OGs induce systemic resistance to Botrytis cinerea
The strong impact of OG treatment in systemic tissues at very early time-points prompted us to investigate whether OGs induce systemic resistance in tomato plants against the necrotrophic pathogen B. cinerea .
Systemic protection was examined by treating tomato roots or leaves with 50 µg/mL of OGs and infecting at 6 hpt (the untreated true sixth leaf) with B. cinerea . Both root and leaf treatments (LT and RT) led to a significant reduction of the necrotic lesions compared to the corresponding control treated leaves (CT-SL), confirming that systemic responses to OG treatment are associated to systemic resistance against this pathogen in tomato. Remarkably, the protection level was similar regardless of the site of OGs application (roots or leaves) (Figure 4a).
Local OG-induced resistance was also examined, by inoculating the OG-treated leaves (LT-TL) at 6 hpt. No reduction of the necrotic symptoms was observed compared to control-treated leaves (CT-TL) at either 50 µg/mL or 200 µg/mL OGs (Figure 4b). Thus, under our experimental conditions and at the time point examined (6 hpt) OG treatment in tomato induced systemic but not local resistance to B. cinerea.