Chromosome studies of some Vernonia species (Asteraceae)

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.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