Grafting has been fundamental in viticulture since the phylloxera crisis of the late 19th century; nevertheless, the functional consequences of vascular connection on the graft union remain poorly understood. The effects of grafting on Vitis vinifera cv. Tempranillo (Te) were evaluated using two complementary approaches: (1) cambial alignment, comparing completely aligned (CA) versus partially aligned (PA) unions; and (2) grafting and scion-rootstock interaction, comparing heterografts (Te/110R and Te/RG8), homografts (Te/Te), and ungrafted Te cuttings. These approaches were tested through three experiments: a vineyard trial and two pot trials under well-watered (WW), moderate water stress (MWS), and recovery (R) regimes. In the vineyard, CA plants exhibited greater vegetative growth and gas exchange, particularly on 110R, whereas the vigorous RG8 rootstock mitigated the effects of misalignment. Under MWS conditions, CA adopted a drought-avoidant strategy with earlier stomatal closure and higher root allocation, whereas PA maintained higher stomatal conductance, recovered photosynthesis faster after rewatering, and prioritised shoot and rootstock growth, especially on RG8. Finally, grafted plants were more sensitive to water stress than ungrafted plants, while homografts accumulated the greatest biomass and root investment, suggesting more efficient vascular connectivity compared with heterografts. Our study highlights that cambial alignment, grafting, and partner interactions influence plant development and physiological performance; however, long-term studies are needed to clarify how vascular connectivity at the graft union affects transport processes, stress responses, and ultimately vine longevity under different scion-rootstock combinations.

The consolidation of scientific knowledge is based on the accumulation and understanding of previous findings. Nowadays, reviews of the scientific literature have become more effective through the use of meta‐analyses, which are systematic evaluations of the results from multiple studies. Similarly, mega‐analyses, which combine raw data from many studies into a single sample for processing and statistical analysis, are a very powerful tool for analyzing results of heterogeneous origin but require a high level of collaboration between the researchers contributing data. In the framework of a collaborative methodology between different Spanish viticultural research groups, this work uses a mega‐analytical approach to quantify the effects of changes in vine water status on vine vegetative growth, yield, and grape composition, integrating a wide range of growing conditions to obtain robust general trends of vine performance under water deficit. The mean seasonal stem water potential data from the different studies allowed a classification into five levels of water status (no deficit ⟶ mild ⟶ moderate ⟶ high ⟶ severe). A progressive decrease in vegetative growth with increasing deficit was observed, while yield decreased more markedly as water deficit progressed from moderate to high. On the other hand, titratable acidity was more sensitive to variation in water status than sugar concentration, with a greater decrease in titratable acidity when changing from no to moderate deficit. Conversely, increasing water deficit from moderate to high resulted in the greatest increases in grape anthocyanin in the red varieties explored. The results obtained in this work provide solid information on general trends in grapevine response to water deficit that can be used in simulation models or incorporated by grape growers in their decision‐making processes in relation not only to irrigation management but also on other agronomic tools to impact grapevine water status.

Severe water stress can lead to hydraulic disfunction, reducing plant conductance or even causing death. Some plants exhibit hydraulic vulnerability segmentation between organs to reduce this risk. However, its role in influencing drought tolerance and resistance in grafted plants, such as grapevine, remains unclear. This study evaluates the physiological responses, drought tolerance, hydraulic vulnerability segmentation, and xylem anatomy of 2-year-old Vitis vinifera cv. Tempranillo scion grafted onto two rootstocks: 110-Richter (110R) and Sélection Oppenheim 4 (SO4). After subjecting the plants to drought conditions until the onset of embolism in the leaf (water potential corresponding to 12% loss of xylem hydraulic conductivity, P12), we analysed the physiological consequences during recovery. Grapevine exhibits hydraulic vulnerability segmentation not only within scion organs but also between the scion and rootstock. Although no differences in scion drought tolerance and embolism resistance were observed between combinations, Tempranillo-110R exhibited higher leaf minimum conductance, leaf P12 values, and root biomass. In contrast, Tempranillo-SO4 displayed larger vessel diameter and higher hydraulic conductance. These differences may explain the slower recovery of Tempranillo-110R compared with Tempranillo-SO4, which showed higher stomatal and root-to-stem hydraulic conductance. These findings indicate that in selecting rootstock, consideration should be given to drought resilience alongside vigour and productivity, especially given the increasing occurrence of severe drought periods due to climate change.

The intensification of drought conditions due to climate change poses a major challenge to sustainable grape production. Rootstocks are essential in supporting grapevine water uptake and drought resilience; however, their physiological responses to water stress are not fully understood. Under the hypothesis that root morphology and anatomy may be key traits in grapevine tolerance to water deficit, this study aimed to investigate these traits across diverse rootstocks under progressive water deficit and recovery phases. Thirteen genotypes, including commercial rootstocks and recently bred RG-series and RM2, were evaluated over two seasons in controlled pot-based conditions. Plants were subjected to five distinct watering stages, from well-watered to severe drought. Root traits, such as length, density, and xylem anatomical features, were analyzed alongside stem water potential (Ψstem) to gauge plant water status. Results showed significant genotype-specific differences in root morphology and anatomy, impacting drought tolerance and recovery. Rootstocks with higher root length density (RLD) and a larger proportion of fine roots maintained Ψstem more effectively under severe drought. Additionally, smaller xylem vessel diameters and reduced xylem area relative to root cross-sectional area correlated with improved water transport efficiency and faster recovery post-drought. A trade-off emerged wherein increased root density enhanced water uptake capacity but came at the cost of reduced transport efficiency. Notably, rootstocks 420A, 41B, RM2, and Fercal displayed superior drought resilience, while the RG-series did not outperform established genotypes like 13-5 Evex, 110 Richter, and 140 Ruggeri. These results underscore the role of root morphology and anatomy in grapevine drought tolerance, suggesting that these traits could be incorporated as criteria for future rootstocks breeding programs. Nevertheless, field-testing under non-limiting soil conditions is essential to validate these findings.

Grafting Vitis vinifera L. (wine traditional cultivars) onto North American grapevine species or hybrids is a common practice in viticulture given their tolerance against phylloxera (Daktulosphaira vitifoliae). However, rootstock genetic background affects the response of grapevines to environmental stresses and their ability for establishing a symbiotic relationship with the microbial communities, and more specifically with arbuscular mycorrhizal fungi (AMF). The aim of this study was to evaluate Monastrell variety (clone ENTAV 369) grafted onto three rootstocks (140Ru, 110R and RG8) characterized by a different genetic background, in combination with AMF inoculation (Rhizophagus irregularis) vs. a non-inoculated control with regards to vegetative growth, leaf gas exchange parameters, and mycorrhization. Potted vines were grown in open-top greenhouses and irrigated by counteracting evapotranspiration. The vines were monitored over the season. Plants were homogenized by measuring the trunk section, and at the end of the season, vegetative growth evidenced differences between rootstocks on the scion annual growth. Neither water potential nor gas exchange parameters were significantly affected by the treatments; however, a trend towards increased carbon assimilation rate was observed in inoculated vines. Assayed rootstocks showed different pattern for mycorrhization, with 140Ru being the rootstock that achieved higher values, but no effect was observed on glomalin secretion. To sum up, results showed that the effect of mycorrhizal inoculation on vine growth and gas exchange parameters was modulated by the rootstock genotype.

Exploring new field strategies for adapting winegrowing regions to the adverse effects of climate change becomes imperative. This study focuses on the effects of canopy architecture through the trellis systems leaning of North–South oriented vineyard’s rows vertical shoot positioned (VSP) system by 30° towards either the East (ESP) or the West (WSP) as a possible adaptation technique. The trial was conducted over two seasons in a Vitis vinifera L. cv. Bobal vineyard located in Requena (Valencia), eastern Spain, under a temperate-warm climate. The canopy leaning was considered to affect the radiation load and its timing with potential effects on vine physiology and grape metabolism and, consequently, on grape and wine quality. Leaning treatments affected vegetative growth, likely due to slight differences in vine water status. In comparison to VSP and ESP, WSP intercepts more light in the morning, when the photosynthetic capacity of the vines is at its highest. However, this results in a more negative vine water potential, which in turn leads to a reduction in vigour with no impact on yield. Musts from the WSP showed a tendency to increase total acidity compared to VSP, while ESP tended to decrease it. This was likely due to the reduction in temperature within the cluster microclimate in WSP in comparison to the ESP and VSP treatments. In addition, musts from the WSP treatment showed higher colour intensity, anthocyanins and polyphenols, potentially attributable to its more negative potentials, likely due to its more negative potentials, which may have prompted the synthesis of phenolic compounds. Consequently, wines from the WSP treatment displayed higher total acidity and lower pH, as well as higher colour intensity, anthocyanins, and polyphenolic content. In addition, WSP wines had higher concentrations of esters and higher alcohols. The improvements in grape and wine composition are likely due to an increased cluster radiation interception in the morning and reduced heating in the afternoon when VPD is higher. Our findings demonstrate that canopy management by leaning VSP vines towards the West can be a useful technique for adapting grape and wine composition to climate change and provide insights into its physiological basis.

Under semiarid and warm climates, field practices for climate change adaptation have to be defined in order to modulate grape composition according to the desired wine styles. Under this context, the present study investigated several viticulture practices in cv. Macabeo for Cava production. The experiment was carried out over 3 years in a commercial vineyard located in the province of Valencia (eastern Spain). The techniques tested were (i) vine shading, (ii) double pruning (bud forcing), and (iii) the combined application of soil organic mulching and shading, all of them tested against a control. Double pruning significantly modified phenology and grape composition, improving the wine alcohol-to-acidity ratio and reducing the pH. Similar results were also achieved by shading. However, the shading strategy did not significantly affect yield, unlike double pruning, which reduced vine yield even in the year following its application. Shading alone or in combination with mulching significantly improved the vine water status, suggesting that these techniques can also be used to alleviate water stress. Particularly, we found that the effect of soil organic mulching and canopy shading on stem water potential was additive. Indeed, all the techniques tested were useful for improving wine composition for cava production, but double pruning is only recommended for premium Cava production.

The use of rootstocks tolerant to soil water deficit is an in-teresting strategy to face the challenges posed by limited water availability. Currently, several nurseries are breeding new genotypes aiming to improve the water stress tolerance of grapevine, but the physiological basis of its responses un-der water stress are largely unknown. For this purpose, an ecophysiological assessment of the conventional 110 -Rich-ter (110R) and SO4, and the new M1 and M4 rootstocks was carried out in ungrafted potted plants. During one season, these Vitis genotypes were grown under greenhouse con-ditions and subjected to two water regimes, well-watered (WW) and deficit irrigation (DI). Water potentials of plants under DI down to <-1.4 MPa, and net photosynthesis (AN) <5 mu mol CO2m-2s-1 did not cause leaf oxidative stress damage compared to WW conditions in all genotypes. The antioxidant capacity was sufficient to neutralize the mild oxidative stress suffered. Under both water regimes, gravimetric differences in daily water use were observed among genotypes, lead-ing to differences in the biomass of roots and shoots. Under WW conditions, SO4 and 110R were the most vigorous and M1 and M4 the least. However, under DI, SO4 exhibited the greatest reduction in biomass, while 110R showed the low-est. Remarkably, under these conditions, SO4 reached the least negative stem water potential and showed the highest hydraulic conductance values. Conversely, M1 reduced the most stomatal conductance, transpiration and AN. Overall, 110R achieved the highest biomass water use efficiency in re-sponse to DI, and SO4 the lowest, while M-rootstocks showed intermediate values. Our results suggest that there are dif-ferences in water use regulation among genotypes attributed not only to differences in stomatal regulation but also to plant hydraulic conductance. Therefore, it is hypothesized that dif-ferences in genotype performance may be due to root ana-tomical-morphological differences and to several physiologi-cal processes such as growth inhibition, osmotic adjustment, antioxidant production, nutrient translocation capacity, etc. Further studies are needed to confirm these differential eco-physiological responses of Vitis species under water stress, particularly under field and grafted conditions.

Achieving more environmentally sustainable vineyards, particularly regarding efficient water use, is paramount in semi-arid grape-growing regions. Rootstocks may be a possible strategy to address these challenges, but require a comprehensive evaluation of their effect on the scion, including ecophysiological traits. The objectives of this study were 1) to characterize the physiological response of Tempranillo cultivar grafted onto five commercial (1103 P, 110 R, 140Ru, 420 A, and SO4), and seven recently bred (RG2, RG3, RG4, RG6, RG7, RG8 and RG9) rootstocks and 2) to elucidate the relationships between agronomic and physiological traits conferred by grapevine rootstocks. This was carried out over three seasons (2018–2020) in a typical Mediterranean vineyard by determining water relations, leaf gas exchange, carbon isotope ratios and vegetative development and yield components. The results highlighted the different behaviour of ‘Tempranillo’ vines due to the rootstock effects on vine water status, photosynthetic performance, hydraulic conductance, vegetative growth and yield parameters. Overall, rootstocks inducing vigour and yield in the scion, such as 140Ru and RG8, showed higher leaf gas exchange rates and hydraulic conductance at the whole-plant level due to less negative water potentials, suggesting a higher water uptake and transport capacity than RG2, RG7 and RG9. The RG rootstocks showed a very wide range of ecophysiological responses, but only RG8 outperformed compared to the most widely used commercial rootstocks. Moreover, this response was modulated by the season and the block soil type, suggesting the importance of rootstock selection according to the edaphoclimatic conditions. Therefore, this study highlights the high potential of rootstocks to adapt to water scarcity by improving crop water productivity in vineyards and provides physiological insights for future studies and breeding programmes.

We aim to develop and transfer to the wine sector a decision support system (DSS) in the frame of WANEGRAPE4.0 project that, integrated into a geographic information system, helps wine growers in i) selecting the most suitable rootstock given some agroecological conditions and oenological objectives; and ii) managing irrigation and nitrogen fertilization in the most suitable way for the selected rootstock and agroecological conditions. The following goals have been achieved. First, the modular structure and information flow of the DSS has been defined. Second, the main algorithms of the water balance module (DSS core part) have been formulated and the module coded in a spreadsheet. Third, this water balance module has been tested with data from field experiments in several regions of Spain. Fourth, the relationships between grapevine water status and production and harvest quality variables have been established, revealing an always-significant effects of the decrease in water stress on vegetative development, yield, and grape composition. Fifth, the nitrogen fertilizer effects on vine performance has been assessed. Sixth, the effects rootstocks have on 5 parameters of vine production and grape quality for winemaking have been established too by doing another meta-analysis of rootstock trials. Seventh, a rootstock selection module has been defined. The WANUGRAPE4.0 project goes on with the integration of all its modules, their coding in a World Wide Web language and their publication on an Internet portal.

Vineyards occupy large areas in many Mediterranean agroecosystems, in which their evapotranspiration is a major component of the water cycle. The correct determination of the actual crop evapotranspiration (ETa) is critical for accurate irrigation scheduling, allowing to match irrigation applications to crop water needs. This study was conducted to monitor the vineyard ETa and its partitioning into soil evaporation (E) and plant tran- spiration (T), under deficit irrigation and rainfed conditions, and to obtain the relationship between the esti- mated relative water stress coefficient (Ks,r) and measured midday stem water potential (psi stem). A 2-year field experiment was carried out in a 'Monastrell' commercial vineyard located in Fuente ' Alamo (Albacete, SE Spain). Thermal infrared radiometers were deployed in both treatments, together with a weather station, to gather all the inputs required in the simplified two-source energy balance (STSEB) approach. Results showed that the accumulated ETa ranged between 183 and 253 mm for the irrigated treatment, and between 121 and 158 mm for the rainfed conditions. Canopy transpiration in the irrigation treatment almost double the value obtained in rainfed conditions for both years, and the ratio T/ETa increases around 8-9% in the irrigation treatment. The E component ranged from 21% for the irrigated treatment up to 50% for the rainfed treatment, confirming its importance in the vineyard water balance. A good linear relationship (r2=0.650) was obtained between Ks,r and psi stem, indicating the potential of using a surface energy balance approach in conjunction with plant radiometric temperature measurements to monitor the vines water status. Moreover, the rainfed treatment reduced the values of stomatal conductance (gs), transpiration (El) and net photosynthesis (AN) compared to the irrigated treatment, whereas no increase in the intrinsic water-use efficiency (WUEi) nor the instantaneous water-use efficiency (WUEinst) was observed. The reported results will be useful for improving deficit irrigation sched- uling techniques for 'Monastrell' red grapes.

Because of climate change and the scarce availability of natural resources there is a need to develop sustainable intensification strategies intended for optimizing water use in vineyards. In this study, water regime, fertilization and soil management practices were assessed in terms of vineyard water use, by evaluating the inter-row and crop line evapotranspiration (ET) components using the Mapping EvapoTranspiration at high Resolution with Internalized Calibration (METRIC) model in combination with unmanned aerial vehicle multispectral and thermal images taken on five dates throughout the growing season. The application of the METRIC-UAV using high-resolution imagery was proven as a useful tool for evaluating the effects of sustainable intensification strategies on water use of crops where vegetation does not completely cover the soil, identifying the most efficient site-specific strategies for water conservation purposes. Moreover, METRIC-UAV allowed evaluating separately their effects on the inter-row and the crop line. Among the assessed sustainable intensification stra-tegies, the application of mulching provided the highest water savings (-28%) when compared to traditional soil tillage management, reducing inter-row soil evaporation by 63%, while increasing crop-line ET by 14%. In spite of this, the mulching application did not affect yield, but significantly enhanced water use efficiency (WUE) in terms of grape yield compared to tillage. The adoption of deficit irrigation (DI) strategies did not result in vine water stress that was severe enough to significantly affect crop line ET when compared with fully irrigated (FI) vines. Both DI and FI strategies increased vine water use by 18% and 27%, respectively, as compared to the rainfed regime, with no differences found in the inter-row water consumption. DI and FI, in turn, significantly increased yield as compared to rainfed crops, leading to significant improvements in WUE. In the short term, the application of supplemental inorganic fertilizers did not modify either the vineyard water use or vine performance.

The nutrient requirements of almond trees grown under optimum conditions are well known. Nowadays, it is necessary to adapt fertilization to face new challenges, such as the increasing scarcity of water resources that force farmers to implement deficit irrigation strategies, or the cultivation of fruit trees intercropped with cover crops or native vegetation that promote additional ecosystem services. The objective of this work is to know the effects on the nutritional status of almond trees subjected to deficit irrigation and cover vegetation (CV), in order to be able to readapt fertilizer recommendations to this approach more in line with the new EU Farm-to-Fork strategy. In a field trial established in southeastern Spain under semi-arid conditions we tested 5 treatments; 1) control trees (irrigated and fertilized at 100%), 2) trees irrigated and fertilized at 66% and where the inter-row was tilled, 3) trees irrigated and fertilized at 66% and with CV, 4) trees irrigated and fertilized at 33%, where the inter-row was tilled, and 5) trees irrigated and fertilized at 33% and with CV. Our results indicate that when the application of water and nutrients decreases, trees maintain a nutrient homeostasis by reducing growth and yield, and that a 66% decrease in water and nutrient supply can be a good strategy where irrigation water is scarce. The cover vegetation reduced growth and yield, but the results do not show a detrimental effect of the CV on the water and macronutrient status of the tree. We observed a reduction of Fe, Mn and Zn in the leaves of trees with cover vegetation, which was more evident in the almond trees under more severe restriction (33%) that probably had to expand their root system and therefore compete more directly with the CV. These results highlight the need to readjust fertilizers when deficit irrigation techniques are applied, as well as to reincorporate the nutrients sequestered by the tree canopy and the CV into the soil.

Selecting genotypes with a better capacity to respond and adapt to soil water deficits is essential to achieve the sustainability of grapevine cultivation in the context of increasing water scarcity. However, cultivar changes are very poorly accepted, and therefore it is particularly interesting to explore the intracultivar genetic diversity in water use efficiency (WUE). In previous studies, the cultivar “Grenache” has shown up to 30% variability in WUE. This research aimed to confirm the intracultivar variability and to elucidate the traits underlying this variability in the response to a water deficit by analyzing the growth rates, water relations, osmotic potential, leaf morphology, leaf gas exchange and carbon isotope discrimination in nine “Grenache” genotypes grown in pots during two seasons. The results showed lower differences in WUE and carbon isotope ratio than in previous field studies, but fairly good consistency in genotype ranking. Leaf mass area and osmotic potential did not underlie differences in stem water potential and in stomatal conductance. Overall, stomatal regulation and photosynthetic capacity seem to underlie differences in WUE among genotypes with an important environmental influence. These results confirm the ability to select clones with higher WUE and present an opportunity for the genetic improvement of WUE in grapevines.

Current water scarcity scenario has led to the implementation of sustainable agricultural practices intended to improve water use efficiency. The present work evaluates during three agricultural campaigns (2018-2020) the response of a young almond orchard to two management practices in terms by combining remote sensing indexes (Normalized Difference Vegetation Index, NDVI; and Soil Adjusted Vegetation Indexes, SAVI) and physiological/morphological measurement (stem water potential, Psi(stem); trunk perimeter and canopy diameter). The management practices included (i) sustained deficit irrigation and (ii) soil management. Severe deficit irrigation resulted in lower vegetation indexes (VI) values, Psi(stem )and tree dimensions (13 %, 23 % and 14 % lower, respectively) than those obtained for full irrigation strategy; whereas moderate deficit irrigation did not affect any of the parameters analysed. The presence of vegetation cover in the inter-row resulted in a VIs increase (19-42 %) and in lower tree dimensions (reductions of 7-8 % for trunk perimeter and 0.34-0.37 m for canopy diameter) when compared to bare soil treatment, but did not have any influence on Psi(stem). The present study proves the suitability of remote sensing and physiological measurements for assessing almond response to the different management practices.

Warm and semi-arid climates are characterized by rainfall scarcity, resulting in the frequent use of low-quality water for irrigation. This work was undertaken to study the effects of water stress and saline irrigation on yield and grape composition of Monastrell grapevines grafted onto 1103P rootstock. The experiment was carried out during three consecutive seasons in a commercial vineyard located in Jumilla (SE Spain) with a loamy-sandy soil. Rainfed vines were compared with five watering regimes including a Control, irrigated with standard water, and four treatments that combined two different schedules for irrigation initiation (pre- and post-veraison) with saline water obtained by adding two types of salts (sulphates and chlorides). Vines from treatments with more severe water stress (i.e., rainfed) showed lower yields and vegetative growth. Moreover, the Rainfed treatment clearly modified grape composition when compared with the Control treatment by increasing berry phenolic content. The application of saline water slightly affected vine performance and grape composition regardless of the type of salts added to the irrigation water. Indeed, the watering regime had a greater effect on yield, vegetative growth and grape composition than the use of different saline waters. Our results suggest that, in the mid-term (3 years), and with a vineyard soil with good drainage, the use of saline waters is not detrimental to vine performance, but does not improve grape composition. Further research is required to assess the long-term effects of saline water application, particularly in view of the important accumulation of chlorides and sodium in leaf tissues observed in vines watered with salty water at the last season of this experiment.

The sustainability of woody crop agroecosystems requires continued improvements to water, nutrient and soil management. In this work, the combination of resource availability or fertigation dose with soil management practices was tested in a 2 × 2 factorial design in a drip irrigated young almond orchard. The fertigation doses were: the farmer supply at 60% of crop evapotranspiration and full nutrient requirements and the half-farmer supply at 30% of crop evapotranspiration and half nutrient requirements. The soil management practices were: bare soil and cover crops in the inter-row (mixture of grasses and legumes). Tree growth, yield, water and nutrient status, and cover crop biomass and nutrient status were determined, as well as inter-row soil C and N concentration. Results showed that the effect of resource availability was independent of soil management and vice versa. The half farmer treatment reduced tree vegetative growth and yield compared to farmer treatment, due to a negative effect on the water status, without observing a decrease in the concentration of nutrients in leaves or fruit. Trees with cover crop also reduced growth and yield compared to bare soil management. This was due to a nutritional competition, mainly of Ca, Fe, Mn and Zn, rather than to a decline in tree water status. Cover crops sequester up to 1 t/ha/year of carbon but do not increase soil organic carbon, nor soil total nitrogen. Cover crops proved to be efficient in reducing soil nitrate concentration in the topsoil and therefore has potential to prevent its leaching. Deficit fertigation and the use of cover crops can be effective practices to preserve and save water and nutrient resources in Mediterranean agroecosystems, but should be established with caution so as not to compromise the profitability of the orchard.

[This corrects the article DOI: 10.3389/fpls.2022.866053.].