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Volatile Organic Compounds Emitted by Fungal Associates of Conifer Bark Beetles and their Potential in Bark Beetle Control.

ABSTRACT: Conifer bark beetles attack and kill mature spruce and pine trees, especially during hot and dry conditions. These beetles are closely associated with ophiostomatoid fungi of the Ascomycetes, including the genera Ophiostoma, Grosmannia, and Endoconidiophora, which enhance beetle success by improving nutrition and modifying their substrate, but also have negative impacts on beetles by attracting predators and parasites. A survey of the literature and our own data revealed that ophiostomatoid fungi emit a variety of volatile organic compounds under laboratory conditions including fusel alcohols, terpenoids, aromatic compounds, and aliphatic alcohols. Many of these compounds already have been shown to elicit behavioral responses from bark beetles, functioning as attractants or repellents, often as synergists to compounds currently used in bark beetle control. Thus, these compounds could serve as valuable new agents for bark beetle management. However, bark beetle associations with fungi are very complex. Beetle behavior varies with the species of fungus, the stage of the beetle life cycle, the host tree quality, and probably with changes in the emission rate of fungal volatiles. Additional research on bark beetles and their symbiotic associates is necessary before the basic significance of ophiostomatoid fungal volatiles can be understood and their applied potential realized.

SUBMITTER: Kandasamy D

PROVIDER: S-EPMC5101256 | biostudies-literature | 2016 Sep

REPOSITORIES: biostudies-literature

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Volatile Organic Compounds Emitted by Fungal Associates of Conifer Bark Beetles and their Potential in Bark Beetle Control.

Kandasamy Dineshkumar D Gershenzon Jonathan J Hammerbacher Almuth A

Journal of chemical ecology 20160929 9

Conifer bark beetles attack and kill mature spruce and pine trees, especially during hot and dry conditions. These beetles are closely associated with ophiostomatoid fungi of the Ascomycetes, including the genera Ophiostoma, Grosmannia, and Endoconidiophora, which enhance beetle success by improving nutrition and modifying their substrate, but also have negative impacts on beetles by attracting predators and parasites. A survey of the literature and our own data revealed that ophiostomatoid fung ...[more]

PMID: 27687998

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Project description:BackgroundColorectal cancer remains a leading cause of mortality and morbidity. The UK Bowel Cancer Screening Programme (BCSP) has demonstrated that detection of colorectal cancer at an earlier stage and identification of advanced pre-malignant adenomas reduces mortality and morbidity.AimTo assess the utility of volatile organic compounds as a biomarker for colorectal neoplasia.MethodsFaeces were collected from symptomatic patients and people participating in the UK BCSP, prior to colonoscopy. Headspace extraction followed by gas chromatography mass spectrometry was performed on faeces to identify volatile organic compounds. Logistic regression modelling and 10-fold cross-validation were used to test potential biomarkers.ResultsOne hundred and thirty-seven participants were included (mean age 64 years [range 22-85], 54% were male): 60 had no neoplasia, 56 had adenomatous polyp(s) and 21 had adenocarcinoma. Propan-2-ol was significantly more abundant in the cancer samples (P < 0.0001, q = 0.004) with an area under ROC (AUROC) curve of 0.76. When combined with 3-methylbutanoic acid the AUROC curve was 0.82, sensitivity 87.9% (95% CI 0.87-0.99) and specificity 84.6% (95% CI 0.65-1.0). Logistic regression analysis using the presence/absence of specific volatile organic compounds, identified a three volatile organic compound panel (propan-2-ol, hexan-2-one and ethyl 3-methyl- butanoate) to have an AUROC of 0.73, with a person six times more likely to have cancer if all three volatile organic compounds were present (P < 0.0001).ConclusionsVolatile organic compound analysis may have a superior diagnostic ability for the identification of colorectal adenocarcinoma, when compared to other faecal biomarkers, including those currently employed in UK. Clinical trial details: National Research Ethics Service Committee South West - Central Bristol (REC reference 14/SW/1162) with R&D approval from University of Liverpool and Broadgreen University Hospital Trust (UoL 001098).

Project description:Bark beetles (sensu lato) colonize woody tissues like phloem or xylem and are associated with a broad range of micro-organisms. Specific fungi in the ascomycete orders Hypocreales, Microascales and Ophistomatales as well as the basidiomycete Russulales have been found to be of high importance for successful tree colonization and reproduction in many species. While fungal mutualisms are facultative for most phloem-colonizing bark beetles (sensu stricto), xylem-colonizing ambrosia beetles are long known to obligatorily depend on mutualistic fungi for nutrition of adults and larvae. Recently, a defensive role of fungal mutualists for their ambrosia beetle hosts was revealed: Few tested mutualists outcompeted other beetle-antagonistic fungi by their ability to produce, detoxify and metabolize ethanol, which is naturally occurring in stressed and/or dying trees that many ambrosia beetle species preferentially colonize. Here, we aim to test (i) how widespread beneficial effects of ethanol are among the independently evolved lineages of ambrosia beetle fungal mutualists and (ii) whether it is also present in common fungal symbionts of two bark beetle species (Ips typographus, Dendroctonus ponderosae) and some general fungal antagonists of bark and ambrosia beetle species. The majority of mutualistic ambrosia beetle fungi tested benefited (or at least were not harmed) by the presence of ethanol in terms of growth parameters (e.g., biomass), whereas fungal antagonists were inhibited. This confirms the competitive advantage of nutritional mutualists in the beetle's preferred, ethanol-containing host material. Even though most bark beetle fungi are found in the same phylogenetic lineages and ancestral to the ambrosia beetle (sensu stricto) fungi, most of them were highly negatively affected by ethanol and only a nutritional mutualist of Dendroctonus ponderosae benefited, however. This suggests that ethanol tolerance is a derived trait in nutritional fungal mutualists, particularly in ambrosia beetles that show cooperative farming of their fungi.

Project description:Bark beetles (Coleoptera: Curculionidae; Scolytinae) are tree-infesting insects that consume subcortical tissues and fungi. Species capable of killing their host trees are most commonly associated with conifers, as very few bark beetle species infest and kill hardwood hosts directly. The alder bark beetle, Alniphagus aspericollis, is a hardwood-killing bark beetle that colonizes and kills red alder, Alnus rubra. Conifer-killing bark beetles have well-known associations with symbiotic ophiostomatoid fungi that facilitate their life histories, but it is unknown whether A. aspericollis has any fungal associates. This study was conducted to identify any consistent filamentous fungal associates of A. aspericollis and characterize the consistency of observed beetle-fungus relationships. Beetles and gallery phloem samples were collected from seven sites throughout the Greater Vancouver region in British Columbia, Canada. Filamentous fungi were isolated from these samples and identified by DNA barcoding using the internal transcribed spacer (ITS) region and other barcode regions for resolution to the species-level for the most dominant isolates. The most common fungal associate was a previously undescribed Neonectria major-like fungus, Neonectria sp. nov., which was isolated from ~67% of adult beetles, ~59% of phloem samples, and ~94% of the beetle-infested trees. Ophiostoma quercus was isolated from ~28% of adult beetles, ~9% of phloem samples, and ~56% of infested trees and deemed a casual associate of A. aspericollis, while a putatively novel species of Ophiostoma was more infrequently isolated from A. aspericollis and its galleries. Cadophora spadicis, a new record for red alder, was rarely isolated and is probably coincidentally carried by A. aspericollis. Overall, A. aspericollis was only loosely associated with ophiostomatoid fungi, suggesting that these fungi have little ecological significance in the beetle-tree interaction, while Neonectria sp. nov. may be a symbiote of A. aspericollis that is vectored by the beetle.

Dataset Information

Volatile Organic Compounds Emitted by Fungal Associates of Conifer Bark Beetles and their Potential in Bark Beetle Control.

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Volatile Organic Compounds Emitted by Fungal Associates of Conifer Bark Beetles and their Potential in Bark Beetle Control.

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