Induced resistance in pepper by Fo47 is associated to changes in gene expression

Abstract: Pepper is an important crop that is used in many ways for gastronomic purposes. Thereare many diseases that affect pepper plants, being Verticillium wilt one of the most important inthe region of Galicia (Northwest of Spain). So far, there is not an effective protection schemebased on fungicides or gene-for-gene resistance for this disease, so it is important to explorealternative strategies of control as induced resistance.In this study we tested the ability of the non pathogenic strain Fo47 to protect pepper plantsagainst Verticillium dahliae. This non pathogenic strain of Fusarium oxysporum was successfullytested in another plant species against Fusarium wilt (Alabouvette & Couteaudier, 1992). In ourbioassay we treated pepper plants with Fo47 and then we challenged them by submerging theroot in a suspension of Verticillium conidia. Symptom evaluation was done by determining thestem length, the fresh and dry weight and the percentage of wilted leaves. A significantprotection against Verticillium wilt was achieved by inducing the plants with Fo47. Systemicresponse against a necrotrophic fungus (Botrytis cinerea) was also tested, but Fo47 failed tocontrol this pathogen.An in vitro pairing assay was performed to observe the possible interactions between Fo47and Verticillium dahliae. Fo47 inhibited partially the growth of the pathogen.In order to check if gene expression associated to plant defence is induced by Fo47 inpepper, we took samples of the roots and stem of the plants after Fo47 treatment and after thechallenge with Verticillium. Gene expression was determined by using quantitative (Real Time)RT-PCR. The genes tested were CASC1, a sesquiterpene cyclase related with the synthesis of aphytoalexin, CACHI2, a gene that encodes a quitinase and CABPR1, a PR-1 protein. Overall, theexpression of the three genes was enhanced by Fo47 both before and after challenge. So far, ourresults suggest that Fo47 control Verticillium both by antagonism and induced resistance.