Effects of Acute and Chronic Gamma Irradiation on Tissue Culture of Cryptocoryne wendtii “brown”

Abstract

The value of aquatic plant exports from Thailand is rising and there is a demand for interesting new varieties of aquatic plants. The objective of this research was to find the appropriate dose of gamma irradiation to induce mutations in Cryptocoryne wendtii “brown.” C. wendtii “brown” was cultured aseptically on MS medium supplemented with BA (2mg/l) and NAA (0.25 mg/l). Samples of the tissue- cultured plantlets were exposed to acute gamma radiation using a Mark I Gamma Irradiator with a Cesium-137 source at doses of 0, 10, 20, 30, 40 and 50 Gy. Other samples were exposed to chronic gamma radiation in a gamma room using a Cobalt-60 source at the Gamma Irradiation Service and Nuclear Technology Research Center of the Faculty of Science, Kasetsart University. The samples were placed at 1.5 and 2.5 m from the source with a dose rate of 1.614 and 0.537 Gy/hr, respectively. The samples at 1.5 m received a total dose of 238.87 and 477.74 Gy (0 for the control) and those at 2.5 m received a total dose of 10.75, 21.50, 32.24 and 42.99 Gy (0 for the control). The number of dead and surviving plantlets and the number of new shoots were recorded at 45 days after irradiation and compared with the controls to calculate the LD50(45) and GR50(45). Under acute irradiation, the LD50(45) and GR50(45) for C. wendtii “brown” were found to be 23 and 20 Gy, respectively. Some variations were observed, such as clumping, dwarfism, darker brown leaves, furled leaves and narrow leaves. Under chronic irradiation it was not possible to calculate the LD50(45) or GR50(45) because at 1.5 m from the source all the samples died and at 2.5 m from the source more than 50% of the samples survived. Some variations were observed, such as shorter plants, green leaves, increased branching, shorter petioles and longer, narrower leaves of a greenish-brown color.