Sphaeropsis sapinea and fungal endophyte diversity in twigs of Scots pine (Pinus sylvestris) in Germany

Abstract

Sphaeropsis sapinea is the causal fungal agent of Diplodia tip blight disease of Scots pine (Pinus sylvestris) and other coniferous trees of relevance to forestry in Germany. In this study, the distribution and occurrence of S. sapinea and accompanying endophytic fungi in twigs of healthy and diseased Scots pine was investigated on a spatial and temporal scale. Sampling of 26,000 twig segments from trees in 105 temperate coniferous forest stands in Germany resulted in isolation of 33,000 endophytic fungi consisting of 103 species identified based on morphological and ITS-DNA sequence analyses. Approximately 98% of the sample was represented by fungi in the Ascomycota, with only two species (Peniophora pini and Coprinellus sp.) belonging to the Basidiomycota. Four species were detected in a frequency greater than 10% (Sphaeropsis sapinea, Sydowia polyspora, Microsphaeropsis olivacea, and Truncatella conorum-piceae) from the collective sample. A typical inhabitant of Scots pine twigs Desmazierella acicola was isolated and additionally typical hardwood colonizers like Biscogniauxia spp. were detected. S. sapinea, an endophytic plant pathogen with saprobic capabilities, was isolated from more than 80% of the studied pine trees, but the majority of trees sampled showed no symptoms of Diplodia tip blight. No invasive, pathogenic quarantine fungi for Germany were isolated from healthy or diseased Scots pines. Advantages and disadvantages of isolation-based endophyte studies over studies using direct DNA-isolation are discussed. Knowledge of the fungal endophyte communities in twigs of Scots pine allowed for identification S. sapinea and other potential pathogens of pines and other forest trees that may possibly contribute to increased disease under repeated periods of drought and heat stress in the future.

Mycobiomes of Young Beech Trees Are Distinguished by Organ Rather Than by Habitat, and Community Analyses Suggest Competitive Interactions Among Twig Fungi

“…The five most abundant fungal taxa from our study of early season organs were Alternaria, Cryptococcus, Hymenoscyphus, Herpotrichia, and Tetracladium, respectively. In pine, twigs were rich in Pleosporales fungi, e.g., Alternaria (Bußkamp et al, 2020). Hymenoscyphus and Lachnum were only found in buds whereas Candida, Chaetomium, Itersonilia, Setomelanomma, Sterigmatomyces, and Sistotrema were only found in twigs.…”

“…(Martín-García et al, 2011), Pinus sp. (Botella et al, 2010;Sanz-Ros et al, 2015;Bußkamp et al, 2020), Abies concolor, and Picea abies (Sieber, 1989). Twig mycobiomes associate with both biotic and abiotic factors, e.g., air quality (Bakys et al, 2009), geography and seasonality (Göre and Bucak, 2007), genotype and growth (Lamit et al, 2014;Sanz-Ros et al, 2015), and plant health (Sieber, 1989;Ragazzi et al, 2003).…”

 Decline of Mongolian Pine Forest by the Combinatory Effect of European Woodwasp Sirex noctilio (Hymenoptera: Siricidae) and Plant Pathogenic Fungi

“…The primary endophytic fungal species from unhealthy uninfested and S. noctilio infested trees were also similar, such as S. sapinea, T. atroviride, O. minus. The results of Simpson dominance index showed that fungal communities had a high concentration in unhealthy uninfested trees compared with the other two samples trees, and healthy uninfested trees has higher fungal diversity 24 (Table 3).…”

“…and widely distributed in Pinus radiata plantations in northern Spain, outbreaks of which have a considerable impact on plantations 23 . It was recognized as the most widespread necrotrophic ascomycete pathogen responsible for dramatic losses of pine trees across the continents 24 . S. sapinea has emerged as an aggressive fungal pathogen all over the world and could directly invade the young shoots of pine trees [25][26][27] .…”

“…Usually, numerous pycnidia of S. sapinea are present in forest stands occurring on twigs, needles branches and stems of pine. A high infection rate may pose a high risk to the forest when there are disease-triggering factors, e.g., hail or insect feeding or extreme weather conditions such as heat and drought, as in the years 2018 und 2019 in German 24 .…”