Cytogenetics of Genus Vernonia Schreber (Compositae).

Abstract

Karyotypes from five species of the genus Vernonia were studied utilizing root tip mitotic metaphases. Vernonia nudiflora and V. polyanthes were tetraploid with 2n=34 (X=17); V. flexuosa and V. simplex were tetraploid with 2n=40 (X=10). V. polyphylla with 2n=64 may be an allotetraploid with X=16 or an autoplolyploid with X=8, that became fertile by diploidization. The basic chromosome numbers are a series of X=7, 8, 9, 10, 15, 16, 17 and 19. We suggest that in Vernonia there is an evolutionary trend towards formation of aneuploid series and polyploidy.