Papers by Helga Reisenzein
Slide of the Euphresco project 'Grapevine flavescence doreé (FD) follow up Vitisens, GRAFDEPI... more Slide of the Euphresco project 'Grapevine flavescence doreé (FD) follow up Vitisens, GRAFDEPI and Qdetect' (GRAFDEPI2)
<em>Xylella fastidiosa</em> is a bacterial pathogen transmitted by insect vectors. In... more <em>Xylella fastidiosa</em> is a bacterial pathogen transmitted by insect vectors. In the Americas, the primary vectors are Cicadellidae, subfamily Cicadellinae, i.e. glassy-winged and blue-green sharpshooters whereas in Europe the common meadow spittlebug or froghopper <em>Philaenus spumarius</em> has been identified as the primary vector beside two other spittlebugs, <em>Neophilaenus campestris</em> and <em>Philaenus italosignus</em>. <em>P. spumarius</em> is abundant in Europe, wide-ranging geographically and present in a variety of habitats as well as being highly polyphagous. However, it is important to recognise that although <em>Philaenus spumarius</em> is the most important vector identified at this time, any xylem feeding insect could potentially act as a vector. Although routine surveillance for <em>X. fastidiosa</em> is carried out on plant material it is also possible to detect the bacterium within the foregut of insects. Recent studies have indicated that, in conjunction with plant surveys, testing vectors for <em>Xylella</em> could be an important tool for monitoring for the bacteria within the wider environment. The main activities of this project focussed on: Surveys of potential vector species and association with plant hosts within different habitats including agroecosystems such as vineyards and olive groves collecting data on abundance and host plant preferences. Evaluation of sampling and trapping methods for vectors surveillance. Sweep netting is the most effective method and is therefore recommended. However yellow sticky-traps or pan-traps as passive trapping methods also proved to be suitable for monitoring for the presence of spittlebugs. Development and evaluation of molecular tests to identify vectors alongside well-established DNA barcoding techniques. CO1 sequences are readily available within GenBank and BOLD for several <em>Philaenus</em> and other species. A specific real-time PCR test was developed for the identification of <em>Philaenus spumarius</em>. Development and evaluation [...]
Modelling the epidemiology of Flavescence dorée in relation to its alternate host plants and vect... more Modelling the epidemiology of Flavescence dorée in relation to its alternate host plants and vectors (Flavid) Funding Non-competitive funding mechanism. Each funder only pays for the participation of their own national researchers. Total funding € 148 000 Picture 1 Picture 1 Picture 1 Goals The goal of the project is to develop a risk analysis system encompassing different risk models for particular epidemiological scenarios. Building on lessons learned from the modelling of different outbreak situation and emergency pathways of FD, risk-based surveillance schemes and control strategies will be elaborated.
Des investigations sur les consequences ecologiques de mesures de production controlees et integr... more Des investigations sur les consequences ecologiques de mesures de production controlees et integrees en viticulture sur quelques organismes de la pedobiocœnose furent conduites en 1998 sur deux parcelles a Seewinkel. L'influence des facteurs (profondeur de l'echantillon, epoque de la prise d'echantillons, site de la prise d'echantillon - rang de vigne ou interligne degre d'enherbement permanent, site et methode de production) sur l'abondance des Nematodes et des spores de Mycorrhizes a ete analysee. On se posa de meme la question de savoir s'il existait une relation entre l'abondance des deux groupes d'organismes. Une investigation differentiee des deux fractions montra que l'abondance des spores de Mycorrhizes dependait du site et de la profondeur du sol. Le nombre de spores par g de terre augmente avec la profondeur dans des sols Tschernosems, alors que dans sols sablonneux la profondeur n'avait aucune influence. L'etude de l'evolution durant l'annee des Mycorrhizes montre en Avril un niveau maximal, alors que l'epoque de prise d'echantillons n'a aucune influence sur le nombre de nematodes. On trouve plus de spores de Mycorrhize dans les rangs de vignes que dans les interlignes, mais ceci n'est pas valable pour les nematodes, On en put pas montrer non plus une relation entre le degre d'enherbement permanent et la presence de ces deux organismes. Si l'on compare les sols Tschernosem et sableux, il apparait que dans ce dernier on trouve e moins de spores de Mycorrhizes mais plus de Nematodes. Les methodes de production n'ont pas d'influence notable sur le nombre de spores de mycorrhizes ou sur l'espece de nematode Xiphinema vuittenezi parasite des racines, mais sur la population totale des nematodes. On trouve le plus d'individus dans la jachere. On constate aussi une plus grande abondance dans le cas de l'enherbement hivernal. Il n'existe pas de relation entre la presence des spores de mycorrhizes et le nombre d'individus de nematode de l'espece Xiphinema vuittenezi.
Archives of Virology, Aug 30, 2020
Bulletin of Insectology, 2011
A long-term survey on the presence of phytoplasmas in Austrian viticulture was conducted from 200... more A long-term survey on the presence of phytoplasmas in Austrian viticulture was conducted from 2004 to 2010. 'Boir noir' was widespread in all Austrian vine growing areas, no other phytoplasmas could be identified until 2009. The first finding of grapevine 'flavescence dorée' (FD) was in Southeast Styria in 2009. FD was identified in Vitis vinifera (cv. "Müller Thurgau" and "Sämling 88"), in an American hybrid (cv. Isabella) and phytoplasmas of the same subgroup were also detected in Clematis vitalba. This first disease outbreak affected four different vineyards. Incidence of few newly-affected grapevines and clematis plants were observed within the infected area, however about 0.5 ha vine growing area has been uprooted until 2010. A second outbreak of FD was detected in the region of South Styria. It was an isolate disease outbreak on two single grapevines (cv. Sämling 88) and FD-related phytoplasmas were also detected in three plants of C. vitalba. The ribosomal group affiliation of all characterized samples from both regions indicated that the phytoplasmas belonged to the ribosomal subgroup 16SrV-C. To prevent further spreading of this quarantine pathogen focus zones and a buffer zones were designated in Southeast Styria and in South Styria.
Acta horticulturae, Feb 1, 2007
Over a period of four years, different study sites were monitored by sampling roots and soil. To ... more Over a period of four years, different study sites were monitored by sampling roots and soil. To assess the possible influence of soil characteristics on phylloxera infestation, in addition to the monitoring of nodosities on rootlets, chemical and physical soil properties were analysed. Furthermore, the structure, porosity and water permeability were described for some study sites. A significant correlation between phylloxera infestation and several soil properties could be stated. Permanent soil properties like pH, carbonate content, organic carbon (C org) and soil texture had an impact on phylloxera infestation. The soil pH of the investigated vineyards ranged from 5.0 to 7.8 and was negatively correlated with phylloxera infestation. With increasing clay and humus content, the abundance of nodosities increased. The specific formation of clay humus complexes, being a very important part of the micro structure of the soil, might be the main factor enhancing the infestation. The sand and carbonate contents of the soil had a negative effect on the infestation. Phylloxera infestation was also closely related to the nutrient availability, especially of phosphorous, potassium, magnesium, copper and zinc. Furthermore, a highly significant correlation between infestation frequency and the K/Mg-ratio could be stated. Surplus or deficiency situations for magnesium and potassium, especially in the lower soil layer, enhanced the phylloxera infestation. In contrast to other investigations, the N mincontent and the total N content did not show any correlation to the infestation. For other physiochemical soil parameters like soil type, silt content, manganese, boron and electric conductivity, but also for soil microbial parameters like soil respiration, microbial biomass, N-mineralization, soil enzyme activities (xylanase, arylsulfatase), no influence could be stated.
Molecular Microbiology, Mar 1, 1993
Regulation of the traM gene, which encodes a factor essential for conjugation of resistance plasm... more Regulation of the traM gene, which encodes a factor essential for conjugation of resistance plasmid R1, was studied in vivo using translational gene fusion. traM&quot;lacZ fusion constructs were transferred to the chromosome via the recombinant phage lambda RZ5. The level of beta-galactosidase expressed by the lysogens indicates that the traM promoters are very active. Expression of traM was diminished five- to sixfold when the single-copy plasmids R1 or R1-19 were present in trans. When recombinant plasmids carrying traM were present at higher copy numbers, traM expression was reduced as much as 45-fold. The negative effect of R1 plasmids on traM expression in trans, which we interpret as autoregulation, was observed regardless of whether the plasmids were conjugatively repressed or derepressed. Site-specific mutagenesis of the region encoding the N-terminus of the TraM protein eliminated the autoregulative effect indicating that the N-terminal amino acids of the protein are important to its DNA-binding function. The autoregulatory behaviour of TraM is allele specific. R1- or P307-encoded TraM molecules were found to recognize only the cognate DNA.
Acta horticulturae, Dec 1, 2011
Vitis: Journal of Grapevine Research, Apr 21, 2015
Vergleichende Untersuchung der bodenbewohnenden Nematodenfauna von mit der Wurzelreblaus (Viteus ... more Vergleichende Untersuchung der bodenbewohnenden Nematodenfauna von mit der Wurzelreblaus (Viteus vitifoliae Fitch) befallenen Weinreben (Vitis spp.) M. HOSCHITZ 1) und H. REISENZEIN 2)
Phytopathologia Mediterranea, 2000
ABSTRACT
Acta horticulturae, Mar 1, 2000
Archives of Virology, Jul 8, 2020
The transmission of the apscaviroid tentatively named apple chlorotic fruit spot viroid (ACFSVd) ... more The transmission of the apscaviroid tentatively named apple chlorotic fruit spot viroid (ACFSVd) was investigated using a one-step reverse-transcription (RT) droplet digital PCR assay for absolute quantification of the viroid, followed by quantification of relative standard curves by RT-qPCR. Our results indicate that ACFSVd is effectively transmitted by grafting, budding and seeds. No transmission has yet been observed to the viroid-inoculated pome fruit species Pyrus sp. and Cydonia sp. ACFSVd was detected in viruliferous aphids (Myzus persicae, Dysaphis plantaginea) and in codling moths (Cydia pomonella). The viroid was also detected systemically in the infected hemiparasitic plant Viscum album subsp. album (mistletoe).
Acta horticulturae, May 1, 2011
In the present study the correlation of visual fire blight symptoms and the migration of a virule... more In the present study the correlation of visual fire blight symptoms and the migration of a virulent E. amylovora strain within the tissue of susceptible and tolerant apple and pear cultivars was investigated. Flowers and shoots of commercial apple cultivars were artificially inoculated. Three cultivars diverged in terms of symptom expression after flower and shoot inoculation, respectively: 'Fuji KIKU 8' ® and 'Topaz' ® developed severe symptoms on shoots but only a relatively low number of flowers were infected. Conversely, 'Golden Delicious Kl. B Laimburg' ® displayed severe necrosis on shoots but was the least susceptible of all the cultivars after flower inoculation. Apple and pear cultivars that have a regional importance for large trees in extensive orchard management were tested for their susceptibility to artificial shoot inoculation. In our experiments the susceptibility (i.e., expression of shoot necrosis) of investigated apple cultivars for commercial and traditional orchards was compared and ranged from 17 to 50%. A lesion length of more than 60% was observed for only one apple cultivar ('Brentewinar'). The opposite situation arose in the tested traditional pear cultivars where 61% showed 60% lesion length. In this study the visual symptoms did not correspond with the spatial distribution patterns and the quantities of E. amylovora within the plant tissue. In apple cultivars most bacteria remained near the site of inoculation. However, in two tested apple cultivars, and in all tested pear cultivars, the pathogen could be detected even in the rootstocks. Also in pear trees, large numbers of the pathogen could be detected in non-inoculated shoots and further downwards. Even the pear cultivar 'Harrow Sweet' and the apple cultivars 'Schmiedberger Renette', and 'Rewena', which had been considered less susceptible, showed an extended endophytic bacterial dissemination. These findings may have an impact on both the evaluation of new cultivars and on sanitary measures regarding fire blight control.
Organic viticulture has grown considerably in the last decade; nonetheless, organic farming still... more Organic viticulture has grown considerably in the last decade; nonetheless, organic farming still has a huge potential for innovation and improved solutions specifically for the control of pests and pathogens. The research project VineMan.org (www.vineman-org.eu), funded by European Union within the CORE Organic II ERA-Net (project no. 249667), aims at improving disease control, one of the most difficult tasks in organic viticulture, through innovative cropping systems based on integration of: i) enhanced plant resistance, ii) vineyard management practices, iii) use of biological control agents, and iv) targeted applications based on disease models. During the first year, the above mentioned components of an integrated system have been developed and tested. Natural compounds were tested with a leaf disk assay and some of them were able to activate plant innate immunity. Early leaf removal, resulting in modified microclimate and changed bunch compactness and berry skin structure, was effective in reducing grey mould incidence on grapes. The entomopathogenic fungus Lecanicillium lecanii was used against the leafhopper Scaphoideus titanus, the vector of the flavescence doree phytoplasma, and proved to be virulent to its second instar nymphs. Disease models for downy and powdery mildews were implemented in a web-based decision support system for organic viticulture, and tested in several Italian vineyards; the number of copper treatments against downy mildew was reduced by 36% on average. Finally, innovative strategies based on these results were designed and evaluated for overall sustainability trough an ex-ante assessment. These strategies are under test in different viticultural areas of Europe.
Pflanzenschutzberichte, 2000
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Papers by Helga Reisenzein