Development And Characterization Of Molecular Markers Of Cytoplasmic Sterile And Genic Genes For Cytoplasmic Male Sterility In Radish (Raphanus Sativus L.)

Radish (Raphanus sativus L.) is a popular root vegetable throughout the world. The heterosis in radish is much significant, especially in increasing yield and improving fiber quality. In plants, cytoplasmic male sterility (CMS) is a maternally inherited trait which is characterized by the inability to produce functional pollen and CMS systems are widely used for the production of commercial F₁ hybrid plants. In Cruciferous plants, radish male sterile cytoplasm is one of the most intensively investigated cytoplasms, because the cytoplasm causes male sterility in not only Raphanus but also Brassica species, and the expression of CMS was not affected by different environmental conditions and different genetic backgrounds. A radish CMS and the corresponding nuclear restorer locus have been introgressed from radish into rapeseed (B. napus L.), but deleterious agronomic characters were also introduced along with the Rf (fertility restorer) gene. Long term goals are to clarify the molecular mechanism of male sterility and fertility restoration in radish and to take full advantage of the radish CMS to breed F₁ hybrid plants in Cruciferous plants. In this thesis, development and characterization of molecular markers of cytoplasmic sterile and nuclear genes for CMS in radish were described. The main results obtained are listed below:A radish CMS system was gained and consists of male sterile line 9802A, maintainer line 9802B and restorer line 9802H. F₁ plants from cross between male sterile line 9802A and restorer line 9802H were all male fertile, indicating that the male fertile type is a dominant character. A F₂ population composed of 300 individuals was constructed. The segregating population was found to fit a segregation ratio 3:1 for either sexual type (male fertile : male sterile). x² test value was highly significant in the F₂ population (x²=0.22, 0.70>p>0.50). These results confirmed that male fertility is recovered by a single dominant gene.Using PCR, we determined that the radish Ogu orf138 gene specific primer pair ORF-F/R resulted in the amplification of a DNA fragment in the radish CMS line 9802A, but no PCR products were detected in the maintainer line 9802B and in the restorer line 9802H. Sequence analysis demonstrated that the DNA fragment was identical to the Ogu orf138, indicating the presence of the orf138 gene, the specific factor inducing Ogu CMS, in the CMS line 9802A. This DNA fragment can be used as a DNA marker to select CMS line in a radish breeding program.Primer pair amplifying a molecular marker specific to the NWB CMS line in radish...