Light-induced alteration of leaf sterol content and late blight disease development in tomato

Abstract

‘Nova’ and 'Beefsteak,' cultivars of tomato (Lycopersicon esculentum Mill.), were grown in chambers under light intensities of 240 or 120 μE∙m−2∙s−1. Thirty-five days after seeding, half of the tomato plants were harvested for sterol analysis and the others were inoculated with a tomato race O isolate of Phytophthora infestons (Mont.) de By. Late blight symptoms were assessed 10 days after inoculation from the number of leaves showing disease (disease incidence) and the amount of blighted area of each leaf (percent colonization). Disease incidence and percent colonization were not influenced by light intensity with 'Nova' plants, but 'Beefsteak' plants grown under low light were significantly [Formula: see text] more diseased than those exposed to the higher light intensity. Changes in free sterol, steryl ester, and total sterol concentrations between plants grown under different light intensities were similar for both cultivars. A significant decrease in the steryl glycoside concentration of low light grown 'Beefsteak' plants correlated with increased disease incidence. The possible role of steryl glycosides and their derivatives in late blight disease development is discussed.