The invention relates to polynucleotides that are closely linked to the bolting gene or B gene within the sugar beet genome and can be used for the development of molecular markers. The invention further relates to molecular markers and kits comprising said markers that can be used for mapping, identification and isolation of the bolting gene or B gene in the sugar beet genome and to discriminate between the annual and biennial genotype or between different haplotypes within plant groupings of sugar beet plants exhibiting a biennial genotype. The invention also relates to assays and methods of breeding sugar beet plants involving said markers.