Abstract: Ogura sterility DNA is used to develop agronomically valuable hybrids that lack the undesirable features of plants having Ogura DNA (chlorosis at low temperature; poor fertile fertility; aberrant flower morphology) but still impart efficient male sterility (which can be easily restored). Ogura sterility is carried by a DNA sequence defined by nucleotides 928-2273 of a 2428 base sequence reproduced in the specification. When present in mitochondrial or nuclear genome of a plant it confers cytoplasmic male sterility. Also disclosed are recombinant plant nuclear and mitochondrial genomes containing a DNA sequence defined by nucleotides 928-1569 of the specified sequence (or its homologous); cytoplasm containing such a mitochondrial genome; Brassica plants or hybrids containing the sterility DNA; and, DNA probes of at least 10 bases from the 928-1569 sequences. DNA probes are used to detect male sterility and for selecting clones without the need for lengthy agronomic/rehybridization steps.