Influence of Inoculation of Leifsonia xyli subsp. xyli on Photosynthetic Parameters and Activities of Defense Enzymes in Sugarcane

Abstract

Ratoon stunting disease of sugarcane, caused by Leifsonia xyli subsp. xyli (Lxx), is one of the most serious diseases that cause substantial losses in yield. The objective of this study was to investigate the influence of inoculation of Lxx on the photosynthetic parameters and activities of defense enzymes in sugarcane. Seedcanes were inoculated with Lxx and planted in pots. Photosynthetic parameters, specific leaf weight (SLW), superoxide anion radical (O2−) and activities of phosphoenolpyruvate carboxylase (PEPC), superoxide dismutase (SOD), catalase (CAT) and peroxidase (POD) in leaves of sugarcane varieties Badila, GT11 and GT29 were measured at 150, 180, 210 and 240 days after Lxx inoculation. The agronomic traits were estimated after inoculation for 11 months at processing maturing stage of sugarcane. The Lxx-inoculated sugarcane showed significant reduction in SLW, PEPC activity, chlorophyll (SPAD index) and plant height from 150 to 240 days, in net photosynthetic rate (Pn) and transpiration rate (Tr) from 180 to 240 days, in stomatal conductance (Gs) at 180 and 240 days, and in intercellular CO2 concentration (Ci) on the 180th day after inoculation. The content of O2− and activities of SOD and POD also were increased, while the activity of CAT decreased for most time after inoculation.