Pathogen extracts treatments
The fungal pathogens Rhizoctonia solani (Rs) and Alternaria brassicicola isolate MUCL2097 (Ab), were cultured on Potato Dextrose agar (PDA) plates at 25 °C. To prepare fungal extracts, the mycelium was first grown until it covered a whole Petri dish (Ø 100 mm), then it was cut into mycelial plugs (1 cm2), inoculated into 100 ml Potato Dextrose medium and incubated at 25 °C and 200 rpm. Mycelium was harvested from liquid cultures after 1.5 weeks, dried from excess medium and placed into a 50 ml tube containing 5 ml demineralised water. All tubes were kept on ice and ultrasonicated 6 times for 1 minute at maximum amplitude, using an ultrasonication probe. After a centrifugation step of 5 min at 4000 rpm, the supernatant was aliquoted in Eppendorf tubes and stored at -20 °C until use.
The bacterial pathogen Xanthomonas campestris pv.campestris race 4 (Xcc) was maintained on yeast extract-dextrose-carbonate agar (YDCA) plates at 28 °C. To prepare bacterial extract, Xcc was grown overnight in 15 ml liquid LB medium at 28 °C and 200 rpm. Cultures of Xcc at OD600 of 0.6 - 0.7 were centrifuged for 10 min at 3000 rpm, resuspended in a minimal amount of demineralised water and ultrasonicated as described above. Tubes were then centrifuged again for 10 min at 3000 rpm and the supernatant was aliquoted in Eppendorf tubes and stored at -20 °C until use. All pathogen extracts were applied using a 1 ml syringe.