Karyotype analysis of natural hybrid Aloe x spinosissima and its parent Aloe arborescens and Aloe humilis, by C, CMA and DAPI chromosome banding

Abstract

The karyotype of three species of Aloe was studied with C-Giemsa, CMA (Chromomycin A₃) and DAPI (4'-6-diamino-2.fenildol) chromosome banding in order to make contributions in their cariomorfometría, location, size studied bands, and discuss cytogenetic evidence of hybrid origin reported in A. x spinossisima. The entities studied have a 2n = 2x = 14 with two pairs of NORs (nucleolar organizer regions) with associated satellites and constitutive heterochromatin CMA + DAPI- (G-C rich regions). The amount of heterochromatin, expressed in % of the total length of the karyotype (LTC), varies between species: 1.92% by A. arborescens, 1.69% in A. humilis and 1.41% in A. x spinossisima. The bands are observed in the long arms of L₂ and L₄ of A. arborescens, in L₃ and L₄ of A. humilis and A. x spinosissima in the pair L₄ and one of the supplements L₂ and L₃ one. A. x spinossisima presents values ​​of LTC haploid and amount of constitutive heterochromatin intermediate between species designated as progenitor. These results and the notorious heteromorphy between different chromosome pairs, supports the hypothesis of the origin of A. x spinosissima, as a hybrid species from the natural crossing of A. arborescens x A. humilis.

Key words:
A. arborescens; A. humilis; A. spinosissima; sympatric species; chromosomal heteromorphy; natural hybrid.