Research

Physiological ripening disorders of grapevine affect yield and berry quality substantially every year. Although physiological ripening disorders are of high economic importance in viticulture, the information are scarce and causes still need to be identified. Therefore, further attention is needed to understand the induction of the ripening disorder berry shrivel including the influence of environmental factors, which has not been studied so far. The project aims to identify potential underlying environmental factors influencing BS abundance in vineyards in order to develop BS risk factors on a local spatial scale with in multi-disciplinary approach. Thereby we follow the hypothesis that a) environmental factors could summarize to a higher probability of BS incidence, b) that we can scale, translate and extrapolate these factors on GIS maps and c) that wine making itself allows a certain percentage of BS grapes included without negative effects on aroma profiles. Our experimental approach can be summarized in three work packages (WPs): 1) Developing a BS monitoring method and bring this information into a BS abundance map linked with spatial (geology, soil and vineyard management) and temporal (microclimate, climate) information. 2) We are going to investigate the consequences of BS on aroma profiles of berries and processed wines in order to provide recommendations for farmers, and targeted metabolites will be determined on a phenological timescale in order to follow BS development. 3) Finally, we aim to extract BS risk factors on a spatial and temporal scale for vineyards of our study region, and additionally process the obtained information to drought risk maps. Methods used will be: GIS mapping, climate models, soil analyses, geological characterization, vine physiology, targeted metabolites and aroma metabolites. Our approach will close a gap of knowledge on the physiological ripening disorder berry shrivel by establishing the frist time a spatial information of BS within a study region involving a set of important influencing factors relevant for grape berry ripening. This multi-disciplinary approach is a novelty to target berry shrivel with the aim to identify inducing factors.

Susceptibility of grape berries to stressors such as drought or heat changes according to the stress intensity and duration, but also depending on the berry developmental status at stress occurrence. For example, grapes in the herbaceous phase are more susceptible to drought stress than berries in the ripening stage. Drought and heat stress, which are predicted to increase in frequency and magnitude due to climate change, share a common effect in increasing the production of cytotoxic reactive oxygen species (ROS) in plant cells. While ROS are produced basally as signaling molecules, and plants have adapted mechanisms to detoxify them, stressful conditions increase their production. Given the economic importance of Vitis vinifera for the wine industry in Austria (and worldwide), it is important to understand how ROS metabolism interacts with other metabolic pathways active at the different stages of berry development, and therefore the effects of the timing of ROS-inducing stress factors. The inability to detoxify ROS may cause changes in berry metabolism and development that affect harvest quality, such as by increasing lipid oxidation, membrane damage, and subsequent cell death, the latter of which can cause symptoms such as berry shriveling in extreme cases. The project will explore the different strategies that grape berries could adopt to counteract an increase in ROS molecules produced in response to stressors, including the boost of the antioxidant pool (or de novo biosynthesis of antioxidant molecules) and the modification in the expression of ROS scavenging enzymes. The ROS scavenging capacity of developing grape tissue will be quantified by enzyme activity assays and gene expression analysis. Damage in berries caused by ROS will be quantified following drought and heat imposition in terms of the extent of lipid oxidation, cell death and changes in berry composition.

Winegrape production is one of the most economically important agrosystems in Europe. Grapevine has a large breadth of genetic diversity at the rootstock, variety, and clone levels. Unfortunately, very little of this diversity is currently utilized and its potential role in abiotic stress response has not been properly quantified. This leaves growers with the open-question of which is the best tool(s) to adapt their vineyards to specific environmental challenges (e.g. heatwaves, drought, waterlogging, etc). At the scientific level, it is essential to understand the genetic plasticity of rootstocks, varieties and clones (and their interactions) to further adapt and improve the current planting material and to preserve the genetic diversity of grape varieties used across Europe. Standards for physiological traits need to be defined, and the influence of the diverse genetic backgrounds to the value and flexibility of these traits under different environmental conditions needs to be understood. With this in mind, project DiverGrape has been designed including partners from four European countries with varying environmental and vineyard conditions. The partnership will exchange pre-doctoral and postdoc researchers using a standardized methodological approach based on both eco-physiology and metabolomics tools to quantify the contribution to environmental response of: i) clonal variation within given local varieties, ii) rootstock material for a given variety and ii) the interaction between rootstock and scion. Taking advantage of existing vineyards with a variety of genetic material located in different European viticulture areas, the partnership will quantify how environment drives grapevine plasticity to specific climates. The results obtained through project DiverGrape will provide grape growers with the knowledge to optimize the existing grapevine genetic diversity in order to adapt their vineyards to more extreme climate situations.