Fungal Communities Associated with Siricid Wood Wasps: Focus on Sirex juvencus, Urocerus gigas, and Tremex fuscicornis

We investigated the diversity and occurrence of wood wasps in Lithuania and determined communities of associated fungi. Trapping of wood wasps resulted in three different species, including Sirex juvencus, Urocerus gigas, and Tremex fuscicornis. Fungal culturing from adult females of T. fuscicornis mainly resulted in fungi from the genera Penicillium and Trichoderma. High-throughput sequencing of ITS2 rDNA resulted in 59,797 high-quality fungal sequences, representing 127 fungal OTUs. There were 93 fungal OTUs detected in U. gigas, 66 in S. juvencus, and 10 in T. fuscicornis. The most common fungi were Fusarium sporotrichioides (63.1% of all fungal sequences), Amylostereum chailletii (14.9%), Penicillium crustosum (7.8%), Microascus sp. 2261_4 (5.0%), and Pithoascus ater (2.1%). Among these, only A. chailletii was found in all three insect species with the highest relative abundance in U. gigas (15.2%), followed by S. juvencus (7.7%), and the lowest in T. fuscicornis (0.3%) (

Diversity and Composition of Belowground Fungal Communities Associated with Picea abies L. (H.) Karst. and Larix sp. Mill.: A Comparative Study

The aim of the presented study was to compare the diversity and composition of fungal communities associated with the roots and the rhizosphere soil of P. abies and Larix sp. in mid-age and mature managed forest stands in Lithuania. We also aimed to assess the presence of fungi-host-specific associations, i.e., whether Larix sp. stands could provide habitats for soil fungi currently associated with P. abies. The study sites were 10 Larix sp. and 10 P. abies forest stands in Lithuania. For the study, 100 root samples and 10 organic and 10 mineral soil samples were collected in P. abies stands as well as the same number in Larix sp. stands, and DNA was isolated, amplified using ITS2 rDNA as a marker and subjected to high-throughput sequencing. The results showed that the Shannon diversity index of fungal communities was similar between the two tree species when compared either between root (H = 4.26 P. abies and H = 3.82 Larix sp.), organic soil (H = 5.12 P. abies and H = 5.13 Larix sp.) or mineral soil (H = 4.71 P. abies and H = 4.29 Larix sp.) samples. Multivariate analysis showed that the fungal community composition in the organic and mineral soil samples of both P. abies and Larix sp. were similar, and thus, overlapping. The analysis also showed that the distribution of fungal species was denser in the roots and organic soil but more scattered in mineral soil. However, several fungi in the roots of either P. abies or Larix sp. showed a certain host specificity

Survival, growth and mycorrhization of containerised pinus sylvestris and picea abies seedlings of different provenances outplanted in a forest clear-cut

We studied field performance of containerised Pinus sylvestris and Picea abies seedlings of different provenances. Shoot height, needle chemical composition, root collar diameter, root mycorrhization and mycorrhizal species composition were evaluated after four growing seasons following outplanting. The results showed that in general spruce had better survival than pine. Ectomycorrhizas on spruce were dominated by Wilcoxina, Amphinema and Tylospora, while on pine by Suillus and Thelephora species. Spruce and pine showing best growth rates were colonised by ectomycorrhizal fungus Amphinema sp. In conclusion, the results demonstrated that forest nursery practices as well as provenance can significantly impact survival, growth and mycorrhization of the containerised pine and spruce seedlings

Fungi Inhabiting Stem Wounds of Quercus robur following Bark Stripping by Deer Animals

We investigated fungal communities in oak wounds to determine how fungal species richness and community composition changes depending on the age of wounds. The sampling of wood cores was carried out from 10-, 20-, 30-, 40-, and 50-year-old wounds. The fungal community was analyzed using high-throughput sequencing of ITS2 rDNA. Sequence analysis showed the presence of 534 fungal OTUs, which were 83.4% Ascomycota, 16.3% Basidiomycota, and 0.3% Mucoromycota. The fungal OTU richness changed over time: it increased as compared between 10- and 20-year-old wounds, remained similar in 20- to 40-year-old wounds, and decreased in 50-year-old wounds. The fungal community composition also changed over time with the largest differences detected between 10-year-old and older wounds (p < 0.001). The most common representatives of Basidiomycota were Laetiporus sulphureus (34.7%), Mycena galericulata (17.0%), and Cylindrobasidium evolvens (6.5%), and the most common of Ascomycota were Aposphaeria corallinolutea (13.6%), Sclerostagonospora cycadis (7.6%), and Cadophora malorum (5.8%). In conclusion, oak wounds of different ages were colonized by a high diversity of fungi including oak-associated species. Fungal communities in oak wounds underwent qualitative and quantitative changes over time, which led to the gradual shift from fungal generalists in young wounds to oak specialists in older wounds

Cytospora friesii and Sydowia polyspora are associated with the sudden dieback of Abies concolor in Southern Europe

Abies concolor was introduced to Europe in the 19th century and commonly planted as an ornamental tree. In 2018, after several very warm and dry vegetation seasons, which has likely caused abiotic stress in the trees, a sudden dieback of A. concolor was observed in the city of Arandelovac in Serbia. The external symptoms were the rapid discoloration of needles in a larger part of the crown and eventually the dieback of the trees. The aim of this study was to identify the possible agents of damage by analysing the fungal communities associated with symptomatic needles using high-throughput sequencing as no symptoms of damage were seen on the branches or stems. Symptomatic needles were collected from the lower branches of five standing trees. Half of the needles were surface sterilised and the remaining were left unsterilised. DNA was extracted, amplified using ITS2 rDNA as a marker and sequenced. Quality filtering showed the presence of 6 191 high quality reads, which, following a clustering analysis, was found to represent 79 non-singletons fungal taxa. The most common fungi in both surface sterilised and unsterilised needles were the pathogens Cytospora friesii (59.7%) and Sydowia polyspora (20.6%). The results demonstrated that C. friesii and S. polyspora can cause a rapid decline of A. concolor trees subjected to abiotic stress

An Overview of Phytophthora Species on Woody Plants in Sweden and Other Nordic Countries

The genus Phytophthora, with 326 species in 12 phylogenetic clades currently known, includes many economically important pathogens of woody plants. Different Phytophthora species often possess a hemibiotrophic or necrotrophic lifestyle, have either a broad or narrow host range, can cause a variety of disease symptoms (root rot, damping-off, bleeding stem cankers, or blight of foliage), and occur in different growing environments (nurseries, urban and agricultural areas, or forests). Here, we summarize the available knowledge on the occurrence, host range, symptoms of damage, and aggressiveness of different Phytophthora species associated with woody plants in Nordic countries with a special emphasis on Sweden. We evaluate the potential risks of Phytophthora species to different woody plants in this geographical area and emphasize the increasing threats associated with continued introduction of invasive Phytophthora species

The Release and Spread of Basidiospores of Red-Listed Wood-Decay Fungus Fistulina hepatica in Oak Stands

The aim of this study was to obtain a better understanding on short-distance basidiospore dispersal of the wood-decay fungus Fistulina hepatica, thereby providing valuable knowledge for the conservation management of this protected species. Specifically, the study was expected to reveal site-specific patterns of basidiospore release and spread in oak stands during one fruiting season under north European conditions. The trapping of fungal spores was carried out between August and October 2022 using passive spore traps placed in three oak stands (>200-year-old) in central Lithuania. The average daily temperature was recorded throughout the period of spore trapping. Collected samples were analyzed using high-throughput sequencing of fungal ITS2 rDNA. The results showed that the relative abundance of F. hepatica reads was influenced by the time of fruitbody maturation, but not by the average daily temperature. Although there was a certain variation among different study sites, the results showed that a great majority of F. hepatica spores were deposited within 50 m from the fruitbody, showing that the fungus to a large extent is dependent on local habitats for colonization

Fungal Diversity in the Phyllosphere of Pinus heldreichii H. Christ-An Endemic and High-Altitude Pine of the Mediterranean Region

Pinus heldreichii is a high-altitude coniferous tree species naturaly occurring in small and disjuncted populations in the Balkans and southern Italy. The aim of this study was to assess diversity and composition of fungal communities in living needles of P. heldreichii specifically focusing on fungal pathogens. Sampling was carried out at six different sites in Montenegro, where 2-4 year-old living needles of P. heldreichii were collected. Following DNA isolation, it was amplified using ITS2 rDNA as a marker and subjected to high-throughput sequencing. Sequencing resulted in 31,831 high quality reads, which after assembly were found to represent 375 fungal taxa. The detected fungi were 295 (78.7%) Ascomycota, 79 (21.0%) Basidiomycota and 1 (0.2%) Mortierellomycotina. The most common fungi were Lophodermium pinastri (12.5% of all high-quality sequences), L. conigenum (10.9%), Sydowia polyspora (8.8%), Cyclaneusma niveum (5.5%), Unidentified sp. 2814_1 (5.4%) and Phaeosphaeria punctiformis (4.4%). The community composition varied among different sites, but in this respect two sites at higher altitudes (harsh growing conditions) were separated from three sites at lower altitudes (milder growing conditions), suggesting that environmental conditions were among major determinants of fungal communities associated with needles of P. heldreichii. Trees on one study site were attacked by bark beetles, leading to discolouration and frequent dieback of needles, thereby strongly affecting the fungal community structure. Among all functional groups of fungi, pathogens appeared to be an important component of fungal communities in the phyllosphere of P. heldreichii, especially in those trees under strong abiotic and biotic stress

The development of foliar fungal communities of nursery-grown Pinus sylvestris seedlings

In forest nurseries, foliar fungi play a key role in the health of tree seedlings. The aim of this study was to study the diversity and the development of foliar fungal species associated with nursery-grown Pinus sylvestris, and to evaluate the effect of two biological control products and two growth-stimulating products on seedling growth and disease control, as well as seedling associated fungal community. The study was conducted at four Swedish forest nurseries. Fungal communities were assessed from non-symptomatic needles using high-throughput sequencing of the ITS2 rRNA region. The fungal pathogens Cladosporium sp. (15.1%), Phoma herbarum (14.5%), and Alternaria alternata (5.5%) were among the most abundant fungi. Results showed that the nurseries and the development of fungal communities influenced the occurrence of dominant fungal taxa. Disease prevalence was low and microbial treatments had no significant impact on seedling growth and survival, nor on the number of fungal operational taxonomic units (OTUs), species diversity, and species evenness (p > 0.05). In conclusion, the results showed a dynamic change in foliar fungal community structure over the growing season. With appropriate nursery management strategies and under suitable climatic conditions, nursery seedlings can remain healthy even in the presence of fungal pathogens