The influence of endophytes on cork oak forests under a changing climate

Abstract

Quercus suber L. is an evergreen tree species with high economic, ecological and social importance within the Mediterranean Basin. Cork oak forests occupy more than 2 million hectares worldwide, being mainly located in Algeria, Morocco, Portugal and Spain. As in other Mediterranean ecosystems, cork oak forests have been reported as important reservoirs of biological diversity, including endemic species that are currently under threat due to abiotic and biotic stress. Despite the adaptation of cork oak to the Mediterranean climate, which is characterised by warm, dry summers and wet winters, the growth and productivity of this species is sensitive to climatic change and variability. Extended periods of high temperature and/or low precipitation leading to low level of available water in the soil, can trigger the decline of cork oak and increase vulnerability to pathogen attack. Plant microbiomes are major factors for preserving plant health and productivity under challenging climates and their endophytic components can have dual ecological function, both as detrimental microbes or as beneficial symbionts. Endophytes can play beneficial roles for plant health and productivity but some can become opportunistic pathogens that take advantage of weakened plants that are stressed by environmental conditions. This review discusses endophytes in the context of Mediterranean bioclimates, the geographic distribution of cork oaks and the spread of opportunistic disease-causing agents. Some studies have begun to characterise and isolate endophytes from cork oak, which represents the first steps towards understanding how cork oak endophytes might help ameliorate the negative impacts of climate change for this tree species.