Involvement of Induced Systemic Resistance in control of Verticillium wiltby fluorescent Pseudomonas spp.

Abstract: Verticillium wilt, caused by Verticillium dahliae Kleb., is a problem in many cropsand the disease is difficult to control. Strains of Pseudomonas fluorescens and P. putida werepreviously isolated from root tissues of olive trees, cv. Picual. Some of them are endophytic andcan control the highly-virulent, defoliating (D) pathotype of V. dahliae in olive. One mode ofaction 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 andthe pathogens P. syringae pv. tomato and Botrytis cinerea. To include V. dahliae in these studieswe inoculated A. thaliana Col-0 with several isolates of this pathogen belonging to differentvegetative compatibility groups (VCG). Isolate V937I (VCG1A, D pathotype) produced severesymptoms in Arabidopsis, and P. fluorescens PICF7 was able to control the disease caused bythis virulent isolate. The use of non-ISR expressing accessions and mutants of A. thaliana willallow to evaluate involvement of ISR in control of Verticillium wilt.