Long-Term Esca Monitoring Reveals Disease Impacts on Fruit Yield and Wine Quality.

Esca is a widespread grapevine trunk disease, and a global increase in esca incidence has been observed in recent decades. Estimates attribute considerable economic losses to esca, and the disease is considered one of the major causes of vine mortality and vineyard dieback. However, accurate quantification of esca incidence is difficult due to symptom inconsistency, and there are very few studies precisely quantifying yield losses and impacts on fruit composition and wine quality. This study carried out an extensive esca surveying program; annually monitoring approximately 57,000 vines across 12 estates in the Bordeaux region for 9 years. In conjunction with this surveying program, we quantified the yield losses of vines with known esca symptom histories and assessed their fruit composition and resulting wine quality. The study revealed that, because of year-to-year variation in symptom expression, accurate rates of esca can only be obtained through monitoring over many years. We found that yield losses in individual vines exhibiting esca can reach up to 50% but they are rarely unproductive, and when scaled to the parcel scale yield losses are low, never exceeding 1 hl/ha. In addition, the quality of the grapes produced is similar to that obtained from vines without symptoms. Finally, the majority of mortality observed in vineyards was not due to esca, with only 40% of dead vines exhibiting an esca history. These results suggest that the impact of esca is likely overestimated and that it is necessary to more broadly investigate other factors contributing to vine mortality and vineyard dieback.[Formula: see text] Copyright © 2022 The Author(s). This is an open-access article distributed under the CC BY 4.0 International license.

Impact of vine water status on berry mass and berry tissue development of Cabernet franc (Vitis vinifera L.), assessed at berry level.

BACKGROUND: Berry size is considered an important quality factor in red wine production. The objective of this work was to study the effect of vine water status on berry mass in field conditions, with a specific focus on berry tissue masses. RESULTS: The study was carried out over 2 years in a plot located in Sicily (Italy). Two irrigation treatments were established. Dynamic evolution of berry mass and berry tissue masses at harvest were recorded. Berries produced under water deficit conditions were smaller and characterized by a higher skin-to-flesh ratio. However, this ratio did not change when berry mass varied independently from vine water status, showing coordinated growth of flesh and skin under these conditions. CONCLUSION: The implications of berry size on skin-to-flesh ratios depend on the factor causing berry size differences. This finding might question the conclusions of most research trying to demonstrate that berry size is, or is not, an important parameter for quality. The factors impacting berry size are likely to differ according to the scale considered. This highlights the importance of investigating the causal effects of varying berry size, before possibly discussing the potential effects on fruit composition and, subsequently, wine quality. Berries produced by grapevines facing water deficit have a higher skin-to-flesh ratio. Hence, limited water conditions, represent a powerful tool to increase the concentration of major solutes involved in wine quality, which are located in berry skins rather than in berry flesh. © 2019 Society of Chemical Industry.

Impact of clonal variability in Vitis vinifera Cabernet franc on grape composition, wine quality, leaf blade stilbene content, and downy mildew resistance.

In this study, 10 clones of Vitis vinifera Cabernet franc (not yet commercial) have been phenotyped on precocity, grape composition, and assessment of wine quality made by microvinification in 2008-2010. Additionally, two original criteria have been considered: concentration of 3-isobutyl-2-methoxypyrazine (IBMP) in grapes and wines (the green bell pepper flavor) and resistance of grapevines to downy mildew ( Plasmopara viticola ) by stilbene quantification upon infection. Precocity of veraison varied up to four days at veraison. Berry size and yield were highly variable among clones. However, these variables were not correlated. Tanins and anthocyanins varied among clones in grapes and wines. Variations in grape and wine IBMP were not significant. Some clones showed lower susceptibility for downy mildew on leaves. Lower susceptibility was linked to a higher production of stilbenic phytoalexins involved in downy mildew resistance mechanisms.