Biological effect and targeted mutation screening of space-induced mutagenesis and heavy ion radiation in rice

Objective  To compare the biological effects and variation frequency of two mutagenesis methods, including space mutation and heavy ion radiation, in different generations of rice (Oryza sativa L.), and provide some methods and theoretical guidances for rice mutation breeding.

Method  The dry seeds of pure line rice variety ‘Huahang 31’ were treated using space mutation and different dose of heavy ion radiation, and the seeds without mutation treatment were used as the control. The phenotypic and cytological mutagenic effects of the 1st generation of mutation (M₁) were analyzed. The amylose content and grain shape trait of the 2nd generation of mutation (M₂) were screened by phenotypic and genotypic targeted screening. The variation frequencies in M₂ of two mutation treatments were compared.

Result  The seed vigor index of space mutation M₁ was 14.62% lower than that of the control. The seed vigor index of heavy ion radiation M₁ showed a saddle effect curve with the increase of radiation dose, and the seed vigor index of 10 Gy heavy ion radiation M₁ was 14.92% lower than that of the control which was like the mutation effect of space mutation. The grain type and amylose content mutation frequencies of space-induced M₂ were 4.14% and 1.61% respectively, while the grain type and amylose content mutation frequencies of 80 Gy heavy ion radiation were 4.88% and 1.55% respectively. When HRM technology was used to scan the 673 bp sequences of four intervals of Wx gene, three SNP mutations were found in 4 736 samples of space-induced with a mutation density of 1/1063.83 kb. Four SNP mutations were found in 4 848 samples of heavy ion radiation with a mutation density of 1/815.68 kb.

Conclusion  Two kinds of mutagenic treatments can induce the character variations of rice. The physiological effects of space-induced mutagenesis M₁ is similar to low-dose heavy ion radiation, and the mutation frequency of M₂ is similar to high-dose heavy ion radiation.