Objective The study aims to create a permanent thermo-sensitive genic male sterile line, with a view to providing support for solving the safety problem of two-line hybrid rice seed production.

Method Based on the creation of a permanent thermo-sensitive genic male sterile line Tianfeng M by using recurrent parents to polymerize thermo-sensitive and reverse thermo-sensitive genic male sterile genes, the genetic characteristics of Tianfeng M sterility were studied.

Result The results showed that the male sterility of Tianfeng M polymerizing the thermo-sensitive and reverse thermosensitive genic male sterile genes was controlled by two pairs of genes, one was thermo-sensitive genic male sterile gene, and the other was regulated by temperature, that is, multiple alleles from thermo-sensitive and reverse thermo-sensitive genic male sterile lines. And the dominant-recessive relationship was switched by temperature. Under high temperature, the genes from thermo-sensitivity was dominant, and the gene regulating sterility was expressed as sterility; under low temperature, the genes from reverse thermo-sensitivity was dominant, and the gene regulating sterility was also expressed as sterility. The performance of population segregation was confirmed from the cross type 4 of different thermo-sensitive and reverse thermo-sensitive genic male sterile sister lines. The combination C₃₁ (Z₁×F₇) showed sterility, fertility and normal fertility at low temperature. The ratooning of sterile plant after stem-cutting was separated to sterility plant and fertile plant. There were 5 permanent male sterile plants, 6 low-temperature sterile and high-temperature fertile plants, 4 low-temperature fertile plants and 7 normal fertile plants, which was consistent with the segregation ratio 1∶1∶1∶1 of 2 pairs of heterozygous genes. This permanent thermo-sensitive genic male sterility controlled by two genes could be inherited and restored, and the permanent sterility could be restored when the thermo-sensitive genic male sterility gene was dominant.

Conclusion Tianfeng M male sterile line can solve the safety problem in seed production of two-line hybrid rice.