Biocontrol Rhizobacterium 23S Induces Systemic Resistance in Tomato ( L.) Against Bacterial Canker subsp. .

Tomato bacterial canker disease, caused by subsp. () is a destructive disease and has been a serious concern for tomato industries worldwide. Previously, a rhizosphere isolated strain of 23S showed antagonistic activity toward . This . 23S was characterized to explore the potential of this bacterium for its use in agriculture. . 23S possesses ability to solubilize inorganic phosphorus, and to produce siderophores, indole acetic acid, and hydrogen cyanide. The strain also showed antagonistic activity against pv. DC 3000. A plant assay indicated that . 23S could promote growth of tomato seedlings. The potential of treating tomato plants with 23S to reduce the severity of tomato bacterial canker by inducing systemic resistance (ISR) was investigated using well characterized marker genes such as [salicylic acid (SA)], [jasmonic acid (JA)], and [ethylene (ET)]. Two-week-old tomato plants were treated with 23S by soil drench, and was inoculated into the stem by needle injection on 3, 5, or 7 days post drench. The results indicated that plants treated with . 23S, 5 days prior to inoculation significantly delayed the progression of the disease. These plants, after 3 weeks from the date of inoculation, had significantly higher dry shoot and root weight, higher levels of carbon, nitrogen, phosphorus, and potassium in the leaf tissue, and the number of population in the stem was significantly lower for the plants treated with 23S. From the real-time quantitative PCR (qRT-PCR) analysis, the treatment with 23S alone was found to trigger a significant increase in the level of transcripts in tomato plants. When the plants were treated with 23S and inoculated with , the level of and transcripts were increased, and this response was faster and greater as compared to plants inoculated with but not treated with 23S. Overall, the results suggested the involvement of SA signaling pathways for ISR induced by 23S.