Cytogenetics of Amaryllidaceae species: heterochromatin evolution in different ploidy levels

Species belonging to the Amaryllidaceae (Zephyranthes and Habranthus) were analyzed by banding with chromomycin A3 (CMA)/4,6-diamidino-2-phenylindole (DAPI) fluorochromes. The patterns of bands were studied in seven species of Zephyranthes Herb. and one of Habranthus Herb. Subterminal and interstitial DAPI+ bands were observed in Z. robusta 2n = 12 and Z. brachyandra 2n = 24. Other species showed no AT-rich heterochromatin. In species with 2n = 12, CMA+ bands were observed on one chromosome pair of Z. robusta and Zephyranthes sp., while in Z. sylvatica an additional small terminal band in the fifth chromosome pair was observed. Z. rosea and Z. grandiflora presented with 2n = 24 and had four CMA+ bands, while in Z. brachyandra, with 2n = 24 + 1B, there were eight interstitial dot bands and a larger terminal band in the short arm of the B chromosome. Z. candida with 2n = 38 presented CMA+ heterochromatin blocks on the long arms of five metacentric pairs and in the short arm of one of the submetacentric pairs; in addition a terminal band was observed on the long arm of one of the homologues of a larger submetacentric pair. H. itaobinus showed a heterozygous pair revealing a strong CMA+ band in only one of the homologues, likely a nucleolus organizing region. Taxonomic implications and karyotype evolution of this group are discussed and correlated with previous data from the literature.