Diversity and pathogenicity of Botryosphaeriaceae and Phytophthora species involved in emerging diseases of Fagus sylvatica in Italy and Slovenia

Abstract

Extensive sunken and bleeding cankers, shoot blight, and root rot symptoms on European beech (Fagus sylvatica L.) trees have recently been observed in several forest ecosystems in Italy and Slovenia. Since there is little information about the aetiology of these diseases and given the high economic and ecological relevance of these formations, a study was conducted from summer to autumn 2023 in ten sites to define the occurrence, distribution and impact of the main pathogens involved. A total of 116 symptomatic samples were collected and processed. Based on colony appearance, morphological features and DNA sequence data, six species belonging to the genera Botryosphaeria, Dothiorella, Diplodia, Neofusicoccum (fungi) and Phytophthora (oomycetes) were isolated and identified. Pathogenicity tests performed on potted European beech seedlings satisfied Koch postulates and highlighted that Diplodia corticola, Neofusicoccum parvum and Phytophthora plurivora are the main agents involved in the extensive decline affecting European beech ecosystems in Italy and Slovenia.

Keywords

• diplodia corticola
• beech decline
• invasive species
• emerging diseases
• co-infections