Genome downsizing and karyotype constancy in diploid and polyploid species of Hippeastrum (Amaryllidaceae): a model of DNA variation.

POGGIO L; REALINI MF; FOURASTIE MF; GARCÍA AM; GONZÁLEZ GE

AoB Plants

Oxfordjournals

Año: 2014 vol. 6 p. 1 - 11

2041-2851

Evolutionary chromosome change involves significant variation in DNA amount in diploids and genome downsizing in polyploids. Genome size and karyotype parameters of Hippeastrum species with different ploidy level were analysed. In Hippeastrum, polyploid species show less DNA content per basic genome than diploid species. Therate of variation is lower at higher ploidy levels. All the species have a basic number x ¼ 11 and bimodal karyotypes. The basic karyotypes consist of four short metacentric chromosomes and seven large chromosomes (submetacentric and subtelocentric). The bimodal karyotype is preserved maintaining the relative proportions of members of the haploid chromosome set, even in the presence of genome downsizing. The constancy of the karyotype is maintained becausechanges in DNA amount are proportional to the length of the whole-chromosome complement and vary independently in the long and short sets of chromosomes. This karyotype constancy in taxa of Hippeastrumwith different genome size and ploidy level indicates that the distribution of extra DNA within the complement is not at random and suggests the presence of mechanisms selecting for constancy, or against changes, in karyotype morphology.