X-irradiated protoplasts of a Brassica napus line carrying the Ogura Raphanus sativus male sterile cytoplasm were fused to protoplasts of male fertile B. napus cv. Olga. Plants were regenerated from six out of 34 randomly selected clones. In one clone, Bn(RS)26, a plant with male sterile flowers was obtained. Mitochondria of this plant are non-parental as revealed by DNA-DNA hybridization using a species specific probe. Its chloroplasts, however, derive from the fertile parent which results in loss of the sensitivity to low temperatures associated with R. sativus plastids in the male sterile parent. The novel cytoplasm of the Bn(RS)26 cybrid was transmitted through seed.