Biocontrol Rhizobacterium Pseudomonas sp. 23S Induces Systemic Resistance in Tomato (Solanum lycopersicum L.) Against Bacterial Canker Clavibacter michiganensis subsp. michiganensis

Abstract

Tomato bacterial canker disease, caused by Clavibacter michiganensis subsp. michiganensis (Cmm) is a destructive disease and has been a serious concern for tomato industries worldwide. Previously, a rhizosphere isolated strain of Pseudomonas sp. 23S showed antagonistic activity toward Cmm in vitro. This Pseudomonas sp. 23S was characterized to explore the potential of this bacterium for its use in agriculture. Pseudomonas sp. 23S possesses ability to solubilize inorganic phosphorus, and to produce siderophores, indole acetic acid, and hydrogen cyanide. The strain also showed antagonistic activity against Pseudomonas syringae pv. tomato DC 3000. A plant assay indicated that Pseudomonas sp. 23S could promote growth of tomato seedlings. The potential of treating tomato plants with Pseudomonas sp. 23S to reduce the severity of tomato bacterial canker by inducing systemic resistance (ISR) was investigated using well characterized marker genes such as PR1a [salicylic acid (SA)], PI2 [jasmonic acid (JA)], and ACO [ethylene (ET)]. Two-week-old tomato plants were treated with Pseudomonas sp. 23S by soil drench, and Cmm was inoculated into the stem by needle injection on 3, 5, or 7 days post drench. The results indicated that plants treated with Pseudomonas sp. 23S, 5 days prior to Cmm inoculation significantly delayed the progression of the disease. These plants, after 3 weeks from the date of Cmm 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 Cmm population in the stem was significantly lower for the plants treated with Pseudomonas sp. 23S. From the real-time quantitative PCR (qRT-PCR) analysis, the treatment with Pseudomonas sp. 23S alone was found to trigger a significant increase in the level of PR1a transcripts in tomato plants. When the plants were treated with Pseudomonas sp. 23S and inoculated with Cmm, the level of PR1a and ACO transcripts were increased, and this response was faster and greater as compared to plants inoculated with Cmm but not treated with Pseudomonas sp. 23S. Overall, the results suggested the involvement of SA signaling pathways for ISR induced by Pseudomonas sp. 23S.

Inoculation With Growth-Promoting Bacteria Associated With the Reduction of Phosphate Fertilization in Sugarcane

“…The use of plant growth promoting bacteria (PGPB) is a promising alternative with low environmental impact to increase the efficiency of use of mineral fertilizers, including phosphate, providing high cost-effective yields (Spolaor et al, 2016). The PGPB promote plant growth due to various mechanisms such as biosynthesis of phytohormones and secondary metabolites (Duca et al, 2014;Tahir et al, 2017), biological nitrogen fixation (Li et al, 2017), induction of resistance to biotic stresses (phytopathogen biocontrol) and abiotic stresses (drought and salinity) (Yan et al, 2016;Takishita et al, 2018) production of siderophores metal accumulator (Ali et al, 2014) and soil nutrient solubilization such as phosphorus and potassium (Gupta et al, 2015;Shen et al, 2016;Patel and Archana, 2017). Bacteria with combination of these mechanisms, promote and increase the productivity of several crops (Kumar et al, 2014;Smith et al, 2015;Galindo et al, 2016).…”

The Interactions of Rhizodeposits with Plant Growth-Promoting Rhizobacteria in the Rhizosphere: A Review

“…Plant growth-promoting rhizobacteria (PGPR) may affect plant growth, development, and disease suppression by one or more direct or indirect mechanisms. Bacterial genera such as Bacillus and Pseudomonas have been extensively studied and utilized as biocontrol agents, biofertilizers, and also have been shown to trigger induced systemic resistance (ISR) [18][19][20][21][22][23][24]. In this review, we discuss the importance, functions, and effects of root-derived organic molecules secreted in the rhizosphere and their interactions with plant growth-promoting rhizobacteria (PGPR) for enhancing plant growth and biological control of plant pathogens.…”

Phytomicrobiome Coordination Signals Hold Potential for Climate Change-Resilient Agriculture

“…Work in our laboratory has shown that the B. thuringiensis strain producing thuricin 17 also produces the very effective insecticide beta-exotoxin. In addition, we have recently isolated a pair of compounds, produced by a plant growth-promoting rhizobacteria (PGPR), that are effective against a tomato pathogen (Takishita et al, 2018). These are examples of compounds produced by the phytomicrobiome that can be commercialized to improve crop productivity.…”