Diff erent Levels of Nitrogen Fertilizer in Nursery Stage Positively Aff ect the Activity of Defense-related Enzymes and Resistance of Tobacco Plant to Phytophthora nicotianae

Abstract

Black shank caused by Phytophthora nicotianae is a serious threat to the production of better-quality fl ue-cured tobacco. Protein’s are executors of plant functions and most disease resistance mechanisms in plants are related to differential expression of proteins. In our previous study, 17 different proteins induced by P. nicotianae were screened out through proteomics analysis. In this study, we evaluated the effect of three different levels of nitrogen fertilizer (High, medium, and low) at the seedling stage on the expression of these proteins, physiological response of fl ue-cured tobacco, and occurrence of black shank disease. Results of this study showed that before and after inoculation of P. nicotianae, the activity of defense-related enzymes except for MDA contents in tobacco plants grown under low- nitrogen level was higher than tobacco plants grown under the high-nitrogen level at seedling stage. Through analysis of 17 different proteins, we found the expression of 12 proteins (three proteins involved in photosynthesis, six proteins involved in oxidative phosphorylation, one protein involved in tricarboxylic acid cycle, one heat shock protein, and one 14-3-3 protein) were up-regulated in tobacco seedlings raised under low nitrogen level. However, the expression of fi ve pathogenesis-related proteins was not detected. This study highlights the effect of effi cient use of nitrogen fertilizer during the nursery growing stage for producing healthy tobacco seedlings. It is concluded that a proper supply of nitrogen fertilizer at the seedling stage ensures the quality production of tobacco seedlings and reduces the incidence of black shank disease.