Genomics of sex determination in dioecious trees and woody plants

Dioecious plant species are characterized by unisexual flowers located on separate male or female individuals. While only about 5–6% of angiosperm species are reported to be dioecious, tree species seem to show a higher percentage of dioecy. Generally, it is presumed that various different genetic and developmental mechanisms underlie unisexuality in different dioecious species. This review focusses on the genomics of sex determination in dioecious woody plant species like trees, shrubs and vines as well as other plant species with a tree-like habitus like papaya and the monocot date palm. Findings for different tree species, including Diospyros lotus and members of the Salicaceae family, are summarized including information on sex-linked markers that enable to identify the sex of a tree before the tree reaches sexual maturity.