Indian Journal of Crop Science

In this study, pretreatment effects of gamma radiation on Improvement of drought tolerance were investigated in rice var. tarom (Iranian local rice variety). Fully mature and perfect seeds were Irradiated with 4 doses of gamma radiation (0, 20, 60, 100 Gy). For callus induction, Irradiated and control seeds were surface sterilized and cultured on MS medium supplemented with 2 mgl⁻¹ 2, 4-D and 0.2 mgl⁻¹ BA. Analysis of data revealed that, 20 Gy irradiated seeds had the highest rate of germination, callus initiation and callus weight. To study the callus growth in response to osmotic stress, certain amount of embryonic callus was transferred to MS medium, supplemented with PEG at different concentrations (0–25%). After two weeks, the callus growth and proline accumulation were assayed in both control and Irradiated samples. Results revealed that in stressed conditions, pretreatment of seeds with gamma radiation cause a significant increase in callus growth compared to those of controls. Interestingly, the stress didn't increase proline level in calli derived from Irradiated seeds. However, proline accumulated more significantly in control samples, while the growth rate was stili less than Irradiated samples. One way to explain these data is that, the radiation may have promoted the level of antioxidants and consequently there would be no need for extra amount of proline to cope with the same problem of oxidative reagents.