Involvement of induced systemic resistance in control of Verticillium wilt by fluorescent Pseudomonas spp

Abstract

Verticillium wilt, caused by Verticillium dahliae Kleb., is a problem in many crops and the disease is difficult to control. Strains of Pseudomonas fluorescens and P. putida were previously isolated from root tissues of olive trees, cv. Picual. Some of them are endophytic and can control the highly-virulent, defoliating (D) pathotype of V. dahliae in olive. One mode of action of disease suppression by fluorescent Pseudomonas spp. is induced systemic resistance (ISR). Pseudomonas spp. strains were tested for ISR in a system using Arabidopsis thaliana and the pathogens P. syringae pv. tomato and Botrytis cinerea. To include V. dahliae in these studies we inoculated A. thaliana Col-0 with several isolates of this pathogen belonging to different vegetative compatibility groups (VCG). Isolate V937I (VCG1A, D pathotype) produced severe symptoms in Arabidopsis, and P. fluorescens PICF7 was able to control the disease caused by this virulent isolate. The use of non-ISR expressing accessions and mutants of A. thaliana will allow to evaluate involvement of ISR in control of Verticillium wilt.