Heat waves and drought stress impact grapevine growth and physiology

Climate change is here. One of the main consequences is an increase in the frequency and severity of abiotic stresses which mostly occur in a combined manner. Grapevine, which grows in a large diversity of pedo-climatic conditions, has presumably evolved different mechanisms to allow this widespread adaptation. Harnessing the genetic diversity in these mechanisms will be central to the future of viticulture in many traditional wine growing areas. The interactions between the scion and the rootstock through grafting add an additional level of diversity and adaptive potential to explore.
At the physiological level, these mechanisms are related to processes such as root system development and functioning (water and nutrient uptake), interactions with the soil microbiome, gas exchange regulation, hydraulic properties along the soil-plant-atmosphere continuum, reserve storage, short and long distance signaling mechanisms and plasticity for some of these traits.

Developments in high-throughput sequencing (HTS) technologies allow us to obtain large amounts of microbial information from wine and must samples. Thus approaches, that are aimed at characterising the microbial diversity during fermentation, can be enhanced, or possibly even replaced, with HTS-based metabarcoding. To reduce experimental biases and increase data reproducibility, we compared 3 DNA extraction methods by evaluating differences in the fungal diversity with Riesling alcoholic fermentation samples at four different vineyards. The fungal diversity profiling was done using the genetic markers ITS2 and D2 using metabarcoding. The extraction methods compared consisted of a commercial kit, a recently published protocol that includes a DNA enhancer, and a protocol based on a buffer containing common inhibitor removal reagents. All methods were able to distinguish vineyard effects on the fungal diversity, but the results differed quantitatively.

Anthocyanin potential of grape berries is an important quality factor in wine production. Anthocyanin concentration and profile differ among varieties but it also depends on the environmental conditions, which are expected to be greatly modified by climate change in the future. These modifications may significantly modify the biochemical composition of berries at harvest, and thus wine typicity. Among the diverse approaches proposed to reduce the potential negative effects that climate change may have on grape quality, genetic diversity among clones can represent a source of potential candidates to select better adapted plant material for future climatic conditions. The effects of individual and combined factors associated to climate change (increase of temperature, rise of air CO2 concentration and water deficit) on the anthocyanin profile of different clones of Tempranillo that differ in the length of their reproductive cycle were studied. The aim was to highlight those clones more adapted to maintain specific Tempranillo typicity in the future. Fruit-bearing cuttings were grown in controlled conditions under two temperatures (ambient temperature versus ambient temperature + 4ºC), two CO2 levels (400 ppm versus 700 ppm) and two water regimes (well-watered versus water deficit), both in combination or independently, in order to simulate future climate change scenarios. Elevated temperature increased anthocyanin acylation, whereas elevated CO2 and water deficit favoured the accumulation of malvidin derivatives, as well as the acylation and tri-hydroxylation level of anthocyanins. Although the changes in anthocyanin profile observed followed a common pattern among clones, such impact of environmental conditions was especially noticeable in one of the most widely distributed Tempranillo clones, the accession RJ43.

The success of grafting in viticulture is deeply influenced by the nutrient composition of both rootstock and scion
materials. Key components such as nitrogen and carbohydrates play a crucial role in graft compatibility, establishment,
and overall plant vigor [1].

Climate is a key parameter when the modulation of berry and subsequent wine composition is considered. Recent decades have already seen an increase in global surface temperatures