The induction of polyploidy by using of colchicine and its identification through cytological traits in Lilium dandie

Breeders are always looking for sources of diversity in different plants. Because spontaneous mutations occur rarely in environment, induced mutation is a more appropriate method for plant diversity. Therefore, the ploidy level instruction through mutagens, especially chemical mutagens in somatic cells, has the potential to improve the ability to produce new varieties with superior and desirable traits in many plant species. Plant species with more than two chromosome (polyploid) sequences are of particular importance due to increased genetic variation in their better adaptation to new environments, natural evolution and plant breeding. Accordingly, an investigation was conducted to induce in vitro polyploidy through colchicine in a new species of asiatic hybrid Lilium dandie, which has high potential for ornamental and medicinal.

In this experiment, in vitro bulb scales were treated in a completely randomized design with factorial arrangement in different concentrations of filter sterilized colchicine solution (0.01, 0.05 and 0.1%) for 6, 12 and 24 hours. Then samples were taken to regenerate and grow normally in a culture medium without growth regulators. After assessing the survival rate, ploidy levels of regenerated plantlets by direct counting of the number of root meristem chromosomes were determined. Length, width and density of leaf apertures using bachelor varnish technique and direct counting of chloroplast number of stomatal guard cells in adult and developed leaves as cytological factors between the control (diploid) and polypoid (triploid) plantlets was compared. plantlet fresh weight was also measured using scales and morphological indices of leaf length and width and root length were measured by precise ruler.

The results of this study showed that with increasing concentration and duration of treatment of colchicine, the survival rate of explants decreased. colchicine was completely effective in inducing polyploidy (triploid) L. dandie and the highest amount of polyploidy (14) occurred during 12 hours. The highest efficiency of productivity was obtained during treatment with 0.01% colchicine. In the polyploid plantlets, the stomatal density decreased significantly compared to the control, while the stomatal length and the number of chloroplasts in the stomatal guard cells showed a positive correlation with the increase in ploidy levels. Fresh weight and morphological characteristics of leaf length and width as well as root length in polyploidy plantlets were significantly increased compared to control.

The use of colchicine in polyploidy induction in L. dandie was completely successful and the highest polyploidy productivity (42.85%) was optimized for 12 hours treatment. Low density and longer stomatal length, as well as high chloroplast count in the chloroplast guard cells in polyploid plantlets, are a good indicator of polyploid plantlets screening than diploid plantlets. Fresh weight indices and morphological characteristics of leaf length and root width and plantlets length increased with increasing ploidy level.