Transcriptomic and metabolomic analyses of cucumber fruit peels reveal a developmental increase in terpenoid glycosides associated with age-related resistance to Phytophthora capsici

Analysis of a rot-resistant cucumber finds multiple mechanisms that could be harnessed to breed resistance. The pathogenic fungus-like organism Phytophthora capsici causes significant losses to crops such as melons, cucumbers and tomatoes. One cucumber variety, ‘Vlaspik,’ shows resistance to Phytophthora, but only in the peel of mature fruits. Rebecca Grumet of Michigan State University, USA, and colleagues used this property to characterize Phytophthora resistance. Comparing the skin of immature and mature fruits of ‘Vlaspik’ and a second cucumber variety, they identified 120 genes with differing activities. Eighty genes were activated in mature ‘Vlaspik’ fruit peel, mostly putative resistance or signaling genes, and forty were deactivated, mostly those involved in growth. They also noted an increase in potentially defensive molecules known as terpenoid glycosides. These results suggest multiple targets for developing resistance to Phytophthora in susceptible crops.