Resistance inducers: A tool for controlling powdery mildew infection in strawberry plants
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Natural plant elicitors have become a promising solution to reduce the use of synthetic pesticides by enhancing plant defence response against diseases. The aim of this research was to investigate the effectiveness of different elicitors to control powdery mildew on strawberry plants and to understand the defence mechanisms activated in plants after treatments. The experiment was conducted in semi-controlled conditions under plastic tunnel on strawberry plants cv. Elsanta. Plants were foliar-treated with natural elicitors (alfalfa hydrolysate, seaweed extract, chitosan, thyme essential oil) and with benzothiadiazole (BTH) and a fungicide (penconazole) as positive controls. The experiment was divided into two steps. Firstly, changes in the expression of selected genes related to the plant defence metabolism (SAR and ISR pathways) were analysed at 0, 2, 3, 4 and 7 days after treatment of strawberry leaves. Secondly, incidence and severity of powdery mildew infection were assessed after a controlled inoculation. Results showed an up-regulation of defense genes expression (including PR1, PR5, PR10, EDS1 and LOX) in leaves treated with BTH. The other tested natural plant elicitors also proved to have an elicitor action on the defence-related genes, even though at a lower level as compared to BTH (fold change expression <2). All treatments significantly reduced the incidence and severity of powdery mildew as compared to control. At 28 days after inoculation, chitosan and thyme essential oil applications performed similarly to their positive controls (BTH and penconazole respectively), showing a significant incidence reduction (by -84 and -92%) as compare to control. To conclude, these results indicate that substances acting as natural plant elicitors could be used as an alternative to fungicides for the control of powdery mildew in strawberry, therefore representing a valuable tool for the control of fungal diseases under the framework of the organic farming production.