Morpho-physiological effects of gamma radiation on Tall fescue (Festuca arundinacea Scurb.)

Gamma radiation is being used to induce mutation in diverse plant species. The present study investigated the growth and physiological responses of two tall fescue genotypes, 75C (native genotype) and Pacer (foreign genotype) to gamma radiation, as well as determination of the proper dose of gamma radiation for the mutation breeding program of this species. Seeds of two genotypes of tall fescue were subjected to different doses, including 50, 100, 150, 200, 300 and 400 Gray (Gy) of gamma ray from a 60Co (Cobalt-60) source. Irradiated and non-irradiated seeds were sown in pots and grown under controlled conditions in the greenhouse. Growth and physiological aspects associated with plant tolerance to oxidative stress were examined. The results revealed that the low dose (50 Gy) of gamma radiation stimulated seedling growth of both genotypes. However, high doses (100-400 Gy) significantly reduced seedling survival and plant height, and enhanced days to seedling emergence. Further, high doses of radiation reduced activities of antioxidant enzymes (especially catalase and superoxide dismutase), and increased the contents of proline and malondialdehyde (MDA) in the seedlings of both genotype as compared with non-iradiated plants. Biplot analysis indicated that positive correlations were found between the growth and survival of plant with antioxidant enzyme activities and negative correlations were obsereved between the plant growth and proline plus MDA contents. The native genotype (75C) was more sensitive to gamma-ray than Pacer genotype. According to the probit analysis, the 50% lethal dose (LD50) for 75C and Pacer genotypes were 212 and 223 Gy of gamma radiation, respectively. Based on the results of the present study, gamma rays stress negatively affected survival, morphological traits, and antioxidant enzymes activities in tall fescue and dosages ranging from 200 to 250 Gy is recommended as the appropriate dose of irradiation for mutation breeding programs in tall fescue.