Karyotypes, heterochromatin, and physical mapping of 18S-26S rDNA in Cactaceae

LAS PEÑAS, M. L.; URDAMPILLETA, J. D.; BERNARDELLO, G.; FORNI MARTINS, E. R.

Cytogenetic and Genome Research

Karger, AG.

Lugar: Suiza; Año: 2009 vol. 124 p. 72 - 80

1424-8581

Karyotype analyses in members of the four Cactaceae subfamilies were performed. Numbers and karyotype formula obtained were: Pereskioideae = Pereskia aculeata (2n = 22; 10 m + 1 sm), Maihuenioideae = Maihuenia patagonica (2n = 22, 9 m + 2 sm; 2n = 44, 18 m + 4 sm), Opuntioideae = Cumulopuntia recurvata (2n = 44; 20 m + 2 sm), Cactoideae = Acanthocalycium spiniflorum (2n = 22; 10 m + 1 sm), Echinopsis tubiflora (2n = 22; 10 m + 1 sm), Trichocereus candicans (2n = 22, 22 m). Chromosomes were small, the average chromosome length was 2.3 _ m. Diploid species and the tetraploid C. recurvata had one terminal satellite, whereas the remaining tetraploid species showed four satellited chromosomes. Karyotypes were symmetrical. No CMA ? /DAPI + bands were detected, but CMA + /DAPI ? bands associated with NOR were always found. Pericentromeric heterochromatin was found in C. recurvata , A. spiniflorum , and the tetraploid cytotype of M. patagonica . The locations of the 18S-26S rDNA sites in all species coincided with CMA + /DAPI ? bands; the same occurred with the sizes and numbers of signals for each species. This technique was applied for the first time in metaphase chromosomes in cacti. NOR-bearing pair no.1 may be homeologous in all species examined. In Cactaceae, the 18S- 26S loci seem to be highly conserved.