Effect of Salicylic Acid on Oxidative Metabolism during Xanthomonas citri subsp. citri Infection of Grapefruit

摘要

Citrus canker, caused by the bacterium Xanthomonas citri subsp. citri (Xcc), is one of the most devastating diseases of citrus in Florida, especially for grapefruit, which is highly susceptible to the disease. There has been much interest in chemicalsthat induce systemic acquired resistance (SAR). Salicylic acid is an endogenous compound known to be part of the SAR mechanism. A strain of bacterial canker was injected into leaves of grapefruit either alone or with salicylic acid (SA) and oxidative metabolism was evaluated over time. We found that Xcc manipulatesH_2O_2 metabolism by suppressing the activity of SOD and increasing the activities of catalase, ascorbate peroxidase, and peroxidase, which collectively lowered the H_2O_2 concentration. Salicylic acid treatment transiently restored the activities of SOD and APOD, but was not sufficient to restrict Xcc growth in vivo.