Inter-subspecific Hybridization And Utilization Of Maize C₄-type Pepc Gene For Improving Photosynthetic Characteristics Of Rice

Super Hybrid Rice Breeding Program had been initiated in 1996. It is a credible assurance to achieve Super Hybrid Rice Breeding Program by further raising photosynthesis efficiency of single leaf while keeping the foundation of the good stub types and the high light efficiency utilization. The F₁ obtained by intersubspecific hybridization and transfer of foreign gene was observed with the focus on studying photosynthesis efficiency of simple leaves. In this study, a Kitaake (Oryza sativa ssp japonica) was crossed with another 5 maternal parents with different genetic differences, resulting in the intersubspecific F₁ that had various heterosises. The 5 maternal parents in question were three indica rices {Oryza sativa ssp indica): Shuhui527, Shuhui881, Mianhui725; American rice Lemont (specific japonica) and Javanica Xiangdali {Oryza sativa ssp Javanica). Performances on photosynthetic characteristics and transportation of dry matters in 5 F₁ were investigated, which would reveal relationships among genetic differences, biological advantage and economical yield advantage. On the other hand, a germplasm with maize pepc gene was used as gene donor, and its specific primer was designed and used to conduct MAS (marker assisted selection). The pepc gene was introduced into the widely used restorer Shuhui881. The improved Shuhui881 with the pepc gene, of which the similarities of genetic background were over 95% as compared with the Shuhui881, was crossed with 3 Indica sterile lines, namely Gang46A, 776A and 2480A. Performances on photosynthetic characteristics in the 3 F₁ and combining ability of agronomic traits in several plant lines of improved Shuhui881 with maize pepc gene were investigated as well. The main conclusion was as follows.1. There were different abilities to assimilate CO₂ in mesophyll cell between F₁ and parents. Under high Photosynthetic Flux Density (PFD), the net photosynthetic rate {Pn) that the 5 F₁ reached was significantly higher than that of their parents (or one of them) and intercellular CO₂ concentration (Ci) in parents, compared with F₁, rose relatively in the condition of non-stomatal limitation.2. The different heterosis on photosynthetic characteristics lies in genetic differences among the 5 F₁. During the investigation of photosynthetic indexes such as apparent...