Fuente: WIPO "biotechnology" This invention relates to a nuclear conditional male sterility system in Brassica napus. Embodiments of the invention provide for the (male sterile) prebasic female (MsMsrfrf), the (male fertile) maintainer line (msmsrfrf), the (male sterile) basic female line (Msmsrfrf), and hybrid lines. Further provided are methods for the production of those lines. Further embodiments of the invention relate to markers associated to the sterility, fertility and maintainer alleles and the use of those markers in providing a hybrid system.