Gamma radio sensitivity study on Papaya cv. Ranchi Local and Arka Surya

Abstract

An investigation was carried out at Horticulture Research Station, Odisha University of Agriculture & Technology, Bhubaneswar, Odisha, India during 2016-2019 to study on “radiosensitivity study on papaya”. The experiment was laid out in a Factorial Randomized Block Design with three levels viz two varieties, two soaking conditions and seven different gamma doses. Cobalt 60 source in gamma chamber was used to treat papaya seeds at the Radiation Standards Section, Radiation Safety Systems Division, Bhabha Atomic research Centre in Mumbai, India. In the preliminary dosimetry study, seeds from two papaya varieties, Ranchi Local and Arka Surya were irradiated with 7 different radiation doses ranging from 10 Gy to 70 Gy at every interval of 10 Gy. The source of radiation in the chamber is Co60, which emits 2 gamma radiation of energy 1.33 and 1.17 MeV per disintegration. The dose rate was of the order of 17 Gy/min. Prior to irradiation in one experiment, seeds were soaked overnight in water and surfacedried and in another experiment, seeds were immersed in water during irradiation. Increasing gamma ray decreased germination percentage, shoot length, plant height (reduction of 49.7% over control), bearing height (reduction of 62.6% over control) in papaya whereas gamma rays enhance root development up to LD 50 dose. Radio sensitivity test of germinated seeds showed that LD50 was 28.35 and 33.13 Gy for presoaked seeds and 24.05 and 23.78 Gy for seeds immersed in water for Ranchi Local & Arka Surya respectively. From the analysis of GR50 for both the irradiated conditions, it was found that 30 Gy (for pre-soaked seeds) and 20 Gy (for seeds immersed in water) was the most effective dose with maximum possibility of desirable mutation. 10 Gy acted as a stimulative dose for plant growth, survival percentage and vigour index.