Polyploidization effect in two diploid cotton (Gossypium herbaceum L. and G-arboreum L.) species by colchicine treatments

Anti-mitotic agents such as colchicine have been used to induce polyploidy in various plants. Here we examined the effects of different doses of colchicine on polyploidy induction in two cotton species ( Gossypium herbaceum and Gossypium arboreum). The data reveal that the dose of colchicine, treatment duration, genotype and their combined effects on the induction of polyploidy and plant growth rate were statistically significant. Increase of either the concentration of colchicine or treatment duration showed adverse affects on seed viability in both species examined. The colchicine treatment is more effective when the length of hypocotyls is between 4-7 mm. The buds of G. arboreum treated with 0.9% colchicine exhibited more tetraploid cells sixteen hours post treatment. Among three methods employed, in vitro treatment of embryos can be conducted in a little space and needs a little amount of colchicines. However, high risk of contamination and high sensitivity of embryos to colchicine is a draw back of this method. Treatment of intact meristems with colchicine requires more amounts of the material and increases the risk of adverse environmental effects. Furthermore, plants treated with this method are susceptible to environmental stimuli including high temperature and should be kept away from direct sunlight. Together, our data reveal that treatment of the cotton seeds with colchicine was more efficient and reliable compared to other methods examined. The optimum dose of colchicine and the incubation time should be adjusted for each variety under various environmental conditions.