Hormone Changes in Tolerant and Susceptible Grapevine Leaves Under Powdery Mildew Infection

The biotrophic fungus Erysiphe necator causes powdery mildew (PM) in grapevine. Phytohormones are major modulators of defensive responses in plants but the analysis of the hormonome associated with grapevine tolerance and susceptibility against this pathogen has not been elucidated. In this study, changes in hormonal profiling were compared between a tolerant (Vitis rupestris x riparia cv. 101-14 Millardet et de Grasset) and a susceptible (Vitis vinifera cv. Aragonez) species upon E. necator infection. Control and PM-infected leaves were collected at 0, 6, 24, 96 h post-infection (hpi), and analysed through LC-MS/MS. The results showed a distinct constitutive hormonome between tolerant and susceptible species. Constitutive high levels of salicylic acid (SA) and indole-3- acetic acid together with additional fast induction of SA within the first 6 hpi as well as constitutive low levels of jasmonates and abscisic acid may enable a faster and more efficient response towards the PM. The balance among the different phytohormones seems to be species-specific and fundamental in providing tolerance or susceptibility. These insights may be used to develop strategies for conventional breeding and/or editing of genes involved in hormonal metabolism aiming at providing a durable resistance in grapevine against E. necator.