Effective Induction of Polyploidy by in vitro Treatment with Colchicine and Characterization of Induced Polyploid Variants in Water Yam (Dioscorea alata L.)

Abstract

Water yam (Dioscorea alata L.) is one of the most popular cultivated species of yams. It is dioecious and scarcely flowers. Moreover, the lack of synchronization in flowering of male and female plants hampers hybridization and sexual reproduction. Although somaclonal variation such as polyploidy has been considered to be useful for improving water yam; no efficient technique for inducing polyploid variants has yet been developed. In the present study, somaclonal polyploid variation was successfully induced at a high frequency by in vitro treatment of water yam with colchicine. The highest rates of polyploid induction, 26.7% and 16.7%, were obtained after 0.1% colchicine treatment in accessions No. 132 and No. 127, respectively. Tetraploid variants tended to display the somewhat rounder leaves than their diploid parents. The size and shape of water yam stoma have also been found to be affected by levels of ploidy. Tetraploid variants exhibit larger stomata at a lower density compared to the diploid parents. The technique of somatic polyploidization presently proposed is considered to be useful for the improvement of water yam.