The original taste of almond kernel is bitter. Due to human domestication, nowadays the majority of cultivated almond varieties are sweet. Since most of the cultivated almonds are heterozygous for bitterness, new bitter almond seedlings are usually obtained in the cross breeding programs. Therefore, it would be interesting to develop a molecular marker that enables the breeder to eliminate early in the nursery the bitter seedlings. Although its biochemical function remains unknown, the Sweet kernel (Sk) locus, was localized in linkage group five (G5) in an almond genetic linkage map. Fine mapping between the molecular markers flanking the Sk/sk gene, has been performed to obtain a shorter interval in which Sk locus should be localized. We will show new single nucleotide polymorphisms found in a 3 Mb region in which Sk locus is included within G5. In bitter almonds, hydrogen cyanide is produced upon hydrolysis of amygdalin following tissue disruption. Amygdalin and its precursor prunasin are cyanogenic glucosides. Amygdalin is mainly present in the kernels, whereas prunasin can be detected in the vegetative parts as well as in the fruit mother tissues. Parallel studies with candidate genes analysis based on the amygdalin pathway are also under study. The elucidation of the polymorphisms defining bitterness will be decisive to identify the Sk locus and the development of a molecular marker for bitterness in almond.
