First report of Cryphonectria carpinicola in the Balkans and Cryphonectria radicalis in Bulgaria

Abstract

The members of Cryphonectria are known to infect deciduous tree genera of forests, orchards and urban spaces. Its most infamous representative, C. parasitica, causes the blight disease in chestnut trees and is considered as the most aggressive Cryphonectria species in Europe. To study the invasion dynamics of C. parasitica, we have conducted sampling campaigns of symptomatic Castanea sativa in the Balkans since the mid 1990-ties. During isolation of fungi from the bark material, in some cases we encountered atypical mycelia, suggesting that different Cryphonectria species may be present in this region. The aim of this study was to identify the species of atypical cultures, excluding the well-studied C. parasitica. For this purpose, we combed through our isolate collection, preserved on dried glass filter, and recultivated up-to-25-year-old samples to obtain DNA from the cultures. If the dry samples were no longer alive, we applied forensic DNA extraction to recover DNA directly from the glass filter. We sequenced the ITS barcode of twelve atypical specimens preserved in our collection, and confirm here the presence of the recently described Cryphonectria carpinicola on a Carpinus tree from the Berkovska Stara Planina Mountain in Bulgaria, collected in 2007. Additionally, we also report the occurrence of Cryphonectria radicalis in the region of Blagoevgrad in Bulgaria isolated from C. sativa in 2005 and 2007. The oldest examined specimen dates from 1998 and is Cryphonectria radicalis from Belasitsa Mountain in North Macedonia, also previously reported. Cryphonectria carpinicola became noticeable only in the last two decades on declining hornbeam trees in urban areas of Central Europe. It shows only slight differences in morphology and anatomy to the two closely related species C. radicalis and C. naterciae, and differs from most other Cryphonectria species due to its preference for Carpinus trees as main hosts, while other Cryphonectria species are found on Castanea or Quercus trees.