Optimising grapevine summer stress responses and hormonal balance by applying kaolin in two Portuguese Demarcated Regions

Abstract

In Mediterranean-like climate areas, field-grown grapevines are typically exposed to severe environmental conditions during the summer season, which can negatively impact the sustainability of viticulture. Despite the short-term mitigation strategies available nowadays to cope with climate change, little is known regarding their effectiveness in different demarcated winegrowing regions with differing climate features. Hence, we applied a kaolin suspension (5 %) to Touriga-Franca (TF) and Touriga-Nacional (TN) grapevine varieties located in two Portuguese demarcated regions (Alentejo and Douro) with different mesoclimates to study its effect on the physiological performance, hormonal balance and ABA-related grapevine leaf gene expression during the 2017 and 2018 growing seasons. Data show that 2017 was warmer than 2018 due to the occurrence of two heatwaves in both locations, highlighting the protective effect of kaolin application under severe environmental conditions. In the first study year, at midday, kaolin enhanced water use efficiency (23 % in Douro and 13 % in Alentejo), carbon assimilation rates (PN; 72 % in Douro and 25 % in Alentejo), and the soluble sugar content of grapevine leaves, while decreasing the accumulation of plant growth regulators (ABA, IAA, and SA) during the ripening stage. The results show an up-regulation of ABA biosynthesis-related genes (VvNCED) in TF treated vines from the Douro vineyard mainly in 2017, suggesting an increased stress response under severe summer conditions. Additionally, kaolin triggered the expression of ABA-responsive genes (VvHVA22a and VvSnRK2.6) mainly in TF, indicating different varietal responses to kaolin application under fluctuating periods of summer stress.

Sustainable Development Directions for Wine Tourism in Douro Wine Region, Portugal

“…The increase in the water use efficiency of grapevine can reduce the irrigation need. The foliar application of kaolin suspension (5%) to Touriga-Franca and Touriga-Nacional varieties over two consecutive growing seasons in DDR enhanced water use efficiency and can be used in the future as a sustainable measure to reduce water use [46].…”

Sunscreen Based on Dicarboxylic Acid Salts Applications to Blueberries (Vaccinium corymbosum L.) Plants: Effects on Water Stress Tolerance and Productivity

“…Based on this, the effectiveness of radiation-reflecting products in improving leaf resilience when subjected to severe environmental conditions, mainly through gas-exchange assessment, can be significantly changed according to the variety, water status, and stress severity [37]. The effects of these products suggest the modulation of indole-3-acetic acid (IAA), salicylic acid (SA), and abscisic acid (ABA) levels in crops cultivated in Mediterranean-type climates [37,44,45]. ABA is a growth regulator that controls stomatal closure, transpiration, and the plant's response to water stress and has been foliar-applied on apples with inconclusive results [46,47].…”

Mediterranean viticulture in the context of climate change

“…Reversely, high doses (6% or more) act as antiperspirants, reducing CO 2 assimilation and transpiration rates, which can be advantageous when it is desired to avoid excessive concentration of sugar in the berries (Dinis et al, 2022). Positive effects on gas exchange parameters under water deficit conditions are regularly reported (Glenn et al, 2010;Dinis et al, 2018a;Frioni et al, 2019Frioni et al, , 2020Palliotti et al, 2019;Bernardo et al, 2021a). However, the amount of net CO 2 assimilation and transpiration rates vary among sites, vineyards plots, varieties and terroir.…”