Severe Water Stress Research Articles

Nanosilicon application changes the morphological attributes and essential oil compositions of hemp (Cannabis sativa L.) under water deficit stress

Various practical strategies have been employed to mitigate the detrimental effects of water deficit stress on plants such as application of nano-stimulants. Nanosilicon plays a crucial role in alleviating the deleterious impacts of both abiotic and biotic stresses in plants by modulating various phyto-morphological and physiological processes. This study aimed to examine the combined effects of drought stress and nanosilicon application on the morphological traits and essential oil content and compositions of hemp (Cannabis sativa L.), in which four-week-old seedlings were subjected to irrigation treatments at four levels, including 100% (control), 80% (mild stress), 60% (moderate stress) and 40% (severe stress) field capacity and nanosilicon at three concentrations (0, 0.5 and 1.5 mM) in a completely randomized factorial design experiment with three replications for 40 days. The results showed that the maximum plant height (109.07 cm), number of nodes (33.3), and number of flowering branches (29.4) were recorded under the treatment of 1.5 mM nanosilicon and 100% FC. The lowest fresh and dry weights of aerial parts were associated to the severe drought stress (40% FC) without nanosilicon application. The mild water stress (80% FC) combined with foliar application of 1.5 mM nanosilicon led to highest EO content (0.17%) compared with the other treatments. However, the highest content of cannabidiol in the essential oil was achieved in the severe water stress (40% FC) and treatment of 0.5 mM nanosilicon. The results showed that the application of nanosilicon improved the morphological characteristics and also changed the content and compositions of the hemp plants under drought stress conditions.

Mitigating negative impacts of drought on oak seedlings performances through plant growth-promoting rhizobacteria.

Drought stress during the plant's growing season is a serious constraint to plant establishment in arid and semiarid Mediterranean ecosystems. Plant growth promoting rhizobacteria (PGPR) as environmentally friendly and innovative management approach can be used to produce seedlings better adapted to these environments. We tested native PGPR strains isolated from drought-tolerant tree and shrub species originating from two climatically contrasting regions: hot-dry (Dehloran) and milder Mediterranean climate (Ilam). These strains were used as a biological input to improve the morphological and physiological traits of Brant's oak (Quercus brantii Lindl.) seedlings in a greenhouse experiment. Seedlings were inoculated with various drought-tolerant strains or a combination of all bacteria (Bmix) and their morpho-physiological traits were measured under three levels of water stress (80% field capacity, FC80: no stress; 60% FC, FC60: moderate water stress and 40% FC, FC40: severe water stress). Strains from Dehloran were the most performant (Bacillus anthracis, B. licheniformis, B. cereus) except Stenotrophomonas maltophilia which originated from Ilam. They demonstrated the ability to solubilize insoluble phosphates (except for the B. licheniformis). They were also all able to produce auxin and the ACC-deaminase enzyme (except S. maltophilia). PGPR application, water stress treatments, and their interaction significantly influenced all the morphological and physiological seedling traits. Most traits significantly (p<0.01) decreased under FC40, in particular average leaf area, shoot fresh weight, and shoot dry weight. This decrease was particularly marked for the control (no inoculation), as the leaf area was reduced by 60% in FC40. In FC40, all bacterial treatments, especially B. cereus and Bmix efficiently improved seedling morphological traits and seedling quality index. The highest amount of chlorophyll a in FC40 was recorded for Bmix and B. licheniformis isolates. Total phenolic content and malondialdehyde levels, as well as proline, showed an increase under water stress conditions, particularly at FC40, irrespective of inoculation conditions. The amounts of malondialdehyde without inoculation increased significantly under water stress and the content were 1.3 and 2 times higher in FC60 and FC40, respectively, compared to FC80 with no inoculation. Under water stress, seedling performances and quality were impacted and the production of substances associated with physiological defense mechanisms, increased. However, the application of PGPR was able to mitigate these effects (in particular for B. cereus and Bmix). We concluded that application of drought tolerant PGPRs can be a cost effective and ecologically sustainable method for producing oak seedlings better adapted to water-scarce environments.

Biochemical and enzymatic alterations of watermelon associated with irrigation management and inoculation with Rhizobacteria

Water stress has caused major losses in the agricultural productivity of crops, inducing the search for alternatives for sustainable cultivation. In this context, the objective of this study was to evaluate the tolerance of watermelon under water stress, inoculated with bacterial strains of the genus Bacillus spp., regarding the biochemical and enzymatic variables in the flowering stage. A randomized block design was adopted in a split-plot 4x4 factorial scheme, with plots consisting of four levels of soil water availability (40%, 60%, 80% and 100% of field capacity - FC) and subplots consisting of four inoculations (Negative Control (NC); XX6.9 bacteria; P6.2 bacteria; MIX – co-inoculation of XX6.9 and P6.2 bacteria), with five replicates. XX6.9 bacteria and NC were the treatments most affected by severe water stress, since at the soil water availability (SWA) level of 40% FC they showed high contents of the oxidative marker (MDA) and proline. Although the inoculation with XX6.9 bacteria promoted a higher content of osmoregulators such as proteins, total soluble sugars and reducing sugars, it was not enough to attenuate the effects of water deficit. On the other hand, treatments with P6.2 bacteria and MIX of bacteria showed reduced levels of MDA at the SWA level of 40% FC, accompanied by high enzymatic activity of POD and CAT, which may contribute to the tolerance of the watermelon crop to water stress.

Exogenous hydrogen peroxide alleviates water stress-induced physiological and biochemical changes in durum wheat (Triticum durum Desf.)

Water scarcity threatens crops, in particular, durum wheat (Triticum durum Desf.), in the world's drought regions. As the water-stress wheat cultivars in the middle east of Algeria are poorly investigated, the present study was, therefore devoted to exploring the effect of water deficiency and, the possible attenuative role of exogenous hydrogen peroxide (H2O2) in Sémito, a commonly cultivated durum wheat (Triticum durum Desf.) variety in the middle eastern regions of Algeria. Here, Water-stressed durum wheat seeds received sufficient water for 48 hours to allow for uniform seed germination and then were subjected to cease the watering phase. The attenuation of water stress severity was examined in water-stressed wheat seeds treated with two different concentrations of H2O2 (20 and 50 mM). Water stress significantly reduced mean root number (MRN), mean root length (MRL), and germination percentage (G %), in addition to a marked decline in total protein content, and increased level of proline content and catalase activity compared to control plants. Moreover, H2O2 co-treatment enhanced the catalase activity, and promoted the accumulation of proline and protein contents, contributing to osmotic adjustment under water stress conditions. Our findings suggest that exogenous H2O2 application ameliorates water stress-induced physiological and biochemical changes in durum wheat, highlighting its potential as a promising strategy to enhance drought tolerance in this economically important crop species.

Soil Application of Selenium in Wheat (Triticum aestivum L.) Under Water Stress Improves Grain Quality and Reduces Production Losses.

Selenium (Se) is an essential element for humans. However, much of the world's human population is deficient in this element, which has become a public health problem. This study aimed to evaluate whether applying severe water stress to wheat plants (Triticum aestivum L.) could allow Se to reduce the production losses and increase the grain quality, thereby contributing to the reduction in hidden hunger. The experiment was conducted in a randomized block design with four replications in a 5 × 2 factorial scheme, with five doses of Se (0.00, 0.25, 0.50, 1.00, and 2.00 mg dm-3) and two irrigation conditions (with and without water deficit). When sodium selenate (Na2SeO4) was applied to the soil, the grains were rich in Se. Under low doses, there was an enrichment of the grains in sulfur, iron, copper, and zinc as well as total free amino acids and total soluble proteins, and lower losses in productivity under severe water stress. Higher doses decreased the concentration of malondialdehyde (MDA) and hydrogen peroxide (H2O2), increased the catalase activity, and increased the water use efficiency (WUE). Therefore, applying Se at a dose of 0.25 mg dm-3 is effective for the biofortification of wheat grains. It enhances grain nutritional quality, increases Se bioaccessibility, and reduces production losses under water stress conditions.

A decision-making framework based on rain-fed crop suitability, water scarcity, and economic benefits for determination multiple-crop rotation strategy

Water scarcity under global climate change has impacted decreased agricultural productivity. Determining the suitable crop rotation strategy under water scarcity applicable to a specific region requires an evaluation of crop suitability, water scarcity, and economic benefits to farmers. This paper aims to improve agricultural productivity and economic benefits through crop rotation strategies under climate change. We developed seven crop rotation strategies, including rice, soybean, maize, and sweet potatoes, that were determined based on preliminary results of the crop suitability index using the EcoCrop model. The water scarcity index (WSI) in historical and future under climate change conditions is estimated using the CropWAT model. In addition, the economic benefit of each crop rotation strategy is evaluated. Finally, multi-criteria decision analysis (MCDA) using the Analytical Hierarchy Process (AHP) was employed to select the most suitable crop rotation strategy applicable to Taoyuan City, Taiwan, based on crop suitability assessment, water scarcity, and economic benefit analysis. Our result shows that WSI values are 0.37, 0.50, and 2.28 in the dry years of 2004, 2015, and 2020, respectively, due to decreasing rainfall and increasing temperatures. The 10-year and 20-year averages were 0.4 and 0.35, respectively, indicating that the issue of agricultural water scarcity is intensifying year by year. Cultivating sweet potatoes has less vulnerability to water scarcity by up to 90 % under climate change than rice. Sweet potatoes also generate farmers’ income, which increases by 338 %, considering both rain-fed and irrigation efficiency conditions. Finally, the MCDA-AHP revealed that sweet potatoes and soybean-maize rotation in Taoyuan City were the most suitable and profitable crops for cultivating in Taoyuan City, especially under high and severe agriculture water stress events. Implementing a crop rotation strategy involving sweet potatoes and soybean-maize can effectively mitigate the impact of climate change and extreme drought on crop yield and ensure a stable income for farmers. Integrated irrigation and crop rotation strategies are crucial for providing farmers and other stakeholders with more informed decision-making in agriculture sectors while enhancing water use efficiency.

Use of seawater as an accelerator in 3D printed concrete (3DPC)

Seawater (SW) is one of the viable alternatives to replace freshwater (FW) for producing concrete in regions facing extremely severe water stress. Seawater has high potential to be used as a set-on-demand accelerator among the other expensive materials being widely researched in additive manufacturing. The current study evaluated the progress of heat of hydration in 3DPC-FW and 3DPC-SW mixes using isothermal calorimetry. Furthermore, fresh and early-age properties of these mixes were studied using a flow table, manual shear vane, uniaxial unconfined compressive strength tests, and dynamic elastic modulus development. Strength development and shrinkage progress up to 28 days were evaluated. A detailed investigation reveals that an increase in compressive strength from the very first hours of hydration, a reduction in workability which could be compensated by modifying SP, and higher shrinkage were observed in SW-mixed 3DPC compared to the FW-mixed counterpart. Furthermore, the potential improvement in the speed of printing is highlighted in this study with 3DPC-SW mix demonstrating acceleration in early strength.

Integrating Morpho-Physiological, Biochemical, and Molecular Genotyping for Selection of Drought-Tolerant Pigeon Pea (Cajanus cajan L.) Genotypes at Seedling Stage.

Pigeon pea (Cajanus cajan (L.) Millsp.), a potential legume as an economic source of protein, is commonly cultivated in tropical and subtropical regions of the world. It possesses medicinal properties and acts as a cash crop, benefiting low-income farmers economically. The identification of pigeon peas exhibiting drought tolerance has become crucial in addressing water scarcity issues in the agriculture sector. In addition, exploring the genetic diversity among genotypes is important for conservation, management of genetic resources, and breeding programs. The aim of this study was to evaluate the morpho-physiological and biochemical responses of selected pigeon pea genotypes under pot-induced water stress conditions through different field capacities as well as the genetic diversity using start codon targeted (SCoT) markers. A significant variation was observed for the physiological traits studied. The accumulation of fresh weight (FW) and dry weight (DW) was significantly reduced in moderate and severe drought stress conditions. The lowest % DW decrease was found in LM (35.39%), KAT (39.43%), and SM (46.98%) than other genotypes at severe drought stress. Analyses of physiological responses including the photosynthetic efficiency (Phi2), the chlorophyll content (SPAD), and the relative water content (RWC) revealed positive and negative correlations with various parameters, reflecting the impact of drought stress on the chlorophyll content. The results revealed that biochemical traits including the total phenolic content, soluble sugars, proline, total protein, total amino acids, and free amino acids were variably and significantly increased under water stress. Antioxidant enzyme activity levels, specifically ascorbate peroxidase (APX) and catalase, varied among the genotypes and in response to severe water stress, offering further insights into adaptive responses. The eight genotypes analysed by use of 20 SCoT markers revealed 206 alleles and an average of 10.3 alleles per locus. Genetic similarity ranged from 0.336 to 0.676, clustering the pigeon pea genotypes into two major groups by the unweighted pair group method of arithmetic averages (UPGMA) cluster analysis. Principal coordinate analysis (PCoA) explained 43.11% of genetic variation and based on analysis of molecular variance, a high genetic variation (80%) within populations was observed, emphasizing the potential for genetic improvement. Among the eight genotypes studied, LM and KAT were drought tolerant and genetically diverse and therefore could be used as parents for developing drought tolerance in pigeon pea.

Evaluation of Genotypes against Water Stress and Salinity in Rice (Oryza sativa L.)

Abiotic stresses pose significant challenges to growth, yield and productivity thus threatening food security. Hence, it is essential to develop climate resilient rice varieties that mitigate the impact of abiotic stress. A study on physiological characterization for water and salinity stress was conducted in twenty-eight rice genotypes during kharif 2023 at Regional Agricultural Research Station, Maruteru. Among all the treatments, root length, shoot length, root and shoot dry weight and chlorophyll content was maximum under control followed by 1% mannitol, 2% mannitol and salinity stress. Visual scoring for water stress at seedling stage revealed that under mild water stress (1% M) more than 90% of plants survived in genotypes viz., AC-35678, FL 478, Ravana, Rahaspunjar, AUS 63, AUS 73, Vandana, NICRA 16, NICRA 17, CR-3439-4-E-17-2-1-B-1-S-1, CR-4215-2-5-2-M-4-SUB-2-5-1. Under severe water stress (2% M) more than 70% of the seedlings survived in NICRA 16, CR-4215-2-5-2-M-4-SUB-2-5-1, CRAC-4423-3, IET -18727, IC-516 149, IET-18716, AC-35678, FL 478, AC 85, Rahaspunjar, AUS 100, NICRA 17, CR-3439-4-E-17-2-1-B-1-S-1. Under salinity stress the score 3 was recorded in FL 478, and 5 in Rahaspunjar, IET -18727, NICRA 16, Ravana, NICRA 17. For both combined stresses, FL 478, Rahaspunjar, NICRA 16 and NICRA 17 were identified as tolerant and can be identified as donors for development of rice varieties having climate resilience.

Assessment of genetic diversity among upland cotton for earliness, fiber quality and yield-related traits using correlation, principal component and cluster analysis

The CRIS-613 drought tolerant cotton cultivar was developed through hybridization conventional breeding method at the experimental field of Sakrand. It significantly produced maximum seed cotton yield in series of trials at Sakrand and at 11 different agro-climatic conditions of Sindh and Pakistan. The CRIS-613 is drought tolerant variety as it given 17.46% and 9.69% higher yield in moderate (21 days of intervals) and severe (29 days of intervals) water stress conditions. It also possesses standard fiber quality parameters. The CRIS-613 has yield potential up to 5000 kg ha-1, but it depends upon the adaptation of best management practices. It is non Bt. variety tolerant to sucking insect pests and disease, its best sowing time is 15th April to 15th May, on flat sowing its need 8-10 kg seed acre-1and on bed furrow 5-6 kg acre-1. Plant to plant spacing 30 cm and row to row 75 cm. 9-10 irrigations on bed furrow and 4-6 on flat sowing. Four-time inter-culturing needed, 1stafter 20 days and subsequent 15-20 days. The optimum dose of N, P and K is 150 kg N + 50 kg P2O5+50 kg K2O hectare-1. Picking 03 (Three) 1st when 40-50 bolls may open at 120 days after sowing. The variety features were presented in technical expert subcommittee and after that proposal was submitted and present in Sindh Seed Council. Keeping in view the performance and silent features of CRIS-613 it was approved and recommended for general cultivation in Sindh during the year 2020

Evaluating a multi-step collocation approach for an ensemble climatological dataset of actual evapotranspiration over Italy

Accurate estimations of actual evapotranspiration (ET) are key in a variety of water balance applications, but divergent results can be obtained due to the large range of available methodologies. The use of an ensemble approach is a suitable alternative, as it summarizes multiple sources in an optimized strategy. In this study, an expert-based multi-step collocation (MC) approach is tested to merge six ET datasets, with the aim of reconstructing a spatiotemporally-consistent monthly dataset for Italy in the climatological period 1991–2020. The merged products are: three water balance datasets (BIG BANG, LSA SAF, and LISFLOOD), two residual surface energy balance model datasets (SSEBop, and ALEXI), and the MODIS standard ET product. The merged product is analyzed for spatio-temporal consistency and evaluated using flux observations from 11 sites. On average, the merged product has higher accuracy (mean absolute difference = 0.47 ± 0.17 mm/d, relative difference = 27.9 ± 7.5 %) than any single base dataset, and it is characterized by limited bias (mean bias error = -0.17 ± 0.26 mm/d), high correlation (r = 0.83 ± 0.10), and more uniform performance across sites. The merged ET dataset is accompanied by an estimation of the ensemble spread, which highlights large differences in ET estimates in some areas and periods characterized by severe water stress, such as in southern Italy during the summer. This large spread seems to be mostly driven by systematic differences among datasets, which affect the estimation of the reference climatology, suggesting how inter-model spread can have a defining role in further improving the merging strategies.

The interaction effect of water deficit stress and seaweed extract on phytochemical characteristics and antioxidant activity of licorice (Glycyrrhiza glabra L.).

With increasing drought stress due to climate change and water scarcity, the agricultural sector has sought innovative strategies to mitigate the detrimental effects on crop productivity. One approach that has received significant attention is the use of fertilizers and biostimulants as potential means of alleviating drought stress. In this study, five different irrigation levels including 100% (control), 80% (slight stress), 60% (mild stress), 40% (moderate stress), and 20% (severe stress) of field capacity (FC) and seaweed extract (SWE) at three concentrations (0, 5, and 10 g/L) were applied to the pots containing one-year-old licorice (Glycyrrhiza glabra L.) plants in a factorial completely randomized design experiment with three replications for eight weeks. The glycyrrhizic acid content increased with water stress intensity without the application of SWE until severe (20% FC) water stress treatment. The application of 10 g/L SWE under 100% FC led to a significant increase in the glycyrrhizic acid value (32.5±0.889 mg/g DW) compared with non-SWE application (30.0±1.040 mg/g DW). The maximum glabridin content (0.270±0.010 mg/g DW) was obtained under irrigation of 20% field capacity with 10 g/L SWE application. In addition, the activity of the all studied enzymes such as APX (ascorbate peroxidase), CAT (catalase), POD (peroxidase), and SOD (superoxide dismutase) were boosted by increasing the water stress levels. The use of SWE further enhanced the increase of some of these metabolites and enzymes, which, in turn, helped the plant to tolerate stress conditions through the scavenging of more ROS (Reactive oxygen species), wherein for this purpose, the SWE 10 g/L was more effective than other concentration. The plants efficiently eliminated ROS driven from drought stress by both non-enzymatic and enzymatic systems.

Investigating the impacts of different degrees of deficit irrigation and nitrogen interactions on assimilate translocation, yield, and resource use efficiencies in winter wheat

Water and nitrogen (N) are recognized as the primary determinants influencing the development and output of winter wheat. They affect the growth of winter wheat not only through their own changes, but also through their interaction. The translocation and accumulation of pre- and post-anthesis assimilates (including dry matter and N) are important physiological processes in winter wheat, which are closely related to the resource use efficiency and yield. However, a dearth of research exists that examines the complex interplay between varying water levels, especially severe water deficit, and N deficiency levels on the growth dynamics of winter wheat. The purpose of this study was to quantify and compare the effects of different degrees of water deficit and N interaction on assimilate translocation, water and N use efficiency and yield of winter wheat. A four-year long-term field experiment conducted under the rain-out shelter including four irrigation and two N levels was launched during 2019–2023. This method avoided the impact of precipitation on water treatment and helped to achieve serious water deficit treatment. The findings indicated that the higher N application improved the wheat's ability by 49.6 % - 362.3 % to utilize the available soil water. The pre- and post-anthesis translocation and accumulation of assimilates (including dry matter and N) in winter wheat increase alongside elevated levels of water and N application, except under severe water deficit treatment. Plants under mild to moderate water deficit were better able to translocate the pre-anthesis assimilates. However, the severe water deficit hindered the re-translocation of assimilates before anthesis. Providing additional N during periods of severe water scarcity leads to a 13.4 % - 44.7 % reduction in water use efficiency (WUE). Furthermore, both the irrigation water use efficiency and WUE diminished by 10.3 % - 60.5 % and 4.5 % - 41.4 % with higher levels of irrigation, while improved by 24.4 % - 48.2 % and 12.6 % - 39.4 % with higher N application rates. Conversely, N partial factor productivity and N use efficiency followed the opposite trend. Similar to WUE, increasing N application under severe water deficit would result in a yield reduction of 38.7 %. The reduction in crop yield resulting from severe water stress was primarily ascribed to the decline in the kernels number per spike (up to 74.9 %), with the reduction in spike number per unit area following closely behind (up to 29.1 %). This integrated approach, combining resource use efficiency with a detailed assessment of assimilate dynamics, provides a holistic view of how water and N management strategies impact winter wheat performance. The findings will offer precise insights for developing targeted irrigation and N scheduling strategies for sustaining both winter wheat production and environmental sustainability.

Examination of Water Use and Social Vulnerability: A Comparison of Four Communities in Alachua County, Florida

It is projected that about 30% of the world’s major cities will face severe water stress and urban drought from 2050 if climate change continues and has the anticipated effects (Florke et al, 2018; www.wrcwebsite.azurewebsites.net). Socio-economic drought, meaning water shortage in urban life, can have significant effects on a city’s inhabitants, including health and quality of life. Social and economic factors play an important role in planning and decision making of a society (Zhang et al, 2020). The analysis investigated the relationship between socio-economic factors and the use of potable water, its associated impact on aquifer recharge, and potentially identifying major factors influencing water demand and resource sustainability. The Centers for Disease Control and Prevention’s Social Vulnerability Index (SVI) and other measures were used for evaluating socio-economic factors. However, since SVI showed weak relationship with water use in the county and the neighborhoods, other socio-economic measures were assessed. Past research had found a correlation between water use and population, GDP, per capita income, electricity usage and irrigated land areas (Alacoma et al., 2007, www.usf.uni-kassel.de/watclim). Therefore, socio economic measures such as population density, household size, per capita income, and poverty rate and irrigation (with and without) potable water were analyzed to evaluate the relationship between water use patterns and these factors across the county and in the communities. The western communities had newer development and less parcels compared to the eastern with much older construction, which impacted their water use. Oakmont with separate reclaimed irrigation meter had lesser usage on potable water. Tioga on the other hand irrigated with potable water. Yearly SVI on a census tract level for the specific years of the study and other socio-economic measures such as population, per capita income, poverty, and household size were used in the analysis. The analysis was performed on four communities in Alachua County, Florida; two at the west and two at the east of the county. Socio-economic measures and physical features were evaluated for communities in the four locations to evaluate whether there is a relationship between water use patterns, spatial characteristics of development such as percent impervious and runoff, and measures of SVI. Spatial and basic statistics was used for this analysis. The western part of the county has had more intensive development in recent years compared to the eastern part of the county. The eastern communities have a high SVI and low potable water use per capita compared to the western communities. The number of households and population were the primary drivers of potable water use per census block. Percent impervious surface and runoff volume did not show any significant. relationship with a community’s SVI. At the parcel level, statistically significant differences were found between communities. For example, potable water use per parcel was lower in communities with high SVI. Keywords: water sustainability, urban water management, social vulnerability index, socio-economic factors, potable water use, aquifer recharge, reclaimed water use, runoff, imperviousness

Triticum durum productivity and adaptability of two genotypes under water deficit in Algerian high plains

Over the past few decades, Algeria has experienced a significant decline in rainfall patterns, which has been exacerbated by increasing hot spells leading to elevated rates of evapotranspiration. This combination of factors has induced severe water stress, critically impacting agricultural productivity, particularly in cereal production. Recognizing the urgency of this issue, our study was conducted over two consecutive cropping seasons at the experimental agricultural site of Ibn Khaldoun University in Tiaret, located in the western region of Algeria. We specifically investigated the performance of two durum wheat cultivars, ACSAD 297 and CTA 159, under conditions of water stress typical of the Algerian high plains. Our research focused on the impacts of water deficits during the grain filling phase, assessing their effects on seed formation, seed quality, and overall yield development. The results highlighted that contributions from various plant components to grain filling were notably affected by water availability, with lower leaves contributing 22%, the flag leaf 15%, the ear 14%, the ear neck 10%, and awns less than 1%. Notably, the ACSAD 297 cultivar exhibited superior drought tolerance compared to CTA 159, indicating its potential for cultivation in arid conditions. Furthermore, we established strong correlations between grain diameter, thousand grain weight, and stem height, which could inform future breeding initiatives. These findings not only provide important targets for enhancing drought resistance in durum wheat but also have broader implications for improving wheat productivity in semi-arid regions around the world, contributing to food security in the face of climate change.

Water Relations and Physiological Response to Water Deficit of ‘Hass’ Avocado Grafted on Two Rootstocks Tolerant to R. necatrix

Avocado (Persea americana Mill.) cultivation has spread to many countries from the tropics to the Mediterranean region, where avocado crops commonly face water shortages and diseases, such as white root rot (WRR) caused by Rosellinia necatrix. The use of drought- and WRR-tolerant rootstocks represents a potential solution to these constraints. In this research, water relations and the morpho-physiological response of avocado ‘Hass’ grafted on two selections of R. necatrix-tolerant rootstocks (BG48 and BG181) were evaluated under well-watered (WW) and at two soil-water-availability conditions (WS, ~50% and ~25% field capacity). Under WW, scion water use was markedly affected by the rootstock, with BG48 displaying a water-spender behavior, showing higher water consumption (~20%), plant transpiration rates (~30%; Eplant) and leaf photosynthetic rates (~30%; AN) than BG181, which exhibited a water-saving strategy based upon a trade-off between leaf-biomass allocation and tight stomatal control of transpiration. This strategy did not reduce biomass, with BG181 plants being more water use efficient. Under WS, BG48 and BG181 exhibited a drought-avoidance behavior based on distinct underlying mechanisms, but increases in leaf mass area (~18–12%; LMA), and decreases in Eplant (~50–65%), plant hydraulic conductance (~44–86%; Kh) and leaf water potential (~48–73%; Ψw) were observed in both rootstocks, which aligned with water stress severity. After rewatering, photosynthetic rates fully recovered, suggesting some ability of these rootstocks to withstand water stress, enabling the ‘Hass’ variety to adapt to region-specific constraints.

Diplodia seriata Isolated from Declining Olive Trees in Salento (Apulia, Italy): Pathogenicity Trials Give a Glimpse That It Is More Virulent to Drought-Stressed Olive Trees and in a Warmth-Conditioned Environment.

The fungi Botryosphaeriaceae are involved in olive declines in both the world hemispheres and in all continents where this species is cultivated. In Salento (Apulia, Italy), the Botryosphaeriaceae Neofusicoccum mediterraneum and N. stellenboschiana have been reported as the agents of a branch and twig dieback that overlaps with olive quick decline syndrome caused by Xylella fastidiosa subsp. pauca. In this study, we report the finding of Diplodia seriata, another Botryosphaeriaceae species, in Salento in Xylella fastidiosa-infected olive trees affected by symptoms of branch and twig dieback. Given that its presence was also reported in olive in the Americas and in Europe (Croatia) with different degrees of virulence, we were prompted to assess its role in the Apulian decline. We identified representative isolates based on morphological features and a multilocus phylogeny. In vitro tests showed that the optimum growth temperature of the isolates is around 25-30 °C, and that they are highly thermo-tolerant. In pathogenicity trials conducted over eleven months, D. seriata expressed a very low virulence. Nonetheless, when we imposed severe water stress before the inoculation, D. seriata significatively necrotized bark and wood in a time frame of 35 days. Moreover, the symptoms which resulted were much more severe in the trial performed in summer compared with that in autumn. In osmolyte-supplemented media with a water potential from -1 to -3 Mpa, the isolates increased or maintained their growth rate compared with non-supplemented media, and they also grew, albeit to a lesser extent, on media with a water potential as low as -7 Mpa. This suggests that olives with a low water potential, namely those subjected to drought, may offer a suitable environment for the fungus' development. The analysis of the meteorological parameters, temperatures and rainfall, in Salento in the timeframe 1989-2023, showed that this area is subjected to a progressive increase of temperature and drought during the summer. Thus, overall, D. seriata has to be considered a contributor to the manifestation of branch and twig dieback of olive in Salento. Coherently with the spiral decline concept of trees, our results suggest that heat and drought act as predisposing/inciting factors facilitating D. seriata as a contributor. The fact that several adverse factors, biotic and abiotic, are simultaneously burdening olive trees in Salento offers a cue to discuss the possible complex nature of the olive decline in Salento.

Impact of extreme seasonal drought on ecosystem carbon‒water coupling across China

Water use efficiency (WUE) is a critical evaluation indicator of ecosystem responses to climate change and its extremes. However, the influence of the timing of extreme drought on the variation of ecosystem WUE under severe water stress has not been studied extensively. In particular, the modulation of drought impacts on WUE under regional hydro-climatic conditions and biome types is poorly understood. Considering observation-based ecosystem flux and drought index datasets, this study examined the impact of extreme seasonal drought on WUE in China and attempted to reveal the underlying drivers of seasonal variations in drought impacts. Results showed that the direction and magnitude of drought impacts on WUE depend on the occurrence time of extreme drought and the seasonal dynamics of regional ecological and climatic conditions. Across the vegetated regions in China, the most widespread reduction in WUE under extreme drought conditions was observed in summer, whereas approximately 60% of the study area showed positive changes in WUE under extreme drought conditions in spring. Furthermore, the co-regulation of drought characteristics and background environmental conditions in determining the impacts of extreme seasonal drought on ecosystem WUE is highlighted. Classification and regression tree analysis results illustrate that leaf area index (LAI) and drought timing dominated ecosystem WUE variation in response to extreme drought in China. Regions with lower LAI experienced more serious reductions in WUE under extreme drought. These findings indicate the importance of accounting for the interaction between drought seasonality and biome features in assessing drought impacts, thus contributing to improving the modelling of terrestrial ecosystem responses to climate extremes under global warming.

Cross‐Generational Effect of Water Deficit Priming on Physiology of Peanut Plants Under Water Stress

ABSTRACTWater deficit priming through regulated deficit irrigation has been shown to be beneficial for peanut cultivation, leading to improved water‐use efficiency during the crop cycle and enhanced stress acclimation. The effects of priming using water deficit can be heritable, but little is known about stress priming effects on the physiology and growth of successive generations undergoing water stress. Two experiments were conducted to assess cross‐generational priming by determining physiological and growth responses of offspring of primed and non‐primed peanut plants of two genotypes, COC‐041 and New Mexico Valencia C (NMV‐C), both previously found to be strongly responsive to priming. Seeds were collected from parental plants subjected to mild water stress by regulated deficit irrigation (primed) or adequate irrigation (non‐primed). These seeds were then planted, and the offspring were monitored for physiological and growth responses to water stress, including on a whole‐plant basis using a high‐throughput physiological phenotyping platform and on individual leaves by periodic single‐leaf measurements. Measurements included whole‐plant transpiration (plant‐Tr), root water uptake, leaf transpiration, stomatal conductance and net CO2 assimilation (leaf‐Tr, leaf‐gs, and leaf‐A), leaf water and osmotic potential (leaf‐Ψw and leaf‐Ψo), leaf osmotic adjustment, leaf relative water content (leaf‐RWC) and cumulative plant‐Tr. Offspring of both genotypes from primed parent plants had faster early establishment, with more uniform germination, and more rapid initial seedling growth compared to offspring from non‐primed parent plants. Although offspring of both non‐primed and primed plants of both genotypes exhibited a significant reduction of plant‐Tr, gas exchange, leaf‐Ψw, leaf‐Ψo, and leaf‐RWC when exposed to water stress, offspring of primed plants showed increased water use efficiency through reduced leaf‐gs, leaf‐Tr and plant‐Tr while maintaining leaf‐A under water stress. Despite offspring of both primed and non‐primed plants being susceptible to severe water stress, offspring of primed plants exhibited overall enhanced water use efficiency, leading to greater dry biomass production per gram of transpired water and a trend of less growth reduction due to water stress compared to offspring of non‐primed plants, especially for the genotype COC‐041. This study shows the potential of water deficit priming to promote cross‐generational changes in physiological function under limited water availability, by enhancing crop stress acclimation in the next plant generation.

Hydrus-1D Model for Simulating Potassium Transport in Rice Crop Irrigated with Alternate Wetting and Drying Practice

ABSTRACT Potassium (K) is one of the essential nutrients that play a crucial role in rice fields; however, its availability, transport, and balance components can be influenced by alternating wetting and drying (AWD) irrigation practice. This study used the Hydrus-1D solute transport model to simulate K transport and balance components in AWD irrigated rice fields. Thirty lysimeter field experiment plots with three different irrigation treatments (No: no soil water stress, MS: mild soil water stress (400 cm), and SS: severe soil water stress (750 cm)) were used for rice cultivation. Daily measurements of soil matric potential head (SMPH) and ponding water depth (PWD) were recorded. Throughout the rice-growing season, leachate water samples from the surface (ponding water) and soil profiles were collected to measure K content. Using the lysimeter field experiment data, the Hydrus-1D model simulated K transport in the AWD rice field. The simulation results indicate that the K distribution predominantly occurred within the top puddled soil layer (0–20 cm) in AWD practice. This suggests that the recommended K fertilizer dose with a 4–5 cm PWD and SMPH of 400 cm optimizes K availability for rice while limiting K leaching loss. The Hydrus-1D model proves to be a valuable management tool, aiding in determining optimal K application rates and ponding water depths for AWD irrigation, ensuring sufficient K nutrients for rice, and controlling K loss for sustainable rice production.