Raquel Sánchez Pérez – University of Copenhagen

Raquel Sánchez Pérez

Associate professor

Cyanogenic glucosides group
Section for Plant Biochemitry
Department for Plant and Environmental Sciences
Faculty of Science


Bitterness in almond

Peaches, nectarines, apricots, almonds and cherries contain the cyanogenic glucosides amygdalin and its precursor prunasin. During cell disruption, these compounds are degraded releasing hydrogen cyanide. Application of cyanide-related compounds has been used for many years to break flower bud dormancy in fruit trees. Once dormancy is broken, flowering takes place. Economy relies on fruit production that is strictly related to flowering time and dormancy released. The objective is to ameliorate fruit trees and crop plants to optimize the dormancy period to counteract negative effects of global climate changes that is seriously affecting all these mentioned traits. 

Among all the fruit species mentioned, almond is the only one where the kernel is eaten. The original taste of almond kernel is bitter and is due to the high content of amygdalin. Because of 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 breeding programs what decreases their efficiency, as industry is predominantly interested in sweet almonds.

Fruit trees have a long juvenile period -defined as time to produce the first flower and therefore the first fruit (i.e. almond is 3-4 years)-. Therefore, it would be interesting to develop a molecular marker that enables the breeder the early elimination in the nursery of 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 is being performed to obtain a shorter interval in which Sk locus is localized. Parallel studies, that involves the sequencing of the almond genome, have allowed the identification of eight candidate genes in this shorter interval. The elucidation of the polymorphisms defining bitterness will be decisive to identify the Sk gene and the development of a molecular marker for bitterness in almond.