CAT and infection: The levels of several enzymes involved in ROS-scavenging and antioxidative defence, such as superoxide dismutase (SOD), peroxidase (POX), and catalase (CAT), were significantly altered in Alternaria-tolerant Brassica lines after infection with Alternaria brassicae and in tomato infected with Botrytis cinerea, indicating that ROS-scavenging enzymes and antioxidants may play significant roles in plant defences against these necrotrophic pathogens (Kuźniak and Skłodowska 2004; Sharma et al., 2007).