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Xylophilus ampelinus is listed as a quarantine pest in Annex II/A2 of EU Directive 2000/29. Grapevine cuttings used either as rooting or grafting material represent a primary source of inoculum because of the systemic nature of bacterial colonization. We describe a PCR-based method for the specific detection of X. ampelinus from various plant materials (trunks, woody branches, growing shoots, leaves and bleeding sap), making the detection of X. ampelinus reliable throughout the year. Bacterial cells were extracted by crushing the plant tissues and soaking them in sterile distilled water for 30–120 min at 4 °C. Bacterial cells were harvested by centrifugation at 13 000 g for 10 min through sterile paper discs, and lysed in SDS buffer. DNA was extracted by a silica-based procedure. Specific DNA amplifications were performed with a pair of primers, of which one was labelled with biotin. A digoxygenin-labelled oligonucleotide with a sequence specific for the amplicon was used as the probe. Finally, amplicons were immobilized in microplate wells coated with streptavidine, and hybridization of the digoxygenin-labelled probe was detected with alkaline phosphatase-conjugated antibiodies in a colorimetric assay. This method was sensitive, specific and allowed experiments with high throughput. 相似文献
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A new bacterial disease of Persian (English) walnut (Juglans regia) has been observed in France. This disease, called vertical oozing canker (VOC), is characterized by vertical cankers on trunks and branches of affected walnut trees with oozing exudates. To determine the aetiology of the disease, a study was carried out in 79 walnut orchards and nurseries located in southeastern and southwestern France. Bacterial analysis from diseased samples yielded 36 strains identified as Xanthomonas arboricola and 32 strains identified as Brenneria nigrifluens on the basis of biochemical tests. The causal agent of VOC was identified as X. arboricola by pathogenicity tests on walnut. Fluorescent amplified fragment length polymorphism (F‐AFLP) was carried out on 36 strains of X. arboricola collected in this study, 24 strains of X. arboricola pv. juglandis isolated from walnut blight symptoms and one strain of X. arboricola pv. corylina included as an outgroup. Based on cluster analysis of F‐AFLP data, most X. arboricola strains responsible for main VOC outbreaks showed a high degree of similarity, forming a cluster clearly separate from strains of X. arboricola pv. juglandis isolated from walnut blight symptoms. It is suggested that VOC is caused by a distinct genetic lineage within the pathovar juglandis of X. arboricola that is also able to cause classical bacterial blight symptoms on walnut leaves and fruits. 相似文献
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Antoine Brin Céline Meredieu Dominique Piou Hervé Brustel Hervé Jactel 《Forest Ecology and Management》2008
Although the volume of dead wood is commonly acknowledged as an indicator of biodiversity in sustainable forest management schemes, only few data are available for plantation forests. To evaluate the volume and qualify the diversity of woody debris along a chronosequence of maritime pine plantations, we sampled downed woody debris, snags and stumps in 143 stands of different ages. To test the hypothesis that the pattern of dead wood accumulation mainly results from silvicultural operations, we developed a predictive model. It combined an empirical growth model evaluating the amount of dead wood produced by successive thinnings with a decay function that estimated the loss of dead wood with time. 相似文献
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Laurent Larrieu Alain Cabanettes Antoine Brin Christophe Bouget Marc Deconchat 《European Journal of Forest Research》2014,133(2):355-367
Recent studies have highlighted the key role of tree microhabitats in forest habitat complexity and have suggested using them as surrogates for local taxonomic biodiversity. However, few practical guidelines have been published to help foresters in managing microhabitats at the stand scale. This paper provides scientific background information to help to develop such guidelines. We surveyed trees in nine long-unmanaged beech–fir forests to model tree microhabitat occurrence and diversity at the tree level. Data were upscaled to a size range of tree cluster, i.e., at the tree population scale, by aggregating observed values of microhabitat occurrence. Accumulation curves were used to estimate the minimum number of trees required to make all the microhabitat types available. Two managed forests were then studied to quantify management effects on microhabitats. Diameter at breast height (dbh) and tree species, respectively, explained 16 and 10 % of the variations in the number of microhabitat-bearing trees, and 21 and 10 % for the number of microhabitat types. Beech trees and firs with a dbh of less than dbh 50 and 65 cm, respectively, did not ensure the provision of all microhabitat types. At least 20 ha of unmanaged forest were necessary to conserve all the microhabitat types. Current management practices have reduced the number of microhabitat-bearing beeches both by reducing the number of very large trees (dbh > 67.5 cm) and by tree selection within mid-size diameters. For fir, only the logging of very large trees (dbh > 62.5 cm) negatively affected microhabitats. These figures may inspire guidelines for conservation-friendly forestry. 相似文献
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Climate‐induced seasonal changes in smallmouth bass growth rate potential at the southern range extent 
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下载免费PDF全文 Christopher R. Middaugh Brin Kessinger Daniel D. Magoulick 《Ecology of Freshwater Fish》2018,27(1):19-29
Temperature increases due to climate change over the coming century will likely affect smallmouth bass (Micropterus dolomieu) growth in lotic systems at the southern extent of their native range. However, the thermal response of a stream to warming climate conditions could be affected by the flow regime of each stream, mitigating the effects on smallmouth bass populations. We developed bioenergetics models to compare change in smallmouth bass growth rate potential (GRP) from present to future projected monthly stream temperatures across two flow regimes: runoff and groundwater‐dominated. Seasonal differences in GRP between stream types were then compared. The models were developed for fourteen streams within the Ozark–Ouachita Interior Highlands in Arkansas, Oklahoma and Missouri, USA, which contain smallmouth bass. In our simulations, smallmouth bass mean GRP during summer months decreased by 0.005 g g?1 day?1 in runoff streams and 0.002 g g?1 day?1 in groundwater streams by the end of century. Mean GRP during winter, fall and early spring increased under future climate conditions within both stream types (e.g., 0.00019 g g?1 day?1 in runoff and 0.0014 g g?1 day?1 in groundwater streams in spring months). We found significant differences in change in GRP between runoff and groundwater streams in three seasons in end‐of‐century simulations (spring, summer and fall). Potential differences in stream temperature across flow regimes could be an important habitat component to consider when investigating effects of climate change as fishes from various flow regimes that are relatively close geographically could be affected differently by warming climate conditions. 相似文献
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