Genome downsizing and karyotype constancy in diploid and polyploid congeners: a model of genome size-variation.

POGGIO LIDIA; REALINI, MARÍA FLORENCIA; FOURASTIÉ, MARIA FLORENCIA; GARCÍA ANA MARÍA; GONZÁLEZ GRACIELA

AoB PLANTS

Oxford University Press

Lugar: Oxford; Año: 2014 p. 1 - 11

Genome size and karyotypical parameters of Hippeastrum species with different ploidy level were analyzed. In Hippeastrum, polyploids species show less DNA content per basic genome than the diploids. The rate of variation is lower at higher ploidy levels. All the species have a basic number x=11 and bimodal karyotypes. The basic karyotypes consist of 4 short metacentric chromosomes and 7 large chromosomes (submetacentric and subtelocentric). The bimodal karyotype is preserved maintaining the relative proportions of the members of the haploid chromosome set, even in presence of genome downsizing. The constancy of the karyotype is maintained because of changes in DNA amount are proportional to the length of the whole chromosome complement and varies independently in the long and short sets of chromosomes. This karyotype constancy in taxa with different genome size and ploidy levels of Hippeastrum indicate that the distribution of extra DNA within the complement is not at random and suggest the presence of mechanisms selecting for constancy, or against changes, in the karyotype morphology.