Changes in the relative abundance of fatty acids in grapevine leaves in response to esca complex disease

Fatty acids play signaling roles in plant resistance against pathogens, modulating basal, effector-triggered, and systemic immunity. In this study, fatty acids levels were measured in asymptomatic leaves of grapevine plants with signs of esca complex disease in the trunks, cordons, or berries, in order to characterize physiological events preceding symptom appearance. Leaves with four degrees of symptom severity were also evaluated to assess the lasting effects of the chemical responses. The presence of brown streak symptoms in the trunks was associated with the accumulation of C18:0, C18:2n6c, C18:3n6, C20:4n6, and the depletion of C18:1n9c, C18:1n9t, C18:2n6t, C16:0 in asymptomatic leaves, indicating an active communication between woods and leaves. Asymptomatic leaves of vines with brown streaks in the cordons or black measles in the berries accumulated C18:1n9c, C18:2n6c, C18:2n6t, C17:1n7, C20:4n6, C22:6n3, and C16:0. These data suggest potential roles of fatty acids in defence, but also the potential involvement of C18 fatty acids in distal signaling in grapevine response to esca-associated pathogens. In the trunks, plant responses are comprised of very few compounds; thus, the intensity of signals is low when the fungi are still in the woods. With the progression of fungi to the cordons and the appearance of symptoms in the leaves and berries, the generated signal is amplified with more fatty acids acting for inducing the activation of the host’s defenses.