Climate change, a booster of disease outbreaks by the plant pathogen Phytophthora in oak forests

In forests, trees such as oaks (Quercus spp.) fulfill key ecological functions, including nutrient and water cycling. In the last decades, climate change and its related environmental disturbances have favored the appearance of disease outbreaks caused by plant pathogenic microorganisms. In this context, several root-inhabiting Phy-tophthora species have emerged as causal agents of "catastrophic tree mortality". A robust body of scientific literature supports the hypothesis for the convergence between Phytophthora and predisposing environmental conditions as warm temperatures, flooding, and drought to establish the optimal conditions for the pathogen proliferation and infection. Due to the climatic alterations and bad agricultural and silvicultural practices tree decline and mortality in extensive zones of forests localized at the Boreal region of America, Asia and Europe, and in Oceania have been observed. Because of global climate change trees have been forced to migrate towards new geographical sites, which in the presence of exotic Phytophthora species have favored the emergence of this pathogen and its outbreaks. Therefore, it is of crucial importance to establish international protocols to avoid pathogen propagation to new sites. In this review, we integrated and discussed state of the art information about the environmental traits and microbial factors that induce forest decline and subsequent tree mortality. Further research directions in the field of Phytophthora - plant interactions with special emphasis on the biochemical and molecular signals involved in pathogen virulence and host defense are suggested. Finally, strategies for disease prevention in forest management and conservation are discussed.