The complexity of mycobiota associated with chestnut galls induced by Dryocosmus kuriphilus in Galicia (Northwestern Spain)

Abstract

The European chestnut tree (Castanea sativa) is a highly valued deciduous species in Galicia (Northwestern Spain), mainly due to economic, landscape, and social or cultural reasons. However, the Asian wasp Dryocosmus kuriphilus, one of the biggest threats to C. sativa, is severely affecting tree vigor and reducing chestnut yields. Some studies indicated that this wasp and the galls that it produces may play an important role in spreading fungal disease. The present work aimed to characterize the complex of fungi associated with galls induced by D. kuriphilus in Galician chestnut trees, focusing on the study of plant-pathogen diversity. For this purpose, branches with necrotic galls were collected from seventy-eight chestnut stands located in the four Galician provinces (A Coruña, Lugo, Ourense, and Pontevedra). In total, 1170 necrotic galls of the year of study were collected at the different sampling sites. In the laboratory, four galls were randomly selected from each point, thus analyzing 312 galls, which were surface disinfected and dissected, and tissue fragments placed on culture media. From the selected galls, 308 fungal colonies were isolated and then identified by the morphology of their fruiting bodies and the molecular analysis of the ITS, beta-tubulin, elongation factor, and histone regions. They were classified into 27 genera and 53 species, of which 5 genera and 29 species of fungi were reported for the first time associated with D. kuriphilus galls, including phytopathogenic fungi. Results show that further research is needed to study in detail the role of galls as entry points and reservoirs of pathogenic fungi.

Keywords

• Asian Chestnut Gall Wasp
• Castanea sativa
• Endophytes
• Phytopathogens