News

Evaluating susceptibility of grape varieties against Botrytis-infections in vitro
 

Varieties with a compact grape bunch structure are particularly susceptible to Botrytis bunch rot as crushed berries provide large entry points for the fungus. However, the characteristics of the grape berry skin is also very important for Botrytis susceptibility. In order to better describe new varieties (PIWIs) with regard to their susceptibility to Botrytis depending on the berry skin structure, in vitro studies are being performed in the project. In the laboratory trials, the susceptibility to grey mould of different grape varieties (PIWIs and traditional varieties) is recorded regardless of the compactness of the grapes during the ripening process. Initial trials at the Dienstleistungszentrum Ländlicher Raum Rheinpfalz (DLR RP) showed clear differences in susceptibility between the varieties, which were largely independent of the berry sugar content. The PIWIs Sauvignac and Souvignier Gris, for example, proved to be more resistant to Botrytis than the traditional varieties tested, such as Chardonnay or Riesling, despite their higher sugar content.

Prototype for simulating heat stress validated
 

At the INRAE center of Colmar a prototype functioning for simulating heat waves was developed and validated. The next step will be to build a larger-scale device to conduct experiments combining heat stress and pathogen infections on resistant varieties in 2025.

Ice age for the berry skin
 

In recent years, it has already been shown that the texture of the berries and the waxes on the berry surface have a significant influence on the susceptibility of a grape variety to grey mould rot caused by Botrytis cinerea. In the WiVitis project, these valuable results have now been expanded by analysing the waxes on the berry skin surface of selected grape varieties using a cryo-scanning electron microscope (cryo-SEM) with a magnification of up to 8,000x by the partners of the Nano Imaging Lab. This magnification makes it possible to make the tiny structures of the wax surface in the nanometre range visible to the human eye.

A high vacuum at room temperature prevails in the SEM itself. The water in the sample, in our case the berry skin, would evaporate so quickly due to the vacuum that the berry skin would collapse immediately. This is why biological samples, such as our prepared piece of berry skin, are shock-frozen in liquid nitrogen beforehand. In this ice bath, which is a frosty -210°C, no ice crystals form and the cells of the sample remain intact and retain their original structure. A true ice age for the berry skin. In the cryo unit, the frozen samples are loaded with gold particles. As these are electrically conductive, signals are derived from the sample by subsequent irradiation with highly accelerated electrons and assembled as an image.

The result is impressive, high-resolution close-up images of berry skin surfaces, which provide the scientists with important insights into the diversity of wax structures of different grape varieties. They are now investigating what influence these structural differences have on resistance to Botrytis on grapes and what characteristics the investigated varieties show at different locations in the Upper Rhine region. This much can already be revealed: Some of the wax structures can be described as moose antlers or the arrangement of their wax platelets is like a bird's eye view of a mosh pit. Take a look for yourself.

Relationship discovered between berry stability and susceptibility to Botrytis bunch rot

As part of the project, infection assays with various pathogens are currently being carried out on different grape varieties at the State Institute for Viticulture and Oenology in Freiburg. The focus of this study is to evaluate the susceptibility of grapes to powdery mildew (Erysiphe necator) and grey mold (Botrytis cinerea). For this purpose, the berries of PIWI varieties and classic cultivars are artificially infected with spores of the pathogens at defined stages of development. The trials are analysed on different days post inoculation (dpi). Initial results suggest that there is a correlation between berry stability and susceptibility to grey mould. The evaluation of the susceptibility of the different varieties to powdery mildew is still pending.

Presentation of the WiVitis project at the 16th scientific days of the Réseau Francophone de Fluxomique et de Métabolomique

As part of the 16th scientific days of the « Réseau Francophone de Fluxomique et de Métabolomique» (RFMF, June 4-6, 2024, Saint-Malo, France), Olivia Ledieu (INRAE Colmar) presented a poster detailing her work as part of the Wivitis project, on the study of grape cuticular lipids by high-resolution mass spectrometry. Discussions with participants led to new avenues for the identification of compounds present in grape cuticles.

Started: Prototype for the simulation of heat stress in grapevines
 

The INRAE center of Colmar, Alsace, takes in charge a part of the WiVitis project centered on developing a device capable to provoke a thermic stress on grapevine. The basic idea is to be able to simulate an extreme climatic event (a heatwave) with an accuracy never reached before in agronomic studies. By simulating a heatwave, the researchers aim to explore the potential effects of heat on PIWI varieties’ resistance to pathogens.

Researchers of both SVQV (Santé de la Vigne et Qualité du Vin: grapevine health and wine quality) and UEAV (Unité Expérimentale Agronomique et Viticole: agronomic and viticultural experimental unit) units, guided by Łukasz Tarkowski, are developing a prototype for a heating device based on the use of infrared radiators. The prototype building and establishment is a key step to understand which parameters should be used for the final device in order to avoid construction mistakes.

As now, the prototype is almost finished and connectivity test are ongoing. Once the connectivity is validated, infrared radiators will be added to the prototype to make the first heat stress simulations.

Stay tuned!

Intensive exchange of the INTERREG VI project network WiVitis on 10 April 2024
 

The annual WiVitis project meeting took place this year at the Julius Kühn Institute (JKI) in Siebeldingen and was attended by (almost) all project partners from Germany, France and Switzerland. As the WiVitis network has only been fully staffed for a few months, all partners involved got to know each other personally and presented their methods and first results. Data collection strategies for the 2024 season were finalised, experimental set-ups discussed and protocols agreed. This is of particular importance, as comparable data sets are collected at the various research sites in the Upper Rhine region and used for cross-site variety characterisation. The PIWI grape varieties being comprehensively analysed in the project include Souvignier Gris, Calardis Blanc, Cabernet Blanc and Floreal.

The meeting began with a brief administrative report by the project coordinator Dr Katja Herzog, who illustrated the methods established at the Institute for Grapevine Breeding Geilweilerhof (JKI) for the high-throughput collection of objective data sets on grape and berry characteristics. The scientists at the JKI Institute will also use these in WiVitis to characterise varieties on the basis of their grape architecture and berry skin surface. These descriptive trait data (= phenotyping data) form the basis for estimating the Botrytis resistance of grape varieties and for developing molecular markers, which are used in vine breeding for the early selection of resistant seedlings. The State Viticulture Institute Freiburg (WBI) impressively demonstrated the infection prognoses for grapevine peronospora for PIWI grape varieties, which were further developed in the VITIFIT project and will be available to the whole of viticulture practice in the online prognosis tool VitiMeteo. In WiVitis, these infection prognoses for PIWI grape varieties will now also be developed for powdery mildew and corresponding tests realised. Microscopic analyses complement these tests and provide insights into the course of infection with the aim of deriving recommendations for action. Infection tests for powdery mildew and botrytis bunch rot and their effects on selected PIWI and traditional grape varieties are also being carried out by the Dienstleistungszentrum Ländlicher Raum (DLR) Rheinpfalz in WiVitis. The question of how Botrytis strains, which have been characterised as differently aggressive, affect the course of infection of Botrytis-resistant PIWIs remains exciting.

INRAE Grand Est Colmar reported on the current status of the analytical analyses of the lipid composition on the berry skin surface (= wax layer) of four PIWIs and two traditional varieties. The method used for this was adapted and newly established for berries in WiVitis. Initial results showed variety-specific differences in the lipid compositions detected, and these results are to be further consolidated in 2024 using samples from different locations. The partners in Colmar are also setting up a test facility to treat potted vines with heat stress and to investigate the effects of massively rising temperatures, such as those that can be found during heatwaves, on powdery and downy mildew infestation.

The Swiss partners from the Research Institute of Organic Agriculture (FiBL) aim to collect data in organically farmed vineyards and reported on sampling for investigations into the lipid composition on the surface of the berry skin and development and infection analyses of the grape varieties selected in the project. The scientific part of the meeting was rounded off by a report from the Basel Nano Imaging Lab (NI-Lab). The use of scanning electron microscopy (cryo-SEM) is the optimal method for characterising the surface quality of berries and structural differences in the overlying waxes. In this way, samples of the selected grape varieties will be collected and analysed in various vineyards in the Upper Rhine programme region.