| 1. |
- Andersson, Pierre, et al.
(author)
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Viridin-like steroids from Hymenoscyphus pseudoalbidus
- 2013
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In: Phytochemistry. - : Elsevier BV. - 0031-9422 .- 1873-3700. ; 86, s. 195-200
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Journal article (peer-reviewed)abstract
- Three furanosteroids were isolated from the ash dieback causing fungus Hymenoscyphus pseudoalbidus along with the known compounds viridiol and demethoxyviridiol. The compounds were characterized by 1D and 2D NMR spectroscopy, LC-HRMS and polarimetry. (C) 2012 Elsevier Ltd. All rights reserved.
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| 2. |
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| 3. |
- Cleary, Michelle
(author)
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FORMATION OF TRAUMATIC RESIN DUCTS IN THE PHLOEM OF WESTERN REDCEDAR (THUJA PLICATA) ROOTS FOLLOWING ABIOTIC INJURY AND PATHOGENIC INVASION BY ARMILLARIA OSTOYAE
- 2011
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In: IAWA Journal. - : Brill. - 0928-1541 .- 2294-1932. ; 32, s. 351-359
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Journal article (peer-reviewed)abstract
- Anatomical changes involved in traumatic phloem resin duct (TPRD) formation in western redcedar (Thuja plicata) roots were examined following abiotic wounding and fungal invasion by Armillaria ostoyae. Following necrophylactic periderm formation, hyperplasia and expansion of a band of phloem parenchyma cells occurred in close proximity to the vascular cambium and schizogenous and lysigenous separation of its derivatives resulted in a series of longitudinal resin ducts in the inner to mid-phloem region. Fungal invasion appeared to amplify traumatic resin duct formation in the phloem. While traumatic cavities in the phloem have been reported for other Cupressaceae, this is the first report documenting TPRD formation in western redcedar.
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| 4. |
- Cleary, Michelle, et al.
(author)
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Genotypes of Fraxinus excelsior with different susceptibility to the ash dieback pathogen Hymenoscyphus pseudoalbidus and their response to the phytotoxin viridiol - A metabolomic and microscopic study
- 2014
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In: Phytochemistry. - : Elsevier BV. - 0031-9422 .- 1873-3700. ; 102, s. 115-125
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Journal article (peer-reviewed)abstract
- Eight European ash (Fraxinus excelsior) genotypes with different known susceptibility to Hymenoscyphus pseudoalbidus were tested against the phytotoxin viridiol and their response described at the microscopic and metabolomic level. All ash genotypes were sensitive to the toxin and necrosis was detectable after 24 h. Among the three viridiol concentrations used in the experiment, the lowest concentration (14.7 mu M) yielded markedly lower mean damage scores compared to those resulting from seedlings tested at higher dosages. The highest damage scores were associated with the susceptible ash clones S-101, S-106 and S-125, but also with resistant clone R-104. Three resistant clones (R-131, R-121, and R-118) had lower mean damage scores compared to susceptible clones. Wilting of leaves was more common 48 h after treatment and more pronounced on seedlings with high damage scores. The resulting lesions generally lacked browning of tissue and displayed only surface disruption of cells in direct contact with the toxin. A delay in symptom development was evident on all five resistant clones tested with the two higher concentrations of viridiol. LC-HRMS and MS/MS analyses of ash seedling extracts suggest several secoiridoid compounds as well as compounds related to abscisic acid (ABA) to be produced in response to viridiol. ABA-cysteine and xanthoxin were found at significantly higher concentrations in susceptible clones compared to resistant clones after treatment with viridiol, suggesting a primary role of ABA in response to stress. The results observed in this study suggest that genetic resistance to H. pseudoalbidus among ash genotypes may be explained, in part, by the varied response to phytotoxins produced by the fungus. (C) 2014 Elsevier Ltd. All rights reserved.
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| 5. |
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| 6. |
- Cleary, Michelle, et al.
(author)
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Natural infection of Fraxinus excelsior seeds by Chalara fraxinea
- 2013
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In: Forest Pathology. - : Wiley. - 1437-4781 .- 1439-0329. ; 43, s. 83-85
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Journal article (peer-reviewed)abstract
- The occurrence of Chalara fraxinea, the fungus responsible for dieback of European ash (Fraxinus excelsior), was investigated in the current and previous seed years collected from symptomatic trees in Latvia and Sweden using molecular techniques (DNA extraction, ITS-PCR, Sanger sequencing). Molecular analysis of seeds revealed the presence of 30 different fungal taxa. Chalara fraxinea was detected in 8.3% of seeds tested from the current year originating from Latvia. The presence of C.fraxinea in seeds of F.excelsior is of great concern to phytosanitary protection authorities in countries outside the current zone of infestation.
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| 7. |
- Cleary, Michelle
(author)
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Pathogenicity and virulence of Armillaria sinapina and host response to infection in Douglas-fir, western hemlock and western redcedar in the southern Interior of British Columbia
- 2012
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In: Forest Pathology. - : Wiley. - 1437-4781 .- 1439-0329. ; 42, s. 481-491
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Journal article (peer-reviewed)abstract
- The frequency of infection, lesion characteristics and anatomical changes in phloem and cambial tissues caused by Armillaria sinapina were studied on inoculated trees of Douglas-fir, western hemlock and western redcedar and compared with results of A. ostoyae inoculations previously reported on the same host species. Similar percentages of inoculations resulting in infection of roots on the three hosts indicate that A. sinapina and A. ostoyae are equally pathogenic. Armillaria ostoyae was more virulent than A. sinapina as demonstrated by fungal exudates from A. ostoyae inoculum blocks, which appeared to cause lesions on roots; the higher frequency at which lignified impervious tissue (IT) and necrophylactic periderm (NP) developed in bark and following cambial invasion, compartmentalization; the large proportion of roots that showed no visible host response; the large zones of IT formed under continuous stimulation by A. ostoyae advancing in inner bark; and the high frequency of breaching of NP barriers. Spread of A. sinapina mycelium in host species appeared slower than that of A. ostoyae, particularly in Douglas-fir and western hemlock. In western redcedar, A. ostoyae induced stronger host responses than those following invasion by A. sinapina, which included further expansion of the induced rhytidome response, traumatic phloem resin duct formation and higher numbers of polyphenolic parenchyma comprising its barrier zone. Where damage by A. sinapina ensued, it was always associated with high inoculum potential. The ecology of virulent and less virulent species of Armillaria in natural forests is discussed.
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| 8. |
- Cleary, Michelle, et al.
(author)
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Stump removal to control root disease in Canada and Scandinavia: A synthesis of results from long-term trials
- 2013
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In: Forest Ecology and Management. - : Elsevier BV. - 0378-1127 .- 1872-7042. ; 290, s. 5-14
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Journal article (peer-reviewed)abstract
- Heterobasidion annosum sensu lato (s.l.), Armillaria ostoyae, and Phellinus sulphurascens are economically important fungal pathogens in temperate forests of the northern hemisphere that cause decay, growth reduction and tree mortality of coniferous hosts. Fungal inoculum residing in roots and stumps after final felling can remain viable for decades and place stands at an increased risk of mortality in subsequent rotations. Stump removal is one strategy that can be used to reduce the impact of root rot fungi in regenerating stands. This paper presents results from five long-term stump removal trials in Canada, Denmark, and Sweden. In all studies, stumps were extracted and larger roots removed. After a period of time ranging between 21 and 50 years, tree mortality, infection or both caused by A. ostoyae, P. sulphurascens and H. annosum s.l. was compared between stumped and non-stumped areas. In all but one trial, efficacy of stump removal to reduce disease occurrence over the long-term was 80-100% for A. ostoyae, 85-100% for P. sulphurascens, and 20-72% for H. annosum s.l. Stump removal for H. annosum s.l. was more effective in the Swedish trial than in the Danish trial, but in both locations the frequency of root disease increased with tree age. Results from trials indicate that stump removal is effective in reducing disease incidence and likely improves site productivity in subsequent rotations. Forest managers should consider stump removal as a routine operation when harvesting, especially on sites that have high hazard for A. ostoyae, P. sulphurascens, or both. Even though stump removal can provide adequate control against H. annosum, use of the biocontrol agent Phlebiopsis gigantea on freshly cut stump surfaces after harvest and following thinnings is perhaps a more cost effective control measure to reduce the frequency of H. annosum rot in next rotation forests. New initiatives involving harvesting of stumps for bioenergy may offer the additional benefit of minimizing disease impacts in next rotation forests. (C) 2012 Crown Copyright and Elsevier B.V. All rights reserved.
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| 9. |
- Cleary, Michelle
(author)
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Tree species selection revisited for plantations in the Interior Cedar Hemlock zone of southern British Columbia
- 2013
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In: Forestry Chronicle. - : Canadian Institute of Forestry. - 0015-7546 .- 1499-9315. ; 89, s. 382-391
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Journal article (peer-reviewed)abstract
- We provide results from two trials comparing performance of species of known provenance planted on logged sites in the southern Interior Cedar Hemlock biogeoclimatic zone of southern British Columbia 20 and 26 years after establishment. The commonly used plantation species, lodgepole pine (Pinus contorta var. latifolia), interior spruce (a naturally occurring hybrid between Picea glauca and P. engelmannii) and Douglas-fir (Pseudotsuga menziesii var. glauca), survived as well as, but grew more slowly than, western larch (Larix occidentalis), western white pine (Pinus monticola) and ponderosa pine (Pinus ponderosa), and faster than western redcedar (Thuja plicata). Site index values were generally higher than published values for similar sites. Numerous pests affected all species in the trials. Mountain pine beetle (Dendroctonus ponderosae) caused heavy mortality in lodgepole pine in part of one trial, and Armillaria root disease caused widespread damage to western larch and Douglas-fir in the other trial. Western white pine from local seed sources were severely damaged by white pine blister rust (Cronartium ribicola) in both trials but a rust-resistant seed source used in one trial survived better. Frost damage reduced survival and growth of Douglas-fir in one trial and may have affected western white pine. Survival of two planted broadleaves (Betula papyrifera) and a hybrid of black cottonwood (Populus trichocarpa) and black poplar (Populus nigra) was severely reduced by drought. The results support ongoing efforts to broaden the number of species used in British Columbia reforestation programs.
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| 10. |
- Hudson, Lawrence N., et al.
(author)
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The PREDICTS database : a global database of how local terrestrial biodiversity responds to human impacts
- 2014
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In: Ecology and Evolution. - : Wiley. - 2045-7758. ; 4:24, s. 4701-4735
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Journal article (peer-reviewed)abstract
- Biodiversity continues to decline in the face of increasing anthropogenic pressures such as habitat destruction, exploitation, pollution and introduction of alien species. Existing global databases of species' threat status or population time series are dominated by charismatic species. The collation of datasets with broad taxonomic and biogeographic extents, and that support computation of a range of biodiversity indicators, is necessary to enable better understanding of historical declines and to project - and avert - future declines. We describe and assess a new database of more than 1.6 million samples from 78 countries representing over 28,000 species, collated from existing spatial comparisons of local-scale biodiversity exposed to different intensities and types of anthropogenic pressures, from terrestrial sites around the world. The database contains measurements taken in 208 (of 814) ecoregions, 13 (of 14) biomes, 25 (of 35) biodiversity hotspots and 16 (of 17) megadiverse countries. The database contains more than 1% of the total number of all species described, and more than 1% of the described species within many taxonomic groups - including flowering plants, gymnosperms, birds, mammals, reptiles, amphibians, beetles, lepidopterans and hymenopterans. The dataset, which is still being added to, is therefore already considerably larger and more representative than those used by previous quantitative models of biodiversity trends and responses. The database is being assembled as part of the PREDICTS project (Projecting Responses of Ecological Diversity In Changing Terrestrial Systems - ). We make site-level summary data available alongside this article. The full database will be publicly available in 2015.
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| 11. |
- Rönnberg, Jonas, et al.
(author)
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Incidence of Heterobasidion spp. following different thinning regimes in Norway spruce in southern Sweden
- 2013
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In: Forest Ecology and Management. - : Elsevier BV. - 0378-1127 .- 1872-7042. ; 289, s. 409-415
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Journal article (peer-reviewed)abstract
- The incidence of Heterobasidion spp. infections following different thinning regimes in Norway spruce was evaluated on 12 plots in a trial in southern Sweden. The plots were established in 1961 and followed until final felling in 2001. The treatments ranged from one light thinning at the experimental set-up to six thinnings. The average incidence of decay was 44% across all thinning regimes of which Heterobasidion spp. was identified in 85% of the cases. There was no difference in the incidence of infections, decayed volumes, and the size or number of Heterobasidion spp. genets among the thinning regimes. The largest genet was though found on the plot with just one light thinning and encompassed 25 trees. On average, 11.1% of the stem volume was decayed and the average height of the decay column was 4 m. Decay incidence was 3.7 times the decayed volume and the height of the decay columns was 19 times the diameter of the decay at stump height. Conclusively, early thinning appears to be more important for disease development than subsequent multiple thinning. To restrict the disease development in the stand later during the rotation period, it is of utmost importance that the earlier thinnings are made during winter conditions or otherwise properly protected against spore infection of Heterobasidion. (C) 2012 Elsevier B.V. All rights reserved.
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| 12. |
- Rönnberg, Jonas, et al.
(author)
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Presence of Heterobasidion infections in Norway spruce stumps after treatment six years earlier with Phlebiopsis gigantea
- 2012
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In: Forest Pathology. - : Wiley. - 1437-4781 .- 1439-0329. ; 42, s. 144-149
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Journal article (peer-reviewed)abstract
- Natural colonization by the root and butt rot causing fungi Heterobasidion spp. on Norway spruce (Picea abies) stumps following thinning and treatment with the biological control agent Phlebiopsis gigantea was investigated on three sites in southern Sweden 6 years after treatment. The fully treated stumps and control stumps were excavated and sampled to compare the survival of Heterobasidion spp. in the long term. Six years post-treatment, 47 and 11% of untreated and treated stumps, respectively, had Heterobasidion infection. There was no difference in the relative infected area in discs collected from the butt and the roots for the different treatments. Control efficacy was 83% for treated stumps. After 6 years, there were no apparent differences between the remaining infections in treated compared with those in untreated stumps regarding the number of colonies, their size or relative infection area. Although infections, 3 months after treatment with P. gigantea, were significantly fewer and smaller than in untreated stumps, Heterobasidion inoculum can survive for at least 6 years in the stump and, when it does, constitute a risk for neighbouring trees.
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| 13. |
- Wang, Liying, et al.
(author)
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Incidence and impact of root infection by Heterobasidion spp., and the justification for preventative silvicultural measures on Scots pine trees: A case study in southern Sweden
- 2014
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In: Forest Ecology and Management. - : Elsevier BV. - 0378-1127 .- 1872-7042. ; 315, s. 153-159
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Journal article (peer-reviewed)abstract
- The distribution of Heterobasidion spp. infection in the root system of Scots pine (Pinus sylvestris) and the relationship between disease severity and growth was investigated in a mid-rotation in southern Sweden stand nine years after thinning. Twenty-four trees were mechanically uprooted to measure whole root systems and determine the percentage of infected root volume. Annual volume increment was retrospectively calculated using discs cut along the stem. No trees showed aboveground symptoms of infection, however the disease incidence belowground was 87.5% and the percentage of infected root volume ranged between 0% and 32%. The percentage of infected root volume was negatively correlated with the difference in volume increment between the last two adjacent five-year periods, indicating reduced growth in more infected trees, but not with other tree-specific growth characteristics such as diameter at breast height, tree volume or root volume. Annual volume increment of individual trees decreased with increasing percentage of infected root volume. The high incidence of Heterobasidion spp. and reduced volume growth in seemingly healthy Scots pine warrants preventative stump treatment during thinnings to minimize the establishment of Heterobasidion, especially in first rotation forests. (C) 2014 Elsevier B.V. All rights reserved.
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| 14. |
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