press, London. -' 1979a. - Synopsis and pollen morphology of Vernonia (Compositae Vernonieae) in the New World. Rhodora, 81: ' 1979b. - Chromosome numbers of Vernonieae (Compositaej Bull. Torrey Bot. Club, 106: , Synoptic classification and pollen morphology of Vernonia (Compositae Vernonieae) in the O/d World Rhodora, KEELEY S.C., A revision of the West Indian Vernonia.1 (Compositaej.J. Arnold Arbor., 59: KEELEY S.C. and TURNER B.L., A preliminary cladistic analysis of the genus Vernonia (Vernonieae Asteraceae) PI. Syst. Evol., Suppl LEVAN A., FREDGA K. and SANDBERG A.A., Nomenclature for centromeric position on chromosomes Hereditas, ROBINSON H., ,Studies in the Lepidaploa complex (Vernonieae Asteraceae) IV The new genus Lessingianthus Proc. BioI. Soc. Wash , Acilepidopsis, a new genus of Vernonieae from South America (Asteraceae) Phytologia, 67: , Studies in the Lepidaploa complex (Vernonieae Asteraceae) VH The genus Lepidaploa Proc. BioI. Soc. Wash., 103: ' 1992a. - Mesanthophora, a new genus of Vernonieae (Asteraceae) from Paraguay Novon, , 1992b. - A new genus Vernonanthura (Vernonieae, Asteraceae) Phytologia, 73: ROMERO ZARCO C., A new method for estimating karyotype asymmetry Taxon, RUAS P.M., RUAS C.F., VIEIRA A.O.S., MATZENBACHER N.I. and MARTINS N.S., Cytogenetics of genus Vernonia Schreber (Compositae) Cytologia, 56: STUTTS].G., Taxonomic revision of Vernonia Subsect Chamaedrys (Compositae Vernonieae) Rhodora, 90: Received 23 December 1998: accepted 9 February 1999