Identification of monogenic dominant male sterility and its suppressor gene from an induced mutation using a broccoli ( Brassica oleracea var. italica ) microspore culture

Male sterility (MS) has been studied intensively in Brassica crops to ensure high purity and the protection of F1 hybrids. In the preceding trial, broccoli microspores were treated with a mutagen, n-nitroso-n-methyl urethane (NMU), during the cultural process to produce MS. Many MS plants were derived from the 0.01 μM and 0.1 μM treatments just before and at the fourth day of culture, respectively. In this study, most MS plants inherited sterility from a single recessive gene. Only one plant, 9-4C-106, which originated from the 0.1 μM treatment on the fourth day, was controlled by a single dominant gene. Another dominant mutant gene suppressing the expression of this dominant MS gene was discovered in a plant treated with 0.01 μM NMU. A hybrid breeding system using this MS structure is discussed.