The present invention relates to a method for determining the genotype of a Cruciferous vegetable plant for a plant with an increased glucosinolate level, comprising obtaining a sample of nucleic acids from said plant or a portion thereof and detecting in said nucleic acids a polymorphism at the Myb28 locus that is genetically linked to an increased glucosinolate level. The polymorphism may comprises at least one of: a) a single nucleotide polymorphism (SNP) at a position corresponding to nucleotide 83, 136, 226, 563, 610, 830, 995, 1116, 1513, 1577, 1606, 1620, 1825, 1863, 1877 or 2026 of SEQ ID NO: 1, or b) a polymorphism in the number of nucleotides present between nucleotides 323 and 332, between nucleotides 521 and 524, between nucleotides 783 and 786, between nucleotides and 909 and 914, between nucleotides 1365 and 1369, between 1811 and 1821, or between nucleotides 2046 and 2056 of SEQ ID NO: 1, or c) a polymorphism in the number of nucleotides present between nucleotides 836 and 837, between nucleotides 867 and 868, or between nucleotides 943 and 944 of SEQ ID NO: 1.