Diversity of fungal endophytic community in Quercus suber L. and detection of opportunistic phytopathogenic fungi

Abstract

Cork oak (Quercus suber L.) is a species of high ecological importance in Mediterranean Basin and has high relevance for Portuguese economy due to cork production and processing. The sustainability of cork oak is currently being threatened by the reduction of water availability that would increase the occurrence of diseases. Charcoal disease, caused by the fungus Biscogniauxia mediterrânea, leads to the death of the tree. Diplodia corticola is involved in various diseases considered responsible for the decline of cork oak in Mediterranean Basin. To identify endophytic fungi in cork oak, including these opportunistic pathogens, four sites of continental Portugal (Bragança, Geres, Alcobaça and Grândola) with differences in water availability were selected to carry out the collection of biological material. The community of fungal endophytes of leaves, stems and roots was evaluated. The roots displayed a more diverse fungal community than the aboveground organs. Although no disease symptoms were detected in studied cork oaks, the referred pathogenic fungi were essentially affecting stems and leaves. In general, Grândola presented the highest colonization frequency and diversity of endophytes, while Alcobaça had the lowest. From all studied sites, cork oaks from Geres showed the most distinct community and did not present those pathogens. D. corticola only infected southern regions, while S. mediterrânea also infected trees in Bragança. The exclusive presence of both pathogens in aboveground organs and the absence of visible disease symptoms in all studied cork oaks encourage the searching of adequate biocontrol agents from the endophytic community for restricting these diseases in cork oak.