Improvement of Chromosome Doubling Efficiency in Cymbidium Hybrids by Colchicine and Oryzalin Treatment

This study aimed to investigate the efficiency of colchicine and oryzalin in inducing polyploidy in two Cymbidium hybrids [Showgirl ‘Silky’ and Mystery Island ‘Silk Road’ (Silk Road-4)]. Colchicine was used at concentrations ranging from 50 to 500 ㎎·L -1 , with treatments lasting 1 to 3 weeks. Oryzalin was used at concentrations ranging from 3 to 20 ㎎·L -1 , with treatments lasting 3 to 6 days or 1 to 3 weeks. The survival rate of PLBs was better in colchicine than in oryzalin solutions. The ploidylevels were screened using flow cytometry. In C. Showgirl ‘Silky’, the highest chromosome doubling efficiencies were obtained with the 1-week treatment in 50 ㎎·L -1 colchicine (60%) and the 2-week treatment in 5 ㎎·L -1 oryzalin (46.7%). In C. Mystery Island ‘Silk Road’ (Silk Road-4), the highest chromosome doubling efficiencies were obtained with the 1-week treatment in 50 ㎎·L -1 colchicine (16.7%) and the 3-day treatment in 10 ㎎·L -1 oryzalin (6.7%). Colchicine was more efficient than oryzalin in terms of polyploidy induction. Furthermore, pre-treatment, which entailed poking 10 times with forceps, improved the efficiency of chromosome doubling.