Changes in oxylipins in compatible and incompatible interactions between oilseed rape and the downy mildew pathogen Peronospora parasitica

In compatible and incompatible interactions between oilseed rape Brassica napus and the downy mildew pathogen Peronospora parasitica, three oxylipins were detected. Two of these compounds were trihydroxy oxylipins (9,12,13-trihydroxy-10(E)-octadecenoic acid [TriHOE1] and 9,12,13-trihydroxy-10(E),15(Z)-octadecenoic acid [TriHOE2]) derived from the 9-lipoxygenase (LOX) pathway, while the other was (13S,9Z,11E,15Z)-13-hydroxy-9,11,15-octadecatrienoic acid [13-HOT], derived from the 13-LOX pathway. In incompatible interactions, the three oxylipins appeared 12 h after inoculation, with concentrations of 13-HOT, for example, of 59 nmol g−1 FW. Concentrations of the three oxylipins fell to considerably lower levels 96 h after inoculation in incompatible interactions. In contrast, the oxylipins did not appear in compatible interactions until at least 48 h after inoculation and concentrations were much lower than those obtained in the incompatible interactions. The possibility that these oxylipins might be involved in signalling and/or as antimicrobial compounds in oilseed rape resisting infection by P. parasitica is discussed.