Appearance of male sterile and black radishes in the progeny of cross between Raphanus raphanistrum and Raphanus sativus

In addition to Ogura cytoplasmic male sterility (CMS), which is used extensively for F(1) hybrid seed production in Brassicaceae crops, two other CMS systems, NWB CMS and DCGMS, have also been identified. The causal gene for the latter two CMS systems has been identified as a novel chimeric gene, orf463. We previously reported that orf463 is specific to black radish cultivars and that it is present in line ‘RS-5’ of Raphanus raphanistrum; however, the orf463 sequence in ‘RS-5’ differed from that of black radish cultivars. Though, R. raphanistrum with an orf463 sequence identical to that found in black radish cultivars was recently identified. We therefore sought to determine whether the orf463 gene in line ‘RS-5’ induces CMS in radishes. We crossed ‘RS-5’ as a female parent with a cultivated radish, ‘Uchiki-Gensuke’, as a male parent, and examined the gross plant morphology and pollen fertility of the resulting progeny. The F(2) population contained both male sterile plants and plants with black roots. The findings showed that R. raphanistrum contains two types of orf463 genes that induce CMS, and that the origin of black radishes could be attributed to R. raphanistrum having orf463 gene.