Predicting the canopy conductance to water vapor of grapevines using a biophysical model in a hot and arid climate.

Canopy conductance is a crucial factor in modelling plant transpiration and is highly responsive to water stress. The objective of this study is to develop a straightforward method for estimating canopy conductance (gc) in grapevines. To predict gc, this study combines stomatal conductance to water vapor (gsw) measurements from grapevine leaves, scaled to represent the canopy size by the leaf area index (LAI), with atmospheric variables, such as net solar radiation (Rn) and air vapor pressure deficit (VPD). The developed model was then validated by comparing its predictions with gc values calculated using the inverse of the Penman Monteith equation. The proposed model demonstrates its effectiveness in estimating the gc, with the highest root-mean-squared-error (RMSE=1.45x10-4 m.s-1) being lower than the minimum gc measured in the field (gc obs=0.0005 m.s-1). The results of this study reveal the significant influence of both VPD and gsw on grapevine canopy conductance.

First Approach to the Aroma Characterization of Monovarietal Red Wines Produced from Varieties Better Adapted to Abiotic Stresses.

Adaptation strategies in the wine sector consist of the use of cultural techniques to limit damages caused by climate change, using, among other resources, varieties better adapted to the scenarios of abiotic stress exacerbation, namely water and thermal stress, as well as those more tolerant to heatwaves. With the intention to determine the aromatic characterization of ten monovarietal wines produced from cultivars with high productive performance in a global warming scenario ('Petit Verdot', 'Marselan', 'Merlot', 'Touriga Franca', 'Syrah', 'Vinhão', 'Bobal', 'Preto Martinho', 'Trincadeira', and 'Alicante Bouschet'), grown in Esporão vineyard (Alentejo, Portugal) and submitted to deficit irrigation (Ks ± 0.5), their aromatic character has been analyzed. Each grape variety was vinified at a small scale, in duplicate, and the wines were evaluated by a sensory panel, which rated several sensory attributes (visual, olfactory, and gustatory). Sensory analysis revealed a discrete appreciation for the monovarietal wines tasted, showing a differentiation at the olfactory level that was not too marked, although present, between the samples. The free volatile compounds were analysed using gas chromatography-olfactometry (GC-O), identified using a gas chromatography-mass spectrometry (GC-MS) technique and semi-quantified using the gas chromatography-flame ionization detector (GC-FID) technique. Based on the interpolation of the results of the various statistical analyses carried out, 49 probable odor active compounds (pOACs) were identified and based on the odor activity values (OAVs), 24 of them were recognized as odor active compounds (OACs) originated mainly during the fermentation processes. An aromatic characterization of the varieties has been proposed.

The role of soil temperature in mediterranean vineyards in a climate change context.

The wine sector faces important challenges related to sustainability issues and the impact of climate change. More frequent extreme climate conditions (high temperatures coupled with severe drought periods) have become a matter of concern for the wine sector of typically dry and warm regions, such as the Mediterranean European countries. Soil is a natural resource crucial to sustaining the equilibrium of ecosystems, economic growth and people's prosperity worldwide. In viticulture, soils have a great influence on crop performance (growth, yield and berry composition) and wine quality, as the soil is a central component of the terroir. Soil temperature (ST) affects multiple physical, chemical and biological processes occurring in the soil as well as in plants growing on it. Moreover, the impact of ST is stronger in row crops such as grapevine, since it favors soil exposition to radiation and favors evapotranspiration. The role of ST on crop performance remains poorly described, especially under more extreme climatic conditions. Therefore, a better understanding of the impact of ST in vineyards (vine plants, weeds, microbiota) can help to better manage and predict vineyards' performance, plant-soil relations and soil microbiome under more extreme climate conditions. In addition, soil and plant thermal data can be integrated into Decision Support Systems (DSS) to support vineyard management. In this paper, the role of ST in Mediterranean vineyards is reviewed namely in terms of its effect on vines' ecophysiological and agronomical performance and its relation with soil properties and soil management strategies. The potential use of imaging approaches, e.g. thermography, is discussed as an alternative or complementary tool to assess ST and vertical canopy temperature profiles/gradients in vineyards. Soil management strategies to mitigate the negative impact of climate change, optimize ST variation and crop thermal microclimate (leaf and berry) are proposed and discussed, with emphasis on Mediterranean systems.

Modulation of the Berry Skin Transcriptome of cv. Tempranillo Induced by Water Stress Levels.

Climate change in the Mediterranean area is making summers warmer and dryer. Grapevine (Vitis vinifera L.) is mostly important for wine production in Mediterranean countries, and the variety Tempranillo is one of the most cultivated in Spain and Portugal. Drought decreases yield and quality and causes important economic losses. As full irrigation has negative effects on quality and water is scarce in this region, deficit irrigation is often applied. In this research, we studied the effects of two deficit irrigation treatments, Sustained Deficit Irrigation (SDI) and Regulated Deficit Irrigation (RDI), on the transcriptome of grape berries at full maturation, through RNAseq. The expression of differentially regulated genes (DEGs) was also monitored through RT-qPCR along berry development. Most transcripts were regulated by water stress, with a similar distribution of up- and down-regulated transcripts within functional categories (FC). Primary metabolism was the more severely affected FC under water stress, followed by signaling and transport. Almost all DEGs monitored were significantly up-regulated by severe water stress at veraison. The modulation of an auxin response repression factor, AUX22D, by water stress indicates a role of this gene in the response to drought. Further, the expression of WRKY40, a TF that regulates anthocyanin biosynthesis, may be responsible for changes in grape quality under severe water stress.

Developmental Regulation of Transcription in Touriga Nacional Berries under Deficit Irrigation.

Grapevine (Vitis vinifera L.) is one of the most economically important crops worldwide, especially due to the economic relevance of wine production. Abiotic stress, such as drought, may contribute to low yield, shifts in quality, and important economic loss. The predicted climate change phenomena point to warmer and dryer Mediterranean environmental conditions; as such, it is paramount to study the effects of abiotic stress on grapevine performance. Deficit irrigation systems are applied to optimize water use efficiency without compromising berry quality. In this research, the effect of two deficit irrigation strategies, sustained deficit irrigation (SDI) and regulated deficit irrigation (RDI), in the grape berry were assessed. The effects of different levels of drought were monitored in Touriga Nacional at key stages of berry development (pea size, véraison, and full maturation) through RNA-Seq transcriptome analysis and by specific differentially expressed genes (DEGs) monitoring through RT-qPCR. Handy datasets were obtained by bioinformatics analysis of raw RNA-Seq results. The dominant proportion of transcripts was mostly regulated by development, with véraison showing more upregulated transcripts. Results showed that primary metabolism is the functional category more severely affected under water stress. Almost all DEGs selected for RT-qPCR were significantly upregulated in full maturation and showed the highest variability at véraison and the lowest gene expression values in the pea size stage.

Climate effects on physicochemical composition of Syrah grapes at low and high altitude sites from tropical grown regions of Brazil.

The major areas of the world where viticulture is practiced enjoy temperate or cool temperature climates. When wine grapes are grown in tropical regions, edaphoclimatic factors result in distinct grape quality attributes, and production techniques also require significant adjustment. The objective of this study was to characterize the chemical compositions, in particular of phenolic compounds, of Syrah grapes grown in two location in northeast Brazil - these are also at widely different altitudes. A range of methods of phenolic extraction were used, along with classical chemical analyses including for organic acids, sugars, monomeric anthocyanins, flavonols, stilbene, condensed tannins and some of the monomeric and small oligomeric procyanidins. The regions and their diverse environments had a larger influence than harvest year. The grapes at higher altitude (Bahia, 1.100 m asl (metres above sea level) were characterized by higher levels of malic acid, anthocyanins and condensed tannins in the skins. The low-altitude grapes (Pernambuco, 350 m asl (metres above sea level) had higher levels of glucose, fructose, 3-O-acetylglucoside anthocyanins and condensed tannins in the seeds. Fruit composition was highly influenced by the region. In the low-altitude region, the grapes were characterized by higher tartaric and citric acid in the must, also of flavonols in skins and of tannins in the seeds. Meanwhile, the fruit from the high altitude, contained higher levels of malic and succinic acid in the must, and of anthocyanins and condensed tannins in the skins.

Chemical characteristics of grapes cv. Syrah (Vitis vinifera L.) grown in the tropical semiarid region of Brazil (Pernambuco state): influence of rootstock and harvest season.

BACKGROUND: Obtaining two or more successive annual vintages from the same vineyard is characteristic of regions with a tropical climate, such as the Submédio of the São Francisco Valley, Brazil. The present study aimed to characterize the chemical composition of grapes in four production cycles (i.e. two calendar years) when considering the interaction between cv. Syrah and two rootstocks. For a broad characterization, two methodologies for the extraction of phenolic compounds were used, as well as different methods of analysis. RESULTS: The results obtained showed that there was an influence of rootstock and harvest season. Grapes from vines grafted onto IAC 313 contained higher concentrations of total condensed tannins (skins) and flavanols than grapes from vines grafted onto 1103P. However, the grape samples from the vines grafted onto 1103P contained higher levels of monomeric anthocyanins than the grape samples from the vines grafted onto IAC 313. The first harvest season was characterized by higher concentrations of most phenolic compounds than the second harvest season. CONCLUSION: In the present study, it was possible to confirm that, in the semiarid region of Brazil, the interaction between the cultivar Syrah and the different rootstocks, as well as the climatic conditions in each harvest season, influenced the composition of the grapes, mainly in relation to phenolic compounds. © 2019 Society of Chemical Industry.

Grape Ripening Is Regulated by Deficit Irrigation/Elevated Temperatures According to Cluster Position in the Canopy.

The impact of water deficit on berry quality has been extensively investigated during the last decades. Nonetheless, there is a scarcity of knowledge on the performance of varieties exposed to a combination of high temperatures/water stress during the growing season and under vineyard conditions. The objective of this research was to investigate the effects of two irrigation regimes, sustained deficit irrigation (SDI, 30% ETc) and regulated deficit irrigation (RDI, 15% ETc) and of two cluster positions within the canopy (east- and west-exposed sides) on berry ripening in red Aragonez (Tempranillo) grapevines. The study was undertaken for two successive years in a commercial vineyard in South Portugal, monitoring the following parameters: pre-dawn leaf water potential, berry temperature, sugars, polyphenols, abscisic acid (ABA) and related metabolites. Additionally, expression patterns for different transcripts encoding for enzymes responsible for anthocyanin and ABA biosynthesis (VviUFGT, VvNCED1, VvßG1, VviHyd1, VviHyd2) were analyzed. In both years anthocyanin concentration was lower in RDI at the west side (RDIW- the hottest one) from véraison onwards, suggesting that the most severe water stress conditions exacerbated the negative impact of high temperature on anthocyanin. The down-regulation of VviUFGT expression revealed a repression of the anthocyanin synthesis in berries of RDIW, at early stages of berry ripening. At full-maturation, anthocyanin degradation products were detected, being highest at RDIW. This suggests that the negative impact of water stress and high temperature on anthocyanins results from the repression of biosynthesis at the onset of ripening and from degradation at later stages. On the other hand, berries grown under SDI displayed a higher content in phenolics than those under RDI, pointing out for the attenuation of the negative temperature effects under SDI. Irrigation regime and berry position had small effect on free-ABA concentration. However, ABA catabolism/conjugation process and ABA biosynthetic pathway were affected by water and heat stresses. This indicates the role of ABA-GE and catabolites in berry ABA homeostasis under abiotic stresses. Principal component analysis (PCA) showed that the strongest influence in berry ripening is the deficit irrigation regime, while temperature is an important variable determining the improvement or impairment of berry quality by the deficit irrigation regime. In summary, this work shows the interaction between irrigation regime and high temperature on the control of berry ripening.