Oxidative metabolism and phenolic compounds in Capsicum annuum L. var. annuum infected by Phytophthora capsici Leon

Changes in peroxide levels, the activity of antioxidant enzymes and phenolic compounds were studied in Capsicum annuum L. var. annuum plants inoculated with Phytophthora capsici P-1UDC (Galician field isolate). The extent of oxidative stress during the interaction Capsicum-Phytophthora was evidenced, at the final period of interaction, by the at least 87% increase in peroxide levels. Catalase activity showed the biggest changes in the stems by 114% increase, ascorbate peroxidase fell during the interaction, peroxidase levels remained constant from the first hours to the fifth day, and only showed an increment by 54 and 90% in stems and leaves, respectively, during the final period of interaction as phenolic compounds (free and bound fraction). Collectively, these results provide evidence that the interaction Capsicum-Phytophthora is accompanied by a substantial increase in oxidative stress, probably as a direct consequence of a progressive decline in the enzymatic systems responsible for catabolism of active oxygen species. (C) 2004 Elsevier B.V. All rights reserved.