Abstract

Spathoglottis plicata Blume is a terrestrial orchid with low genetic diversity. This study was successful in using gamma irradiation to induce mutation lines of S. plicata Blume and to identify the mutants by AFLP marker analysis. Three-month-old seedlings were irradiated with acute gamma radiation at the doses of 0, 2, 4, 6, 8 and 10 Krad before transferring to culture on Vacin and Went medium (VW) without growth regulators. Seedlings irradiated with gamma ray higher than 2 Krad did not survive. A gamma ray dose of 1.43 Krad was calculated as 50% of the lethal dose (LD<inf>50</inf>). Seedlings treated with 2 Krad produced new plantlets and multiple shoots from their old shoots that could be separated into 27 clones. From these only 5 clones survived and flowered. They were characterized by a lower plant height, leaf number, leaf length, leaf width and inflorescence length as compared to nonirradiated plants (p≤0.5). Based on the flower shape and structure, non-irradiated plants could be divided into 3 groups. For irradiated plants, only clone 13 did not differ from the control. Indeed, clones 19, 22, 25, and especially clone 23 showed significant morphological differences from non-irradiated plants. The latter clone was healthy, had a dwarf stem, low tillering number, thick leaf and short inflorescence with long spots on the sepals and petals and undulate petal margin and could be promoted as a new cultivar for commercial production. Moreover, the identification of irradiated clones by AFLP technique confirmed genetic diversity of variants with the polymorphism rate of 1.89-29.85%.