S20 - Session O3 - Role of fatty acids in the systemic defense of grapevine against esca complex disease-associated fungi

Authors: Piebiep Goufo *, Isabel Cortez

Fatty acids play signaling roles in plant resistance against pathogens, modulating basal, effector-triggered, and systemic immunity. In this study, fatty acids levels were determined in asymptomatic leaves of grapevine with the Esca complex disease infection in trunks, cordons and berries, in order to characterize physiological events preceding symptom appearance. Leaves with four levels of symptom severity were also evaluated to assess the duration of chemical signals. For trunks where fungi Phaeoacremonium aleophilum and Phaeomoniella chlamydospora were found, the presence of brown streak was associated with the accumulation of C18:0, C18:2n6c, C18:3n6, and C20:4n6 in asymptomatic leaves, and a depletion of C18:1n9c, C18:1n9t, C18:2n6t, and C16:0. A sharp increase in C18:1n9c, C18:2n6c, C18:2n6t, C17:1n7, C20:4n6, C22:6n3, and C16:0 was observed in asymptomatic leaves of vines with brown streak in the cordons, indicating an active communication of signals between woods and leaves. Asymptomatic leaves of vines with black measles in the berries showed Esca-induced increases in C18:1n9c, C18:2n6c, C18:2n6t, C20:4n6, and C16:0. These data strongly supports the involvement of C18 fatty acids in distal signaling in grapevine response to Esca complex disease, likely for inducing defense gene activation. However, the intensity of signals is low when fungi are still in trunks, involving few compounds. With the progression of fungi to cordons and the apparition of symptoms in the aboveground parts, the generated signal is amplified with more fatty acids acting as transduction mediators. This additional knowledge on physiological mechanisms occurring during grapevinenesca interaction could lead to ways to exploit host defenses to control the disease, in light of the finding that increasing C18 levels via genetic mutations upregulates the expression of resistance genes in several plants.