Polyploidy induction in black cumin (Nigella sativa L.) by colchicine treatment on seeds

Nigella Sativa L. is an annual plant from Ranunculacea family. Its seeds contain protein, alkaloids, kinons, saponin, and volatile essential oil used as antibacterial agent and treatment of some diseases. This study was aimed to investigate the polyploidy induction in Nigella sativa via seed treatment at colchicine concentrations of 0, 0.025%, 0.05%, 0.1%, and 0.2% for 8, 24 and 48 hours. The study was conducted in a factorial experiment based on completely randomized design with three replications. The percentage of tetraploid plants was determined through the morphological and chromosomal studies. Results of analysis of variance showed that effects of colchicine level, treatment duration, and the interaction between them were significant on the survival of plants and percentage of tetraploidy induction. The seed germination and viability of plants significantly decreased with increasing of colchicine concentration and treatment duration. The lowest number of survived plants was observed at a concentration of 2.0% colchicine and a treatment time of 24 and 48 hours. The highest percentage of induced tetraploid plants (9.9%) was obtained at a concentration of 0.05% colchicine with a treatment time of 48 hours, showing no significant difference with concentrations of 1 and 2 % at the same treatment time. The plants treated with colchicine showed higher plant height, internodes length, capsule width and length compared to that of control plants. Furthermore, they had larger stomata with lower number as compared with diploid plants.