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

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 (2n=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 + 10sm), V. polyphylla Sch.Bip. (2n=64= 40m + 20sm + 4st), V. squarrosa Less. (2n=64) and V. teyucuarensis Cabrera (2n=160) are also confirmed. For Ir. aurea Man. 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 proportion 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 chromosome 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. lilacina and V. tarijensis suggests that these species, included actually in other group, should be transferred to the subsection Macrocephalae.