Station de Recherche Agroscope Changins Wadenswil ACW

Nyon, Switzerland

Station de Recherche Agroscope Changins Wadenswil ACW

Nyon, Switzerland
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Johannesen J.,University of Mainz | Foissac X.,French National Institute for Agricultural Research | Foissac X.,University of Bordeaux Segalen | Kehrli P.,Station de recherche Agroscope Changins Wadenswil ACW | Maixner M.,Julius Kuhn Institute
PLoS ONE | Year: 2012

Dissemination of vector-transmitted pathogens depend on the survival and dispersal of the vector and the vector's ability to transmit the pathogen, while the host range of vector and pathogen determine the breath of transmission possibilities. In this study, we address how the interaction between dispersal and plant fidelities of a pathogen (stolbur phytoplasma tuf-a) and its vector (Hyalesthes obsoletus: Cixiidae) affect the emergence of the pathogen. Using genetic markers, we analysed the geographic origin and range expansion of both organisms in Western Europe and, specifically, whether the pathogen's dissemination in the northern range is caused by resident vectors widening their host-plant use from field bindweed to stinging nettle, and subsequent host specialisation. We found evidence for common origins of pathogen and vector south of the European Alps. Genetic patterns in vector populations show signals of secondary range expansion in Western Europe leading to dissemination of tuf-a pathogens, which might be newly acquired and of hybrid origin. Hence, the emergence of stolbur tuf-a in the northern range was explained by secondary immigration of vectors carrying stinging nettle-specialised tuf-a, not by widening the host-plant spectrum of resident vectors with pathogen transmission from field bindweed to stinging nettle nor by primary co-migration from the resident vector's historical area of origin. The introduction of tuf-a to stinging nettle in the northern range was therefore independent of vector's host-plant specialisation but the rapid pathogen dissemination depended on the vector's host shift, whereas the general dissemination elsewhere was linked to plant specialisation of the pathogen but not of the vector. © 2012 Johannesen et al.


Zufferey V.,Station de Recherche Agroscope Changins Wadenswil ACW | Smart D.R.,University of California at Davis
Functional Plant Biology | Year: 2012

We examined stomatal behaviour of a grapevine cultivar (Vitis vinifera L. cv. Syrah) following partial root removal under field conditions during progressively developing water deficits. Partial root removal led to an increase in hydraulic resistances along the soil-to-leaf pathway and leaf wilting symptoms appeared in the root-pruned plants immediately following root removal. Leaves recovered from wilting shortly thereafter, but hydraulic resistances were sustained. In comparison with the non-root pruned vines, leaves of root-pruned vines showed an immediate decrease in both pre-dawn (PD) and midday (leaf) leaf water potential. The decline in PD was unexpected in as much as soil moisture was not altered and it has been shown that axial water transport readily occurs in woody perennials. Only ∼30% of the functional root system was removed, thus leaving the system mainly intact for water redistribution. Stem water potential (Stem) and leaf gas exchanges of CO2 (A) and H2O (E) also declined immediately following root pruning. The lowering of PD, leaf, Stem, A and E was sustained during the entire growing season and was not dependent on irrigation during that time. This, and a close relationship between stomatal conductance (gs) and leaf-specific hydraulic conductance (Kplant), indicated that the stomatal response was linked to plant hydraulics. Stomatal closure was observed only in the root-restricted plants and at times of very high evaporative demand (VPD). In accordance with the Ball-Berry stomatal control model proposed by Ball et al. (1987), the stomatal sensitivity factor was also lower in the root-restricted plants than in intact plants as soil water availability decreased. Although PD, Stem and Leaf changed modestly and gradually following root removal, gs changed dramatically and abruptly following removal. These results suggest the involvement of stomatal restricting signals being propagated following removal of roots. © CSIRO 2012.


Bruggisser O.T.,University of Fribourg | Sandau N.,University of Fribourg | Blandenier G.,University of Fribourg | Blandenier G.,Center Suisse Of Cartographie Of La Faune Cscf | And 5 more authors.
Basic and Applied Ecology | Year: 2012

Species abundance in local communities is determined by bottom-up and top-down processes, which can act directly and indirectly on the focal species. Studies examining these effects simultaneously are rare. Here we explore the direct top-down and direct and indirect bottom-up forces regulating the abundance and predation success of an intermediate predator, the web-building spider Argiope bruennichi (Araneae: Araneidae). We manipulated plant diversity (2, 6, 12 or 20 sown species) in 9 wildflower strips in a region of intensive farmland. To identify the major factors regulating the distribution and abundance of A. bruennichi, we quantified three characteristics of vegetation (species diversity, composition and vegetation structure) as well as the spider's prey community and natural enemies. The distribution and abundance of A. bruennichi was regulated by combined bottom-up and top-down processes as well as by direct and indirect interactions between trophic levels. Four main factors were identified: (1) the strong direct effect of vegetation structure, (2) the positive effect of plant species diversity, which affected spider abundance directly and indirectly through increased densities and size of flower-visiting prey species, (3) the positive or negative direct effects of different plant species, and (4) the strongly negative direct effect of predacious hornets. The advantage of taking a global approach to understand the regulation of species abundance is highlighted first by the quantification of the relative importance of factors, with a surprisingly strong effect of hornet predators, and second by the discovery of a direct effect of plant diversity, which raises intriguing questions about habitat selection by this spider. © 2012 Gesellschaft für Ökologie.


Bischoff A.,University of Fribourg | Bischoff A.,National Institute of Horticulture and Landscape Planning INHP | Steinger T.,Station de recherche Agroscope Changins Wadenswil ACW | Mller-Scharer H.,University of Fribourg
Restoration Ecology | Year: 2010

The increased translocation of plant species for biodiversity restoration and habitat creation has provoked a debate on provenance and genotypic diversity of the used plant material. Nonlocal provenances are often not adapted to the local environmental conditions, and low population genotypic diversity may result in genetic bottlenecks hampering successful establishment. We tested provenance differentiation of four plant species used in agri-environment schemes to increase biodiversity of agricultural landscapes (wildflower strips). Provenances were collected close to the experimental field and at four further sites of different distances ranging from 120 to 900 km. In two of these provenances, different levels of genotypic diversity were simulated by sowing seed from a high and low number of mother plants. We found a large provenance differentiation in fitness-related traits, particularly in seedling emergence. There was no evidence for a general superiority of the local population. The productivity was greater in populations of high genotypic diversity than in those of low diversity, but the effect was only significant in one species. Productivity was also more constant among populations of high diversity, reducing the risk of establishment failure. Our results indicate that the choice of an appropriate provenance and a sufficient genotypic diversity are important issues in ecological restoration. The use of local provenances does not always guarantee the best performance, but a spread of superior alien genotypes can be avoided. A sufficient genotypic diversity of the sown plants might be a biological insurance against fluctuations in ecosystem processes increasing the reliability of restoration measures. © 2008 Society for Ecological Restoration International.


Spring J.-L.,Station de Recherche Agroscope Changins Wadenswil ACW | Verdenal T.,Station de Recherche Agroscope Changins Wadenswil ACW | Zufferey V.,Station de Recherche Agroscope Changins Wadenswil ACW | Viret O.,Station de Recherche Agroscope Changins Wadenswil ACW
Journal International des Sciences de la Vigne et du Vin | Year: 2012

Aims: The impact of canopy management on the nitrogen (N) content in grapevines was studied. Methods and Results: Two trials were carried out between 2001 and 2010 on Vitis vinifera cvs. Chasselas and Pinot noir. The observed factors of variation were the intensity of lateral shoot removal for the first trial and the severity of shoot trimming for the second trial. The N content was evaluated in parallel by leaf diagnosis, the chlorophyll index and the yeast available N concentration (YAN) found in the musts. When the yields were the same, a significant dilution of N in proportion to the development of the leaf area was revealed. Treatments resulting in excessive leaf area presented N deficiency in the leaves and the musts. Conclusion: The N content in both the vines and grapes was influenced by the canopy management (lateral shoot removal and shoot trimming), and the magnitude of the response appeared to be even greater in the absence of water stress. In addition, the risk of N deficiency was found to increase beyond a maximum value of the leaf-fruit ratio. Significance of the study: Canopy management has a significant influence on the N content in foliage and grapes, and the risk of N deficiency increases under a situation that produces an excessive leaf area. © Vigne et Vin Publications Internationales.


Kehrli P.,Station de recherche Agroscope Changins Wadenswil ACW | Delabays N.,Station de recherche Agroscope Changins Wadenswil ACW
Journal of Applied Entomology | Year: 2012

Bois noir is an important grapevine yellows disease that can cause serious economical losses in European grapevine production. Hyalesthes obsoletus Signoret (Hemiptera, Cixiidae) is the principal vector of bois noir in Switzerland and stinging nettle (Urtica dioica) is its favourite host plant species in vineyards. As bois noir disease can hardly be cured and direct control measures against H. obsoletus are ineffective, viticultural control practices target stinging nettle, the actual reservoir and source of both the pathogen and its vector. Currently, it is recommended to apply herbicides against stinging nettle at the end of the season to kill developing H. obsoletus nymphs. To verify if this late period of herbicide application is justified, stinging nettle patches were treated with glyphosate in the autumn, in the spring or were left untreated as a control. Herbicide applications at both dates controlled the growth of stinging nettle very well in the subsequent summer, although the autumnal treatment was slightly more efficient. To study glyphosate's direct impact on the development of H. obsoletus nymphs, emergence traps were placed directly in the centre of treated and untreated stinging nettle patches. There was no significant difference among the three treatments in the total number of adults emerging. Thus, an aerial application of glyphosate in either spring or autumn did not inhibit the nymphs' development on the roots of stinging nettle in the soil. Our results challenge current recommendations of applying herbicides against stinging nettle at the end of the season and suggest that stinging nettle could also be controlled in spring, alike other viticultural weeds. © 2011 Blackwell Verlag, GmbH.


Zufferey V.,Station de Recherche Agroscope Changins Wadenswil ACW | Cochard H.,University Blaise Pascal | Ameglio T.,University Blaise Pascal | Spring J.-L.,Station de Recherche Agroscope Changins Wadenswil ACW | Viret O.,Station de Recherche Agroscope Changins Wadenswil ACW
Journal of Experimental Botany | Year: 2011

The impact of water deficit on stomatal conductance (gs), petiole hydraulic conductance (K petiole), and vulnerability to cavitation (PLC, percentage loss of hydraulic conductivity) in leaf petioles has been observed on field-grown vines (Vitis vinifera L. cv. Chasselas). Petioles were highly vulnerable to cavitation, with a 50% loss of hydraulic conductivity at a stem xylem water potential (Ψx) of-0.95MPa, and up to 90% loss of conductivity at a Ψx of-1.5MPa. K petiole described a daily cycle, decreasing during the day as water stress and evapotranspiration increased, then rising again in the early evening up to the previous morning's K petiole levels. In water-stressed vines, PLC increased sharply during the daytime and reached maximum values (70-90%) in the middle of the afternoon. Embolism repair occurred in petioles from the end of the day through the night. Indeed, PLC decreased in darkness in water-stressed vines. PLC variation in irrigated plants showed the same tendency, but with a smaller amplitude. The Chasselas cultivar appears to develop hydraulic segmentation, in which petiole cavitation plays an important role as a 'hydraulic fuse', thereby limiting leaf transpiration and the propagation of embolism and preserving the integrity of other organs (shoots and roots) during water stress. In the present study, progressive stomatal closure responded to a decrease in K petiole and an increase in cavitation events. Almost total closure of stomata (90%) was measured when PLC in petioles reached >90%. © 2011 The Author(s).


Van Leeuwen C.,University of Bordeaux 1 | Roby J.-P.,University of Bordeaux 1 | Alonso-Villaverde V.,Mision Biologica de Galicia CSIC | Gindro K.,Station de Recherche Agroscope Changins Wadenswil ACW
Journal of Agricultural and Food Chemistry | Year: 2013

In this study, 10 clones of Vitis vinifera Cabernet franc (not yet commercial) have been phenotyped on precocity, grape composition, and assessment of wine quality made by microvinification in 2008-2010. Additionally, two original criteria have been considered: concentration of 3-isobutyl-2- methoxypyrazine (IBMP) in grapes and wines (the green bell pepper flavor) and resistance of grapevines to downy mildew (Plasmopara viticola) by stilbene quantification upon infection. Precocity of veraison varied up to four days at veraison. Berry size and yield were highly variable among clones. However, these variables were not correlated. Tanins and anthocyanins varied among clones in grapes and wines. Variations in grape and wine IBMP were not significant. Some clones showed lower susceptibility for downy mildew on leaves. Lower susceptibility was linked to a higher production of stilbenic phytoalexins involved in downy mildew resistance mechanisms. © 2012 American Chemical Society.


Kessler S.,Station de recherche Agroscope Changins Wadenswil ACW | Kessler S.,University of Neuchatel | Schaerer S.,Station de recherche Agroscope Changins Wadenswil ACW | Delabays N.,Station de recherche Agroscope Changins Wadenswil ACW | And 3 more authors.
Entomologia Experimentalis et Applicata | Year: 2011

Bois noir is an important grapevine yellows disease in Europe that can cause serious economic losses in grapevine production. It is caused by stolbur phytoplasma strains of the taxonomic group 16Sr-XII-A. Hyalesthes obsoletus Signoret (Hemiptera: Cixiidae) is the most important vector of bois noir in Europe. This polyphagous planthopper is assumed to mainly use stinging nettle [Urtica dioica L. (Urticaceae)] and field bindweed [Convolvulus arvensis L. (Convolvulaceae)] as its host plants. For a better understanding of the epidemiology of bois noir in Switzerland, host plant preferences of H. obsoletus were studied in the field and in the laboratory. In vineyards of Western Switzerland, adults of H. obsoletus were primarily captured on U. dioica, but a few specimens were also caught on C. arvensis, hedge bindweed [Calystegia sepium (L.) R. Brown (Convolvulaceae)], and five other dicotyledons [i.e., Clematis vitalba L. (Ranunculaceae), Lepidium draba L. (Brassicaceae), Plantago lanceolata L. (Plantaginaceae), Polygonum aviculare L. (Polygonaceae), and Taraxacum officinale Weber (Asteraceae)]. The preference of the vector for U. dioica compared to C. arvensis was confirmed by a second, more targeted field study and by the positioning of emergence traps above the two plant species. Two-choice experiments in the laboratory showed that H. obsoletus adults originating from U. dioica preferred to feed and to oviposit on U. dioica compared to C. arvensis. However, H. obsoletus nymphs showed no host plant preference, even though they developed much better on U. dioica than on C. arvensis. Similarly, adults survived significantly longer on U. dioica than on C. arvensis or any other plant species tested [i.e., L. draba and Lavandula angustifolia Mill. (Lamiaceae)]. In conclusion, although nymphs of H. obsoletus had no inherent host plant preference, adults tested preferred to feed and oviposit on U. dioica, which is in agreement with the observed superior performance of both nymphal and adult stages on this plant species. Urtica dioica appears to be the principal host plant of H. obsoletus in Switzerland and plays therefore an important role in the epidemiology of the bois noir disease in Swiss vineyards. © 2011 The Authors. Entomologia Experimentalis et Applicata © 2011 The Netherlands Entomological Society.


Reynard J.-S.,Station de Recherche Agroscope Changins Wadenswil ACW | Zufferey V.,Station de Recherche Agroscope Changins Wadenswil ACW | Nicol G.-C.,Station de Recherche Agroscope Changins Wadenswil ACW | Murisier F.,Station de Recherche Agroscope Changins Wadenswil ACW
Journal International des Sciences de la Vigne et du Vin | Year: 2011

Aims: The aim of the study was to assess whether, for vineyards in Vaud (Switzerland), vine water status might be a major natural factor in determining wine sensory characteristics, i.e., responsible for the so-called ≪terroir≫ effect. Methods and Results: The impact of vine water status on fruit and wine characteristics was examined for 23 non-irrigated locations with different soil water holding capacities during three seasons (2007-2009). In 2009, a close relationship was observed between 813C and soil water holding capacity. Furthermore, the level of vine water status influenced both fruit and wine composition. Berry weight was strongly correlated to vine water status. The highest grape soluble solids content (SSC) at harvest was reached when water deficit was mild. Wine colour was related to vine water status: wine made from grapevines with low water status showed a significantly higher colour density. However, sensory analysis did not discriminate between wines from different water conditions. Conclusion: In a dry year like 2009, vine water status was related to soil water holding capacity and determined grape and wine characteristics. However, no clear relationship was observed between wine sensory characteristics and vine water status. Significance and impact of the study: This study confirms the importance of soil in determining grape and wine characteristics through its effect on vine water status. © Vigne et Vin Publications Internationales (Bordeaux, France).

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