Exploring of Lethal Dose (LD50) Using Gamma Rays and Its Impact on Seed Germination and Seedling Survival in Stevia rebaudiana Bertoni cv. CIM-Madhu

Stevia rebaudiana Bertoni an natural alternative to sugar and is known for production of sweet glycosides. The impact of gamma radiations in developing new stevia mutants was carried out at Department of Horticulture, University of Agricultural Sciences, GKVK, Bengaluru. Seeds of stevia cv. CIM-Madhu were collected and irradiated with various dosages of gamma rays viz. 50, 100, 200, 300, 400, 500 and 600 Gy to assess the LD50 value. The maximum germination (65%) was seen in the non-mutagenized control group followed by 61 percent in treatment comprising of 50 gy gamma irradiation with 6.15 per cent reduction in germination over the control. The maximum survival percentage was recorded in non-mutagenized control group (89%). Non-mutagenized control group took significantly lesser number of days (12 days) for germination and the treatment comprising of 200 Gy and 500 Gy took maximum number of days for germination (20 days). LD50 a dose that causes 50% mortality to the seeds was found at 150 Gy. This LD50 dose can be used as reference for initiating mutation breeding in other cultivars of stevia.