Studying heat stress response of grapevine berries in the field often relies on weather conditions during the growing season. We constructed a mobile heating device, able to induce controlled heat stress on grapes in vineyards. The heater consisted of six 150 W infrared lamps mounted in a profile frame. Heating power of the lamps could be controlled individually by a control unit consisting of a single board computer and six temperature sensors to reach a pre-set temperature. The heat energy applied to individual berries within a cluster decreases by the squared distance to the heat source, enabling the establishment of temperature profiles within individual clusters. These profiles can be measured by infrared thermography once a steady state has been reached. Radiant flux density received by a berry depending on the distance was calculated based on a view factor and measured lamp surface temperature and resulted to 665 Wm-2 at 7cm. Infrared thermography of the fruit surface was in good agreement with measurements conducted with a thermocouple inserted at epidermis level. In combination with infrared thermography, the presented device offers possibilities for a wide range of applications like phenotyping for heat tolerance in the field to proceed in the understanding of the complex response of plants to heat stress. Sunburn necrosis symptoms were artificially induced with the aid of the device for cv. Bacchus and cv. Sylvaner in the 2020 and 2021 growing season. Threshold temperatures for sunburn induction (LT5030min) were derived from temperature data of single berries and visual sunburn assessment, applying logistic regression. A comparison of threshold temperatures for the occurrence of sunburn necrosis confirmed the higher susceptibility of cv. Bacchus. The lower susceptibility of cv. Sylvaner did not seem to be related to its phenolic composition, rendering a thermoprotective role of berry phenolic compounds unlikely.

In northern cold climate conditions, chilling requirement fulfillment in dormant grapevine buds is slowed or stopped by subzero temperatures impacting the transcriptional processes needed to complete chilling requirement. Cabernet Franc and Reisling in Geneva, NY were used to determine the impact of natural oscillating temperatures on grapevine bud transcriptional activity during light and dark periods of a two-week period in January with fluctuating diurnal winter temperatures. Cabernet Franc and Reisling bud samples were collected at 32 time points during the natural vineyard temperature cycle at 6:00 (dark), 14:00 (light) and 18:00 (dark) hours) to monitor gene expression in consecutive freezing and non-freezing temperature oscillations. Genotype, light and dark, and temperature oscillations conditions were explored.

Valpolicella is a wine region characterized by a wide use of the technology of grape drying for the production of two red passito wines, recognized as PDOs, “Recioto della Valpolicella” and the most famous “Amarone della Valpolicella”. Geographical origin of the grapes can influence wine composition by grape chemical composition yeast behaviour during fermentation. This study investigates the impact of different commercial yeast strains on aroma profiles of wines produced with withered grapes of different origins. In addition, the influence of spontaneous fermentation is also considered. METHODS: Experimental red wines were produced with a standard winemaking protocol with withered Corvina and Corvinone grapes obtained from two different geographical areas within the Valpolicella region. Fermentations were carried out with four different commercial yeasts plus a spontaneous fermentation. Wines were analysed by means of SPE- and SPME-GC-MS techniques and sensory analysis (sorting task).

Context and purpose. Climate change and the demand for reducing inputs, including chemical compounds, present significant challenges for perennial fruit crops like grapes and apples.

An experimental vineyard with a radial array was planted in 2018, to provide valuable information on the relationship between orientation and planting density on plant physiology and cluster microclimate, and the consequent impacts on grape secondary metabolites, including aromas and polyphenols.