In vitro induction and identification of autotetraploid of Bletilla striata (Thunb.) Reichb.f. by colchicine treatment

Polyploidy breeding has proved to be a valuable approach for acquiring the high yield superior varieties in medicinal plants. An effective protocol for obtaining Bletilla striata autotetraploid is in vitro induction of protocorms with colchicine. The protocorms of B.striata were soaked in different concentrations of colchicine solution [0.05, 0.1 and 0.2% (w/v)] for 12, 24, 36, 48 and 60 h, and the ploidy of the seedlings was identified by chromosome counting and flow cytometry analysis. The results showed that the optimal condition for induction of autotetraploid of B. striata protocorms was treated with 0.2% colchicine for 36 h with the induction rate reached as high as 26.7%. In addition, the morphological and anatomical characteristics were observed and compared between the diploid and tetraploid plants. And we found that the features of tetraploid plants were significantly different from diploid plants, such as tetraploid plants possessed thicker and deeper green leaves, larger stomata and more chloroplast number, which could be used as simple and efficient parameters for screening tetraploid. This study laid a foundation for breeding superior varieties of B. striata.