Changes in phenols composition and activity of phenylalanine-ammonia lyase in apples after fungal infections

The defensive reaction of apple cultivar Idared (Malus domestica Borkh.) was studied after inoculation with three different pathogens (Penicillium expansum, Monilinia fructigena, and Gloeosporium spp.). Changes in phenolic content and activity of phenylalanine-ammonia lyase were determined after 7, 14, and 21 days after the inoculation. The significant differences were discovered in the progress of rotting after the inoculation. The increase in phenols concentration and in phenylalanine-ammonia lyase activity varied in the place of fungal attack, in the tissues around rotten zone and in the healthy part. The response to the infection was different in the fruit peel and flesh. Very good correlation was found between the activity of phenylalanine-ammonia lyase and total phenol content (r = 0.76-0.98).