92 research outputs found

    Plant parasitic nematodes and their management in the Maritime provinces of Canada

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    Cet article prĂ©sente une revue des nematodes phytoparasites qui causent des problĂšmes au Nouveau-Brunswick, en Nouvelle-Ecosse et Ă  l'Ăźle-du Prince-Édouard, ainsi que les approches de lutte utilisĂ©es. Le nĂ©matode des lĂ©sions des racines (Pratylenchus penetrans) est la seule espĂšce de nĂ©matode de la rĂ©gion qui provoque rĂ©guliĂšrement des baisses de rendement. Le nĂ©matode des nodositĂ©s des racines (Meloidogyne hapla) cause occasionnellement des dommages aux carottes (Daucus carota) mais les niveaux de population de ce nĂ©matode sont gĂ©nĂ©ralement trĂšs faibles. Le nĂ©matode du kyste du trĂšfle (Heterodera trifolii) est rĂ©pandu mais il n'a pas causĂ© de dommages aux rĂ©coltes de la rĂ©gion. Les techniques de production utilisĂ©es afin de rĂ©duire l'impact des nematodes phytoparasites dans les Maritimes, Ă  savoir la rotation des cultures, les traitements nĂ©maticides, le renforcement des rĂšglements de quarantaine et les pratiques de labourage, sont discutĂ©es. Un service-conseil sur les nematodes est Ă©galement considĂ©rĂ©.This paper presents a review of the plant parasitic nematodes that are of concern in New Brunswick, Nova Scotia, and Prince-Edward-Island, and the approaches used to manage them. The root lesion nematode (Pratylenchus penetrans) is the only nematode species in the region that regularly reduces crop yields. The northern root-knot nematode (Meloidogyne hapla) occasionally causes damage to carrots (Daucus carota), but population levels of this nematode species usually are very low. The clover cyst nematode (Heterodera trifolii) is widespread, but has not caused any damage to crops in the region. Management procedures used to reduce the impact of plant parasitic nematodes in the Maritime provinces, e.g. crop rotations, nematicide treatments, enforcement of quarantine regulations, and tillage practices are discussed. A nematode advisory service is also considered

    Effects of aldicarb and fungicides on Pratylenchus penetrans populations, root rot and net blotch severity on barley

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    Les populations du nematode des lĂ©sions (Pratylenchus penetrans), lequel produit des lĂ©sions nĂ©crotiques dans le cortex racinaire, ont Ă©tĂ© mesurĂ©es dans des parcelles expĂ©rimentales d'orge (Hordeum vulgare) en 1988,1989 et 1990. Les nematodes des lĂ©sions ont Ă©tĂ© les seuls nematodes endoparasites extraits des racines d'orge et ils Ă©taient le groupe de nematodes dominant dans le sol. En se basant sur les moyennes des 3 annĂ©es, les mesures de la pourriture racinaire, causĂ©e principalement par le Cochliobolus sativus et les Fusarium spp., ont augmentĂ© de 27 % selon l'Ă©chelle de croissance de Zadoks (ZGS) 30-32 en juillet, Ă  73% Ă  ZGS 70-72 Ă  la fin d'aoĂ»t et au dĂ©but de septembre. La rayure rĂ©ticulĂ©e, causĂ©e par le Pyrenophora teres, a Ă©tĂ© supprimĂ©e par un traitement fongicide consistant en une application de carbathiine et de thirame lors du semis et une application foliaire de propiconazole. L'aldicarbe a supprimĂ© les populations de nematodes des lĂ©sions dans le sol, dans tout le systĂšme racinaire, ainsi que dans les racines sĂ©minales et dans les racines du collet de l'orge. Les rendements ont augmentĂ© d'environ 30% lorsque l'aldicarbe et les fongicides Ă©taient appliquĂ©s en traitement combinĂ©. La densitĂ© des populations de nematodes des lĂ©sions Ă©tait plus Ă©levĂ©e dans les racines sĂ©minales que dans les racines du collet Ă  ZGS 30-32 et ZGS 55-60. Les coefficients de corrĂ©lation entre les populations de nematodes et les rendements Ă©taient souvent significativement nĂ©gatifs (P≀ 0,05). Il n'a pas Ă©tĂ© possible d'Ă©tablir une relation significative entre les populations de nematodes des lĂ©sions dans les racines ou dans le sol et l'incidence de la rayure rĂ©ticulĂ©e ou de la pourriture racinaire del'orge.Population levels of the root lesion nematode, Pratylenchus penetrans, which produces necrotic lesions in the root cortex, were recorded in barley (Hordeum vulgare) in experimental plots during 1988, 1989, and 1990. Root lesion nematodes were the onlyendoparasitic nematodes recovered from barley roots and were the dominant nematode group found in the soil. Based on 3-yr averages, root rot ratings, caused primarily by Cochliobolussativusand Fusarium spp., increased from 27% at Zadoks Growth Stage (ZGS) 30-32 in July to 73 % at ZGS 70-72 in late August and early September. Net blotch (incited by Pyrenophora teres) was suppressed by a fungicide treatment consisting of a seed application of carbathiin and thiram, and a foliar application of propiconazole. Aldicarb suppressed the populations of root lesion nematodes in the soil, in the total root System, and in crown and seminal roots of barley. Yields were increased by ca 30% where aldicarb and fungicides were applied as a combined treatment. Population densities of root lesion nematodes were much greater in seminal roots than in crown roots at ZGS 30-32 and 55-60. Correlation coefficients between nematodes and yield data were often negative and significant (P≀0.05). There were no consistent trends in the numerical relationships between numbers of root lesion nematodes in roots or soil, and incidences of net blotch or root rot of barley

    Invasion and reproduction of Pratylenchus penetrans in birdsfoot trefoil cultivars

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    Des essais en serre ont eté menés afin de déterminer les niveaux d'envahissement de cultivars et de lignées du lotier cornicule (Lotus corniculatus) par le nématode des lésions racinaires (Pratylenchus penetrans). Le nombre de nematodes présents dans les racines a été déterminé 6 semaines aprÚs la plantation dans des pots de démarrage de polystyrÚne de 50 cm3. Des nematodes ont été trouvés dans les racines de tous les cultivars et lignées, cependant les degrés d'envahissement différaient significativement. Dans le premier essai de triage, effectué en 1994 avec 23 cultivars et lignées, NB90-104, Upstart et Viking contenaient les plus faibles densités de population de nematodes dans les racines avec des niveaux inférieurs à 1 000 g-1 de matiÚre sÚche, alors que Fergus et EPF avaient des densités de population supérieures à 30 000 g-1 de matiÚre sÚche. Dans le deuxiÚme essai de triage, réalisé en 1995, les neuf cultivars et lignées étudiés, y compris NB90-104, Upstart et Viking, avaient des niveaux de nematodes supérieurs à résultats montrent que les cultivars et ont une grande variabilité génétique par des lésions racinaires.Greenhouse trials were conducted to determine the levels of invasion of birdsfoot trefoil(Lotus corniculatus) cultivars and lines by the root-lesion nematode (Pratylenchuspenetrans). Numbersof nematodesin roots grown in 50-cm3 polystyrene starter pots were determined 6 weeks after planting. Nematodes were detected in the roots of all cultivars and lines, though the degree of invasion varied significantly. In the first screening trial, carried out in 1994 on 23 cultivars and lines, NB90-104, Upstart, and Viking harbored the lowest population densities of nematodes with levels below 1 000 g-1 of dry root, while Fergus and EPF had population densities over 30 000 g-1 of dry root. In the second screening trial conducted in 1995, all nine cultivars and lines tested, including NB90-104, Upstart, and Viking, had nematode levels greater than 7 900 g-1 of dry root. The results indicated that the cultivars and lines tested in this study exhibited wide genetic variability for invasion by root-lesion nematodes

    Invasion and reproduction by rootlesion nematode (Pratylenchus penetrans) differs among selected lines of red clover (Trifolium pratense)

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    Dans une étude en serre, les réponses relatives à l'inoculation par le nématode des lésions racinaires (Pratylenchus penetrans) ont été évaluées pour dix-huit cultivars et lignées pour l'amélioration du trÚfle rouge (Trifolium pratense). La fréquence d'envahissement des plantes et la concentration des nématodes dans les racines étaient généralement correlées, mais il y avait des exceptions. La fréquence d'envahissement des plantes était faible pour un cultivar (Florex), mais la concentration des nématodes dans les racines des plantes envahies était élevée. Trois des plantes testées (CRS 15, CRS 5 et CRS 11) avaient une faible fréquence d'envahissement et une faible concentration de nématodes dans les racines. Un cultivar, AC Kingston, a été évalué comme étant trÚs sensible, alors que la fréquence d'envahissement et la concentration des nématodes dans les racines variaient pour les autres plantes testées.Eighteen cultivars and breeding lines of red clover (Trifolium pratense) were evaluated in a greenhouse study for their relative response to inoculation by the root-lesion nematode (Pratylenchus penetrans). The incidence of plants invaded and the nematode concentration in the roots were generally related but not always. One cultivar (Florex) had a low incidence of plants being invaded, but a high concentration of nematodes in the roots of invaded plants. Three entries (CRS 15, CRS 5, and CRS 11) displayed a low incidence of plants being invaded and a low concentration of nematodes in the root. One cultivar, AC Kingston, was judged to be highly susceptible, while the remaining entries had differing invasion incidences and differing concentrations of root-lesion nematodes in the roots

    Influence of previous crops and nematicide treatments on root lesion nematode populations and crop yields

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    Nous avons Ă©tudiĂ© au champ l'influence du prĂ©cĂ©dent cultural, de la sĂ©quence culturelle et de traitements Ă  l'aldicarbe sur les populations de nematodes des nodositĂ©s et sur les rendements de diverses cultures Ă  l'Ăźle-du Prince-Édouard. La culture prĂ©cĂ©dente a eu le plus grand impact sur le nombre de nematodes. Les sĂ©quences des cultures ont parfois eu une influence sur les populations de nematodes des nodositĂ©s (principalement Pratylenchus penetrans) et sur les rendements. Dans les champs commerciaux d'orge (Hordeum vulgare), les nematodes des nodositĂ©s Ă©taient plus nombreux lorsque l'orge suivait une culture combinĂ©e de trĂšfle rouge (Trifolium pratense) et de flĂ©ole (Phleum pratense) et les nematodes du rabougrissement (Tylenchorynchus spp., principalement T. dubiuset Merlinius spp.) Ă©taient plus nombreux quand l'orge Ă©tait semĂ©e pendant deux annĂ©es consĂ©cutives. La masse de la matiĂšre sĂšche combinĂ©e du feuillage et du grain Ă©tait plus importante lorsque l'orge Ă©tait semĂ©e auprĂšs des pommes de terre (Solanum tuberosum) et cette masse Ă©tait plus faible avec deux cultures successives d’orge ou avec un mĂ©lange de trĂšfle rouge et de flĂ©ole. En conditions expĂ©rimentales au champ, les populations de nĂ©matodes des nodositĂ©s Ă©taient plus Ă©levĂ©es dans les racines d’orge lorsque celle-ci Ă©tait cultivĂ©e aprĂšs des pommes de terre et les rendements en grain Ă©taient plus faibles lorsque l’orge Ă©tait cultivĂ©e pendant deux annĂ©es consĂ©cutives. Les changements dans les populations de nĂ©matodes chez la pomme de terre n’étaient pas associĂ©s aux sĂ©quences dĂ©butant avec le blĂ© (Triticum aestivum) ou l’orge que dans les sĂ©quences dĂ©butant avec les pommes de terre ou le soya (Glycine max). L’aldicarbe a rĂ©duit le nombre de nĂ©matodes des nodositĂ©s en plus d’accroĂźtre les rendements en pommes de terre et en soya.A field study assessing the influence of the previous crop, the crop sequence, and aldicarb treatments on root lesion nematode populations and crop yields was carried out in Prince-Edward-Island, Canada. The most recent crop had the greatest impact on nematode numbers. The crop sequences had an influence in some cases on root lesion nematode populations (primarily Pratylenchus penetrans) and on crop yields. In commercial barley (Hordeum vulgare) fields, root lesion nematodes in roots were greatest when barley followed a red clover (Trifolium pratense) timothy (Phleum pratense) ley, and stunt nematodes (Tylenchorhynchus spp., primarily T. dubius, and Merlinius spp.) were more common when barley followed barley. The combined dry weight of foliage and grain was larger when barley was planted after potato (Solanumtuberosum) and smaller when barley followed barley or a red clover-timothy mixture. Under experimental field conditions, root lesion nematode populations were largest in barley roots when barley followed potato and grain yields were smallest when barley followed barley. Changes in nematode populations in potato were not associated with crop sequences. Potato tuber yields were higher in the sequences that began with wheat (Triticum aestivum) or barley than in the sequences that began with potato or soybean (Glycine max). Aldicarb reduced the numbers of root lesion nematodes in roots with concomitant yield increases in potato and soybean

    Electrodiagnostic assessment of the autonomic nervous system: A consensus statement endorsed by the American Autonomic Society, American Academy of Neurology, and the International Federation of Clinical Neurophysiology

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    Evaluation of disorders of the autonomic nervous system is both an art and a science, calling upon the physician's most astute clinical skills as well as knowledge of autonomic neurology and physiology. Over the last three decades, the development of noninvasive clinical tests that assess the function of autonomic nerves, the validation and standardization of these tests, and the growth of a large body of literature characterizing test results in patients with autonomic disorders have equipped clinical practice further with a valuable set of objective tools to assist diagnosis and prognosis. This review, based on current evidence, outlines an international expert consensus set of recommendations to guide clinical electrodiagnostic autonomic testing. Grading and localization of autonomic deficits incorporates scores from sympathetic cardiovascular adrenergic, parasympathetic cardiovagal, and sudomotor testing, as no single test alone is sufficient to diagnose the degree or distribution of autonomic failure. The composite autonomic severity score (CASS) is a useful score of autonomic failure that is normalized for age and gender. Valid indications for autonomic testing include generalized autonomic failure, regional or selective system syndromes of autonomic impairment, peripheral autonomic neuropathy and ganglionopathy, small fiber neuropathy, orthostatic hypotension, orthostatic intolerance, syncope, neurodegenerative disorders, autonomic hyperactivity, and anhidrosis

    Root‐lesion nematodes of potato: current status of diagnostics, pathogenicity and management

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    Root‐lesion nematodes of the genus Pratylenchus are migratory endoparasites with worldwide economic impact on several important crops including potato, where certain species like P. penetrans, P. neglectus and P. scribneri reduce the yield and quality of potato tubers. Morphological identification of Pratylenchus spp. is challenging, and recent advancements in molecular techniques provide robust and rapid diagnostics to differentiate species without need of specialist skills. However, the fact that molecular diagnostics are not available for all Pratylenchus species means that there are limitations in worldwide application. In general, root‐lesion nematodes are difficult to manage once introduced into agricultural land and damage can be related to pathogenicity and population densities. In addition, root‐lesion nematodes interact with fungi such as V. dahliae, resulting in disease complexes that enhance the damage inflicted on the potato crop. Management interventions are often focused on limiting nematode reproduction before planting crops and include the application of nematicides, and cultural practices such as crop rotation, cover crops, biofumigation, and biological control. Understanding the limitations of the available crop protection strategies is important and there are many gaps for further study. This review discusses the status of the diagnosis, distribution, pathogenicity and management of the main species of root‐lesion nematodes, reported to infect potatoes worldwide, and highlights areas for potential future research

    Synergistic NGF/B27 Gradients Position Synapses Heterogeneously in 3D Micropatterned Neural Cultures

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    Native functional brain circuits show different numbers of synapses (synaptic densities) in the cerebral cortex. Until now, different synaptic densities could not be studied in vitro using current cell culture methods for primary neurons. Herein, we present a novel microfluidic based cell culture method that combines 3D micropatterning of hydrogel layers with linear chemical gradient formation. Micropatterned hydrogels were used to encapsulate dissociated cortical neurons in laminar cell layers and neurotrophic factors NGF and B27 were added to influence the formation of synapses. Neurotrophic gradients allowed for the positioning of distinguishable synaptic densities throughout a 3D micropatterned neural culture. NGF and B27 gradients were maintained in the microfluidic device for over two weeks without perfusion pumps by utilizing a refilling procedure. Spatial distribution of synapses was examined with a pre-synaptic marker to determine synaptic densities. From our experiments, we observed that (1) cortical neurons responded only to synergistic NGF/B27 gradients, (2) synaptic density increased proportionally to synergistic NGF/B27 gradients; (3) homogeneous distribution of B27 disturbed cortical neurons in sensing NGF gradients and (4) the cell layer position significantly impacted spatial distribution of synapses
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