Search

In Europe, Pinus sylvestris and Picea abies are the most common coniferous tree species used in commercial forestry, which rely on high‐quality reproductive material for successful reforestation. Clear‐cut harvested forest sites are often replanted using tree seedlings, which are produced in forest nurseries using seeds from seed orchards. However, incidences of fungal diseases in seedling production show that a better knowledge of seedborne fungi, including fungal pathogens, is needed to manage diseases in forest nurseries. This study aimed to assess seedborne fungal communities associated with commercial seeds of P. abies, P. sylvestris and Larix sp. seeds originated from geographically separated regions in Sweden, Belarus, Finland and Poland. Fungal communities were obtained first from the seed surface and then from the seed tissue. These were analysed using high‐throughput sequencing of the ITS2 rDNA region. The results showed that fungal diversity and community composition differed between the seed surface and the seed tissue. Picea abies accommodated a higher fungal diversity than P. sylvestris. In addition, a strong host affinity of the fungal community composition on the seed surface and a weaker association in the seed tissue was found. Fungal communities on P. abies and P. sylvestris seed surface differed significantly between geographical regions, whereas no regional differences were found in the seed tissue. The seedborne fungal communities included a high proportion of plant pathogens, among which the most abundant were Sydowia polyspora (13.3%), Phoma herbarum (11.2%) and Sirococcus conigenus (3.8%). In conclusion, the results showed (a) characteristic fungal diversity and community composition between the seed surface and the seed tissue; (b) a host‐specific fungal community composition on the seed surface and in the seed tissue; (c) regional difference in fungal communities on P. abies and P. sylvestris seed surface, thus the movement of seeds between different regions can contribute to the spread of fungal diseases; and (d) the presence of a high incidence of seedborne fungal pathogens which suggest a potential need of preventative or control measures to reduce the occurrence of these fungi on the seed surface. [ABSTRACT FROM AUTHOR]

We assessed the diversity and composition of fungal communities in different functional tissues and the rhizosphere soil of Pinus sylvestris and Picea abies stands along the latitudinal gradient of these tree species distributions in Europe to model possible changes in fungal communities imposed by climate change. For each tree species, living needles, shoots, roots, and the rhizosphere soil were sampled and subjected to high-throughput sequencing. Results showed that the latitude and the host tree species had a limited effect on the diversity and composition of fungal communities, which were largely explained by the environmental variables of each site and the substrate they colonize. The mean annual temperature and mean annual precipitation had a strong effect on root fungal communities, isothermality on needle fungal communities, mean temperature of the warmest quarter and precipitation of the driest month on shoot fungal communities, and precipitation seasonality on soil fungal communities. Fungal communities of both tree species are predicted to shift to habitats with a lower annual temperature amplitude and with increasing precipitation during the driest month, but the suitability of these habitats as compared to the present conditions is predicted to decrease in the future. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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 Aranđelovac 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. [ABSTRACT FROM AUTHOR]

Climate change, which leads to higher temperatures, droughts, and storms, is expected to have a strong effect on both health of forest trees and associated biodiversity. The aim of this study was to investigate the diversity and composition of fungal communities associated with the functional tissues and rhizosphere soil of healthy-looking Picea abies to better understand these fungal communities and their potential effect on tree health in the process of climate change. The study sites included 30 P. abies stands, where needles, shoots, roots, and the rhizosphere soil was sampled. DNA was isolated from individual samples, amplified using ITS2 rRNA as a marker and subjected to high-throughput sequencing. The sequence analysis showed the presence of 232,547 high-quality reads, which following clustering were found to represent 2701 non-singleton fungal OTUs. The highest absolute richness of fungal OTUs was in the soil (1895), then in the needles (1049) and shoots (1002), and the lowest was in the roots (641). The overall fungal community was composed of Ascomycota (58.3%), Basidiomycota (37.2%), Zygomycota (2.5%), Chytridiomycota (1.6%), and Glomeromycota (0.4%). The most common fungi based on sequence read abundance were Aspergillus pseudoglaucus (7.9%), Archaeorhizomyces sp. (3.6%), and Rhinocladiella sp. (2.0%). Pathogens were relatively rare, among which the most common were Phacidium lacerum (1.7%), Cyphellophora sessilis (1.4%), and Rhizosphaera kalkhoffii (1.4%). The results showed that the detected diversity of fungal OTUs was generally high, but their relative abundance varied greatly among different study sites, thereby highlighting the complexity of interactions among the host trees, fungi, and local environmental conditions. [ABSTRACT FROM AUTHOR]

The horse chestnut leaf-miner (Cameraria ohridella Deschka & Dimić, Lepidoptera, Gracillariidae) is an invasive pest causing extensive damage to leaves of the horse-chestnut (Aesculus hippocastanum L.) in Europe. In Lithuania, C. ohridella invaded in 2002 causing wilting, browning and premature fall of A. hippocastanum leaves. The aim was to get a better understanding of possible linkages between foliar fungal communities and leaf-miner damage in A. hippocastanum. Leaves of A. hippocastanum, differentially damaged by C. ohridella, were collected in 10 sites in Lithuania. The fungal communities were described through DNA isolation and amplification using an ITS rRNA marker and Ion Torrent-sequencing. Clustering of 214,897 high-quality sequences resulted in 1017 non-singleton fungal taxa, among which Aureobasidium pullulans (28.2% of all fungal sequences), Endoconidioma populi (27.7%), Phoma fungicola (11.3%), Cladosporium ramotenellum (7.6%) and Cryptococcus sp. 2185_4 (5.0%) were most common. Correspondence analysis showed that fungal communities from heavily and slightly damaged leaves were largely intermingled, showing that in both types of samples fungal communities were similar. In conclusion, the study demonstrated that the phyllosphere of A. hippocastanum is inhabited by a high diversity of fungal species, the majority of which constitute generalist endophytes, epiphytes and saprotrophic fungi. The occurrence of common phyllosphere fungi was unrelated to the degree of damage by C. ohridella. [ABSTRACT FROM AUTHOR]

Forest nurseries in Sweden produce ca. 360 million seedlings of Pinus sylvestris L. and Picea abies (L.) Karst. annually. Fungi represent the largest microbial component in rhizospheres and may significantly affect health and, consequently, quality of the seedlings. The aim of this study was to assess fungi focusing on pathogens in roots and the sphagnum peat growth substrate of healthy-looking P. sylvestris and P. abies seedlings from nine forest nurseries situated in northern, central and southern regions of Sweden. We hypothesized that nursery stock and the growth substrate can provide a venue for dissemination of fungal diseases. In each nursery and for each tree species, 100 seedlings with the growth substrate were collected during the dormant period. DNA was isolated from parts of root systems and from samples of the growth substrate, amplified using internal transcribed spacer of rDNA as a marker and 454-sequenced. Clustering at 98.5% similarity of 169,844 high-quality sequences resulted in 619 non-singleton fungal taxa. Although results showed that management practices in forest nurseries generally give a healthy stock, latent establishment of pathogenic fungi in both roots and the growth substrate supported the hypothesis. Furthermore, seedling roots and the growth substratewere inhabited by distinct communities of fungi, and lifestyles of these fungi largely determined community segregation into particular ecological niche. [ABSTRACT FROM AUTHOR]

The aim of this study was to assess fungal communities in roots of healthy-lookingPinus sylvestrisL. andPicea abies(L.) Karst. seedlings in nine forest nurseries in Sweden using a combination of traditional culturing and direct sequencing of internal transcribed spacer of fungal ribosomal RNA (ITS rRNA) from the roots. Culturing from 1800 surface-sterilised root segments resulted in 2387 fungal cultures representing 42 different taxa. Direct sequencing from 180 root segments resulted in 119 ITS rRNA sequences representing 25 different taxa. In total, 55 different fungal taxa were detected using both methods. Although direct sequencing was more efficient than culturing in detecting different fungal taxa, both methods provided complementary information about fungal communities in roots since each detected rather different groups of fungi. The most dominant taxa detected by culturing wereTrichoderma viridePers. (19.5%), Phoma mucivoraDavey & Currah (19.1%),Phialocephala fortiniiWang & Wilcox (17.4%) andMeliniomyces variabilisHambl. & Sigler (10.2%), whileThelephora terrestrisEhrh. (26.1%), Unidentified sp. NS126 (25.2%) andHeliotalessp. C20 (10.1%) were most commonly detected by direct sequencing. In conclusion, results showed that forest nurseries in Sweden harbour diverse communities of fungi associated with the roots of healthy-lookingP. sylvestrisandP. abiesseedlings. Although fungal communities were often dominated by saprotrophs and endophytes, several facultative pathogens were also detected indicating that under suitable conditions they may be a potential threat to the plants. [ABSTRACT FROM PUBLISHER]

The production of tree seedlings in forest nurseries and their use in the replanting of clear-cut forest sites is a common practice in the temperate and boreal forests of Europe. Although conifers dominate on replanted sites, in recent years, deciduous tree species have received more attention due to their often-higher resilience to abiotic and biotic stress factors. The aim of the present study was to assess the belowground fungal communities of bare-root cultivated seedlings of Alnus glutinosa, Betula pendula, Pinus sylvestris, Picea abies and Quercus robur in order to gain a better understanding of the associated fungi and oomycetes, and their potential effects on the seedling performance in forest nurseries and after outplanting. The study sites were at the seven largest bare-root forest nurseries in Lithuania. The sampling included the roots and adjacent soil of 2–3 year old healthy-looking seedlings. Following the isolation of the DNA from the individual root and soil samples, these were amplified using ITS rRNA as a marker, and subjected to high-throughput PacBio sequencing. The results showed the presence of 161,302 high-quality sequences, representing 2003 fungal and oomycete taxa. The most common fungi were Malassezia restricta (6.7% of all of the high-quality sequences), Wilcoxina mikolae (5.0%), Pustularia sp. 3993_4 (4.6%), and Fusarium oxysporum (3.5%). The most common oomycetes were Pythium ultimum var. ultimum (0.6%), Pythium heterothallicum (0.3%), Pythium spiculum (0.3%), and Pythium sylvaticum (0.2%). The coniferous tree species (P. abies and P. sylvestris) generally showed a higher richness of fungal taxa and a rather distinct fungal community composition compared to the deciduous tree species (A. glutinosa, B. pendula, and Q. robur). The results demonstrated that the seedling roots and the rhizosphere soil in forest nurseries support a high richness of fungal taxa. The seedling roots were primarily inhabited by saprotrophic and mycorrhizal fungi, while fungal pathogens and oomycetes were less abundant, showing that the cultivation practices used in forest nurseries secured both the production of high-quality planting stock and disease control. [ABSTRACT FROM AUTHOR]

Conifer bark beetles are well known to be associated with fungal complexes, which consist of pathogenic ophiostomatoid fungi as well as obligate saprotroph species. However, there is little information on fungi associated with Ips acuminatus in central and eastern Europe. The aim of the study was to investigate the composition of the fungal communities associated with the pine engraver beetle, I. acuminatus, in the forest-steppe zone in Ukraine and to evaluate the pathogenicity of six associated ophiostomatoid species by inoculating three-year-old Scots pine seedlings with these fungi. In total, 384 adult beetles were collected from under the bark of declining and dead Scots pine trees at two different sites. Fungal culturing from 192 beetles resulted in 447 cultures and direct sequencing of ITS rRNA from 192 beetles in 496 high-quality sequences. Identification of the above revealed that the overall fungal community was composed of 60 species. Among these, the most common were Entomocorticium sp. (24.5%), Diplodia pinea (24.0%), Ophiostoma ips (16.7%), Sydowia polyspora (15.1%), Graphilbum cf rectangulosporium (15.1%), Ophiostoma minus (13.8%) and Cladosporium pini-ponderosae (13.0%). Pathogenicity tests were done using six species of ophiostomatoid fungi, which were inoculated into Scots pine seedlings. All ophiostomatoid fungi tested successfully infected seedlings of Scots pine with varying degrees of virulence. Ophiostoma minus was the only fungus that caused dieback in inoculated seedlings. It is concluded that I. acuminatus vectors a species-rich fungal community including pathogens such as D. pinea and O. minus. The fungal community reported in the present study is different from that reported in other regions of Europe. Pathogenicity tests showed that O. minus was the most virulent causing dieback in seedlings of Scots pine, while other fungi tested appeared to be only slightly pathogenic or completely non-pathogenic. [ABSTRACT FROM AUTHOR]

The aim of this study was to investigate the composition of the fungal community associated with the red-haired bark beetle (Hylurgus ligniperda Fabricius) in two plantations of Pinus sylvestris L. located in the Kharkiv and Luhansk regions (ca. 250 km apart) in the forest-steppe zone in eastern Ukraine. In each plantation, 48 beetles were collected from butts of living trees and 48 beetles from stems of fallen trees, i.e., a total of 96. Half of the beetles from each site were used for culturing fungi and the other half for direct sequencing the internal transcribed spacer of fungal ribosomal RNA (ITS rRNA ). Thirty distinct fungal taxa were identified by culturing and 31 by direct sequencing. When pooled, there were 40 fungal taxa among which Ophiostoma piceae (Münch) Sydow & P. Sydow (10.3%), Alternaria alternata (Fries) Keissler (9.7%), Ogataea neopini Nagatsuka, S. Saito & Sugiyama (8.0%), Botryotinia fuckeliana (de Bary) Whetzel (5.1%), Cladosporium sp. Link (5.1%) and Sydowia polyspora (Brefeld & Tavel) E. Müller (4.6%) were the most common. Species of the genus Ophiostoma were the most abundant and included five different taxa O. piceae, O. bicolor R.W. Davidson & D.E. Wells, O. ips (Rumbold) Nannfeldt, O. canum (Münch) Sydow & P. Sydow and O. rectangulosporium Ohtaka, Masuya & Yamaoka, all of which are known to be at most weak pathogens of trees. The plant pathogen Botryotinia fuckeliana and insect pathogens Isaria farinose (Holmskjold) Fries and Beauveria bassiana (Balsamo-Crivelli) Vuillemin were also detected. Basidiomycetes were rare, among which three wood-decaying fungi Bjerkandera adusta (Willdenow) P. Karsten, Fomitopsis pinicola (Swartz) P. Karsten and Heterobasidion annosum (Fries) Brefeld were detected. In conclusion, in the forest-steppe zone in eastern Ukraine H. ligniperda is a vector of diverse communities of fungi the majority of which, if at all, are only weak pathogens of trees. [ABSTRACT FROM AUTHOR]