Screening and identification of salt-tolerant mutants at germination stage from space mutagenesis and heavy ion radiation of rice

Objective To screen salt-tolerant mutants during germination, provide excellent germplasm resources for creating and breeding new salt-tolerant rice varieties.

Method The dried seeds of the high quality indica rice variety ‘Hangjuxiangsimiao’, were treated with spatial mutagenesis and heavy ion mutagenesis, and the mutagenised progeny were subjected to targeted screening for salt-tolerant mutants. Wild type (WT) ‘Hangjuxiangsimiao’ seeds were treated with different concentrations of NaCl solution to explore the appropriate concentration for screening salt-tolerant mutants at the germination stage, and then 5 205 M₂ mutant materials were screened using germination rate as an index and verified in the M₃ generation. The wild type and mutants were measured and analysed for salt-tolerance-related physiological indices and agronomic traits; 48 SSR markers were used to assess the genetic similarity between the mutant progeny and the wild type.

Result The appropriate NaCl concentration for screening salt-tolerant mutants at the germination stage was 340 mmol/L, and 12 salt-tolerant mutants were screened at the germination stage. The results of physiological indices showed that the SOD, POD, CAT and APX activities of two representative mutants 9-8 and 22-7 were significantly higher than those of WT, and the MDA, H₂O₂ and O²⁻ contents were significantly lower, the salt-tolerant mutants exhibited stronger antioxidant capacity. The results of SSR marker detection showed that there were no SSR differentiation loci between the wild-type ‘Hangjuxiangsimiao’ seedlings and 19-49, 20-15, 20-49, 20-62, 15-6, 16-65, 22-7, 20-19 and 20-38, and one differentiation SSR loci between them and 9-8, 19-18, 42-113.

Conclusion In this study, 12 salt-tolerant mutants were screened at the germination stage, which were highly consistent with the genetic background of wild-type ‘Hangjuxiangsimiao’. It has certain theoretical and practical significance for the breeding of new salt-tolerant rice varieties and the study of the genetic mechanism of salt tolerance.