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The aim of the study was to select, optimize and characterize RT‐PCR tests for the detection of Tobacco ringspot virus (TRSV) in post‐entry quarantine. Among five different tests, the Poojari et al. (Journal of Virological Methods 235, 112–118) and Jossey & Babadoost (Plant Disease 90, 1361) conventionnal RT‐PCR tests were chosen and optimized for this purpose. Ten TRSV isolates, 17 healthy plants from the genera Vitis, Prunus and Malus, four other Nepoviruses or Secoviridae isolates and serial dilutions of three TRSV isolates were used for the complete characterization of the optimized tests. In the tested conditions, the Poojari and Jossey & Babadoost tests respectively showed 100% and 95% inclusivity, 100% and 100% exclusivity, 100% and 96.4% analytical specificity, 100% and 100% diagnostic specificity, [10?7; 10?1] and [10?8; 10?2] limit of detection dilution factors (analytical sensitivity), 91.1% and 90.0% repeatability, 90.3% and 91.1% reproducibility and 100% and 100% selectivity. Due to its higher inclusivity, the optimized Poojari test is recommended for the detection of TRSV isolates for post‐entry quarantine purposes, but can also be used for global surveys. The optimized Jossey & Babadoost test showed the best analytical sensitivity, suggesting that combining both tests can further enhance detection.  相似文献   
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The use of T-61 as a sole euthanasia agent for birds was investigated. Nine broiler chickens (Gallus gallus domesticus) were euthanized by intravenous T-61 and assessed for insensibility [brainstem reflexes: nictitating membrane reflex (NIC), palpebral blink reflex (PAL)], brain death [isoelectric electroencephalogram activity (EEG)], cessation of audible heartbeat, and abnormal electrocardiogram. Birds were considered dead when the heart rate was less than 180 beats/minute with an isoelectric EEG. No vocalization or wing flapping occurred. Both NIC and PAL were lost 10.5 s from start of injection and audible heartbeat ceased at 24.5 s. Latency to isoelectric activity was 16.6 s. All but 1 bird died within 60 s. Rapid induction of insensibility meant birds did not experience pain and distress within 10.5 s from start of injection and birds were not conscious during cardiac and circulatory arrest. Intravenous injection of T-61 is an effective and efficient euthanasia method for birds.  相似文献   
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Scab is an important disease of apple and its control depends almost exclusively on frequent use of fungicides. Primary scab infection in the spring assumes several steps: ascospore maturation, liberation of ascospores that become airborne, deposition on susceptible tissues, and infection. However, the spatial heterogeneity of ascospores within the tree canopy is unknown. Aerial concentration of ascospore (ACA), ascospore concentration in rain water (ACR) and ascospore deposition (AD) were therefore measured at six heights (20–257 cm from the ground) with rotating-arm air samplers, funnels, and greased glass slides, respectively, during five rain events in 2001 and in 2002. In addition, ACR and AD were measured at eight locations within tree canopy at 196 cm height. Apple scab was assessed at the end of the primary infection period in each sampling location within the apple tree. A similar experimental design was used in 2003 to study the spatial heterogeneity of both AD and primary scab lesions. ACA and AD decreased with increasing height, while ACR increased with increasing height. Based on both variance to mean ratio and the power law relationship in both years, the ACR was heterogeneous, while AD was heterogeneous only during the peaks of ascospore release. The ACR was significantly higher at the centre of the trees and the AD was significantly higher at the centre and at the western edge of the trees. Only the cumulative AD was significantly correlated with apple scab lesions at the same location (r = 0.83). In 2003, a similar pattern of spatial heterogeneity within the tree canopy was observed for AD and primary scab lesion counts and there was a linear relationship (R 2 = 0.84) between these two variables. It was concluded that ACR and AD within the tree canopy are not randomly distributed at least during peaks of ascospore release and that AD is a good estimate of primary scab lesion development. This spatial heterogeneity should be considered when estimating ascospore deposition using mathematical models or when quantifying ascosporic inoculum using spore samplers.  相似文献   
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The spatial distribution of non-native, invasive plants on the landscape is strongly influenced by human action. People introduce non-native species to new landscapes and regions (propagule pressure) as well as increase ecosystem invasibility through disturbance of native ecosystems. However, the relative importance of different landscape drivers of invasion may vary with landscape context (i.e., the types and amounts of surrounding land cover and land use). If so, data collected in one context may not be appropriate for predicting invasion risk across a broader landscape. To test whether independent occurrence datasets suggest similar landscape drivers of invasion, we compared landscape models based on data compiled by the Invasive Plant Atlas of New England (IPANE), which are contributed opportunistically by trained citizen scientists, to models based on Forest Stewardship plans (FSPs), which are located in privately owned and relatively undisturbed forests. We evaluated 16 landscape variables related to propagule pressure and/or disturbance for significant predictors of invasive plant presence based on presence/absence and count regression models. Presence and richness of invasive plants within FSPs was most influenced by proportion of open land and proximity to residential areas, which are both sources of propagules in forest interiors. In contrast, IPANE invasive plant presence and richness for the same area was influenced by distance to roads and streams. These results suggest that landscape drivers of invasion vary considerably depending on landscape context, and the choice of occurrence dataset will strongly influence model results.  相似文献   
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The tropical lowlands of southern Mexico and Central America are composed of a complex mosaic of landscapes that presented a variety of possibilities and challenges to the subsistence practices of the ancient Maya. The Yalahau Regional Human Ecology Project has been investigating ancient Maya agricultural practices and use of resources in a unique fresh-water wetland zone located in the northeast corner of the Yucatán Peninsula. While containing only a sparse population today, the Yalahau region once supported numerous Maya communities and civic-ceremonial centers, particularly during the Late Preclassic and Early Classic periods, between approximately 100 B.C. and A.D. 450. Our investigations have developed evidence that the ancient Maya manipulated and cultivated the wetland landscape of the region, used soil or algae from the wetlands to enrich upland garden plots, and cultivated trees within their communities. We suggest that the study of ancient Maya agricultural practices can contribute to sustainable development of the area today and in the future.  相似文献   
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Diatoms are unicellular algae with plastids acquired by secondary endosymbiosis. They are responsible for approximately 20% of global carbon fixation. We report the 34 million-base pair draft nuclear genome of the marine diatom Thalassiosira pseudonana and its 129 thousand-base pair plastid and 44 thousand-base pair mitochondrial genomes. Sequence and optical restriction mapping revealed 24 diploid nuclear chromosomes. We identified novel genes for silicic acid transport and formation of silica-based cell walls, high-affinity iron uptake, biosynthetic enzymes for several types of polyunsaturated fatty acids, use of a range of nitrogenous compounds, and a complete urea cycle, all attributes that allow diatoms to prosper in aquatic environments.  相似文献   
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A 3-year-old Boxer was presented with progressive diarrhea, vomiting, and lethargy of 5-months duration. The dog had watery black feces, a mature neutrophilia, and microcytic anemia. Cytologic evaluation of a direct fecal smear stained with Wright's-Giemsa revealed numerous encapsulated, narrow-based, budding organisms consistent with Cryptococcus sp. Pyogranulomatous inflammation and Cryptococcus organisms also were observed in ultrasound-guided fine-needle aspirates of the small intestine and mesenteric lymph nodes, and in histologic sections of colonic biopsies obtained by endoscopy. Multifocal chorioretinitis by fundic examination was consistent with systemic mycosis, and the reciprocal antigen titer (1600) on a cryptococcal antigen latex agglutination test for Cryptococcus neoformans was markedly increased. Using immunohistochemistry, the organism was identified further as C neoformans var. grubii (C neoformans var. neoformans serotype A). After 3 weeks of antifungal treatment, ultrasound examination revealed urinary bladder wall thickening, and Cryptococcus organisms were found in a urine sediment preparation. After 4 months of treatment, the dog was clinically normal and had no abnormal findings on CBC, serum biochemistry, urinalysis, or fecal cytology; however, the antigen titer remained unchanged, mesenteric lymphadenomegaly and jejunal wall thickening were still evident, and cytologic evaluation of fine-needles aspirates of the jejunal wall revealed budding Cryptococcus organisms. Intestinal involvement in dogs with cryptococcosis is rare, and diagnosis by fecal cytology has not been documented previously.  相似文献   
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