Antioxidant response of sweet pepper fruits infected with Alternaria alternata

Abstract

Capsicum annuum is valuable source of many bioactive compounds with the protective role in plants against biotic and abiotic stress as well as beneficial effect on humans’ health. This vegetable is susceptible to many infections, including postharvest decay caused by fungus Alternaria alternata. In order to better understanding pepper fruits defense system, the concentration of phenols and ascorbic acid, scavenging activity and antioxidant enzyme activity in three kapia type sweet pepper fruits (Amfora, Una and Kurtovka kapia) infected with fungus A. alternata were determined in this study. Amfora fruits had the highest tolerance to Alternaria infection. Amfora and Una increase total phenol and vitamin C content after wounding and inoculation, while Kurtovska kapia decreased amount of vitamin C. Depending on reaction mechanism, antioxidant tests showed no changes or decrease in antioxidant capacity in treated fruits. Except for phenylalanine ammonia-lyase activity in Amfora and Kurtovska kapia and ascorbate peroxidase activity in wounded Kurtovska kapia fruits, all measured enzyme activity showed no changes or decrease by wounding and/or Alternaria infection. According to results of intensity of lipid peroxidation as biological marker of oxidative stress, it can be concluded that wounding and infection disturb redox balance in all examined genotypes. The tested genotypes showed certain difference in antioxidant defence against wounding and pathogen stress.