Effects of acute gamma irradiation on in vitro culture of Exacum affine Balf.f. ex Regel

Exacam affine Balf. f. ex Regel (Persian Violet) is an ornamental plant with small, purple flowers having yellow pollen in their center and it is mostly cultivated as a houseplant. The effect of acute gamma irradiation on in vitro cultures of E. affine was studied by treatment with gamma radiation using a Mark I Gamma Irradiator at the Nuclear Technology Research Center, Kasetsart University, Thailand with a Cesium-137 source at doses of 0, 10, 20, 30, 40, 50 and 60 Gy and a dose rate of 3.74 Gy/min. After irradiation, subcultures were grown on new Murashige and Skoog (MS) medium; then, after 60 d, the numbers of new branches on surviving plantlets were counted. Samples were subsequently subcultured to new MS medium for morphological study. The median lethal dose was 45 Gy and the 50% decreasing growth rate was 32 Gy. Some variations were observed in irradiated samples in M1V2, such as changes in the number of petals in a flower (four and six petals), flower color (light purple, white), smaller leaves, curled-shaped leaves, variegated leaves, lighter-green leaves and shorter internodes than the control.