Active Oxygen-producing and -scavenging Enzymes in Pepper Leaves Infected with Xanthomonas campestris pv. vesicatoria

Lipoxygenase (LOX), peroxidase (POX), superoxide dismutase (SOD) and catalase (CAT) activities were determined in pepper (Capsicum annuum) leaves infected with Xanthomonas campestris pv. uesicatoria, from 3 to 15 days after inoculation, before symptom appearance and during the development of the disease. Strong Stimulation of LOX and POX activities was observed in infected leaves at an advanced stage of the disease (12–15 days after inoculation), when bacterial water-soaked spots and a slight chlorosis of the inoculated leaf areas were evident and a decrease in chlorophyll content of infected tissue was detected. The infection also induced a significant increase in CAT activity at the day 9 and a decrease in SOD and CAT activities at the day 12. On the basis of the changes observed, uncontrolled production of active oxygen species at advanced stages of infection is hypothesized.