In light of climate change and its impacts on plant physiology, optimizing water usage and improving irrigation practices play a crucial role in crop management. In recent years, new optical remote sensing techniques have become widespread since they allow a non-invasive evaluation of plant water stress dynamics in a timely manner. Unmanned aerial vehicles (UAV) currently represent one of the most advanced platforms for remote sensing applications. In this study, remote and proximal sensing measurements were compared with plant physiological variables, with the aim of testing innovative services and support systems to farmers for optimizing irrigation practices and scheduling. The experiment, conducted in two vineyards located in Sardinia, Italy, consisted of two regulated deficit irrigation (RDI) treatments and two reference treatments maintained under stress and well-watered conditions. Indicators of crop water status (Crop Water Stress Index—CWSI—and linear thermal index) were calculated from UAV images and ground infrared thermal images and then related to physiological measurements. The CWSI values for moderate water deficit (RDI-1) were 0.72, 0.28 and 0.43 for ‘Vermentino’, ‘Cabernet’ and ‘Cagnulari’ respectively, while for severe (RDI-2) water deficit the values were 0.90, 0.34 and 0.51. The highest differences for net photosynthetic rate (Pn) and stomatal conductance (Gs) between RDI-1 and RDI-2 were observed in ‘Vermentino’. The highest significant correlations were found between CWSI with Pn (R = −0.80), with Φ_PSII (R = −0.49) and with Fv’/Fm’ (R = −0.48) on ‘Cagnulari’, while a unique significant correlation between CWSI and non-photochemical quenching (NPQ) (R = 0.47) was found on ‘Vermentino’. Pn, as well as the efficiency of light use by the photosystem II (PSII), declined under stress conditions and when CWSI values increased. Under the experimental water stress conditions, grapevines were able to recover their efficiency during the night, activating a photosynthetic protection mechanism such as thermal energy dissipation (NPQ) to prevent irreversible damage to the photosystem. The results presented here demonstrate that CWSI values derived from remote and proximal sensors could be valuable indicators for the assessment of the spatial variability of crop water status in Mediterranean vineyards.

Maximizing water use efficiency, yield, and plant survival under drought is a relevant research issue for almond-tree-growing areas worldwide. The intraspecific diversity of this species may constitute a valuable resource to address the resilience and productivity challenges that climate change poses to crop sustainability. A comparative evaluation of physiological and productive performance of four almond varieties: ‘Arrubia’, ‘Cossu’, ‘Texas’, and ‘Tuono’, field-grown in Sardinia, Italy, was performed. A great variability in the plasticity to cope with soil water scarcity and a diverse capacity to adapt to drought and heat stresses during fruit development were highlighted. The two Sardinian varieties, Arrubia and Cossu, showed differences in water stress tolerance, photosynthetic and photochemical activity, and crop yield. ‘Arrubia’ and ‘Texas’ showed greater physiological acclimation to water stress while maintaining higher yields, as compared to the self-fertile ‘Tuono’. The important role of crop load and specific anatomical traits affecting leaf hydraulic conductance and leaf gas exchanges efficiency (i.e., dominant shoot type, leaf size and roughness) was evidenced. The study highlights the importance of characterizing the relationships among almond cultivar traits that affect plant performance under drought in order to better assist planting choices and orchard irrigation management for given environmental contexts.

The aim of this study was to develop a technique easy to apply in order to induce seed-tuber dormancy breakage. Over a two-year study, more than seven dormancy-breaking treatments were tested through evaluating different temperature effects alone or combined with gibberellins application, cutting in half of seed-tubers, and early haulm killing. Three varieties per year were considered: Spunta and Monalisa (medium and long dormancy) in both years, Europa during the first year and Arinda during the second year (both characterized by a short dormancy period). We found firstly that Europa and Arinda promptly responded to thermal treatments, and secondly to the same thermal treatments in combination with the application of gibberellins. Although not easily applicable, especially when a large volume of seed-tubers has to be handled (seed-tuber producers), the cutting in half of the seed-tubers also had a satisfactory result. Notwithstanding that treatments did not perfectly overlap between the two experiments, results were qualitatively similar. Therefore, these findings allow us to conclude that treatment with post-harvest storage at 20 °C, followed by a treatment with gibberellic acid at 38 days from harvesting, is the most efficient in releasing dormancy, in ensuring a good vegetative growth and productive performance at field-level irrespective of the variety.

We propose an index for proximal detection of water requirements to optimize the use of water resources in arid and semi-arid wine growing regions. To test the accuracy and representativeness of the proposed irrigation need index (I_IN), plant water status and physiological performances were monitored during seasons 2019 and 2020 in two grapevine varieties with different anisohydric degree (Vermentino and Cannonau) grown in 3 sites in Sardinia (Italy). Daily leaf gas exchange curves and stem water potential were recorded. Canopy temperature was monitored, using both thermistor sensors (Tc) and infrared thermometry (IR). Meteorological data, including dry and wet bulb temperatures were collected to compute and parametrize I_IN, based on energy balance equation. Vineyard water balance, thermal time and irrigation water productivity were characterized. Linear regression analysis allowed to validate I_IN for both varieties and to establish target thresholds for mild, moderate and severe water deficit to optimize irrigation for high yield and quality objectives. I_IN well represents plant water status, using either Tc or IR, and allows rapid and easy detection of water and heat stress condition, even when a stricter stomatal control determines slighter variation and lower response of stem water potential, as in plants with low anisohydric degree.

ISHS VI International Symposium on Irrigation of Horticultural Crops EFFECTS OF THE IRRIGATION REGIME AND PARTIAL ROOTZONE DRYING IN 'VERMENTINO' GRAPEVINES IN SARDINIA, ITALY

ISHS International Symposium on Precision Management of Orchards and Vineyards Water status monitoring in grapevines with traditional and new automated sensors