Induction and identification of polyploidy in basil (Ocimum basilicum L.) medicinal plant by colchicine treatment

Basil (Ocimum basilicum) is one of the important medicinal plant species. In order to produce an autotetraploid population of basil (Ocimum basilicum) by colchicine, different concentrations (0.00, 0.05, 0.10, 0.20, 0.50 and 0.75%) and four treatment methods were examined (seed, the growing point of seedlings at the emergence of cotyledone leaves stage and emergence of true two type leaves stage, and root treatment) to determine the best treatment for the induction of tetraploid plants. Autotetraploid plants were produced only by treatment of growing point of seedlings, at the emergence of cotyledone leaves stage, and treatment with 0.5% proved to be the most effective in producing autotetraploids. The induced tetraploids in basil was accompanied by larger stomata and pollen grains, increase in chloroplast number in guard cells and decrease in stomata density, compared to diploid control plants. In order to distinguish the induced colchicine tetraploid plants from the diploids, morphological changes and techniques as stomata size, number of chloroplasts per guard cell, pollen grain diameter and flow cytometry were considered and proved that these methods are suitable, quick and easy methods for identification the ploidy level of Ocimum basilicum in various stages of the plant development of these species and among this methods flow cytometry as found to be the most efficient method for detecting induced changes in ploidy level.