Tetraploidy induction and identification in Dendrobium nobile Lindl (Orchidaceae)

The induction of the chromosomal duplication is an important tool in plant breeding programs, so it usually promotes the increase of the flower size, color and essence, as well as the restoration of the rare hybrids fertility. This research aimed to induce and identify the polyploids in Dendrobium nobile Lindl. For the poliploidy induction, plants with medium height of 5.0 cm were completely submerged, in dark conditions, in 0.05% and 0.1% colchicine solutions for 24; 48; 72 and 96 hours. Seven months later, the plants were evaluated for survival rate, height and diameter of the pseudo bulb and for ploidy levels. The ploidy level determination was made through the counting of chromosomes in the mitotic metaphase cells. It was verified that the colchicina treatment in the two concentrations and until a maximum period of immersion of 96 hours, did not affect the survival of the treated plants. The induced tetraploids plants (2n = 4x = 76 chromosomes) were obtained after 72 and 96 hours of immersion periods in the two concentrations of tested colchicine. The immersion of plants in 0.1% colchicine over 96 hours induced more tetraploids plants. Mixoploids plants were not observed.