| Rapeseed is one of the major oilseed crops in China. It contributes to appropriately 50% of the vegetable oil consumption. In the past and the near future, canola breeders still face the common and major goal of improving the productivity level of rapeseed. To achieve this, heterosis utilization is proved to be a very effective way, and now genie male sterility (GMS) is becoming a practicable approach to improve yield performance in Brassica napus.Li et al (1985) had reported several new GMS mutants in Brassica napus, also they proposed that the sterility of these mutants followed a digenic mode of inheritance with epistasic interaction. This hypothesis hence provides a theoretical base for employing the GMS in hybrid seed production. This GMS system is a promising approach to be use in hybrid breeding, because its sterility is stable and complete, no negative cytoplasmic effects are involved and, it can be used in a "three-line" system. To make this GMS system a wider application, it is necessary to initiate further study on it.In the present study, Rsl046AB, a homozygous GMS two-type line in Brassica napus, is used as one of the parent to cross with several Brassica napus accessions to study: genetic analysis of the dominant GMS; fertility performance of the dominant GMS under various genetic background, cytoplasm and environments; genetic mapping of the dominant GMS gene (My); genetic mapping of the suppressor gene (Rf) and the establishment of a MAS system for breeding dominant GMS three lines. Main results of the present studies are as follow:1. Three out of the fourteen accessions carrying Rfallele were identified by test-crossing, which could be served as restorers. The other eleven accessions did not carry Rfallele and were possibly in recessive nature of Rf and Ms loci, which could be served as temporary maintainers.2. Using Rsl046B as the mother parent, eleven crosses were made with eleven accessions having different genetic background. Fertility investigation showed that the percentage of male sterile plants varied among the eleven F1populations (from minimum of 22.7% to maximum of 55.3%), and a few partial fertile plants were observed in some FI populations, it seemed that a special genetic background had influence on the expression of the genie male sterility gene.3. Six pairs of reciprocal crosses were made by crossing Rsl046B with two cultivars in recessive nature of Rf and Ms loci. Statistic analysis revealed that the percentage of male sterile plants in the reciprocal crosses were not significantly differrents, which indicated that the expression of the male sterility gene is not influenced by cytoplasm.4. Seven crosses were grown in Lanzhou (from May to October) and Wuchang (from October to May in the next year). Fertility investigation showed that the percentage of male sterile plants in seven crosses grown in Lanzhou were near the expected 50%, but this values decrease sharply in five of the seven crosses grown in Wuchang, thisindicated that fertility performance could be affected by environments.5. A few partial fertile flowers could be observed in the FI male sterile plants (Msmsrfrf). When selfmg such plant, an unexpected 1 : 1 fertility segregating ratio could be observed in the resulting progeny, in which when sibmating sterile plants with fertile plants, the heterozygous GMS two-type line could be bred. Furthur genetic analysis revealed that the partial fertile plants generated two kinds of female gametes (Msrf and msrf) but only one kind of male gamete (msrf). This might partially account for the 1 : 1 fertility segregation in the progeny derived from partial fertile plant.6. In the BCi population of [(Rsl046AX "Samourai" ) X "Samourai" ], AFLP technology in conjunction with bulked segregant analysis were perform to identify genetic markers for the male sterility gene. From the survey of 480 pair of AFLP primers, five markers closely linked to the male sterility were obtained. Four of them (E3M15100. E7Ml230. P13M84oo and PlOMl3 350) flanking the male steri... |
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