Intra- and inter-specific variations in the mitochondrial gene orf138 of Ogura-type male-sterile cytoplasm from Raphanus sativus and Raphanus raphanistrum

In order to gain a better understanding of the evolution of Ogura male-ster ile cytoplasm in radish, a large-scale sequence analysis of mitochondrial o rf138 was conducted using 107 Japanese wild radishes, 29 cultivated radishe s and seven Raphanus raphanisturum. A single approximately 0.8-kb fragment containing the orf138 locus was amplified from each plant by PCR, and the n ucleotide sequence of an entire coding region of orf138 was determined by d irect-sequencing procedures. An identical sequence to the published orf138 (Type A) was identified in Japanese wild radish, including a single plant i n a population near Kagoshima prefecture where Ogura (1968) first found 'Og ura male-sterile radish'. Thus, it was confirmed that the 'Ogura male-steri le cytoplasm' was derived from Japanese wild radish, with a Type A orf138 s equence, growing in this area. A total of six nucleotide changes and a sing le insertion/deletion (indel) were found in orf138 from both wild and culti vated radishes. By a combination of mutations, the orf138 sequences of the 143 radish plants were classified into nine types. Based on the pattern of mutations and the distribution of orf138 variants, it was concluded that th e orf138 variants are derived from Type B or C, after Ogura-type cytoplasm was introduced from R. raphanistrum into Japanese wild radish.