Karyotype comparison between three shrub-tree species of Erythrina L. (Leguminosae: Papilionoideae) from Brazil

Abstract

Erythrina consists of 112 leguminous trees and shrubs, distributed throughout the tropical regions. Species of Erythrina are of great biological interest because they are pollinated by hummingbirds, which promote a high pollen flow and high chance of homogenization of recombinant forms. The karyotypes of E. speciosa, E. falcata and E. mulungu were cytogenetically analyzed in order to establish relationships among these three species of contrasting strategies. The chromosome count showed 2n = 42, with small chromosomes, prophasic condensation of the proximal type and non-reticulate to semi-reticulate nuclei with evident chromocenters. Chromosome banding showed AT-rich heterochromatic blocks in the pericentromeric region of most chromosomes and GC-rich regions in the terminal region of the largest pairs. In situ hybridization with 45S rDNA probes exhibited ten terminal signals in E. falcata and E. speciosa and eight in E. mulungu, while the 5S rDNA probe showed only two signals, also terminals in three species. The results show quite conserved karyotypes, with small variations in the size and number of 45S rDNA sites, which can be considered the only elements of karyotype differentiation, independent of plant size and strategies.