Chromosome studies of some Vernonia species (Asteraceae)

Abstract

Chromosomes of 12 Vernonia species (Asteraceae) from South America were studied. First counts were reported for: V. alpestris Gardn. (n = 17), V. chalybaea Mart. ex DC. (2n = 32), V. cotoneaster Less. (2n = 30), V. fruticulosa Mart. ex DC. (n = 16) and V. lithospermifolia Hieron. (n = 10, 2n = 20). Furthermore, in V. aurea Mart. ex DC. (2n = 32), V. mollissima D. Don (n = 32) and V. saltensis Hieron. (2n = 64) numbers different from those reported in the literature were found. Karyotypes were described for some species. V. aurea contains 24m + 8sm chromosomes, V. chalybaea contains 22m + 10sm chromosomes, V. cincta Griseb. 36m + 16sm + 8st and V. cotoneaster 18m + 12sm. The basic chromosome numbers x = 10, 14, 15, 16 and 17 were confirmed for South American Vernonia species. The results are discussed in relation to previous chromosome studies for the genus.<br>Os cromossomos de doze espécies sul-americanas de Vernonia (Asteraceae) foram estudados, sendo que as contagens foram feitas pela primeira vez em V. alpestris Gardn. (n = 17), V. chalybaea Mart. ex DC. (2n = 32), V. cotoneaster Less. (2n = 30), V. fruticulosa Mart. ex DC. (n = 16) e V. lithospermifolia Hieron. (n = 10, 2n = 20). Além disso, encontram-se em V. aurea Mart. ex DC. (2n = 32), V. mollissima D. Don (n = 32) e V. saltensis Hieron. (2n = 64) números diferentes dos relatados na literatura. Os cariótipos foram descritos para algumas espécies: V. aurea contém 24m + 8sm, V. chalybaea contém 22m + 10sm, V. cincta Griseb. 36m + 16sm + 8st e V. cotoneaster 18m + 12sm. Os números cromossômicos básicos x = 10, 14, 15, 16 e 17 foram confirmados para essas espécies sul-americanas de Vernonia. Os resultados são discutidos em relação a prévios estudos cromossômicos para o gênero Vernonia

Karyotype characterization of two populations of Vernonia geminata (Asteraceae, Vernonieae) using banding and FISH techniques

“…According to Ruas et al (1991), Dematteis (1996Dematteis ( , 1998, Fernández (1998, 2000) and Oliveira et al (2007a,b), despite the occurrence of variation in chromosome number among species of Vernonia, the karyotypes with conventional techniques do not discriminate well the species already studied, due to small variation in chromosome size and centromeric position. Among the species of Vernonia that belong to the group Axilliflorae Benth., studied by Oliveira et al (2007a), V. geminata has the most differentiated karyotype, showing chromosomes with greater variation in length (2.0 to 4.6 mm) and greater proportion of submetacentric chromosomes, in relation to the metacentrics (6m + 4sm), where it is the only one with 2n = 20 chromosomes (pattern of the group is x = 16).…”

“…These extra-chromosomes occur in some species of Vernonia (Dematteis, 1997(Dematteis, , 1998 and other Asteraceae, such as Mikania Willd. (Maffei et al, 1999), Crepis capillaris (L.) Wallr.…”

“…(Asteraceae, Vernonieae) comprises small herbs to large trees (Stutts, 1988), occurring in tropical regions of Asia, Africa and Americas (Dematteis, 1998). It is one of the most complex genera of the family (Dematteis and Fernández, 1998), with more than 1000 species (Robinson, 1999).…”

“…The karyotypes determined with conventional techniques include only 5% of the species of Vernonia, and they do not discriminate very well species with the same chromosome number, due to small variation in chromosome size and centromeric position (Ruas et al, 1991;Dematteis, 1996Dematteis, , 1998Fernández, 1998, 2000;Oliveira et al, 2007a,b). To date, information obtained by techniques that allow the linear differentiation of the chromosomes [chromosome banding and fluorescent in situ hybridization (FISH)] exists for only one species, Vernonia condensata Baker (2n = 40).…”

Chromosomal studies of three species of Bidens (L.) (Asteraceae)

“…Historically, chromosomal numbers have been used to define generic and infrageneric taxa in Asteraceae (Sunderberg et al 1986;Dematteis 1998;Dematteis and Ferná ndez 2000;Vallès et al 2001). Studies of some genera of Asteraceae have suggested that polyploidy is the most frequent chromosomal change within and among populations and species in South America (Dematteis and Ferná ndes 2000).…”