Three novel species of fungi associated with pine species showing needle blight-like disease symptoms

Abstract

Pine needle diseases, such as red band and brown spot needle blight, are serious pine diseases that threatens forests in many countries. Several outbreaks have been reported resulting in loss of productivity and mortality in both exotic and native plantations of Pinus spp. Symptomatology of these two diseases is quite similar and characterized by the appearance of yellowish areas/bands on hosts’ leaves that subsequently lead to the appearance of more extensive lesions and/or necrotic areas. In an attempt to understand the main causes of needle blight-like disease symptoms a study was carried in two pine stands that were apparently affected by red band and brown spot needle blights. Needles showing spots and/or bands with fruiting bodies were sampled. From 25 pine trees samples, 82 fungal isolates were successfully retrieved. The most common fungal genera were Pestalotiopsis (42.68%, n = 35), Rhizosphaera (28.04%, n = 23) and Cladosporium (9.75%, n = 8). Seven isolates could not be assigned to a species through molecular identification by ITS sequence analysis, potentially representing novel taxa. Based on multilocus phylogenetic analyses, using ITS, tub2 and tef1-α sequences, and morphological data, we propose three novel fungal species: Didymocyrtis pini sp. nov., Pestalotiopsis iberica sp. nov. and Rhizosphaera pinicola sp. nov. These species are potential active players in the symptomatology initially associated to red band and brown spot needle blight diseases. Although the pathogenicity of these fungi needs to be confirmed, this study suggests a high complexity underlying fungal species associated with these diseases which may impact disease epidemiology and management.