Soluble phenolic acids in Capsicum annuum stems infected with Phytophthora capsici

The soluble phenolic acids of the stems of three Capsicum annuum cultivars associated with differing resistance to Phytophthora capsici showed qualitative and quantitative variation after inoculation, notably an increase in the total phenolic acid content in the resistant and intermediate varieties. The soluble phenolic acids also retarded myeelial growth of P. capsici in culture. The most pronounced inhibitory effect was produced by f‐cinnamic acid, followed by p‐hydroxybenzoic, vanillic and salicylic acids. Colonization and necrosis spread throughout the stem of the susceptible cultivar whereas the stem of the resistant cultivar was only partially invaded. In the latter, invasion of the tissue adjacent to necrosis occurred in only 20% of the plants.