Interspecific variations in the chiasma frequencyand nuclear DNA content in some species of Ferocactus (Cactaceae)

Meiotic studies of pollen mother cells and nuclear 4C DNA content inten species of Ferocactus (Cactaceae) revealed significant interspecific variations.The haploid chromosome number n=11was found in all the studied species. The chiasma frequency per nucleus varied from 18.20 in F. echidne to 21.75 in F. gracilis in meiotic metaphase I. The formation of univalent's in some of the cells and/or spindle anomalies lead to the formation of pentads, hexads or octads. Pollen sterility varied between 7.66% in F. emoryi to 9.74% in F. gracilis. The 4C DNA content in root tip cells varied from 7.37 pg in F. histrix and 9.74 pg in F.gracilis. Significant variations of in situ nuclear DNA content as well as chiasma number per bivalent was evidient in interspecific level.