Induction of polyploidy in saffron (Crocus sativus L.) using colchicine

Saffron (Crocus sativus L.) is triploid (2 n = 3x = 24, x = 8), which limits its improvement through crop breeding programs. This study was initiated to induce hexaploidy with the intent of restoring sexual stability in saffron. Corms were treated with colchicine concentrations of 0.0%, 0.025%, 0.05%, and 0.1% for 3-h, 6-h, and 9-h. A total of 16 in-vitro shoots showed signs of polyploidization. These colchiploid shoots showed slow but robust growth and produced large-sized cormlets (6.0 g) compared to the control (2.8 g). Leaf epidermal cell morphology, stomatal size and density showed evidence of polyploidization. Hexaploidy (2 n = 6x = 48) was confirmed by root-tip cytology. The hexaploid corms germinated but could not establish in the field. We were able to develop a protocol for in-vitro induction of hexaploidy in C. sativus, but the subsequent growth of hexaploid corms in the field remains a major challenge in restoring the sexual stability in saffron.