Research On Improvement Of Resistance To Both Bacterial Blight And Stem Borer In Hang 1, A Restorer Line Of Three-Line Hybrid Rice

Bacterial blight of rice is one of the three most destructive diseases throughout the world. As an effective measure, the exploitation of host resistance genes can be used for the improvement of disease resistance. On the other hand, pests are the main bottleneck for rice production due to the lack of host resistance genes. Nowadays, we can develop resistant cultivars by transferring pests-resistant Bt gene. Hang 1 is an elite restorer line of three-line hybrid, which is widely used in the cultivation of hybrid rice. The super hybrids, Teyouhang 1 andⅡyouhang 1, which were mated using Hang 1 as male parent, have the characteristics of high yield and novel quality. In order to improve its resistance to both bacterial blight and stem bore such as Cnaphalocrocis medinalis. Xa7, Xa21 and cry1C* genes were transferred from Huahui 20 and TIC-19 respectively to the genetic background of Hang 1 by traditional breeding combining with MAS firstly, then the two-gene lines (Xa7+cry1C* or Xa21+cry1C*) and three-gene lines (Xa7+Xa21+cry1C*) were obtained by multiple cross. The specific Xanthomonas oryzae pv. oryzae strains, ZHE173 (Ⅳ) and GD1358 (Ⅴ) were used for identifying the improved lines' resistance to bacterial blight by artificial inoculation under the field condition. The experiment of resistance to stem borer for the improved lines was carried out under the field condition also. The quality traits of improved lines and their hybrids have been measured and analyzed in the research. The 9 improved lines of Hang 1 were hybridized with 5 sterile lines C815S,Ⅱ-32A, Chuannong 1 A, Jinke 1A and Jufeng A according to NCII design, and the combining ability for 8 main agronomic traits of the hybrids were investigated. The main result in the research is as follows:1. We have obtained two improved lines with genetic background of Hang 1 which contain Xa7 and cry1C* genes, Xa21 and cry1C* genes and Xa7, Xa21 and cry1C* genes respectively.2. The improved lines and their hybrids' resistance level to bacterial blight has been greatly improved. The improved lines and their hybrids showed high resistance level to Cnaphalocrocis medinalis.3. The result of rice quality traits shows that all the meterials studied are generally inferior to CK (Yangliangyou 6) on quality traits, and chalky trait and milled rice rate are main limiting factors.4. The result of usage of rice heterosis shows that only a part of improved lines' agronomic traits and combining ability are similar to Hang 1. And Jinke 1A/JY8020-1, Jufeng A/Hang 1, Jufeng A/JY8021-1, Jufeng A/JY8022-1, Jufeng A/JY8024-1 and Jufeng A/JY8232-1 were selected in the research.All in all, Xa7, Xa21 and cry1C* genes were transferred into the genetic background of Hang 1 successfully. The improved lines and their hybrids's resistance levels to both bacterial blight and stem borer were increased obviously. These lines have a good prospect in future practical use.