Gamma radiosensitivity study on rice (Oryza sativa L.)

It has been long known that plants are sensitive to ionizing radiations such as beta particles and gamma rays. Seeds or unfertilized flower buds and whole plant or part of it have been irradiated in order to investigate the effects of these radiations on crop plants. Studies have shown that radiation of different types at various intensities can either inhibit growth or kill the plant completely. The radiosensitivities of different plants vary greatly according to source of radiation. In present investigation, nine popular rice varieties cultivated in Andhra Pradesh, were used to examine varietal differences in radio sensitivity to gamma radiation during the wet season of 2012. Dry seeds of Nine rice varieties BPT 5204 (Samba mahsuri), JGL 384 (Polasaprabha), Surekha, Vijetha (MTU- 1001), JGL 1798 (Jagithal Sannalu), NLR 34449, Swarna, MTU 1010 (Cottondora sannalu) and Erramallelu (WGL 20471)) were exposed to gamma radiation ranging from 0.20 kGy to 2.00 kGy using continuous gamma sterilization plant (GC 5000, designed by Board of Radiation & Isotope Technology, Mumbai) with 444 TBq (12000Ci) and Cobalt – 60 source at Quality Control Laboratory, Acharya N. G. Ranga Agricultural University, Rajendranagar, Hyderabad- 500 030 with a specific activity of 2.64 kGy hr-1, to determine their response to radiation stress and the effective radiation dose for identification of Lethal dose 50 (LD50). Data on germination parameter was generated as per [10]. Percentage germination was measured on 7th day after germination in irradiated sample. The results indicated that increasing doses of gamma irradiation had significant effect on germination for the first seven days under laboratory conditions. With increase in radiation above 0.80 kGy a reduction in percentage of germination under laboratory conditions was observed in irradiated seeds as compared to control. Increase in gamma ray doses from 0.20kGy to 0.60 kGy had little or no effect on germination percentage as there were no significant differences in germination percentage of irradiated seeds and non-irradiated (control) for all the varieties evaluated. The LD50 values determined from linear regression analysis (Polynomial fit using Origin Pro 8 software) based on percentage of germination ranged from 0.89 kGy (JGL 1798) to 1.88 kGy (Vijetha). The varieties JGL 1798 and BPT 5204 had highest radiosensitivity while Vijetha and Surekha were relatively tolerant. However, the varieties MTU 1010 (1.66kGy), Erramallelu (1.57 kGy), Swarna (1.56 kGy), JGL 384 (1.38 kGy) and NLR 34449 (1.32 kGy) are moderately tolerant. These ranges of LD50 values determined for the different rice varieties could be useful in rice varietal improvement programmes.

Author(s): D. Pavan Kumar*, Anurag Chaturvedi, M. Sreedhar, M. Aparna, P. Venu-Babu and R. K. Singhal

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