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Salicylic Acid Biosynthetic Genes Expressed in Pseudomonas fluorescens Strain P3 Improve the Induction of Systemic Resistance in Tobacco Against Tobacco Necrosis Virus

July 1998 , Volume 88 , Number  7
Pages  678 - 684

M. Maurhofer , C. Reimmann , P. Schmidli-Sacherer , S. Heeb , D. Haas , and G. Défago

First, third, and sixth authors: Institute of Plant Science/Phytopathology, Swiss Federal Institute of Technology, CH-8092 Zürich; and second, fourth, and fifth authors: Institute de Biologie Microbienne, Université de Lausanne, CH-1015 Lausanne, Switzerland

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Accepted for publication 24 March 1998.

Application of salicylic acid induces systemic acquired resistance in tobacco. pchA and pchB, which encode for the biosynthesis of salicylic acid in Pseudomonas aeruginosa, were cloned into two expression vectors, and these constructs were introduced into two root-colonizing strains of P. fluorescens. Introduction of pchBA into strain P3, which does not produce salicylic acid, rendered this strain capable of salicylic acid production in vitro and significantly improved its ability to induce systemic resistance in tobacco against tobacco necrosis virus. Strain CHA0 is a well-described biocontrol agent that naturally produces salicylic acid under conditions of iron limitation. Introduction of pchBA into CHA0 increased the production of salicylic acid in vitro and in the rhizosphere of tobacco, but did not improve the ability of CHA0 to induce systemic resistance in tobacco. In addition, these genes did not improve significantly the capacity of strains P3 and CHA0 to suppress black root rot of tobacco in a gnotobiotic system.

Additional keywords: Nicotiana glutinosa , N. tabacum , plant growth-promoting rhizobacteria , strain improvement , Thielaviopsis basicola .

© 1998 The American Phytopathological Society