Genetic study of the forest pest Tomicus piniperda (Col., Scolytinae) in Yunnan province (China) compared to Europe: new insights for the systematics and evolution of the genus Tomicus

Spatial Distribution Pattern and Sampling Plans for Two Sympatric Tomicus Species Infesting Pinus yunnanensis during the Shoot-Feeding Phase

Tomicus minor (Hartig) and Tomicus yunnanensis Kirkendall and Faccoli are two sympatric species that infest Pinus yunnanensis (Franchet) in southwest China, contributing to growth losses. Accurate sampling plans are needed to make informed control decisions for these species. We investigated three pine forests within experimental sites in Yuxi, Yunnan province, China from 2016 to 2018. The spatial distribution patterns of two pine shoot beetles during the shoot-feeding phase were determined using Taylor's power law. The optimum sample sizes and stop lines for precision levels of 0.25 and 0.10 were calculated. The model was validated using an additional 15 and 17 independent field datasets ranging in density from 0.06 to 1.90 beetles per tree. T. minor and T. yunnanensis adults showed aggregated spatial distributions. For T. minor, sample sizes of 41 and 259 trees were adequate for a D of 0.25 and 0.10, respectively, while for T. yunnanensis, a mean density of one individual per tree required sample sizes of 33 plants (D = 0.25) and 208 plants (D = 0.10). The software simulations of this sampling plan showed precision levels close to the desired levels. At a fixed-precision level of 0.25, sampling is easily achievable. This sampling program is useful for the integrated pest management (IPM) of two sympatric Tomicus species.

Identification of ophiostomatalean fungi associated with Tomicus pilifer infesting Pinus koraiensis in Northeastern China

Ophiostomatalean fungi usually facilitate bark beetles to infest tree hosts and seriously endanger the health of coniferous forests. Tomicus pilifer Spessivtsev is a common endemic bark beetle in Asia and primarily threatens Pinus koraiensis. Tomicus species have similar morphology; however, they can be differentiated by their genetic characteristics through phylogenetic analyses. To date, the 28S rDNA sequence of T. pilifer and the diversity of ophiostomatalean fungi associated with T. pilifer have not been reported. In this study, we aimed to clarify the taxonomic status of T. pilifer and identify ophiostomatalean fungi associated with T. pilifer infesting P. koraiensis in northeastern China. In total, 315 ophiostomatalean fungal strains were isolated from 62 adults of T. pilifer and 220 tissue samples from T. pilifer galleries in Jilin Province. Thirty-five representative strains were further identified by comparing their morphological and physiological characteristics and conducting the phylogenetic analysis of ITS, ITS2-LSU, TUB2, and TEF1-α. We identified nine species of ophiostomatalean fungi belonging to four genera, which included six novel species (Ceratocystiopsis changbaiensis sp. nov., Leptographium linjiangense sp. nov., Leptographium qieshaoense sp. nov., Ophiostoma piliferi sp. nov., Ophiostoma tonghuaense sp. nov., and Ophiostoma yaluense sp. nov.), two previously described species (Graphilbum interstitiale and Ophiostoma fuscum), and one undefined specie (Ceratocystiopsis sp. 1). To the best of our knowledge, this is the first report of G. interstitiale and O. fuscum in China and the fungal diversity of ophiostomatalean in T. pilifer. The dominant species were O. piliferi and L. qieshaoense, representing 39.37% and 35.87% of the isolates, respectively. The results of this study provide valuable information on the symbiotic relationship between bark beetles and ophiostomatalean fungi.

DNA Barcoding Subtropical Aphids and Implications for Population Differentiation

DNA barcoding has proven its worth in species identification, discovering cryptic diversity, and inferring genetic divergence. However, reliable DNA barcode reference libraries that these applications depend on are not available for many taxonomic groups and geographical regions. Aphids are a group of plant sap sucking insects, including many notorious pests in agriculture and forestry. The aphid fauna of the subtropical region has been understudied. In this study, based on extensive sampling effort across main subtropical areas, we sequenced 1581 aphid specimens of 143 morphospecies, representing 75 genera, and 13 subfamilies, to build the first comprehensive DNA barcode library for subtropical aphids. We examined the utility of DNA barcodes in identifying aphid species and population differentiation and evaluated the ability of different species delimitation methods (automatic barcode gap discovery (ABGD), generalized mixed Yule-coalescent (GMYC), and Bayesian Poisson tree processes (bPTP)). We found that most aphid species demonstrated barcode gaps and that a threshold value of 2% genetic distance is suitable for distinguishing most species. Our results indicated that ten morphospecies may have species divergence related to factors such as host plant or geography. By using two pest species Aphis spiraecola and A. gossypii as examples, we also discussed the effect of the sampling scale of host plants on the results and reliability of DNA barcoding of phytophagous insects. This DNA barcode library will be valuable for future studies and applications.

Diaphorina citri (Hemiptera: Psylloidea) in China: Two Invasion Routes and Three Transmission Paths

Diaphorina citri Kuwayama (Hemiptera: Liviidae) is one of the most common pests impacting citrus orchards in southern China. Samples of D. citri were collected in southern China in order to systematically explore the genetic architecture of the species. Mitochondrial cytochrome b (Cytb) and cytochrome coxidase subunit I (COI) were amplified by polymerase chain reaction (PCR) which allowed highlighting low haplotype and nucleotide diversities among the population. Two clades could be observed in the haplotype network. Moreover, Bayesian and maximum parsimony phylogenetic trees were constructed based on the sequences of Cytb and COI. Here, we report on the significant genetic variation of the species when comparing southwestern China with other regions of southern China (southern and southeastern). This analysis also suggested that the genetic structure of D. citri in China originates may from long-term climate fluctuations concomitant with recent disturbances resulting from human activity. Combined with previous data, the present work indicates that D. citri potentially entered China through two distinct invasion routes and spread within the country via three transmission paths.

Semiochemical Regulation of the Intraspecific and Interspecific Behavior of Tomicus yunnanensis and Tomicus minor during the Shoot-Feeding Phase

Two pine shoot beetles, Tomicus yunnanensis and Tomicus minor, are the most destructive pests of Pinus yunnanensis in southwestern China. We investigated behavioral responses within and between these two species during the shoot-feeding phase using walking bioassays. We also identified the pheromonal aspects of beetles by static solid phase microextraction (SPME) and hindgut extraction following interactive communication by gas chromatography-mass spectroscopy (GC-MS). Both species were significantly attracted by their own species and the same sex, and attraction was inhibited by exposure to additional beetles or to the hindgut extracts of beetles which had shown interaction. Female and male T. minor and T. yunnanensis hindguts contained 0.19, 0.09, 0.22, and 0.05 ng/individual of (-)-trans-verbenol, respectively; following interaction with additional beetles, this increased to 16.74-292.71 ng/individual in T. minor females. Mean concentration of verbenone detected in the hindguts of female/male individuals of T. minor and T. yunnanensis under natural conditions were 0.16, 0.06, 0.03, and 0.05 ng/individual, respectively, but these correspondingly increased to 5.90, 2.43, 0.06, and 0.19 ng/individual after exposure to additional insects. In T. yunnanensis, the amounts of detectable (-)-trans-verbenol and verbenone extracted from hindguts were lower than those from T. minor. The levels of cis-verbenol and (-)-trans-verbenol most attractive to walking T. yunnanensis and T. minor were 0.1 and 1.0 ng/μl, respectively. Verbenone was not attractive at any of the concentrations tested. The addition of verbenone to cis-verbenol or (-)-trans-verbenol reduced the attraction responses. We conclude that the (-)-trans-verbenol produced by these two pine shoot beetles is attractive at low concentrations and repellant at high concentrations, thereby fostering intraspecific competition. Verbenone is produced to prevent overcrowding via interspecific inhibition, and to expel beetles during shoot-feeding.

Landscape-scale genetic differentiation of a mycangial fungus associated with the ambrosia beetle, Xylosandrus germanus (Blandford) (Curculionidae:Scolytinae) in Japan

In this study, we examined the genetic structures of the ambrosia fungus isolated from mycangia of the scolytine beetle, Xylosandrus germanus to understand their co‐evolutionary relationships. We analyzed datasets of three ambrosia fungus loci (18S rDNA, 28S rDNA, and the β‐tubulin gene) and a X. germanus locus dataset (cytochrome c oxidase subunit 1 (COI) mitochondrial DNA). The ambrosia fungi were separated into three cultural morphptypes, and their haplotypes were distinguished by phylogenetic analysis on the basis of the three loci. The COI phylogenetic analysis revealed three distinct genetic lineages (clades A, B, and C) within X. germanus, each of which corresponded to specific ambrosia fungus cultural morphptypes. The fungal symbiont phylogeny was not concordant with that of the beetle. Our results suggest that X. germanus may be unable to exchange its mycangial fungi, but extraordinary horizontal transmission of symbiotic fungi between the beetle's lineages occurred at least once during the evolutionary history of this symbiosis.

Genomic Mining of Phylogenetically Informative Nuclear Markers in Bark and Ambrosia Beetles

Deep level insect relationships are generally difficult to resolve, especially within taxa of the most diverse and species rich holometabolous orders. In beetles, the major diversity occurs in the Phytophaga, including charismatic groups such as leaf beetles, longhorn beetles and weevils. Bark and ambrosia beetles are wood boring weevils that contribute 12 percent of the diversity encountered in Curculionidae, one of the largest families of beetles with more than 50000 described species. Phylogenetic resolution in groups of Cretaceous age has proven particularly difficult and requires large quantity of data. In this study, we investigated 100 nuclear genes in order to select a number of markers with low evolutionary rates and high phylogenetic signal. A PCR screening using degenerate primers was applied to 26 different weevil species. We obtained sequences from 57 of the 100 targeted genes. Sequences from each nuclear marker were aligned and examined for detecting multiple copies, pseudogenes and introns. Phylogenetic informativeness (PI) and the capacity for reconstruction of previously established phylogenetic relationships were used as proxies for selecting a subset of the 57 amplified genes. Finally, we selected 16 markers suitable for large-scale phylogenetics of Scolytinae and related weevil taxa.

Attack pattern and reproductive ecology of Tomicus brevipilosus (Coleoptera: Curculionidae) on Pinus yunnanensis in Southwestern China

Tomicus brevipilosus (Eggers) (Coleoptera: Curculionidae, Scolytinae) was recently discovered as a new pest of Yunnan pine (Pinus yunnanensis Franchet) in Yunnan Province in southwestern China. However, little was known on its reproductive biology and pattern of trunk attack on Yunnan pine. The objectives of this study were to better understand the reproductive biology of T. brevipilosus by investigating the seasonality of trunk attacks by parent adults for the purpose of reproduction (i.e., breeding attacks) and the within-tree pattern of these attacks. Our results showed that T. brevipilosus breeding attacks in P. yunnanensis generally started in early March and ended in early June in Anning County, Yunnan. T. brevipilosus exhibited two general patterns of infestation. From early March to mid-April, T. brevipilosus bred preferentially in the trunks of Yunnan pine trees that were already infested by Tomicus yunnanensis Kirkendall and Faccoli and Tomicus minor (Hartig), colonizing spaces along the trunk (mostly in the mid- and lower trunk) that were not already occupied by the other two Tomicus species. Later, from about mid-April to early June, when there were no Yunnan pine trees newly infested by T. yunnanensis and T. minor, T. brevipilosus attacked Yunnan pine by itself, infesting the lower parts of the trunk first and then infesting progressively upward along the trunk into the crown. Infestation by T. brevipilosus extends the total period that P. yunnanensis trees are under attack by Tomicus beetles in southwestern China, which helps explain why Yunnan pine has suffered high levels of tree mortality in recent decades.

Origin and expansion of the Yunnan Shoot Borer, Tomicus yunnanensis (coleoptera: scolytinae): a mixture of historical natural expansion and contemporary human-mediated relocation

The Yunnan shoot borer, Tomicus yunnanensis, is a recently-discovered, aggressive pest of the Yunnan pine stands in southwestern China. Despite many bionomics studies and massive controlling efforts, research on its population genetics is extremely limited. The present study, aimed at investigating the origin and dispersal of this important forestry pest, analyzed the population genetic structure and demographic history using a mitochondrial cox1 gene fragment. Our results showed that T. yunnanensis most likely originated from the Central-Yunnan Altiplano, and the divergence time analysis placed the origin approximately 0.72 million-years ago. Host separation and specialization might have caused the speciation of T. yunnanensis. Genetic structure analyses identified two population groups, with six populations near the origin area forming one group and the remaining six populations from western and eastern Yunnan and southwestern Sichuan comprising the other. Divergence time analysis placed the split of the two groups at approximately 0.60 million-years ago, and haplotype phylogenetic tree, network, as well as migration rate suggested that populations of the latter group were established via a small number of individuals from the former one. Migration analysis also showed a certain degree of recent expansion from southwestern Sichuan to eastern Yunnan. Our findings implied that T. yunnanensis underwent both historical expansion and recent dispersal. The historical expansion may relate to the oscillation of regional climate due to glacial and interglacial periods in the Pleistocene, while human-mediated transportation of pine-wood material might have assisted the relocation and establishment of this pest in novel habitats.

Ancestral state reconstruction for Dendroctonus bark beetles: evolution of a tree killer

While most bark beetles attack only dead or weakened trees, many species in the genus Dendroctonus have the ability to kill healthy conifers through mass attack of the host tree, and can exhibit devastating outbreaks. Other species in this group are able to successfully colonize trees in small numbers without killing the host. We reconstruct the evolution of these ecological and life history traits, first classifying the extant Dendroctonus species by attack type (mass or few), outbreaks (yes or no), host genus (Pinus and others), location of attacks on the tree (bole, base, etc.), whether the host is killed (yes or no), and if the larvae are gregarious or have individual galleries (yes or no). We then estimated a molecular phylogeny for a data set of cytochrome oxidase I sequences sampled from nearly all Dendroctonus species, and used this phylogeny to reconstruct the ancestral state at various nodes on the tree, employing maximum parsimony, maximum likelihood, and Bayesian methods. Our reconstructions suggest that extant Dendroctonus species likely evolved from an ancestor that killed host pines through mass attack of the bole, had individual larvae, and exhibited outbreaks. The ability to colonize a host tree in small numbers (as well as gregarious larvae and attacks at the tree base) apparently evolved later, possibly as two separate events in different clades. It is likely that tree mortality and outbreaks have been continuing features of the interaction between conifers and Dendroctonus bark beetles.

What is Next in Bark Beetle Phylogeography?

Bark beetle species within the scolytid genera Dendroctonus, Ips, Pityogenes and Tomicus are known to cause extensive ecological and economical damage in spruce and pine forests during epidemic outbreaks all around the world. Dendroctonus ponderosae poses the most recent example having destroyed almost 100,000 km² of conifer forests in North America. The success and effectiveness of scolytid species lies mostly in strategies developed over the course of time. Among these, a complex system of semiochemicals promotes the communication and aggregation on the spot of infestation facilitating an en masse attack against a host tree's defenses; or an association with fungi that evolved either in the form of nutrition (ambrosia fungi) or even by reducing the resistance of host trees (blue-stain fungi). Although often specific to a tree genus or species, some bark beetles are polyphagous and have the ability to switch on to new hosts and extend their host range (i.e., between conifer genera such as Pityogenes chalcographus or even from conifer to deciduous trees as Polygraphus grandiclava). A combination of these capabilities in concert with life history or ecological traits explains why bark beetles are considered interesting subjects in evolutionary studies. Several bark beetle species appear in phylogeographic investigations, in an effort to improve our understanding of their ecology, epidemiology and evolution. In this paper investigations that unveil the phylogeographic history of bark beetles are reviewed. A close association between refugial areas and postglacial migration routes that insects and host trees have followed in the last 15,000 BP has been suggested in many studies. Finally, a future perspective of how next generation sequencing will influence the resolution of phylogeographic patterns in the coming years is presented. Utilization of such novel techniques will provide a more detailed insight into the genome of scolytids facilitating at the same time the application of neutral and non-neutral markers. The latter markers in particular promise to enhance the study of eco-physiological reaction types like the so-called pioneer beetles or obligate diapausing individuals.

Spatial genetic structure of the mountain pine beetle (Dendroctonus ponderosae) outbreak in western Canada: historical patterns and contemporary dispersal

Environmental change has a wide range of ecological consequences, including species extinction and range expansion. Many studies have shown that insect species respond rapidly to climatic change. A mountain pine beetle epidemic of record size in North America has led to unprecedented mortality of lodgepole pine, and a significant range expansion to the northeast of its historic range. Our goal was to determine the spatial genetic variation found among outbreak population from which genetic structure, and dispersal patterns may be inferred. Beetles from 49 sampling locations throughout the outbreak area in western Canada were analysed at 13 microsatellite loci. We found significant north-south population structure as evidenced by: (i) Bayesian-based analyses, (ii) north-south genetic relationships and diversity gradients; and (iii) a lack of isolation-by-distance in the northernmost cluster. The north-south structure is proposed to have arisen from the processes of postglacial colonization as well as recent climate-driven changes in population dynamics. Our data support the hypothesis of multiple sources of origin for the outbreak and point to the need for population specific information to improve our understanding and management of outbreaks. The recent range expansion across the Rocky Mountains into the jack/lodgepole hybrid and pure jack pine zones of northern Alberta is consistent with a northern British Columbia origin. We detected no loss of genetic variability in these populations, indicating that the evolutionary potential of mountain pine beetle to adapt has not been reduced by founder events. This study illustrates a rapid range-wide response to the removal of climatic constraints, and the potential for range expansion of a regional population.

Global transcriptome profiling of the pine shoot beetle, Tomicus yunnanensis (Coleoptera: Scolytinae)

Background

The pine shoot beetle Tomicus yunnanensis (Coleoptera: Scolytinae) is an economically important pest of Pinus yunnanensis in southwestern China. Developed resistance to insecticides due to chemical pesticides being used for a long time is a factor involved in its serious damage, which poses a challenge for management. In addition, highly efficient adaptation to divergent environmental ecologies results in this pest posing great potential threat to pine forests. However, the molecular mechanisms remain unknown as only limited nucleotide sequence data for this species is available.

Methodology/Principal Findings

In this study, we applied next generation sequencing (Illumina sequencing) to sequence the adult transcriptome of T. yunnanensis. A total of 51,822,230 reads were obtained. They were assembled into 140,702 scaffolds, and 60,031 unigenes. The unigenes were further functionally annotated with gene descriptions, Gene Ontology (GO), Clusters of Orthologous Groups (COG), and Kyoto Encyclopedia of Genes and Genome (KEGG). In total, 80,932 unigenes were classified into GO, 13,599 unigenes were assigned to COG, and 33,875 unigenes were found in KO categories. A biochemical pathway database containing 219 predicted pathways was also created based on the annotations. In depth analysis of the data revealed a large number of genes related to insecticides resistance and heat shock protein genes associated with environmental stress.

Conclusions/Significance

The results facilitate the investigations of molecular resistance mechanisms to insecticides and environmental stress. This study lays the foundation for future functional genomics studies of important biological questions of this pest.

Genetic structure of Japanese populations of Xylosandrus brevis (Curculionidae: Scolytinae)

We examined the genetic structure of populations of an ambrosia beetle, Xylosandrus brevis (Eichhoff) (Curculionidae: Scolytinae), to understand its colonization dynamics. We collected specimens from 20 sites in Japan and studied the genetic structure of these populations using portions of the mitochondrial cytochrome oxidase I gene (COI). A phylogenetic analysis showed three distinct lineages (clades A, B, and C) within X. brevis. Clade A had 65 haplotypes from all the populations, except for populations from Nagano (Chiisagata-gun) and the Ryukyu Islands (Ishigaki), whereas clade B had 14 haplotypes from nine populations (Yamagata, Saitama, Shimo-Minochi-gun, Chiisagata-gun, Toyota, Watarai-gun, Wakayama, Tottori, and Kochi), and clade C had 6 haplotypes from the Ryukyu Islands (Ishigaki) population (and nowhere else). Nested clade phylogeographic analysis showed 65 clade A haplotypes and 14 clade B haplotypes geographically structured in two clades, respectively. A contact zone was identified in the Chubu and Tokai areas. Our results suggest that gene flow and individual movement of X. brevis between the Ryukyu Islands and the other three main islands of Japan has been rare, and X. brevis may be divided into two populations, eastern-central and northern-western, with little gene flow between the four areas of western Japan (Kinki, Chugoku, Shikoku, and Kyushu).

Comparative analysis of sequences and secondary structures of the rRNA internal transcribed spacer 2 (ITS2) in pollen beetles of the subfamily Meligethinae (Coleoptera, Nitidulidae): potential use of slippage-derived sequences in molecular systematics

A comparative analysis of ITS2 sequences and secondary structures in 89 species of pollen beetles of the subfamily Meligethinae (Coleoptera, Nitidulidae) was performed. The ITS2 folding pattern was highly conserved and comparable with the general model proposed for eukaryotes. Simple sequence repeats (SSRs) were responsible for most of the observed nucleotide variability (approximately 1-3%) and length variation (359-459bp). When plotted on secondary structures, SSRs mapped in expansion segments positioned at the apices of three ITS2 helices ('A', 'B' and 'D1') and appeared to have evolved under mechanisms of compensatory slippage. Homologies among SSRs nucleotides could not be unambiguously assigned, and thus were not useful to resolve phylogeny. However, slippage-derived motifs provided some preliminary genetic support for newly proposed taxonomic arrangements of several genera and subgenera of Meligethinae, corroborating existing morphological and ecological datasets.

Responses of the Mediterranean pine shoot beetle Tomicus destruens (Wollaston) to pine shoot and bark volatiles

The pine shoot beetle Tomicus destruens has two dispersal phases per generation. In the first, mature adults move toward trunks of dying pines to lay eggs; in the second, callow adults move toward the shoots of healthy pines for maturation feeding. However, there is no information on the chemical stimuli that govern host selection by T. destruens adults. The aims of this study were: (1) to identify the volatiles released by shoots and bark of stone pine that are behaviorally and electrophysiologically active on T. destruens; (2) to verify which blends and concentrations of such volatiles are differently active on males and females, as well as on callow and mature adults, during the two host search phases (breeding and feeding). A four-arm olfactometer was used to test the behavior of walking T. destruens adults toward various sources of volatiles including fresh shoots and bark, their collected volatiles, and two synthetic blends. For each odor, the behavior of both callow and mature males and females was recorded individually. Shoot and bark extracts were analyzed by coupled gas chromatography and mass spectrometry (GC-MS), and tested by gas chromatography coupled with electroantennography (GC-EAD) on T. destruens males and females. Two blends of two (alpha-pinene and beta-myrcene; blend A) and three (alpha-pinene, beta- myrcene, and alpha-terpinolene; blend B) synthetic compounds, chosen among those that induce EAD responses and known to be attractive for other bark beetle species, were tested in the olfactometer at five concentrations. Insect behavior was affected by the degree of sexual maturation but not by sex. Callow insects were attracted by shoots and their extracts, while mature individuals by bark and its extracts. Six extracted compounds were active on T. destruens antennae: limonene, (Z)-3-hexen-1-ol and beta-caryophyllene, alpha-pinene, beta-myrcene, and alpha-terpinolene. alpha-Terpinolene, released only by bark, was active only on mature insects, whereas (Z)-3-hexen-1-ol, released only by shoots, was active only on callows. Males and females showed similar EAD responses. Of the six extracted volatiles, two were attractive for callow adults (blend A) and three for matures (blend B). In both cases, responses were positively correlated with blend concentration, although a repellent effect was noted at the highest concentrations.

Phylogeographic structure and past history of the circum-Mediterranean species Tomicus destruens Woll. (Coleoptera: Scolytinae)

Phylogeographic studies are often focused on temperate European species with relict footholds in the Mediterranean region. Past climatic oscillations usually induced range contractions and expansions from refugial areas located in southern Europe, and spatial distribution of genetic diversity show that northward expansions were usually pioneer-like. Actually, few studies have focused on circum-Mediterranean species, which probably were not influenced in the same way by climatic oscillations. We present the phylogeography of the bark beetle Tomicus destruens, which is restricted to the whole Mediterranean basin and the Atlantic coasts of North Africa and Portugal. We systematically sequenced 617 bp of the mitochondrial genes COI and COII for 42 populations (N = 219). Analysis revealed 53 haplotypes geographically structured in two clades, namely eastern and western clades, that diverged during the Pleistocene. A contact zone was identified along the Adriatic coast of Italy. Interestingly, we found contrasting levels of genetic structure within each clade. The eastern group was characterized by a significant phylogeographic pattern and low levels of gene flow, whereas the western group barely showed a spatial structure in haplotype distribution. Moreover, the main pine hosts were different between groups, with the Aleppo-brutia complex in the east and the maritime pine in the west. Potential roles of host species, climatic parameters and geographical barriers are discussed and the phylogeographic patterns are compared to classical models of postglacial recolonization in Europe.

A new Leptographium species associated with Tomicus piniperda infesting pine logs in Korea

During the course of a survey of sapstaining fungi in Korea, a Leptographium was isolated from Pinus densiflora and P. koraiensis logs, infested with the bark beetle Tomicus piniperda. The fungus grew optimally at 25 C on 2% malt extract agar and showed a high level of tolerance to cycloheximide. The Leptographium has unusually short conidiophores and is morphologically similar to L. pini-densiflorae, L. lundbergii, L. yunnanense, and the Leptographiumn anamorph of Ophiostoma crassivaginatum. Comparisons of DNA sequence data for three gene regions, as well as morphological characteristics, confirmed that this fungus represents an undescribed taxon. We consequently provide the name Leptographium koreanum sp. nov. for it here.