•Repeated water stress over years causes the increase of leaf transpiration.•Plants subject to multiple water stress operate at lower hydraulic safety margin.•Plants with water stress "memory" ...suffers smaller reduction of leaf transpiration during drought periods.
Frequency of extreme drought events are expected to increase due to climate change. Perennials are increasingly exposed to recurrent drought during their life span. The aim of the present work was to study the effect of recurrent droughts on the behavior of Vitis vinifera under water stress. Sangiovese and Montepulciano vines were exposed to severe drought stress for 4 years (WS-S). A dry-down experiment was carried out to compare their behavior with a set of vines kept at 90% field capacity during the whole seasons in the previous 4 years (WW-S). WS-S vines had higher transpiration and stomatal conductance than WW-S vines. Net photosynthesis was almost unaffected by the treatment. Stomatal conductance was higher at more negative Ψstem in WS-S vines than in control vines. Leaf petiole percentage loss of hydraulic conductance, measured during water stress, was higher in WS-S than in WW-S vines. Results indicate that previous water stress can lead to less conservative plant strategy toward water loss and decreased water use efficiency. This behavior seems to be coordinated with the different stomatal response to decreasing water potential that caused a reduction of xylem hydraulic safety margin in WS-S vines in comparison with WW-S vines.
Although vertical shoot positioned (VSP) training systems, either cane- or spur-pruned, are adopted in the great majority of the vineyards worldwide, the lianas nature of the grapevine and the ...presence of long and flexible canes confer high plasticity and render structural and pruning changes quite easy. The focus of this review is if, in light of the most consistent features triggered by global warming (e.g., longer growing season, earlier phenology, faster ripening, higher incidence of overheating stress and sunburn, higher frequency of extreme weather events), the type and management of training systems should also be reconsidered. We surveyed the main methods to assess training system efficiency and the current attempts and outlook toward exploiting the training system as an adaptation tool to climate change. For the latter, we considered 12 main trellis types and scored them based on climate-related features and general traits such as vigor, yield control, susceptibility to fungal diseases, and suitability according to wine types (still or sparkling). The resulting balance of positive and negative recommendations leads to a re-evaluation of either old, nonmechanizable trellis types (e.g., Raggi-Bellussi and pergola types), divided canopy systems (e.g., GDC and Scott Henry) or, among the single canopy types, of the single high wire (SHW) trellis. However, historical systems traditionally used by best regions and producers (e.g., goblet and VSP either cane- or spur-pruned) overall show less adherence to the chosen evaluation criteria. To direct future evolution of training systems, regardless of the broadly shared need for suitability to partial or full mechanization, the scenario looks different depending on cool and temperate (warm) areas. The former experiences an outburst of interest as warming is broadening growing areas and affordable genotypes. Under such circumstances, training systems should help accelerate or favor the ripening process through vigor control and lower yield, better cluster exposure, and nonlimiting leaf area-to-fruit ratio. Whereas, in warm areas that are now becoming sub-tropical areas in the worst cases, the SHW gains credit as compared to goblet and traditional VSP. The latter requires an increasing number of canopy manipulations and a rethinking of some planting choices to accommodate the needs of slower and more delayed ripening, more cluster shading, and higher cordons, the latter reducing the probability of incurring significant frost damage.
Water saving under drought stress is assured by stomatal closure driven by active (ABA-mediated) and/or passive (hydraulic-mediated) mechanisms. There is currently no comprehensive model nor any ...general consensus about the actual contribution and relative importance of each of the above factors in modulating stomatal closure in planta. In the present study, we assessed the contribution of passive (hydraulic) vs active (ABA mediated) mechanisms of stomatal closure in V. vinifera plants facing drought stress. Leaf gas exchange decreased progressively to zero during drought, and embolism-induced loss of hydraulic conductance in petioles peaked to ~50% in correspondence with strong daily limitation of stomatal conductance. Foliar ABA significantly increased only after complete stomatal closure had already occurred. Rewatering plants after complete stomatal closure and after foliar ABA reached maximum values did not induced stomatal re-opening, despite embolism recovery and water potential rise. Our data suggest that in grapevine stomatal conductance is primarily regulated by passive hydraulic mechanisms. Foliar ABA apparently limits leaf gas exchange over long-term, also preventing recovery of stomatal aperture upon rewatering, suggesting the occurrence of a mechanism of long-term down-regulation of transpiration to favor embolism repair and preserve water under conditions of fluctuating water availability and repeated drought events.
Viticulture is widely practiced in dry regions, where the grapevine is greatly exposed to water stress. Optimizing plant water use efficiency (WUE) without affecting crop yield, grape and wine ...quality is crucial to limiting use of water for irrigation and to significantly improving viticulture sustainability. This study examines the use in vineyards of particle film technology (engineered kaolin) and compares it to a film-forming antitranspirant (pinolene), traditionally used to limit leaf water loss, and to an untreated control. The trial was carried out under field conditions over three growing seasons, during which moderate to very severe plant water stress (down to -1.9 MPa) was measured through stem water potential. Leaf stomatal conductance (gs) and photosynthesis rate (An) were measured during the seasons and used to compute intrinsic WUE (WUEi, defined as An/gs ratio). Leaf temperature was also recorded and compared between treatments. Bunch quantity, bunch and berry weight, sugar accumulation, anthocyanin and flavonoid contents were measured. Finally, microvinifications were performed and resultant wines subjected to sensory evaluation.Results showed that the use of kaolin increased grapevine intrinsic WUE (+18% on average as compared to unsprayed vines) without affecting berry and bunch weight and quantity, or sugar level. Anthocyanin content increased (+35%) in kaolin treatment, and the wine was judged more attractive (p-value <0.05) and slightly more appreciated (p-value < 0.1) than control. Pinolene did not increase WUEi, limiting An more than gs; grapes with this treatment contained lower sugar and anthocyanin content than control, and the obtained wine was the least appreciated. This study demonstrates that particle film technology can improve vine WUEi and wine quality at the same time, while traditional antitranspirants were not as effective for these purposes. This positive effect can be used in interaction with other already-demonstrated uses of particle film technology, such as pest control and sunburn reduction, in order to achieve more sustainable vineyard management.
Summer pruning encompasses a series of operations typically performed on the grapevine during the growing season. This review provides an update on the research conducted over the last 20 years on ...the modalities and strategies of main summer pruning operations, which include shoot positioning and thinning, shoot trimming, leaf removal, and cluster thinning, with a special focus on their adaptation to climate change occurring in Mediterranean areas. Three main novelties emerged from the survey. First, due to a common need to shelter clusters against overheating and sunburn-related damages, shoot thinning and leaf removal are practices that are now being applied in a much more cautious and conservative manner. Second, the meaning of summer pruning is evolving because operations are being used as precious tools to direct ripening toward a desired direction rather than being received passively. Third, some operations, such as leaf removal, have disclosed very high plasticity, which means that, depending on the timing and modalities of the intervention, yield can be either increased or decreased and ripening anticipated or postponed. In an era where economic and environmental sustainability have to find a good compromise, cluster thinning is increasingly being depicted as an extraordinary operation that should be left to occasional occurrences of overcropping. Moreover, summer pruning is a tool through which growers can, to an extent, exploit the potentialities offered by climate change. For instance, the crop-forcing technique, under the different configurations of single and double cropping within the same season, has been trialed promisingly in several regions and cultivars. The principle of forcing is to unlock the dormant bud during the first year by removing at least the young organs present on the shoot within a time window between the end of the flowering and pea-size stages. In particular, when it is applied in a double-cropping mode, the preliminary results related to Pinot noir, Grenache, Tempranillo, and Maturana tinta indicate that two harvests separated by 30-50 days can be obtained, with the latter having superior quality in terms of a lower level of pH and higher levels of acidity, anthocyanins, and phenolics.
Analysis of the spectral response of vegetation using optical sensors for non-destructive remote monitoring represents a key element for crop monitoring. Considering the wide presence on the market ...of unmanned aerial vehicle (UAVs) based commercial solutions, the need emerges for clear information on the performance of these products to guide the end-user in their choice and utilization for precision agriculture applications. This work aims to compare two UAV based commercial products, represented by DJI P4M and SENOP HSC-2 for the acquisition of multispectral and hyperspectral images, respectively, in vineyards. The accuracy of both cameras was evaluated on 6 different targets commonly found in vineyards, represented by bare soil, bare-stony soil, stony soil, soil with dry grass, partially grass covered soil and canopy. Given the importance of the radiometric calibration, four methods for multispectral images correction were evaluated, taking in account the irradiance sensor equipped on the camera (M1–M2) and the use of an empirical line model (ELM) based on reference reflectance panels (M3–M4). In addition, different DJI P4M exposure setups were evaluated. The performance of the cameras was evaluated by means of the calculation of three widely used vegetation indices (VIs), as percentage error (PE) with respect to ground truth spectroradiometer measurements. The results highlighted the importance of reference panels for the radiometric calibration of multispectral images (M1–M2 average PE = 21.8–100.0%; M3–M4 average PE = 11.9–29.5%). Generally, the hyperspectral camera provided the best accuracy with a PE ranging between 1.0% and 13.6%. Both cameras showed higher performance on the pure canopy pixel target, compared to mixed targets. However, this issue can be easily solved by applying widespread segmentation techniques for the row extraction. This work provides insights to assist end-users in the UAV spectral monitoring to obtain reliable information for the analysis of spatio-temporal variability within vineyards.
Crop-regulation techniques applied as preflowering defoliation (D), early cluster thinning at preflowering (ECT), and cluster thinning at lag-phase of berry growth (LCT) were tested over three ...seasons on high-yielding Vitis vinifera L. Sangiovese and compared to non-defoliated, unthinned control vines. Treatment severity consisted of removing primary leaves and any laterals developed from nodes 1 to 6 in D and of thinning 50% of clusters chosen from among distal clusters or those inserted on weak shoots in ECT and LCT plots. Although yield per vine was not as reduced in D (−32%) as in ECT and LCT treatments (−45%) as compared to the control, D vines also had largely improved sugar and total anthocyanin concentrations and the highest total phenolics. Yield components were also markedly affected by treatments: D vines had smaller clusters and berries, leading to improved cluster looseness and to higher relative skin and seed growth. While all crop-regulating treatments led to an increase in the final leaf-to-fruit ratio, parameters of technological maturity were essentially uncoupled, as equally high Brix levels corresponded to the highest titratable acidity in D and, conversely, to lowest titratable acidity and highest pH in ECT and LCT. Overall results showed that different final yield-grape composition patterns can be reached depending on the technique used for crop regulation as a primary consequence of a diversified degree of compensation triggered on single-yield components.
Increasing the use of cover crops (CCs) is a necessity in sustainable viticulture, although it might clash with possible excessive competition towards vines. Especially in a climate-change scenario, ...the latter feature should be minimized while maintaining ecosystem services. Aimed at identifying CCs for vineyard floor management, the trial characterized several species according to their evapotranspiration (ET) rates, root growth patterns, and soil aggregate stability potential. The study was performed in 2020 in Piacenza (Northern Italy) on 15 CC species grown in pots kept outdoor and classified as grasses (GR), legumes (LE) and creeping (CR). Together with bare soil (control), they were arranged in a complete randomized block design. CCs ET was assessed through a gravimetric method, starting before mowing and then repeated 2, 8, 17 and 25 days thereafter. Above-ground dry biomass (ADW), root length density (RLD), root dry weight (RDW) and root diameter class length (DCL) were measured, and mean weight diameter (MWD) was calculated within 0-20 cm depth. Before mowing, ET was the highest in LE (18.6 mm day
) and the lowest in CR (8.1 mm day
) the latter being even lower than the control (8.5 mm day
). The high ET rates shown by LE were mainly related to very fast development after sowing, rather than to a higher transpiration per unit of leaf area. After mowing, the 15 species' ET reduction (%) plotted vs leaf area index (LAI, m
m
) yielded a very close fit (R
= 0.94), suggesting that (i) a linear decrease in water use is expected anytime starting with an initial LAI of 5-6, (ii) a saturation effect seems to be reached beyond this limit. Selection of cover crop species to be used in the vineyard was mainly based on diurnal and seasonal water use rates as well as dynamic and extent of root growth patterns. Among GR, Festuca ovina stood out as the one with the lowest ET due to its "dwarfing" characteristics, making it suitable for a permanent inter-row covering. CR species confirmed their potential for under-vine grassing, assuring rapid soil coverage, lowest ET rates, and shallow root colonization.
Abstract
A web-based app was developed and tested to provide predictions of phenological stages of budburst, flowering and veraison, as well as warnings for meteorological drought. Such predictions ...are especially urgent under a climate change scenario where earlier phenology and water scarcity are increasingly frequent. By utilizing a calibration data set provided by 25 vineyards observed in the Emilia Romagna Region for two years (2021–2022), the above stages were predicted as per the binary event classification paradigm and selection of the best fitting algorithm based on the comparison between several metrics. The seasonal vineyard water balance was calculated by subtracting daily bare or grassed soil evapotranspiration (ET
s
) and canopy transpiration (T
c
) from the initial water soil reservoir. The daily canopy water use was estimated through a multiple, non-linear (quadratic) regression model employing three independent variables defined as total direct light, vapor pressure deficit and total canopy light interception, whereas ET
S
was entered as direct readings taken with a closed-type chamber system. Regardless of the phenological stage, the eXtreme Gradient Boosting (XGBoost) model minimized the prediction error, which was determined as the root mean square error (RMSE) and found to be 5.6, 2.3 and 8.3 days for budburst, flowering and veraison, respectively. The accuracy of the drought warnings, which were categorized as mild (yellow code) or severe (red code), was assessed by comparing them to in situ readings of leaf gas exchange and water status, which were found to be correct in 9 out of a total of 14 case studies. Regardless of the geolocation of a vineyard and starting from basic in situ or online weather data and elementary vineyard and soil characteristics, the tool can provide phenology forecasts and early warnings of meteorological drought with no need for fixed, bulky and expensive sensors to measure soil or plant water status.
Climate change scenarios and the need of sustainable tools to reduce global warming impact on agriculture have led to the formulation of a large number of natural products or biostimulants that ...should increase plant resilience to abiotic stress.
Ascophyllum nodosum
(AN) extract is one of the most studied biostimulants to increase tolerance to drought stress, but the physiological mechanism underlying its action is still poorly understood. The aim of the present work was to determine AN extract impact on grapevine gas exchange under well-watered and water stress conditions and to examine its mode of action under stress (light and temperature). AN caused a slight increase in stomatal conductance that resulted in an increase of water plant conductivity to atmosphere. Increased transpiration induced by AN improved leaf thermoregulation, facilitating vine recovery after a stress period. AN increased transpiration through a reduction of stomatal sensitivity to VPD. AN action on stomata regulation indicated that this biostimulant could be a new potential tool to limit leaf damage during events of extreme temperature, even when they are not combined with water stress conditions.
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