The present invention relates to leaf chicory (Cichorium intybus subsp. intybus var. foliosum) nuclear recessive male sterile mutants, to a newly identified polymorphic molecular marker for the nuclear recessive male sterile character in this species, to methods for the selection of leaf chicory nuclear recessive male sterile mutants, to methods for the production of seed parent male sterile and pollen donor male fertile inbred lines of leaf chicory, including all cultivated types of radicchio, that are, respectively, homozygous for the nuclear recessive male sterile mutant allele or homozygous for the male fertile wildtype allele, and to methods for the constitution of F1 hybrids that are all heterozygous at the ms locus.
