Interspecific Variations of Nuclear DNA Content and Karyotype Diversity in Ferocactus

Abstract

Karyotype analysis, determination of somatic chromosome number, total chromosome length and volume, cytophotometric estimation of 4C DNA content and Interphase Nuclear Volume (INV) were carried out in 6 species of Ferocactus of the family Cactaceae. Significant interspecific variations in nuclear DNA amount were noted with a constant somatic chromosome number (2n=22). The 4C DNA content varied from 7.04 pg in F. horridus to 9.20 pg in F. wislizeni. The INV varied from 330.22 μm³ in F. latispinus to 482.36 μm³ in F. wislizeni. The 4C DNA content showed a significant positive correlation with both mean chromosome volume and INV; mean chromosome volume also showed a significant correlation with mean INV. The structural alterations in the chromosomes as well as loss or addition of highly repetitive sequences in the genome suggest variations in the nuclear DNA at interspecific level during macro- and micro-evolution of the species.