Transmission of Bursaphelenchus xylophilus between Monochamus alternatus and Monochamus saltuarius through interspecific mating behaviour

Cerambycid adults of the genus Monochamus transmit the pine wood nematode (Bursaphelenchus xylophilus [Steiner et Buhrer] Nickle), the causative agent of pine wilt disease. To confirm the transmission of B. xylophilus between vector species, nematode‐infected Monochamus alternatus Hope and nematode‐free Monochamus saltuarius (Gebler) adults were paired and their behaviour was observed for 107–220 min. In three pairs that exhibited mounting without copulation, nematode transmission occurred, whereas it was not found in another pair without mountings. The effect of nematode transmission between different vector species on the invasion biology of B. xylophilus is discussed.     

Trapping strategy for Monochamus sutor and Monochamus galloprovincialis: potential vectors of the pine wood nematode in Scandinavia

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松材线虫及其关键传媒墨天牛的研究进展

松材线虫Bursaphelenchusxylophilus (Steiner&Buhere,1 93 4Nickle,1 981 )是一种世界多国公认的重大外来生物。其原产地在美国 ,但松材线虫并不严重危害该国松林 ;日本受害最重 ,经过几十年的研究与防治 ,现已基本能控制松材线虫病大发生。自 1 982年我国南京中山陵首次发现松材线虫以来 ,其在我国的扩散趋势越来越明显 ,现已成为我国一种重要入侵病原生物。它不但对我国南方数百万公顷松林构成毁灭性威胁 ,影响我国经济和社会可持续发展 ,而且将破坏我国一些著名风景名胜区、文化遗产地。同时 ,松材线虫正成为一项技术壁垒 ,严重影响我国的进出口贸易。该文简要从松材线虫及其关键传煤墨天牛Monochamusspp .的生物学特性、分布状况 ,松材线虫病的蔓延条件及影响因素等方面概述国内外的研究动态 ,以期为我国对松材线虫的研究与防治工作提供参考     

Transmission of the pine wood nematode Bursaphelenchus xylophilus through feeding activity of Monochamus galloprovincialis (Col., Cerambycidae)

Abstract:  Transmission of the pinewood nematode (PWN) Bursaphelenchus xylophilus (Steiner & Bührer) Nickle to Pinus pinaster Aiton branches through feeding wounds of its vector in Portugal, Monochamus galloprovincialis Olivier, was studied under laboratory conditions. All the B. xylophilus -infected beetles transmitted nematodes to branches they fed. The transmission was more frequent during the first 6 weeks after emergence, with transmission peaks during the second and the sixth week. The adult M. galloprovincialis transmitted nematodes for a mean of 5 weeks, independently of the beetle's sex or longevity. No relation was found between beetle feeding intensity and effective transmission of B. xylophilus to the branches. The nematode transmission ceased after the ninth week, even in insects which still had B. xylophilus on their bodies. The longevity of the nematode-free insects (control group) was slightly higher than the B. xylophilus -infected beetles, although with no significant difference. The results emphasize the necessity to control the immature stages of M. galloprovincialis prior to emergence and develop efficient strategies to capture and eliminate the recently emerged beetles, as majority of the nematode infection of healthy pine trees occurs during a short period of few weeks after beetle emergence.     

季也蒙假丝酵母对松材线虫病的抑制作用

松材线虫病是重要的森林病害,该病与松材线虫携带的病原菌和松树的内生病原菌密切相关。在室内条件下,初步研究了从人工培养的松材线虫上分离到的菌株C对松材线虫病的抑制作用。在健康的水培马尾松枝上分别接种松材线虫接种液、菌株C接种液、松材线虫与菌株C的混合接种液。处理后松枝的相对重量与相对蒸腾强度均为:接种菌株C的松枝>混合接种的松枝>接种线虫的松枝。处理后15d时,接种线虫的松枝与混合接种的松枝的相对重量有显著性差异(p<0.05)。接种线虫松枝的存活期显著短于其它处理松枝的存活期(p<0.05)。接种菌株C的针叶褐变株数少于接种线虫的松枝,两者有显著性差异(p<0.05)。从接种线虫和混合接种的所有松枝中都分离到松材线虫,且分离出的线虫量没有显著性差异。将8个月生的断根马尾松苗插入菌株C的查彼培养液的滤液中培养,6d后松苗的平均感病指数和感病株率均显著少于对照(p<0.05)。这表明,菌株C对松材线虫病有抑制作用,菌株C培养液中产生的某些代谢物质有利于松苗的抗病和存活。菌株C可能抑制了松树上的内生病原菌和松材线虫携带的病原微生物,或提高了松树的生长力和抗逆能力。经电子显微镜观察并参照AP I 20 C AUX鉴定系统鉴定,菌株C为季也蒙假丝酵母C and id a gu ilierm ond ii。     

2‐(Undecyloxy)‐ethanol is a major component of the male‐produced aggregation pheromone of Monochamus sutor

The small white‐marmorated longicorn beetle, Monochamus sutor (L.) (Coleoptera: Cerambycidae), is widely distributed throughout Europe and Asia. It is a potential vector of the pine wood nematode, Bursaphelenchus xylophilus (Steiner et Buhrer) Nickle, the causal agent of the devastating pine wilt disease. Volatiles were collected from both male and female beetles after maturation feeding. In analyses of these collections using gas chromatography (GC) coupled to mass spectrometry, a single male‐specific compound was detected and identified as 2‐(undecyloxy)‐ethanol. In analyses by GC coupled to electroantennography the only consistent responses from both female and male antennae were to this compound. Trapping tests were carried out in Spain, Sweden, and China. 2‐(Undecyloxy)‐ethanol was attractive to both male and female M. sutor beetles. A blend of the bark beetle pheromones ipsenol, ipsdienol, and 2‐methyl‐3‐buten‐2‐ol was also attractive to both sexes in Spain and Sweden, and further increased the attractiveness of the 2‐(undecyloxy)‐ethanol. The host plant volatiles α‐pinene, 3‐carene, and ethanol were weakly attractive, if at all, in all three countries and did not significantly increase the attractiveness of the blend of 2‐(undecyloxy)‐ethanol and bark beetle pheromones. 2‐(Undecyloxy)‐ethanol is thus proposed to be the major, if not only, component of the male‐produced aggregation pheromone of M. sutor, and its role is discussed. This compound has been reported as a pheromone of several other Monochamus species and is another example of the parsimony that seems to exist among the pheromones of many of the Cerambycidae. Traps baited with 2‐(undecyloxy)‐ethanol and bark beetle pheromones should be useful for monitoring and control of pine wilt disease, should M. sutor be proven to be a vector of the nematode.     

Pine wilt disease in Yunnan,China: Evidence of non-local pine sawyer Monochamus alternatus (Coleoptera: Cerambycidae) populations revealed by mitochondrial DNA

Abstract Monochamus alternatus (Hope) specimens were collected from nine geographical populations in China, where the pinewood nematode Bursaphelenchus xylophilus (Steiner et Buhrer) was present. There were seven populations in southwestern China in Yunnan Province (Ruili, Wanding, Lianghe, Pu’er, Huaning, Stone Forest and Yongsheng), one in central China in Hubei Province (Wuhan), and one in eastern China in Zhejiang Province (Hangzhou). Twenty-two polymorphic sites were recognized and 18 haplotypes were established by analyzing a 565 bp gene fragment of mitochondrial cytochrome oxidase subunit II (CO II). Kimura two-parameter distances demonstrated that M. alternatus populations in Ruili, Wanding and Lianghe (in southwestern Yunnan) differed from the other four Yunnan populations but were similar to the Zhejiang population. No close relationship was found between the M. alternatus populations in Yunnan and Hubei. Phylogenetic reconstruction established a neighbor-joining (NJ) tree, which divided haplotypes of southwestern Yunnan and the rest of Yunnan into different clades with considerable bootstrapping values. Analysis of molecular variance and spatial analysis of molecular variance also suggested significant genetic differentiation between M. alternatus populations in southwestern Yunnan and the rest of Yunnan. Our research suggests that non-local populations of M. alternates, possibly from eastern China, have become established in southwestern Yunnan.     

Combining pheromone and kairomones for effective trapping of the pine sawyer beetle Monochamus galloprovincialis

Monochamus galloprovincialis (Olivier) (Coleoptera: Cerambycidae) is a secondary wood borer that acquired primordial importance since it was identified as the European vector of Bursaphelenchus xylophilus, the causal agent of pine wilt disease (PWD). An effective trapping method is needed as a tool for managing this insect vector and allowing early detection of nematode transportation. Among effective attractants identified in recent years are the specific M. galloprovincialis aggregation pheromone, host pine kairomones such as α‐pinene and bark beetle kairomones like ipsenol and methyl‐butenol. The main objective of this study was to optimize the combination of these volatiles to improve lure attractiveness and specificity. Based on ten complementary field experiments, we found a pheromone dose‐response of trap catches. The best combination of attractants was the aggregation pheromone plus two bark beetle kairomones, ipsenol and methyl‐butenol. Addition of pine terpenes, such as α‐pinene, did not significantly improve M. galloprovincialis trap capture, but did increase catch of non target species, including natural enemies. The use of pine terpenes would be advisable only if priorizing to maximize removal of vectors. While this research has lead to the development a new, highly attractive commercial lure for mature pine sawyers, none of the tested blends were successful in attracting immature pine sawyer adults. Further investigation is needed to develop attractants for these beetles.     

皮下接种松墨天牛卵及幼虫致死松树的研究

为了探明松墨天牛MonochamusalternatusHope直接致死松树的作用 ,作者采用在健康松树皮下接入松墨天牛卵或初孵幼虫方法做了试验和观察。结果表明 ,接入卵或初孵幼虫的松树平均枯死率为41 . 7%。松树枯死取决于松墨天牛幼虫取食时对松树韧皮部的破坏程度。每株接入 5个单位 (1单位指1粒卵或条初孵幼虫 ) ,松树枯死率达 85. 7% ;接入 1个单位 ,枯死率为 1 0 %。初步结论是 ,松墨天牛是引起松树枯死的主要原因之一 ;大力防治松墨天牛是保护我国松林的关键。     

Dispersal capacity of Monochamus galloprovincialis,the European vector of the pine wood nematode,on flight mills

The pine wood nematode (Bursaphelenchus xylophilus), which causes the symptoms of pine wilt disease, is recognized worldwide as a major forest pest. It was introduced into Portugal in 1999. It is transmitted between trees almost exclusively by longhorn beetles of the genus Monochamus, including, in particular, M. galloprovincialis (Coleoptera: Cerambycidae) in maritime pine forests. Accurate estimates of the flight capacity of this insect vector are required if we are to understand and predict the spread of pine wilt disease in Europe. Using computer‐linked flight mills, we evaluated the distance flown, the flight probability and speed of M. galloprovincialis throughout adulthood and investigated the effects of age, sex and body weight on these flight performances, which are proxies for dispersal capacity. The within‐population variability of flight performance in M. galloprovincialis was high, with a mean distance of 16 km flown over the lifetime of the beetle. Age and body weight had a significant positive effect on flight capacity, but there was no difference in performance between males and females. These findings have important implications for managing the spread of the pine wood nematode in European forests.     

Pathogenesis in Pine Wilt Caused by Pinewood Nematode, Bursaphelenchus xylophilus

The progression of events in the development of pine wilt disease following the invasion by Bursaphelenchus xylophilus is reviewed from early migration through pine tissues until symptom development on foliage. Disease resistance in pines, especially the hypersensitive reaction that is successful in controlling many potential pests and pathogens, is explored. Pathologies resulting from the activities of pinewood nematode include cortical trails and cavities; formation of cambial gaps and traumatic resin cysts; browning and death of cortex, phloem, cambium, and ray tissues; granulation and shrinkage of cell cytoplasm in rays; and destruction of resin canal epithelial and ray parenchyma cells. Death of parenchyma, production of toxins, and leakage of oleoresins and other material into tracheids are typical of the hypersensitive reaction occurring in pines following migration of small numbers of pinewood nematodes. The hypothesis presented is that a spreading hypersensitive reaction results in some of the observed pathologies and symptoms and eventually causes pine death. The growth-differentiation balance hypothesis is used to help explain predisposition, oleoresin production and toxicity, susceptibility and resistance, and the effects of variation in climate on host pines as related to pinewilt disease.     

Effect of Monochamus carolinensis on the Life History of the Pinewood Nematode,Bursaphelenchus xylophilus

The development of Bursaphelenchus xylophilus in pine wood infested with and free of Monochamus carolinensis was investigated. Formation of third-stage dispersal juveniles occurred in the presence and absence of pine sawyer beetles. The proportion of third-stage dispersal juveniles in the total nematode population was negatively correlated with moisture content of the wood. Formation of nematode dauer juveniles was dependent on the presence of the pine sawyer beetle. Dauer juveniles were present in 3 of 315 wood samples taken from non-beetle-infested Scots pine bolts and 81 of 311 samples taken from beetle-infested bolts. Nematode densities were greater in wood samples taken adjacent to insect larvae, pupae, and teneral adults compared with samples taken from areas void of insect activity. Nematodes recovered from beetle larvae, pupae, and teneral adults were mostly fourth-stage dauer juveniles, although some third-stage dispersal juveniles were also recovered. Dauer juvenile density was highest on teneral adult beetles.     

A novel,easy method for estimating pheromone trap attraction range: application to the pine sawyer beetle Monochamus galloprovincialis

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Geographical variation in seasonality and life history of pine sawyer beetles Monochamus spp: its relationship with phoresy by the pinewood nematode Bursaphelenchus xylophilus

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Population dynamics of bacteria associated with different strains of the pine wood nematode Bursaphelenchus xylophilus after inoculation in maritime pine (Pinus pinaster)

For a long time it was thought that Bursaphelenchus xylophilus was the only agent of the pine wilt disease. Recently, it was discovered that there are bacteria associated with the nematodes that contribute to the pathogenesis of this disease, mainly through the release of toxins that promote the death of the pines. Among the species most commonly found, are bacteria belonging to the Bacillus, Pantoea, Pseudomonas and Xanthomonas genera.The main objective of this work was to study the effect of inoculation of maritime pine (Pinus pinaster) with four different nematode isolates, in the bacterial population of nematodes and trees, at different stages of disease progression. The monitoring of progression of disease symptoms was also recorded. Also, the identification of bacteria isolated from the xylem of trees and the surface of nematodes was performed by classical identification methods, by the API20E identification system and by sequencing of bacterial DNA.The results showed that for the symptoms progression, the most striking difference was observed for the pines inoculated with the avirulent isolate, C14-5, which led to a slower and less severe aggravation of symptoms than in pines inoculated with the virulent isolates. In general, it was found that bacterial population, inside the tree, increased with disease progression. A superior bacterial quantity was isolated from pines inoculated with the nematode isolates HF and 20, and, comparatively, few bacteria were isolated from pines inoculated with the avirulent isolate. The identification system API20E was insufficient in the identification of bacterial species; Enterobacter cloacae species was identified in 79% of the isolated bacterial colonies and seven of these colonies could not be identified by this method. Molecular identification methods, through bacterial DNA sequencing, allowed a more reliable identification: eleven different bacterial species within the Bacillus, Citrobacter, Enterobacter, Escherichia, Klebsiella, Paenibacillus, Pantoea and Terribacillus genera were identified. General bacterial diversity increased with the progression of the disease. Bacillus spp. were predominant at the earlier stage of disease progression and Klebsiella oxytoca at the later stages. Furthermore, bacterial species isolated from the surface of nematodes were similar to those isolated from the xylem of pines.In the present work new bacterial species were identified which have never been reported before in this type of study and may be associated with their geographical origin (Portugal). P. pinaster, the pine species used in this study, was different from those commonly grown in Japan and China. Furthermore, it was the first time that bacteria were isolated and identified from an avirulent pine wood nematode isolate.     

Synergistic attraction of pine sawyer Monochamus saltuarius (Coleoptera: Cerambycidae) to monochamol and α‐pinene

Monochamus (Coleoptera: Cerambycidae) species are longhorn pine sawyers that serve as insect vectors of the pinewood nematode Bursaphelenchus xylophilus (Nematoda: Parasitaphelenchidae), which are responsible for debilitating pine wilt disease. An aggregation pheromone, 2‐(1‐undecyloxy)‐1‐ethanol (hereafter referred to as monochamol), was shown to be effective at attracting Monochamus species. However, attraction of the pine sawyers to aggregation pheromones varied depending on semiochemicals, including host plant volatiles and kairomones. In this study, we investigated the abilities of monochamol and the host‐plant volatiles α‐pinene and ethanol to attract M. saltuarius in a pine forest in Cheongsong, Gyeongsangbuk‐do, Korea. A total of 91 M. saltuarius (28 males and 63 females) were captured. The combination of monochamol (700 mg) with α‐pinene and ethanol exhibited a synergistic effect on attracting M. saltuarius (11.0 beetles per trap), whereas monochamol alone and a mixture of α‐pinene and ethanol resulted in the capture of 3.2 beetles and 3.6 beetles per trap, respectively. Our results suggest that multi‐funnel traps baited with a blend of monochamol, α‐pinene and ethanol are highly effective for monitoring M. saltuarius and M. alternatus in pine forests.     

Temperature Effects on the Transmission of Bursaphelenchus xylophilus (Nemata: Aphelenchoididae) by Monochamus alternatus (Coleoptera: Cerambycidae)

The object of this research was to investigate the effects of ambient temperature on the transmission of the pinewood nematode, Bursaphelenchus xylophilus, by its vector, Monochamus alternatus. Ninety M. alternatus were reared individually at one of three constant temperatures (16, 20, and 25 °C). As the ambient temperature decreased from 25 to 16 °C, longevity of vectors decreased, nematode transmission efficiency decreased, and the peak period of nematode transmission was delayed and its peak height decreased. Low temperature may inhibit the transmission process, and this inhibition could be partially responsible for preventing pine wilt disease from devastating pine forests in cool regions.     

A Nondestructive Method of Determining Bursaphelenchus xylophilus Infestation of Monochamus spp. Vectors

Pine wilt is caused by the nematode Bursaphelenchus xylophilus, which is transported to host trees in the trachea of Monochamus spp. (Coleoptera: Cerambycidae). The study of the relationship between the nematode and its beetle vectors has been hampered by the inability to estimate nematode presence or density within live beetles. This report describes a rapid method for estimating nematode load within live M. carolinensis and M. alternatus by visual examination of the atrium of the first abdominal spiracle. Visual estimates of nematode numbers correlated highly with actual nematode numbers. This method is a timesaving technique for determining relative numbers of B. xylophilus in pine wilt research.     

Cloning and characterization of a 2-cys peroxiredoxin in the pine wood nematode, Bursaphelenchus xylophilus, a putative genetic factor facilitating the infestation

The pine wood nematode, Bursaphelenchus xylophilus, is an invasive plant parasitic nematode and a worldwide quarantine pest. An indigenous species in North America and the causal agent of pine wilt disease, B. xylophilus has devastated pine production in Southeastern Asia including Japan, China, and Korea since its initial introduction in the early 1900s. The reactive oxygen species (ROS) is the first line of defense utilized by host plants against parasites, while nematodes, counteractively, employ antioxidants to facilitate their infection. Peroxiredoxins (Prxs) are a large class of antioxidants recently found in a wide variety of organisms. In this report, a gene encoding a novel 2-cysteine peroxiredoxin protein in B. xylophilus was cloned and characterized. The 2-cysteine peroxiredoxin in B. xylophilus (herein refers to as "BxPrx") is highly conserved in comparison to 2-cysteine peroxiredoxins (Prx2s) in other nematodes, which have two conserved cysteine amino acids (Cp and Cr), a threonine-cysteine-arginine catalytic triad, and two signature motifs (GGLG and YF) sensitive to hydrogen peroxide. In silico assembly of BxPrx tertiary structure reveals the spatial configuration of these conserved domains and the simulated BxPrx 3-dimensional structure is congruent with its presumed redox functions. Although no signal peptide was identified, BxPrx was abundantly expressed and secreted under the B. xylophilus cuticle. Upon further analysis of this leader-less peptide, a single transmembrane α-helix composed of 23 consecutive hydrophobic amino acids was found in the primary structure of BxPrx. This transmembrane region and/or readily available ATP binding cassette transporters may facilitate the transport of non-classical BxPrx across the cell membrane. Recombinant BxPrx showed peroxidase activity in vitro reducing hydrogen peroxide using glutathione as the electron donor. The combined results from gene discovery, protein expression and distribution profiling (especially the "surprising" presence under the nematode cuticle), and recombinant antioxidant activity suggest that BxPrx plays a key role in combating the oxidative burst engineered by the ROS defense system in host plants during the infection process. In summary, BxPrx is a genetic factor potentially facilitating B. xylophilus infestation.