Role of Salicylic Acid in Systemic Resistance Induced by Pseudomonas spp. Against Pythium aphanidermatum in Cucumber Roots |
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Authors: | Chunquan Chen Richard R. Bélanger Nicole Benhamou Timothy C. Paulitz |
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Affiliation: | (1) Department of Plant Science, Macdonald Campus of McGill University, 21,111 Lakeshore Rd., Ste. Anne de Bellevue, Québec, Canada, H9X 3V9;(2) Département de Phytologie, Université Laval, Ste. Foy, Québec, Canada, G1K 7P9 |
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Abstract: | Pseudomonas corrugata strain 13 and P. aureofaciens strain 63-28, applied to roots, induced systemic resistance against Pythium aphanidermatum in cucumber roots. Salicylic acid (SA) from bacterial culture or plant tissues was quantified by high performance liquid chromatography. Both strains produced SA in King's B broth and also induced cucumber root to accumulate endogenous SA one day after bacterial inoculation. Using a split root system, more SA accumulated in roots treated with bacteria than in distant roots on the opposite side of the root system in the first two days, but this difference disappeared after 3–4 days. SA levels were significantly higher in plants treated with bacteria compared to the split control, from one to five days after bacterization. SA did not inhibit mycelial growth of Pythium aphanidermatum at 100–200µgml–1 in vitro, but higher levels inhibited mycelial growth. Zoospore germination increased at concentrations of 10–500µgml–1, but decreased at 1000µgml–1 compared to lower concentrations. Exogenously applied SA failed to induce local or systemic resistance against a challenge infection by the pathogen in planta. The results of this study show that exogenous applied SA does not induce systemic resistance to cucumber root rot caused by P. aphanidermatum, but endogenous SA accumulation in cucumber roots may be involved in induced systemic resistance. |
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Keywords: | cucumber root rot high performance liquid chromatography induced systemic resistance plant growth-promoting rhizobacteria Pseudomonas aureofaciens Pseudomonas corrugata |
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