Karyological Studies in Grain Amaranths.

Abstract

The karyotypes and total DNA content of four species of grain amaranths (A. caudatus 2n=32, A. cruentus 2n=34, A. hypochondriacus 2n=32 and A. mantegazzianus 2n=32) werc studied. The results indicate that these kind of studies allow the differenciation of grain species of Amaranthus. There are differences in the karyotype formulae and asymmetry indexes A1 and A2. One pair of chromosomes with a satellite is present in the four species. The Ag-Nor staining reveals a maximum of two nucleoli per cell in mitotic interphase and one nucleolus in young meiocites. A. mantegazzianus (2C=1.46±0.015pg) and A. caudatus (2C=1.35±0.013pg) have significant differences in DNA content between them, and with the other two species, while A. cruentus (2C=1.26±0.013pg) and A. hypochondriacus (2C=1.26±0.018pg) do no differ significantly. The species with higher DNA content (A. mantegazzianus and A. caudatus) have C+ bands in most of the chromosomes, and the species with lower DNA content show C+ blocks only in few chromosomes. The results suggest that the differences in DNA content among species could be attributed, at least in part, to differences in heterochromatin content.