Submitted to: HortScience
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: July 12, 2009
Publication Date: December 10, 2009
Citation: Sakhanokho, H.F., Rajasekaran, K., Kelley, R.Y. 2009. Induced Polyploidy in Diploid Ornamental Ginger (Hedychium muluense) Using Colchicine and Oryzalin. HortScience. 44(7):1809-1814. Interpretive Summary: Knowledge of the ploidy level (the complete set of chromosomes) of a plant species is crucial for any hybridization program as desirable crosses are usually difficult to obtain between parents of different ploidy levels. Increased ploidy level (or induced polyploidy) can result in more vigorous plants with larger flowers and the removal of hybridization barriers due to difference in ploidy levels. The objective of this study was to determine and increase the ploidy level in Hedychium muluense, an ornamental ginger also known as Hedychium philippinense or “Borneo ginger”, using the chemical compounds colchicine and oryzalin. Conventional chromosome count was used to determine the ploidy level of H. muluense, which was found to be a diploid (2n = 2x = 34). Triploid, tetraploid, and mixoploid plants were obtained with both colchicine and oryzalin treatments. The highest induction (15%) of tetraploid plants was achieved when embryogenic callus was exposed to 60 µM oryzalin for 72 hours.
Technical Abstract: The ploidy level of H. muluense, a diploid (2n = 2x = 34) and dwarf ornamental ginger species, has been determined and is reported for the first time. Oryzalin and colchicine were successfully used to induce polyploidy in Hedychium muluense in vitro. Embryogenic cell lines were treated with oryzalin (30, 60, or 120 mM) and colchicine (2.5, 5, or 10 mM) for 24, 48, or 72 h. The control contained no antimitotic agent. Flow cytometry, chloroplast count, and stomatal frequency were more effective and reliable than stomatal length as methods for assessing ploidy. Overall, oryzalin was more effective than colchicine in inducing polyploidy. The highest induction frequency (15%) of tetraploidy was achieved when embryogenic callus was exposed to 60 mM oryzalin for 72 h. For colchicine, exposure of embryogenic callus to the 2.5 mM colchicine for 24 h was the most effective in creating tetraploid (13%) plants.