Chromosome studies on nine South American species of Vernonia (Vernonieae, Asteraceae)

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1 CARYOLOGIA Vol. 53, no. 1: 55-61, 2000 Chromosome studies on nine South American species of Vernonia (Vernonieae, Asteraceae) MASSIMILIANO DEMATTEIS 1;* and AVELIANO FERNANDEZ 1 ' 2 Institute de Botanica del Nordeste (UNNE-CONICET), Casilla de Correo 209, 3400 Corrientes, Argentina. 1 Facultad de Ciencias Exactas y Naturales y Agrimensura (UNNE), 2 Miembro de la carrera del Investigador Cientifico del CONICET. Abstract A chromosome analysis on nine Vernonia species (Vernonieae, Asteraceae) from South America was carried out. First chromosome counts are notified in four species: V. lilacina Mart. (2n=32= 24m + 6sm + 2st), V. oxyodonta Malme (2w=128), V. pulverulenta Baker (2n=96) and V. tarijensis (Griseb.) Hieron. (2n=32= 24m + 8sm). Furthermore, the somatic chromosome numbers of V. chalybaea Mart, ex DC. (2n=32= 22m + l0sm), V. polyphylla Sch.Bip. (2n=64= : 40m + 20sm + 4st), V. squarrosa Less. (2n=64) and V. teyucuarensis Cabrera (2n=160) are also confirmed. For V. aurea Mart, ex DC. is presented an unreported chromosome number (2n=32= 24m + 8sm). The karyotype analysis made on five species mainly showed metacentric and submetacentric chromosomes, differing in propor tion between the species. In V. lilacina and V. polyphylla were also found one and two subtelocentric pairs respectively. The nine analyzed species presented x=16, a basic chromo some number very frequent in South America, specially in species from the subsect. Macrocephalae Baker. The chromosome number 2n=32 found in V. aurea, V. chalybaea, V. liladna and V. tarijensis suggests that these species, included actually in other group, should be transferred to the subsection Macrocephalae. Key words: chromosome number, karyotype, polyploidy, taxonomy, Vernonia. INTRODUCTION The large genus Vernonia Schreb. constitutes the central core of the tribe Vernonieae Cass. (Asteraceae) and it is widely distributed in the tropical regions of Asia, Africa and America (JONES 1977). In South America it is represented by about species which mostly occur in the southeast of Brazil, northern Argentina, Paraguay and Bolivia. At the present, the genus Vernonia has been scarcely studied from the cytological viewpoint, with less than 20% of the species examined for chromosome number (CAVE 1960, 1965; FE- DOROV 1969; MOORE 1973, 1974, 1977; GOLD-BLATT 1981, 1984, 1985, 1988; GOLDBLATT and JOHNSON 1990, 1991, 1994, 1996). In South America have been reported the karyotypes of only 32 species, several of which are not closely related (RUAS et al. 1991; DEMATTEIS 1996, * Corresponding author: fax ; ibone@espacio.com.ar. 1997, 1998; DEMATTEIS and FERNANDEZ 1998). However, the limited information available in this matter shows that chromosomes are largely variable in number and morphology within the genus, suggesting a possible application for taxonomic studies (KEELEY and TURNER 1990; RUAS et al. 1991; DEMATTEIS and ROBINSON 1997; ROBINSON 1999). The cytological data in Vernonia indicates that Old World species have basic chromosome numbers x=9 and x=10, while New World taxa present x=10, x=14, x=15, x=16, x=17, x=19 and x=31 (TURNER 1981; KEELEY and TURNER 1990; RUAS et al. 1991; DEMATTEIS 1998). Besides, in New World species polyploidy is relatively frequent, meanwhile in Old World species the polyploidy is uncommon and only some tetraploids and hexaploids have been notified exceptionally (JONES 1979). In this work are reported original chromosome numbers and karyotypes of nine Vernonia taxa from Argentina, Uruguay, Paraguay and Brazil. The significance of the results is discussed in relation to the taxonomic position and relationships of the analyzed species.

2 56 DEMATTEIS and FERNANDEZ MATERIALS AND METHODS The origin of the studied materials is detailed in Table 1. Voucher specimens have been deposited at the herbaria of Institute de Botanica del Nordeste (CTES) and the Prefeitura Municipal de Curitiba (MBM). Cytological observations were made on mitotic cells of root-tips obtained from germinating seeds. After a pretreatment of about hours in 8-hydroxyquinoline M solution, the rootlets were fixed in acetic acid ethanol (1:3) and then stained according to the Feulgen's technique. Nomenclature applied for the karyotype description is that suggested LEVAN et al. (1964). The level of karyotype asymmetry was established using the methodology proposed by ROMERO ZARCO (1986). For elaboration of the idiograms and estimation of the chromosome measures were utilized ten met aphase plates from 8-10 individuals for each species. RESULTS The somatic chromosome numbers of the Vernonia species analyzed are detailed in Table 1. Chromosome counts of four entities are reported for the first time (*). Karyotype formula and satellite positions of five analyzed entities are presented in Table 2 and their respective chromosome sizes and asymmetry indexes are summarized in Table 3. The nine species analyzed here presented basic chromosome number x=16, although showed five different ploidy levels. V. aurea, V. chalyhaea, V. lilacina (Fig. 1) and V. tarijensis (Fig. 5) were diploids (2n=32), V. polyphylla (Fig. 2) and V. squarrosa (Fig. 4) resulted tetraploids (2n=64), V. pulverulenta (Fig. 3) was hexaploid (2n=96), V. oxyodonta octoploid (2n=128) and V. teyucuarensis was decaploid (2n=160). Most the analyzed species presented karyotype formulas often composed of metacentric and submetacentric chromosomes (Figs. 6-10), with exception of V. lilacina and V. polyphylla which also showed one and two subtelocentric pairs respectively (Figs. 8-9). The mean chromosome size ranged from 1.43 um in V. lilacina to 2.08 in V. aurea. Total chromosome length (TCL) varied between pm in V. lilacina and um in V. polyphylla. TABLE 1 Chromosome number of some Vernonia species from South America. * Chromosome counts reported for the first time.

3 CHROMOSOMES IN VERNONIA 57 TABLE 2 Karyotype formula and satellite position of five Vernonia species. The karyotype asymmetry resulted of moderate level in all the entities owing to the prevailing of metacentric chromosomes over submetacentrics and subtelocentrics. The intrachromosomal (A 1 ) and interchromosomal (A 2 ) asymmetry indexes of the five species are presented in Table 2. The dispersion diagram resultant of both indexes is showed in Fig. 11. The species having the more asymmetric karyotype was V. polyphylla which presented higher values of A 1 and A 2 indexes. All the species showed satellites that were commonly placed in the short arm of the small submetacentric pair N 15 (Figs. 6-10). The sin gle exception was V. polyphylla which presented a satellite located in the long arm of a metacentric chromosome pair (Fig. 9). DISCUSSION The nine species of Vernonia analyzed in this study presented x=16, a basic chromosome number relatively frequent in South American species. Almost all these entities based on x=16 belong to the large subsection Macrocephalae Baker, which is considered actually a different genus called Lessingianthus by ROBINSON (1988). This group contains perennial herbs and shrubs with xylopodia, having median or large sized heads disposed in seriate- cymose inflorescences and type "B" pollen. Despite its similar inflorescence pattern and pollen morphology, the taxonomic position and relationships from some these species is still uncertain. V. aurea, V. chalybaea, V. lilacina and V. tarijensis were recently included by ROBINSON (1990) in a different genus named Lepidaploa over the basis of its lesser heads size. However, the presence of 2n=32 in all these species strongly suggests that its should be transferred to the Macrocephalae or Lessingianthus group, which always presents basic chromosome number x=16 (DEMATTEIS 1998). The group Lepidaploa segregated from Vernonia by ROBINSON (1990) apparently comprises a heteroge neous group of species that show different pol len types and chromosome numbers (ROBINSON 1990, 1999) and likely require a more exhaus tive revision. The chromosome number found in V. aurea (2n=32) differ substantially from the n=17 determined by JONES (1982) for a Brazilian population. Although a possible explanation for this disagreement could be the occurrence of aneuploidy, this type of chromosomal variation has been not reported previously within Vernonia species. All the studies accomplished on South American entities suggest that the more frequent chromosome change between popula tions is the polyploidy (GALIANO and HUNZIKER 1987; DEMATTEIS 1997). TABLE 3 Mean chromosome length (X), size range, total chromosome length in pm (TCL), total form percentage (TF%), intrachromosomal (A 1) and interchromosomal (A 2) asymmetry indexes in Vernonia species.

4 58 DEMATTEIS and FERNANDEZ Figs. 1-5 Somatic chromosomes of Vernonia. 1. V. lilacina, 2n= V. polyphylla, 2n= V. pulvemlenta, 2n= V. squar-rosa, 2n= V. tarijensis, 2n=32. Scale=5µm.

5 CHROMOSOMES IN VE RNONIA 59 Figs Idiograms of Vernonia. 6. V. aurea, 24m + 8sm. 7. V. chalybaea, 22m + losm. 8. V. lilacina, 24m + 6sm + 2st. 9. V. polyphylla, 40m + 20sm + 4st. 10. V. tarijensis, 24m + 8sm. Scale=2µm.

6 60 DEMATTEIS and FERNANDEZ genus (MATHEW and MATHEW 1982; RUAS et al. 1991). The single two species with subtelocentric chromosomes were V. lilacina and V. polyphylla that showed one and two pairs respectively. The subtelocentric chromosomes are exceptional in Vernonia, but its appears to be frequent in some species of the genus based on x=16 (RUAS et al 1991; DEMATTEIS 1998). More karyotype studies should furnish essential information in order to understand the taxonomy and evolution of the genus. The wide variation in chromosome number and karyotype formula reported at the time is sufficiently interesting to justify further cytological studies on Vernonia. The results obtained in V. chalybaea (2n=32), V. squarrosa (2n=64) and V. teyucuarensis (2n=160) agree with a recent analysis car ried out on material from different source to the examined here (DEMATTEIS 1997). The karyotypic study made on V. polyphylla (2n=64= 40m + 20sm + 4st) differ from an earlier analysis on specimens from Rio Grande do Sul (Brazil) which reports 2n=64=42m + 18sm + 4st (RuAS et al. 1991). However, the disparity in the karyotype formulas would be probably attributed to the different pretreatment applied in each case or well to the particular appreciation of the chromosome morphology. The karyological data available for Vernonia indicates that the Macrocephalae or Lessingianthus group presents the greater number of polyploid species and the more high ploidy levels within the genus. The chromosome number found in V. teyucuarensis (2n=10x=160) apparently constitutes the higher number reported for the genus. The major somatic number notified at the present was 2 n=136 in V. glabrata Less. (JONES 1979), a species closely related to V. teyucuarensis and V. oxyodonta (2n=128). In addition to the ploidy level, the chromosome analysis revealed many other differences between the species, specially in karyotype formula, total chromosome length and asymmetry level. The karyotypes were mostly constituted of metacentric and submetacentric chromosomes in the five species analyzed, which is in concordance with the available literature for the Acknowledgments I would like to specially thank Dr. Gert Hatschbach and Mr. Aurelio Schinini for the plant material collection made in southern Brazil. This work has been supported by grants from the Secretaria General de Ciencia y Tecnica of the Universidad Nacional del Nordeste and the Consejo Nacional de Investigaciones Cientificas y Tecnicas (CONICET). REFERENCES CAVE M.S., 1960 Index to plant chromosome numbers ( ), I (1-4). The University of North Carolina Press, Chapel Hill., 1965 Index to plant chromosome numbers ( ), II (5-9). The University of North Carolina Press, Chapel Hill. DEMATTEIS M., 1996 Estudios cromosomicos en especies argentinas de Vernonia (Asteraceae). Bonplandia, 9: , 1997 Numeros cromosomicos y cariotipos de algunas especies de Vernonia (Asteraceae). Bol. Soc. Argent. Bot., 33: , 1998 Karyotype analysis in some Vernonia species (Asteraceae) from South America. Caryologia, 51: DEMATTEIS M. and FERNANDEZ A., 1998 Karyotypes of seven South American species of Vernonia (Asteraceae). Cy-tologia, 63: DEMATTEIS M. and ROBINSON H., 1997 Chromosome studies and taxonomic considerations in Acilepidopsis (Vernonieae, Asteraceae). Phytologia, 83: FEDOROV A., 1969 Chromosome numbers of flowering plants. O. Koeltz Sci. Publ. Koeningstein, West Germany. GALIANO N.G. and Hunziker J.H., 1987 Estudios cariologi-cos en Compositae. IV. Vernonieae y Eupatorieae. Darwiniana, 28: 1-8. GOLDBLATT P., 1981 Index to plant chromosome numbers Monogr. Syst. Bot., 5. Missouri Bot. Card., St. Louis., 1984 Index to plant chromosome numbers Monogr. Syst. Bot., 8. Missouri Bot. Card., St. Louis., 1985 Index to plant chromosome numbers Monogr. Syst. Bot., 13. Missouri Bot. Gard., St. Louis., 1988 Index to plant chromosome numbers Monogr. Syst. Bot., 23. Missouri Bot. Gard., St. Louis.

7 CHROMOSOMES IN VERNONIA 61 GOLDBLATT P. and JOHNSON D.E., 1990 Index to plant chromosome numbers Monogr. Syst. Bot., 30. Missouri Bot. Gard., St. Louis., 1991 Index to plant chromosome numbers Monogr. Syst. Bot., 40. Missouri Bot. Gard., St. Louis., 1994 Index to plant chromosome numbers Monogr. Syst. Bot., 51. Missouri Bot. Gard., St. Louis., 1996 Index to plant chromosome numbers Monogr. Syst. Bot., 58. Missouri Bot. Gard., St. Louis. JONES S.B., 1977 Vernonieae systematic review. In: Heywood V.H., Harborne J.B. and Turner B.L. (Eds.), "The Biology and Chemistry of the Compositae", I: Academic Press, London., 1979 Chromosome numbers of Vernonieae (Compositae). Bull. Torrey Bot. Club, 106: , 1982 In IOPB chromosome numbers reports LXXIV. Taxon, 31: KEELEY S.C. and TURNER B.L., 1990 A preliminary cladistic analysis of the genus Vernonia (Vernonieae: Asteraceae). PL Syst. Evol., Suppl. 4: LEVAN A., FREDGA K. and SANDBERG A.A., 1964 Nomenclature for centromeric position on chromosomes. Hereditas, 52: MATHEW A. and MATHEW P.M., 1982 Studies on the South Indian Compositae IV. Karyomorphology of eight species of Vernonia Schreb. Cytologia, 47: MOORE R.L., 1973 Index to plant chromosome numbers Regnum Veg., 90. Utrecht., 1974 Index to plant chromosome numbers for Regnum Veg., 91. Utrecht., 1977 Index to plant chromosome numbers Regnum Veg., 96. Utrecht. ROBINSON H., 1988 Studies in the Lepidaploa complex (Vernonieae: Asteraceae). IV. The new genus Lessingianthus. Proc. Biol. Soc. Wash., 100: , 1990 Studies in the Lepidaploa complex (Vernonieae: Asteraceae) VII. The genus Lepidaploa. Proc. Biol. Soc. Wash., 103: , 1999 Generic and subtribal classification of American Vernonieae. Smithsonian Contr. Bot., 89: ROMERO ZARCO C., 1986 A new method for estimating karyotype asymmetry. Taxon, 35: RUAS P.M., RUAS C.F., VIEIRA A.O.S., MATZENBACHER N.I. and MARTINS N.S., 1991 Cytogenetics of genus Vernonia Schreber (Compositae). Cytologia, 56: TURNER B.L., 1981 New species and combinations in Vernonia sections Leiboldia and Lepidonia (Asteraceae), with a revisional conspectus of the groups. Brittonia, 33: Received 10 May 2000; accepted 6 June 2000