Karyotype analysis in eight species of Vernonia (Vernonieae, Asteraceae) from South America

Abstract

The somatic chromosome number and karyotypes of eight species of Vernonia were analyzed. The results include the first chromosome count for V. hexantha Sch.Bip. (2n=30), which is diploid with base number x=15. The karyotypes are analyzed for the first time for two cytotypes of Vernonia cognata Less. (2n=40= 28m + 12sm; 2n=80= 48m + 32sm), V. hexantha (2n=30= 24m+6sm), V. membranacea Gardner (2n=34= 24 + 10sm), V. salzmannii DC. (2n=20= 10m + 10sm) and V. verbascifolia Less. (2n=20= 12m + 8sm). All the studied species

showed a predominance of metacentric chromosomes, with a lower proportion of submetacentric pairs. In V. brev- ifolia Less. 0 to 3 accessory or B chromosomes were found. The chromosomes varying in length from 1.25 to 3.98

μm. The differences in the symmetry of the karyotypes were small, for which it is possible to assume that the great diversification of the genus has been accompanied by very small changes in the structure of the chromosomes.