Search Results (35)

Over the last few decades, the frequency of outbreaks of Ips acuminatus has rapidly increased in Latvia. These beetles are commonly associated with blue-stain fungi, which increase tree mortality and decrease the timber quality of affected trees. The aims of this study were: (i) to identify fungi associated with I. acuminatus in Latvia and (ii) to determine the influence of different factors (such as locality, month of beetle capture, beetle sex) on the diversity of associated fungi. From a total of 590 analysed I. acuminatus beetles, 564 resulted in fungal growth and yielded 1247 fungal isolates, representing 36 fungal taxa. Among the fungi isolated, the most common were Akanthomyces muscarius, followed by Penicillium spp., Mucor spp., Cladosporium cladosporioides, Leptographium cucullatum, Ophiostoma minus, and Graphilbum acuminatum. No significant differences in fungal diversity between different locations and between male and female I. acuminatus were observed. However, significant seasonal differences were observed between months in which I. acuminatus beetles were captured and fungal communities isolated from them. More research is needed on the potential of the entomopathogenic fungi isolated in this study for the biological control of I. acuminatus. Also, the pathogenicity of isolated Ophiostomatoid fungi and their ability to cause blue-stain in Pinus sylvestris timber could be further evaluated. Full article

Bark beetles (Coleoptera: Scolytinae) play a dual ecological role in forest ecosystems as disturbance agents and vectors of symbiotic fungi, including blue-stain taxa that affect wood quality and tree health. This study assessed fungal communities specific to four bark beetle species—Ips acuminatus (Gyllenhal, 1827), Ips sexdentatus (Börner, 1776), Ips typographus (Linnaeus, 1758), and Pityogenes chalcographus (Linnaeus, 1761)—colonizing Scots pine (Pinus sylvestris L.) in Slovakia. Fungal DNA was extracted from beetle surfaces and analyzed using ITS2 metabarcoding on the Illumina MiSeq platform to characterize the diversity and structure of associated mycobiota. Alpha- and beta-diversity analyses revealed a taxonomically and functionally rich fungal assemblage dominated by Ascomycota, comprising over one thousand operational taxonomic units. Fungal richness and diversity varied among beetle species: I. typographus and P. chalcographus supported the most diverse communities, I. sexdentatus harbored the least diverse assemblages, and I. acuminatus showed contrasting patterns depending on the index used. Beta-diversity analysis indicated that community composition was primarily structured by beetle species identity, with weaker effects of locality and sampling method. Ophiostomatoid fungi, particularly Geosmithia pallida (G. Sm.) M. Kolařík, Kubátová & Pažoutová, Ophiostoma distortum (R.W. Davidson) de Hoog & R.J. Scheff., and Ophiostoma minus (Hedgc.) Syd. & P. Syd., were consistently prevalent and formed the core mycobiome. Random forest classification and differential abundance analyses confirmed host-specific enrichment of several ophiostomatoid and yeast taxa. Yeasts (e.g., Kuraishia, Candida, Yamadazyma), saprotrophic molds (e.g., Penicillium, Davidiella), and the entomopathogen Beauveria bassiana (Bals.-Criv.) Vuill. also occurred frequently. These findings provide the first DNA-based evidence of host-specific fungal assemblages in Scots pine bark beetles in Slovakia and emphasize their ecological significance for beetle–fungus symbioses and pine forest health. Full article

Background/Objectives: Within their host trees, mountain pine beetles (MPBs, Dendroctonus ponderosae) interact with many fungal species, each releasing a unique profile of volatile organic compounds (VOCs). The FVOCs released by the two primary symbionts of MPBs, Grosmannia clavigera and Ophiostoma montium, have been found to enhance MPB attraction in the field and laboratory studies. Opportunistic, saprophytic fungal species, such as Aspergillus sp. and Trichoderma atroviride, are also common in MPB galleries and can negatively impact MPB fitness. However, little is known about the FVOCs produced by these fungal species and how they may impact MPB feeding and attraction. Methods: To address this knowledge gap, we characterized the FVOC profile of T. atroviride, and performed bioassays to test the effects of its FVOCs on MPB attraction and feeding activity. Results: Our chemical analysis revealed several FVOCs from T. atroviride known to inhibit the growth of competing fungal species and impact subcortical-beetle attraction. Conclusions: From those FVOCs, we recommended four compounds—2-pentanone, 2-heptanone, 2-pentanol, and phenylethyl alcohol—for use in future field tests as anti-attraction lures for MPBs. In bioassays, we also observed strong MPB repellency from FVOCs released by T. atroviride, as well as the mild effects of FVOCs on MPB feeding activity. Our findings highlight the potential for these FVOCs to be utilized in the development of more effective MPB anti-attractant lures, which are crucial for the monitoring and management of low-density MPB populations. Full article

Pinus species are extensively abundant in Europe and, as pioneer trees, prominently influence local ecology. However, pine forests in Lithuania, Montenegro, and Ukraine have been significantly damaged by pine bark beetles (Tomicus sp.), which are closely associated with ophiostomatoid and other pathogenic fungi. This study aimed to identify the diversity of ophiostomatoid and other fungi associated with Tomicus sp. in these three countries. Fungi were isolated from beetles and identified. High-throughput sequencing of ITS2 rDNA yielded 285,828 reads, of which 91,141 high-quality reads were retained, representing 561 fungal operational taxonomic units (OTUs). The most important groups of fungi included ophiostomatoids, yeasts, and plant pathogens. While the fungal communities associated with Tomicus spp. were influenced more by environmental factors than by beetle species, the presence of known pathogens such as Ophiostoma spp. indicates that Tomicus spp. could play a significant role in dispersing harmful fungi. Although the virulence of these fungi may vary, their association with potentially pathogenic species suggests that Tomicus spp. may contribute to forest health decline, especially if environmental conditions or host susceptibility change. Full article

The red turpentine beetle Dendroctonus valens is an invasive forest pest that has been rapidly spreading northward since its introduction in China. Some ophiostomatalean associates of D. valens are essential contributing factors for this beetle to become an aggressive pine killer in China. In this study, a survey was conducted in a new invasive area of this beetle’s habitat in Liaoning Province. A total of 126 ophiostomatalean fungal associates of D. valens were isolated. Based on the combination of morphological characteristics and phylogeny, these isolates were identified as Ceratocystiopsis jianpingensis sp. nov., along with two new records, Leptographium terebrantis and Ophiostoma gilletteae. Ophiostoma gilletteae was the dominant species, with an isolation rate of 85.7%. The results of this study show that more shared ophiostomatalean fungi are associated with D. valens in China and North America, and accumulate resources for the development of fungal associate-mediated bark beetle management strategies. Full article

Subcortical beetle communities interact with a wide range of semiochemicals released from different sources, including trees, fungi, and bark beetle pheromones. While the attraction of bark beetles, their insect predators, and competitors to bark beetle pheromones is commonly studied, the attraction of these beetle communities to other sources of semiochemicals remains poorly understood. We tested the attraction of bark and wood-boring beetles and their predators to host stress volatiles, fungal volatiles, and a mountain pine beetle lure in the field. Host stress volatiles were derived from lodgepole pine trees stressed by three fungal symbionts of mountain pine beetle and two common phytopathogens. Our results showed that bark beetles, particularly mountain pine beetles, show a preference for a combination of fungal volatiles, particularly 2-methyl-1-butanol and its lures. Without the addition of lures, 2-methyl-1-butanol was also identified as a key fungal volatile in the attraction of mountain pine beetle competitors from the Cerambycidae and Buprestidae families. Predators in the Elateridae and Staphylinidae families showed attraction to host stress volatiles and the healthy tree volatile profiles. These findings suggest that these semiochemicals warrant further field testing for potential use in monitoring and management of subcortical beetle populations. Full article

Globally, forest decline and tree mortality are rising due to climate change. As one of the important afforestation trees in northeast China, Pinus sylvestris var. mongolica is suffering from forest decline and the accompanying pests. Certain fungi from the ophiostomatalean contribute to forest pest outbreaks and can be pathogenic to pine trees. However, only a limited number of ophiostomatalean fungi associated with beetles infesting Pinus sylvestris var. mongolica have been identified. In this study, 293 ophiostomatalean fungi were isolated from Acanthocinus griseus, Ips chinensis, and Pissodes nitidus infesting Pinus sylvestris var. mongolica in Heilongjiang Province, including Graphilbum griseum sp. nov., Gra. nitidum sp. nov., Graphilbum sp., and Ophiostoma ips. Ophiostoma ips was the dominant species, followed by Graphilbum sp., Graphilbum griseum, and Gra. nitidum, which accounted for 73.38, 17.41, 7.17, and 2.05% of the isolated ophiostomatalean fungi, respectively. Fungi associated with different beetles are diverse, even within the same host. This study deepens our understanding of the pest-associated fungi of P. sylvestris var. mongolica and provides a basis for exploring the causes of forest decline. Full article

Pine wilt disease (PWD) is a devastating disease that occurs worldwide and affects conifers infested by the pine wood nematode (PWN, Bursaphelenchus xylophilus). PWD has caused serious economic and ecological losses in China. The mechanism of disease outbreak is complex, with the associated fungi, specifically ophiostomatoid fungi, thought to play an essential role. However, few ophiostomatoid fungal associates of PWD have been accurately identified. In the present study, we isolated fungi from bark beetles collected from Pinus thunbergii infested by the pine wood nematode on Laoshan Mountain, Shandong province. Three ophiostomatalean fungi were identified and assigned to Graphilbum and Ophiostoma based on phylogenetic analyses and comparison of morphological and cultural features, namely Gra. laoshanense sp. nov., Gra. translucens, and O. ips. This study increases the understanding of the diversity of ophiostomatoid fungi associated with PWD and provides resources for parsing this complex disease. Full article

The objective of this research was to investigate natural products for their potential against pathogenic microorganisms. Sabinene hydrate (SH), a monoterpenoid, is synthesised by numerous different plants as a secondary metabolite. At present, there is a lack of definite investigations regarding the antimicrobial activity of SH itself and its different isomers. The antimicrobial effects of commercially available SH (composed mainly of trans-isomer) were evaluated within a range of concentrations in three types of contact tests: solid and vapor diffusion and the macro-broth dilution method. Moreover, the effects of SH on the rate of linear growth and spore germination were also examined. Ethanolic SH solutions were tested against an array of microorganisms, including blue-stain fungi (Ceratocystis polonica, Ophiostoma bicolor, O. penicillatum), frequently originating from bark beetle galleries; three fungal strains (Musicillium theobromae, Plectosphaerella cucumerina, and Trichoderma sp.) isolated from a sapwood underneath bark beetle galleries (Ips typographus) on spruce (Picea abies) stems; Verticillium fungicola, isolated from diseased I. typographus larvae; two Gram-positive bacteria (Bacillus subtilis and Staphylococcus aureus), two Gram-negative bacteria (Escherichia coli and Pseudomonas aeruginosa); five yeasts (Candida albicans, C. krusei, C. parapsilosis, Saccharomyces cerevisiae, and Rhodotorula muscilaginosa), and two saprophytic fungi (Aspergillus niger and Penicillium notatum). In solid agar disc diffusion tests, Gram-positive bacteria exhibited greater susceptibility to SH than Gram-negative bacteria, followed by yeasts and fungi. The most resistant to SH in both the disc diffusion and broth macro-dilution methods were P. aeruginosa, A. niger, and Trichoderma sp. strains. Blue-stain fungi and fungi isolated from the Picea sapwood were the most resistant among the fungal strains tested. The minimum inhibition concentrations (MICs) generated by SH and determined using a disc volatilization method were dependent on the fungal species and played an important role in the development of microorganism inhibition. The two Gram-positive bacteria, B. subtilis and S. aureus (whose MICs were 0.0312 and 0.0625 mg/mL, respectively), were the organisms most susceptible to SH, followed by the Gram-negative bacterium, E. coli (MIC = 0.125 mg/mL) and two yeasts, C. albicans and C. kruei (MIC was 0.125 mg/mL and 0.25 mg/mL, respectively). C. parapsilosis (MIC = 0.75 mg/mL) was the yeast most resistant to SH. The investigation of antimicrobial properties of plant secondary metabolites is important for the development of a new generation of fungicides. Full article

In 2019, the bark beetle Ips amitinus (native to central Europe) was identified in south-western Siberia at a distance exceeding 2500 km east of its previously known easternmost location in the European part of Russia. In Siberia, its invasive populations are characterised by high abundance and harmfulness. Here, I. amitinus accomplishes primary attacks on standing vital trees of Pinus sibirica with a lethal outcome. This invasion has already resulted in massive dieback in stands of pine over a large geographic territory. By, 2021, the invaded area was estimated to cover at least 31,200 km². The objectives of this study were to investigate fungi associated with/vectored by I. amitinus in its invasive area in south-western Siberia and wood decay fungi that cause root and butt rots to P. sibirica. This led to the following conclusions: (i) DNA analysis of sixty adult beetles of Ips amitinus collected from P. sibirica in south-west Siberia revealed the presence of 143 fungal taxa; (ii) species richness was significantly higher in beetles collected from dead branches than from (more recently infested) dying branches; (iii) fungal communities were >90% dominated by yeasts, among which the most common were Nakazawaea holstii, Kuraishia molischiana, and N. ambrosiae; (iv) entomopathogenic Beauveria bassiana s.l. was the most common fungus isolated from dead/mycosed beetles of I. amitinus, followed by Lophium arboricola and four Ophiostoma spp.; and (v) Heterobasidion parviporum was the most common decay fungus detected, which was causing heart rot in stems of P. sibirica. Full article

Forest decline is a significant issue affecting critical ecosystem processes worldwide. Here, we describe mortality in Pinus sylvestris L. monitored trees caused by the inhabitation of pine bark beetles (Tomicus minor Hart.) in symbiosis with ophiostomatoid fungi (Ophiostoma piceae (Munch) H. et P. Sydow) infection in the forest-steppe of central Siberia. Stem sap flow (Q) and stem diameter fluctuations (dRc) were monitored in eight pine trees during seven consecutive growing seasons (2015–2021). In addition, microcore sampling every ten days allowed the determination of stem wood formation in monitored trees in the 2021 growing season. During 2020 and 2021, two cases of Q termination were recorded among the monitored trees, with microcores revealing no cambium formation. Thus, the seasonal Q onset matches the beginning of the beetle dispersal period when they attack and inhabit tree stems. The decline of circumferential stem size began 10–12 days after Q onset, during the massive inhabitation of beetles into the stems. The disturbance of Q in trees occurred in 21–23 days, and total cessation of Q was observed 23–26 days after the Q onset at the beetle’s egg development phase. The timing of dRc disturbance and Q cessation observed directly coincides with the beetle life cycle. Thus, the phenology of pine trees and T. minor beetles is driven by seasonal weather conditions, particularly the cumulative air temperature (>0 °C). Full article

Polylactic acid (PLA) is the main biobased plastic manufactured on an industrial scale. This polymer is synthetized by chemical methods, and there is a strong demand for the implementation of clean technologies. This work focuses on the microbial fermentation of agro-industrial waste rich in starch for the production of lactic acid (LA) in a consolidated bioprocess, followed by the enzymatic synthesis of PLA. Lactic acid bacteria (LAB) and the fungus Rhizopus oryzae were evaluated as natural LA producers in pure cultures or in fungal–lactobacteria co-cultures formed by an LAB and a fungus selected for its metabolic capacity to degrade starch and to form consortia with LAB. Microbial interaction was analyzed by scanning electron microscopy and biofilm production was quantified. The results show that the fungus Talaromyces amestolkiae and Lactiplantibacillus plantarum M9MG6-B2 establish a cooperative relationship to exploit the sugars from polysaccharides provided as carbon sources. Addition of the quorum sensing molecule dodecanol induced LA metabolism of the consortium and resulted in improved cooperation, producing 99% of the maximum theoretical yield of LA production from glucose and 65% from starch. Finally, l-PLA oligomers (up to 19-LA units) and polymers (greater than 5 kDa) were synthetized by LA polycondensation and enzymatic ring-opening polymerization catalyzed by the non-commercial lipase OPEr, naturally produced by the fungus Ophiostoma piceae. Full article

Bark beetles maintain symbiotic associations with a diversity of microbial organisms, including ophiostomatoid fungi. Studies have frequently reported the role of ophiostomatoid fungi in bark beetle biology, but how fungal symbionts interact with host chemical defenses over time is needed. We first investigated how inoculations by three fungal symbionts of mountain pine beetle affect the terpene chemistry of live lodgepole pine trees. We then conducted a complimentary laboratory experiment specifically measuring the host metabolite degradation by fungi and collected the fungal organic volatiles following inoculations with the same fungal species on lodgepole pine logs. In both experiments, we analyzed the infected tissues for their terpene chemistry. Additionally, we conducted an olfactometer assay to determine whether adult beetles respond to the volatile organic chemicals emitted from each of the three fungal species. We found that all fungi upregulated terpenes as early as two weeks after inoculations. Similarly, oxygenated monoterpene concentrations also increased by several folds (only in logs). A large majority of beetles tested showed a strong attraction to two fungal species, whereas the other fungus repelled the beetles. Together this study shows that fungal symbionts can alter host defense chemistry, assist beetles in overcoming metabolite toxicity, and provide possible chemical cues for bark beetle attraction. Full article

Vascular wilts are important diseases caused by plant pathogenic fungi that result in the rapid death of their plant hosts. This is due to a systemic defense mechanism whereby the plant induces the compartmentalization of the infected vascular system in order to reduce the propagation of the fungus. The ascomycete class Sordariomycetes contains several species that cause vascular wilts in diverse plant hosts, and they can be classified into four taxonomic orders. The genetic mechanisms of pathogenesis have already been investigated in Fusarium and Verticillium species, but they have not yet been compared with other well-known wilt-causing species, especially fungi causing oak wilt or Dutch elm disease (DED). Here we analyzed 20 whole genome assemblies of wilt-causing fungi together with 56 other species using phylogenetic approaches to trace expansions and contractions of orthologous gene families and gene classes related to pathogenicity. We found that the wilt-causing pathogens evolved seven times, experiencing the largest fold changes in different classes of genes almost every time. However, some similarities exist across groups of wilt pathogens, particularly in Microascales and Ophiostomatales, and these include the common gains and losses of genes that make up secondary metabolite clusters (SMC). DED pathogens do not experience large-scale gene expansions, with most of the gene classes, except for some SMC families, reducing in number. We also found that gene family expansions in the most recent common ancestors of wilt pathogen groups are enriched for carbohydrate metabolic processes. Our study shows that wilt-causing species evolve primarily through distinct changes in their repertoires of pathogenicity-related genes and that there is the potential importance of carbohydrate metabolism genes for regulating osmosis in those pathogens that penetrate the plant vascular system. Full article

Ophiostoma novo-ulmi continues to be one of the most dangerous invasive fungi, destroying many autochthonous elm forests and cultures throughout the world. Searching for natural genotypes tolerant to Dutch elm disease (DED) is one of the main objectives of silviculturists all over the northern hemisphere in order to save the susceptible elms and to restore their ecosystem biodiversity. In this regard, the first trial was established between 1991 and 1994, in south-west Romania (Pădurea Verde, Timișoara), using three elm species (Ulmus minor, U. glabra, and U. laevis) with 38 provenances. A local strain of Ophiostoma novo-ulmi was used to artificially inoculate all elm variants and the DED evolution was observed. Furthermore, in 2018–2021 the trial was inventoried to understand the local genotype reaction to DED in the local environmental conditions after almost 30 years. The outcomes of the present study proved the continuous presence of the infections in the comparative culture and its proximity, but the identified pathogen had a new hybrid form (found for the first time in Romania) between O. novo-ulmi ssp. americana x O. novo-ulmi ssp. novo-ulmi. Wych elm (U. glabra) was extremely sensitive to DED: only 12 trees (out of 69 found in 2018) survived in 2021, and only one tree could be selected according to the adopted health criteria (resistance and vigour). The field elm (U. minor) was sensitive to the pathogen, but there were still individuals that showed good health status and growth. In contrast, the European white elm (U. laevis) proved constant tolerance to DED: only 15% had been found dead or presented severe symptoms of dieback. Overall, the results of this study report the diverse reactions of the Romanian regional elm genotypes to DED over the last three decades, providing promising perspectives for improving the presence of elms in the forest ecosystems of the Carpathian basin. Full article