Heat-waves hit drought grapevines – Impact on Austrian grape physiology and biochemistry

Heat-waves have occurred frequently in last years in many Austrian wine regions. Such events verify mostly during dry summer periods leading to a combined effect of drought and heat stress on grapevines. Nevertheless, very few studies have addressed the combination of the two factors in a systematic way. Moreover, most of the knowledge we have on the topic comes from arid or semi-arid regions, while the response to such events on continental climates such as in the Austrian wine regions is lacking. Therefore, this 3-years project aims to study the combined effects of the two stressors (heat and drought stress) on the grapevine physiology response and its consequences on berry metabolism and composition with particular focus on key metabolites determining wine quality such as flavonoids and aroma compounds. For the study, Riesling and Blaufränkisch, two widely cultivated winegrapes in Austria particularly rich in aroma compounds such as norisoprenoids, will be considered. The experiments will be carried out under semi-controlled conditions where 2-years old potted vines will be sheltered from rain to fully control water availability. Heatwaves on the other hand will be artificially imposed by means of infrared lamps on the canopy. Parameters such as the photosynthetic efficiency and water use, as well as key metabolites will be investigated in the plant and berries to characterize the physiology adaptation. The partners involved, BOKU-IWOB, Wein&Obst Klosterneuburg RTD, and HBLA Klosterneuburg, are leading institution for research in viticulture and enology with the expertise to achieve the project objectives. In particular, BOKU-IWOB is responsible for the field experiments and vine physiology studies, while the analytical power of the Klosterneuburg institute will allow the detailed analyses of the secondary metabolites in the grape berries.