Fig. 4

Quantification of defense signals and glucosinolates. a Experimental design. Quantification of jasmonic acid (JA) b, salicylic acid (SA) c and total glucosinolates (GS) d in single and combined stress. Leaf discs (blue circle) were collected on 5-week-old B. nigra plants pretreated for 3 days with P. brassicae egg extract (EE) or Xanthomonas campestris pv. raphani (Xcr) and further challenged with P. brassicae (P) larvae feeding for 24 h at the site or distal to the site of treatment. Controls consisted of untreated plants (CTL) or plants exposed to a single treatment. -, sample distal from the combined treatment. Values (± SE) are the mean of three independent experiments. Letters indicate significant difference between treatments (ANOVA followed by Tukey’s honest significant difference test, P < 0.05)