MOLECULAR AND BIOLOGICAL STUDIES ON MALE-STERILE CYTOPLASM IN THE CRUCIFERAE .4. OGURA-TYPE CYTOPLASM FOUND IN THE WILD RADISH, RAPHANUS-RAPHANISTRUM

The orf138 gene, which is specific to Ogura male-sterile cytoplasm, wa s analysed in mitochondrial DNA (mtDNA) of the wild radish, Raphanus r aphanistrum, by polymerase chain reaction (PCR), Southern hybridizatio n and sequencing. The effect of R. raphanistrum cytoplasm on the expre ssion of male sterility was also examined in progeny with R. sativus. A PCR-aided assay and Southern hybridization revealed that three out o f six strains analysed included plants with orf138. The sequence of wi ld type orf138 was same as that of Ogura, except for one or two nucleo tide substitutions. Southern hybridization showed a novel mtDNA config uration in R. raphanistrum, in addition to the normal and Ogura types identical to those in R. sativus. Among interspecific hybrids, all the F-1 had normal pollen fertility. In the F-2 progeny between female wi ld plants having orf138 and the maintainer of Ogura male sterility, ma le-sterile plants were segregated, fitting the ratio of 3 fertile:1 st erile plant. R. raphanistrum has cytoplasm that induces male sterility in radishes, and contains a dominant fertility restorer gene.