Abstract：sbHLH1 gene encoded one of transcription factors in bHLH (basic helix-loop-helix) family, which is involved in cold tolerance. The expression of Bar gene can relieve the toxicity of glufosinate, a highly effective and low toxicity herbicide.The OsbHLH1 and Bar genes were transformed into rice cultivar Huai C17 (Oryza sativa L. subsp. japonica Kato) by Agrobacterium tumefaciens mediation. The herbicide resistance, cold tolerance and agronomic traits of transformants with Bar and OsbHLH1 genes were identified in this study. The existance of Bar gene and its expression in transgenic lines were identified by stress of glufosinate. The integration of OsbHLH1 gene and its expression were also detected and confirmed by PCR, Southern blot, RT-PCR and Real-time PCR. The T3 generation of the transgenic line No. 6 had been treated with 2℃ for 6 days at the germination stage. And the dead seedling of this transgenic line was 17.8% while that of control was 61.1%. Under stress of 8~10℃ for 7 days at the seedling stage, the root length of transgenic lines No. 5, 6, 9 and 11 of T3 generation were longer than that of control (P<0.05), and the root number of line No. 3, 5 and 11 were more than that of control (P<0.05) and the fresh weight of No. 3 line was higher than that of control (P<0.05). The increase of cold tolerance at germination and seedling stage of transgenic lines showed that the over-expression of OsbHLH1 gene could improve the cold tolerance of rice. Based on the investigation of the main agronomic traits, there were differences (P<0.05) in plant height, panicle length, 1000-grain weight, seed setting and theoretical yield between transgenic lines of T2 generation and control, which indicated that the over-expression of exogenous gene had obvious influence on rice agronomic traits. The new germplasm created in this study will be available for breeding of new japonica hybrid rice with cold and herbicide tolerance
