| Leaf is one of the main organs for photosynthesis, which plays the vital roles in plant growth process. Variation of leaf color will affect the photosynthesis and growth of plants. Leaf color mutant is not only the important material for the research of photosynthesis in higher plant, but also plays an important role in the investigation of chlorophyll biosynthesis, chloroplast development, genetic differentiation and understanding of nucleo-cytoplasmic interaction. Leaf color mutant is also used as a marker for identifying the purity of hybrids.Chlorophyll-deficient mutant bnaC.ygl was developed from EMS treating seeds of T6 line of Brassica napus. The phenotype of bnaC.ygl mutant is controlled by a single recessive nuclear locus. The locus of bnaC.ygl was mapped on Chromosome 17. In this study, the mutant bnaC.ygl and the wild-type T6 were used as material to analyze the chlorophyll content and the chloroplast shape and development. The major findings are as follows:1. At seeding stage, pigment content of bnaC.ygl and the wild-type T6 were measured respectively. The chlorophyll content of bnaC.ygl is decreased compare with the wild-type, chlorochyll a and chlorophyll b are decreased 40.3% and 57.7% respectively, indicating that the yellow leaf trait may due to sharp dropping of the total chlorophyll content. While the ratio of Chl a/Chl b in bnaC.ygl is exceed the wild-type dramatically. This shows that the decline of Chl b is much more significantly than that of Chl a.2. By the use of Transmission Electron Microscope, we observed the shape and development of chloroplast of the mutant. It shew that the chloroplast shape of mutant bnaC.ygl was similar with T6 which was used as control, both of them were fusiform, but the granal stackes of mutant appeared less dense and lack granal membranes compared with T6. This indicated that the chloroplast development of mutant was affected compared with wild type.3. We developed the F2, BC3 and BC4 population from the cross between the bnaC.ygl mutant and Bing 409. Green seedings pools and yellow seedings pools of F2 and BC3 were screened by EM, PM and TE primers of AFLP. Individuals of the F2 and BC3 were screened with the primers displaying polymorphism in the two pools. Then Primers showing polymorphism in BC3 were used to screen the 2400 plants of BC4. Twenty-eight markers linked adjacently with bnaC.ygl. Twenty of them located very near with bnaC.ygl and the genetic distance was about 0.42cM. |
