Influence of light on peroxidase activity associated with resistance of tomato cultivars to Septoria lycopersici

Abstract

Peroxidase activity in leaves of tomato, Lycopersicon esculentum Mill, cultivars Bounty, Campbell 1327, Heinz 1350, and Rutgar, infected by Septoria lycopersici Speg. and exposed to various intensities and wavelengths of light was assayed by means of acrylamide flat gel electrophoresis and 3-amino 9-ethyl carbazole stain. Under controlled environmental conditions noninoculated plants of the four cultivars showed similar peroxidase activity during 11 days. Inoculated plants of cultivars Bounty, Campbell 1327, Heinz 1350, and Rutgar, in order, showed increasing resistance to the early blight disease through increasing peroxidase activity in the host and decreasing numbers of lesions produced by the leaf spot pathogen. In decreasing light intensities the inoculated plants of the four cultivars showed increasing peroxidase activity and increasing resistance to the disease, with a notable exception occurring at a light intensity of 14 200 ergs/cm2 per second. When grown in various wavelengths of light the inoculated plants of the four cultivars also showed increasing peroxidase activity and increasing resistance to the disease, respectively, in green (515 nm), orange (640 nm), red (720 nm), yellow (546–550 nm), and blue (430–436 nm) light. The differences in the peroxidase activity per lesion between the control plants grown at 35 500 ergs/cm2 per second of white light and the inoculated plants grown in various decreasing light intensities and in various wavelengths of light were of a magnitude to be highly significant in the parasite–host interrelationship.