| 93-11 served as an elite restorer line of two-line hybrid, which was widely used in our country's rice production, is also a restorer line of three-line hybrid of the HL type. The super-hybrid rice, Liangyou Pei 9 and Honglianyou 6, .which was mated by 93-11, has the characteristics of high yield and good grain quality. In order to enhance its resistance to bacterial blight (BB) and lepidopteran such as leaffolder, striped stem borer and yellow stem borer etc, we intergessed Xa21 and Bt genes into the genetic background of 93-11 by backcross scheme, combining with molecular marker-assisted selection and phenotypic selection. Through three backcross and two self generations, eight-families that have homozygous Xa21 and Bt genes were obtained in the BC3F3 families. Two families show higher recovery percentage of 93-11 even up to 90.59%. In the subsequent field evaluation, 93-11 (Bt/Xa21) and its hybrid show high resistance to BB and stem borer. The agronomic performance of improved 93-11 (Bt), 93-11 (Xa21) and 93-11 (Bt/Xa21) was very similar to original 93-11 under normal condition. But on the natural stem.borer infestation condition, the improved 93-11 contained Bt gene and its hybrid was not damage by stem borer. This result shows: It has a quickly and excellent efficiency to introduce multiple genes simultaneously into a certain improved parent by MAS conjunction with conventional breeding method. The improved line persist the main agronomic trait and combining ability of 93-11, show wide spectrum to Xoo strains and enhanced resistance to BB and stem borer. Thus, this line has good prospect in future practical use.Additionally, in order to let 93-11 can restore the fertility of the WA type, we also introduce the strong restorer gene, Rf(u) that located on chromosome 10 in Minghui63, into genetic background of 93-11 by conventional backcross scheme, combining with marker-assisted selection. Through three backcross generation, 67 individuals has heterozygous Rf (u) gene were obtain in BC3F1 population and three positive individuals were selected to cross with Zhengshan97A to test their fertility restoring ability. Simultaneously, 20 positive individuals were selected according to their agronomic trait such as seed setting rate plant height heading time etc. is similar to 93-11, then were selfed to obtain homozygous individuals. In the F1 population derived from the cross between Zhenshan97A and 93-11 Rf (u) , the seed setting rate of fertile individuals vibrated from 71.4 to 91.6%, the mean of seed setting rate was 82.3%. But the seed setting rate of sterile individuals vibrated from 1.4 to 40.4%, the mean of seed setting rate was 17.3%. Chi square test show that the segregation of fertile to sterile in this population were 1:1 that is agreement with the ration of singleMendalian segregation, indicating the Rf (u) gene was introduced into genetic background of 93-11 completely and show a strong restoring ability. Finally, 54 individuals have homozygous Rf{u) gene were obtained with strong restoring ability in the BC3F2 population. The evaluation of agronomic performance and combining ability of improved 93-11 is in preceeding. |
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