Abstract:

Radiosensitivity，which is defined as visible damage or stimulus to seedling growth by physical or chemical mutation treatments, is a very important characteristic in the field of induced mutation breeding. In the present study, the radiosensitivity and mutagenic effects were studied using 24 different rice cultivars by treatments of space carrying of spacecraft “Shen-Zhou 4” which was launched in 2002 in China and ⁶⁰Co γ-irradiation on the ground. Radiosensitivity was expressed based on the total physiological damage or stimulus of seedling height and seed setting rate in M₁ generation, and mutations of plant height and heading date in M₂ were observed. The results indicated that japonica rice had stronger radiosensitivity of space environment mutation and γ-irradiation than indica rice, bred cultivars stronger than landraces, medium-late indica and late indica stronger than early indica whereas no significant differences among different japonica climate ecotypes. Most cultivars non-sensitive to γ-irradiation were also non-sensitive to space mutation and only one-fourth of cultivars sensitive to γ-irradiation showed radiosensitivity to space mutation (Table 1). Space flight had obvious stimulus effects on seedling growth for 54.2% cultivars. In M₂ generation, mutations of plant height and heading date could be induced by both space environment and γ-irradiation but the mutation frequencies were quite different (Table 2). There were significant correlations between the total physiological damage in M₁ and the mutation frequencies of dwarfing, high plant and early maturity in M₂ after space flight. A conclusion is that space environment shares incomplete same mutagenic mechanisms with γ-irradiation. The results in the present study provide some useful information for rice space mutation breeding in the future.

Key words: Rice, Space environment mutation, γ-irradition, Radiosensitivity, Mutagenic effects