Salicylic Acid Produced by the Rhizobacterium Pseudomonas aeruginosa 7NSK2 Induces Resistance to Leaf Infection by Botrytis cinerea on Bean

Abstract

De Meyer, G., and Höfte, M. 1997. Salicylic acid produced by the rhizobacterium Pseudomonas aeruginosa 7NSK2 induces resistance to leaf infection by Botrytis cinerea on bean. Phytopathology 87:588-593.Selected strains of nonpathogenic rhizobacteria can induce a systemic resistance in plants that is effective against various pathogens. In an assay with bean plants, we investigated which determinants of the rhizobacterium Pseudomonas aeruginosa 7NSK2 are important for induction of resistance to Botrytis cinerea. By varying the iron nutritional state of the bacterium at inoculation, it was demonstrated that induced resistance by P. aeruginosa 7NSK2 was iron-regulated. As P. aeruginosa 7NSK2 produces three siderophores under iron limitation, pyoverdin, pyochelin, and salicylic acid, we investigated the involvement of these iron-regulated metabolites in induced resistance by using mutants deficient in one or more siderophores. Results demonstrated that salicylic acid production was essential for induction of resistance to B. cinerea by P. aeruginosa 7NSK2 in bean and did not exclude a role for pyochelin. A role for pyoverdin, however, could not be demonstrated. Transcriptional activity of salicylic acid and pyochelin biosynthetic genes was detected during P. aeruginosa 7NSK2 colonization of bean. Moreover, the iron nutritional state at inoculation influenced the transcriptional activity of salicylic acid and pyochelin biosynthetic genes in the same way as it influenced induction of systemic resistance to B. cinerea.

Salicylic acid-independent plant defence pathways

“…2c). Some rhizobacteria trigger the SAR pathway by producing salicylic acid at the root surface 40,41 , and in other cases, ISR-inducing rhizobacteria trigger a different signalling pathway that does not require salicylic acid [42][43][44][45] .…”

MYB72 Is Required in Early Signaling Steps of Rhizobacteria-Induced Systemic Resistance in Arabidopsis

“…Plants that carry a mutation in the NPR1 gene accumulate normal or even higher levels of SA after pathogen infection, but are impaired in their ability to transcriptionally activate PR genes and to mount a SAR response. Although some rhizobacterial strains can activate the SA-dependent SAR pathway (De Meyer and Hö fte, 1997), the large majority of the reported resistance-inducing fluorescent Pseudomonas spp. strains have been shown to trigger ISR in a SA-independent manner (Van Loon and Bakker, 2005).…”

Influence of phylloplane colonizing biocontrol agents on the black spot of rose caused byDiplocarpon rosae

“…Increase in mRNAs encoding PAL and Chalcone synthase were recorded in the early stages of the interaction between bean roots and various rhizobacteria (Zdor & Anderson 1992). De Meyer and Hofte (1997) reported that rhizosphere colonization by P. aeruginosa TNSK2 activated PAL in bean roots and increased the salicylic acid levels in leaves. Increased activity of PAL was recorded in P. fluorescens isolate Pf1 treated tomato and hot pepper seedlings challenged with the pathogen reached maximum on the third day after challenge inoculation and was maintained at higher levels throughout the experimental period (Ramamoorthy et al 2002).…”