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This paper highlights the evolution and impact of the SWAP model (Soil – Water – Atmosphere – Plant), which was initiated by R.A. Feddes and colleagues fifty years ago, in 1974. Since then, the SWAP model has played a crucial role in the advancement of agrohydrology. This paper highlights some major advances that have been made, especially focussing on the last fifteen years. The domain of the SWAP model deals with the simulation of the soil water balance in both unsaturated and saturated conditions. The model solves the Richards equation using the water retention and hydraulic conductivity functions as described by the Van Genuchten – Mualem equations. Bimodal extensions of the Van Genuchten - Mualem relationships have been implemented, as well as modifications near saturation and addressing hysteresis. An important sink term in the Richards equation is root water uptake. Crop development plays an important role in a robust simulation of root water uptake. That is why a link has been made with the dynamic crop growth model WOFOST. Instead of using a prescribed crop development, a distinction between potential and actual crop development is calculated by reducing the potential photosynthesis as a result of water or oxygen stress. Since the early days of SWAP, empirical and macroscopic concepts have been used to simulate root water uptake. Recently two process-based concepts of root water uptake and oxygen stress have also been implemented. Another important sink-source term in the Richards equation is the interaction with artificial drains. In SWAP, drainage can be simulated by either using prescribed or simulated drain heads and simulation of controlled drainage with subirrigation is possible. Finally, we briefly elaborate on three studies using SWAP: water stresses in agriculture in the Netherlands, regional water productivity in China, and controlled drainage with subirrigation. We finish discussing promising developments for the near future.

The DOWNY MILDEW RESISTANCE 6 (DMR6) protein is a 2-oxoglutarate (2OG) and Fe(II)-dependent oxygenase, involved in salicylic acid (SA) metabolism. SA is recognized as an abiotic stress-tolerance enhancer, and in tomato the inactivation of DMR6 was found increase its level and induce disease-resistance against several pathogens. By applying the CRISPR/Cas9 technique, we generated Sldmr6-1 tomato mutants and tested their tolerance to drought as well as to Late Blight. Wild-type tomato cultivar ‘San Marzano’ and its Sldmr6-1 mutants were subjected to water deprivation for 7 days. WT plants exhibited severe wilting, while T2 Sldmr6-1 mutants showed turgid leaves and maintained higher Soil Relative Water Content. Eco-physiological measurements highlighted that Sldmr6-1 mutants adopted a water saving behavior reducing transpiration rate by decreasing stomatal conductance. Under drought stress the assimilation rate decreased as well, resulting in no alteration of the CO2 concentration in the sub-stomatal chamber and increasing the Water Use Efficiency. Furthermore, in Sldmr6-1 mutants the drought stress induced up-regulation of the anti-oxidant related genes SlAPX and SlGST as well as down-regulation of SlCYP707A2 gene, which is involved in ABA catabolism. At last we highlighted, for the first time in tomato, that Sldmr6-1 mutants exhibited a reduced susceptibility to Phytophthora infestans, the causal agent of Late Blight.

This master’s thesis project investigates the utilization of a low-cost hyperspectral (HS) imaging rig to identify and classify drought stress in pine plants. Drought stress is a widespread environmental challenge affecting global forestry, requiring more resources as the industry grows and global warming rises. This provokes a need for affordable, and efficient monitoring methods. HS imaging, with its ability to capture a wide range of spectral information, offers promising methods for quick and precise measurements of plant stress. The project methodology is comprised of redesigning an existing HS imaging rig, with the camera employing push-broom technology, to yield precise and consistent HS images. This involved exploring the camera’s spectral range, designing components to ensure consistent artificial lighting using blackbody radiation sources, and calibrating the HS camera for focal depth and aberrations like smile and keystone. Two experiments were conducted to obtain the data for pine stress detection, first for two binary categories: Control, and 100% Drought, and later introducing a third semi-drought category in the second experiment. The data analysis encompassed preprocessing the HS images to correct the lighting intensity distributions and normalization of pixel values. Accompanied by filtering, resampling spectral data, and feature extraction facilitating consistent drought identification, and data management. To identify stress patterns in pine plants and temporal decay rates, methods such as spectral reflectance analysis, various vegetation indices (VI), and statistical learning techniques like discriminant analysis and logistic regression were evaluated for distinguishing between stressed and healthy plants. The results demonstrate the accuracy of the HS imaging rig in measuring spectral reflectances from plants, capturing changes between 550 − 670 nm in the visible spectrum and 750 − 890 nm in the near-infrared (NIR) spectrum due to increasing str

Differential response of bread wheat seedlings to contrasting water regimes can be used to determine traits related to drought tolerance. The F1 offspring from eight crosses and 11 selected parental genotypes were simultaneously grown in hydroponic cultivation-polyethylene glycol (PEG) induced drought stress vs. control conditions. Criteria for selection of maternal and paternal genotypes were desirable traits in terms of increased tolerance to drought: longer stem length, longer primary root, large number of seminal roots, large root dry mass and stem dry mass, beginning of root branching at the greatest possible distance from beginning of the root, contrasting angle of seminal roots. The traits were measured on 14 day old seedlings: primary root length (PRL), distance to the first branch on the primary root (DFBR), number of seminal roots (NSR), total seminal root length (TSRL), angle of seminal roots (ASR), stem length (SL), root dry mass (RDM), stem dry mass (SDM), and the ratio of root dry mass to stem dry mass (RDM/SDM). Drought stress led to a decrease in the mean values of all root and stem traits by 11% on average, except for RDM/SDM which was increased. The most sensitive trait to drought stress was DFBR (25% reduction), causing root systems to branch at a shallower depth. In conditions of induced drought stress, the strongest statistically significant correlation was found among RDM and RDM/SDM (r = 0.794), SL and ASR (r = 0.708), RDM and TSRL (r = 0.673). The stress tolerance index had the strongest positive correlation with the SDM, PRL, TSRL, SL, and the stress susceptibility index with the NSR. The highest heterosis mean value was observed for PRL (24.6%) and for SL (15.6%) under drought stress. The different directions of average heterosis in induced drought stress vs. control conditions were observed for DFBR, RDM, and SDM, indicating differential traits to account for when planning breeding bread wheat for drought tolerance. Selected traits as crit

A total of 11 genotypes from the collection of 101 bread wheat genotypes, with desirable traits in terms of increased tolerance to drought, were chosen for parents and eight crosses were performed. Number of seminal roots (NSR), total root length (TRL), root dry mass (RDM), number of shoots per plant (NS), main shoot length (MSL), shoot dry mass (SDM), number of leaves per plant (NL), leaf area per plant (LA), leaf dry mass (LDM), aboveground dry mass (ADM), SDM/LDM, RDM/ADM were analysed at the boot stage (Z45). The F1 progeny had on average higher mean values (P < 0.001) than parents for four traits: RDM, NS, LA and RDM/ADM. The highest broad sense heritability values were determined for RDM (97.6%) and NSR (93.9%). Factor analysis indicated that a large root system, higher RDM and TRL are associated with higher NS, NL, LA and LDM. For Euclid x CHI-4 and WWBMC2 x Ingenio combinations the highest heterosis values were observed for TRL (34.1%) and SDM (23.7%), for RDM (28.6%) and LA (26.8%), respectively. PEG-induced drought stress in the seedling stage, in most of the new germplasm, caused an increased redistribution of dry matter in the root compared to the stem.

This master’s thesis project investigates the utilization of a low-cost hyperspectral (HS) imaging rig to identify and classify drought stress in pine plants. Drought stress is a widespread environmental challenge affecting global forestry, requiring more resources as the industry grows and global warming rises. This provokes a need for affordable, and efficient monitoring methods. HS imaging, with its ability to capture a wide range of spectral information, offers promising methods for quick and precise measurements of plant stress. The project methodology is comprised of redesigning an existing HS imaging rig, with the camera employing push-broom technology, to yield precise and consistent HS images. This involved exploring the camera’s spectral range, designing components to ensure consistent artificial lighting using blackbody radiation sources, and calibrating the HS camera for focal depth and aberrations like smile and keystone. Two experiments were conducted to obtain the data for pine stress detection, first for two binary categories: Control, and 100% Drought, and later introducing a third semi-drought category in the second experiment. The data analysis encompassed preprocessing the HS images to correct the lighting intensity distributions and normalization of pixel values. Accompanied by filtering, resampling spectral data, and feature extraction facilitating consistent drought identification, and data management. To identify stress patterns in pine plants and temporal decay rates, methods such as spectral reflectance analysis, various vegetation indices (VI), and statistical learning techniques like discriminant analysis and logistic regression were evaluated for distinguishing between stressed and healthy plants. The results demonstrate the accuracy of the HS imaging rig in measuring spectral reflectances from plants, capturing changes between 550 − 670 nm in the visible spectrum and 750 − 890 nm in the near-infrared (NIR) spectrum due to increasing str

Under stress or in optimum conditions, plants foster a specific guild of symbiotic microbes to strengthen pivotal functions including metabolic regulation. Despite that the role of the plant genotype in microbial selection is well documented, the potential of this genotype-specific microbial assembly in maintaining the host homeostasis remains insufficiently investigated. In this study, we aimed to assess the specificity of the foliar metabolic response of contrasting olive genotypes to microbial inoculation with wet-adapted consortia of plant-growth-promoting rhizobacteria (PGPR), to see if previously inoculated plants with indigenous or exogenous microbes would display any change in their leaf metabolome once being subjected to drought stress. Two Tunisian elite varieties, Chetoui (drought-sensitive) and Chemleli (drought-tolerant), were tested under controlled and stressed conditions. Leaf samples were analyzed by gas chromatography–mass spectrometry (GC-TOFMS) to identify untargeted metabolites. Root and soil samples were used to extract microbial genomic DNA destined for bacterial community profiling using 16S rRNA amplicon sequencing. Respectively, the score plot analysis, cluster analysis, heat map, Venn diagrams, and Krona charts were applied to metabolic and microbial data. Results demonstrated dynamic changes in the leaf metabolome of the Chetoui variety in both stress and inoculation conditions. Under the optimum state, the PGPR consortia induced noteworthy alterations in metabolic patterns of the sensitive variety, aligning with the phytochemistry observed in drought-tolerant cultivars. These variations involved fatty acids, tocopherols, phenols, methoxyphenols, stilbenoids, triterpenes, and sugars. On the other hand, the Chemleli variety displaying comparable metabolic profiles appeared unaffected by stress and inoculation probably owing to its tolerance capacity. The distribution of microbial species among treatments was distinctly uneven. The tested s

Predicting the adaptability of forest tree populations under future climates requires a better knowledge of both the adaptive significance and evolvability of measurable key traits. Phenotypic plasticity, standing genetic variation and degree of phenotypic integration shape the actual and future population genetic structure, but empirical estimations in forest tree species are still extremely scarce. We analysed 11 maritime pine populations covering the distribution range of the species (119 families and 8 trees/family, ca. 1300 trees) in a common garden experiment planted at two sites with contrasting productivity. We used plant height as a surrogate of fitness and measured five traits (mean and plasticity of carbon isotope discrimination, specific leaf area, needle biomass, Phenology growth index) related to four different strategies (acquisitive economics, photosynthetic organ size, growth allocation and avoidance of water stress).

One of the main climate change-related variables limiting agricultural productivity that ultimately leads to food insecurity appears to be drought. With the use of a recently discovered nanopriming technology, seeds can endure various abiotic challenges. To improve seed quality and initial growth of 8-day-old field pea seedlings (cv. NS Junior) under optimal and artificial drought (PEG-induced) laboratory conditions, this study aimed to assess the efficacy of priming with three different nanomaterials: Nanoplant Ultra (Co, Mn, Cu, Fe, Zn, Mo, and Se), Nanoplant Ca-Si (Ca, Si, B, and Fe), and Nanoplant Sulfur (S). The findings indicate that nanopriming seed treatments have a positive impact on seed quality indicators, early plant growth, and drought resilience in field pea plants established in both optimal and drought-stressed conditions. Nevertheless, all treatments showed a positive effect, but their modes of action varied. Nanoplant Ultra proved to be the most effective under optimal conditions, whereas Nanoplant Ca-Si and Nanoplant Sulfur were the most efficient under drought stress. After a field evaluation, the examined comprehensive nanomaterials may be utilized as priming agents for pea seed priming to boost seed germination, initial plant growth, and crop productivity under various environmental conditions.

Here we address the combined impact of multiple stressors that are becoming more common with climate change. To study the combined effects of a lower water table (WT) and increased frequency of drought periods on the resistance and resilience of peatlands, we conducted a mesocosm experiment. This study evaluated how the photosynthesis of lawn Sphagnum mosses responds to and recovers from an experimental periodic drought after exposure to the stresses of a deep or deepened WT (naturally dry and 17-year-long water level drawdown [WLD] in fen and bog environments). We aimed to quantify if deep WTs (1) support acclimation to drought, or (2) increase the base-level physiological stress of mosses or (3) exacerbate the impact of periodic drought. There was no evidence of acclimation in mosses from drier environments; periodic drought decreased the photosynthesis of all Sphagnum species studied. WLDdecreased the photosynthesis of bog-originating mosses prior to periodic drought, indicating that these mosses were stressed by the hydrological change. Deep WTs exacerbated Sphagnum vulnerability to periodic drought, indicating that the combination of drying habitats and increasing frequency of periodic drought could lead to a rapid transition in lawn vegetation. Water-retaining traits may increase Sphagnum resilience to periodic drought. Large capitula size was associated with a higher resistance; the bog originating species studied here lacked large capitula or dense carpet structure and were more vulnerable to drought than the larger fen originating species. Consequently, lawns in bogs may become threatened. Recovery after rewetting was significant for all mosses, but none completely recovered within 3 weeks. The most drought-resilient species had fen origin, indicating that fens are less likely to undergo a sudden transition due to periodic drought. Synthesis: Water level drawdown associated with climate change increases the sensitivity of Sphagnum mosses to periods of droug

Differential response of bread wheat seedlings to contrasting water regimes can be used to determine traits related to drought tolerance. The F1 offspring from eight crosses and 11 selected parental genotypes were simultaneously grown in hydroponic cultivation-polyethylene glycol (PEG) induced drought stress vs. control conditions. Criteria for selection of maternal and paternal genotypes were desirable traits in terms of increased tolerance to drought: longer stem length, longer primary root, large number of seminal roots, large root dry mass and stem dry mass, beginning of root branching at the greatest possible distance from beginning of the root,contrasting angle of seminal roots. The traits were measured on 14 day old seedlings: primary root length (PRL),distance to the first branch on the primary root (DFBR), number of seminal roots (NSR), total seminal root length (TSRL), angle of seminal roots (ASR), stem length (SL), root dry mass (RDM), stem dry mass (SDM), and the ratio of root dry mass to stem dry mass (RDM/SDM). Drought stress led to a decrease in the mean values of all root and stem traits by 11% on average, except for RDM/SDM which was increased. The most sensitive trait to drought stress was DFBR (25% reduction), causing root systems to branch at a shallower depth. In conditions of induced drought stress, the strongest statistically significant correlation was found among RDM and RDM/SDM (r = 0.794), SL and ASR (r = 0.708), RDM and TSRL (r = 0.673). The stress tolerance index had the strongest positive correlation with the SDM, PRL, TSRL, SL, and the stress susceptibility index with the NSR. The highest heterosis mean value was observed for PRL (24.6%) and for SL (15.6%) under drought stress. The different directions of average heterosis in induced drought stress vs. control conditions were observed for DFBR, RDM, and SDM, indicating differential traits to account for when planning breeding bread wheat for drought tolerance.Selected traits as criteri

Understanding the impact of future climates on crop performance is essential for sustainable agricultural production. In the current research, the development and biological behavior of soybean plants during gradual desiccation of the soil (from the 100% of pot water holding capacity to the gs of plant decreased to 10% of that of the control plants) at ambient [CO2] (a[CO2], 400 ppm) and elevated [CO2] (e[CO2], 800 ppm) were investigated. The results showed that plants grown under e[CO2] conditions had remarkably higher photosynthetic rate (An) but lower stomatal conductance (gs) and transpiration rate (E) compared to plants at a[CO2] conditions, which led to an enhanced water use efficiency at both stomatal (WUEi) and leaf levels (WUEleaf). In addition, the e[CO2]-grown soybeans showed a stunted gs response to progressive soil drying, coinciding with a decrease in the susceptibility of gs to the ABA signaling, though they tended to maintain a better leaf water status under drought than the a[CO2]-grown plants. Although the leaf nitrogen concentration (Nleaf) and the total plant N content were notably lower at the e[CO2] condition, the specific leaf N content (SLN) was similar at different [CO2] conditions. Compared to soybean grown under e[CO2], the greater number of nodules at e[CO2] treatment would lead to an enhanced N-fixation, yet, it did not improve the N nutrition of the plants. Nevertheless, by sustaining the SLN, the soybean plants enhanced An when growing at e[CO2], particularly under dry conditions. This knowledge is essential for sustaining soybean production in future climate change scenarios.

Understanding the impact of future climates on crop performance is essential for sustainable agricultural production. In the current research, the development and biological behavior of soybean plants during gradual desiccation of the soil (from the 100% of pot water holding capacity to the gs of plant decreased to 10% of that of the control plants) at ambient [CO2] (a[CO2], 400 ppm) and elevated [CO2] (e[CO2], 800 ppm) were investigated. The results showed that plants grown under e[CO2] conditions had remarkably higher photosynthetic rate (An) but lower stomatal conductance (gs) and transpiration rate (E) compared to plants at a[CO2] conditions, which led to an enhanced water use efficiency at both stomatal (WUEi) and leaf levels (WUEleaf). In addition, the e[CO2]-grown soybeans showed a stunted gs response to progressive soil drying, coinciding with a decrease in the susceptibility of gs to the ABA signaling, though they tended to maintain a better leaf water status under drought than the a[CO2]-grown plants. Although the leaf nitrogen concentration (Nleaf) and the total plant N content were notably lower at the e[CO2] condition, the specific leaf N content (SLN) was similar at different [CO2] conditions. Compared to soybean grown under e[CO2], the greater number of nodules at e[CO2] treatment would lead to an enhanced N-fixation, yet, it did not improve the N nutrition of the plants. Nevertheless, by sustaining the SLN, the soybean plants enhanced An when growing at e[CO2], particularly under dry conditions. This knowledge is essential for sustaining soybean production in future climate change scenarios.

La sécheresse est un facteur limitant de la production agricole et deviendra un problème majeur avec les changements climatiques prévus. Au Canada, cela sera particulièrement important dans les Prairies, une région importante contribuant à l’agriculture canadienne. Cela entraînera une réduction des rendements dans de nombreuses grandes cultures, y compris le blé. Une façon novatrice d’améliorer rapidement la résistance du blé aux stress environnementaux serait de modifier son microbiote. En effet, plusieurs études ont montré des liens entre différents microorganismes associés aux plantes et la résistance des plantes à la sécheresse. Néanmoins, il n'y a pas suffisamment d'éléments pour prouver un lien causal avec certitude ou encore de comprendre la manière dont les communautés microbiennes et le blé interagissent, et encore moins comment les modifier. Le but de ma thèse est de modifier le microbiote du blé pour améliorer sa résistance à la sécheresse. Ainsi, l’hypothèse principale suggère que l’ensemencement du blé par une communauté microbienne présélectionnée pour sa performance au laboratoire sera plus bénéfique pour le blé qu’une communauté naturellement existante ou aléatoirement sélectionnée. Pour répondre à cette hypothèse, ma thèse se compose de trois chapitres de recherche. Le premier a pour objectif d'étudier l'effet de la sécheresse sur le microbiote du blé cultivé au champ expérimental de l'INRS, ainsi que sur ses microorganismes isolés de la rhizosphère et de la plante de blé au laboratoire. Les résultats de ce premier objectif ont été publiés sous forme d'un article de recherche. Le deuxième chapitre consiste à concevoir différentes communautés microbiennes synthétiques (SynCom) et à tester leur effet sur la croissance de blé sous stress hydrique. Nous avons également suivi la présence ou la disparition des microorganismes ensemencés dans la plante et la rhizosphère du blé. Le troisième chapitre vise à étudier l'effet de l’ensemencement de la SynCo

Numerous studies have shown that under a limited water supply, a larger root biomass is associated with an increased above-ground biomass. Root biomass, while genetically controlled, is also greatly affected by the environment with varying plasticity levels. In this context, understanding the relationship between the biomass of shoots and roots appears prudent. In this study, we analyze this relationship in a large dataset collected from multiple experiments conducted up to different growth stages in bread wheat (Triticum aestivum L.) and its wild relatives. Four bread wheat mapping populations as well as wild and domesticated members of the Triticeae tribe were evaluated for the root and shoot biomass allocation patterns. In the analyzed dataset the root and shoot biomasses were directly related to each other, and to the heading date, and the correlation values increased in proportion to the length of an experiment. On average, 84.1% of the observed variation was explained by a positive correlation between shoot and root biomass. Scatter plots generated from 6353 data points from numerous experiments with different wheats suggest that at some point, further increases in root biomass negatively impact the shoot biomass. Based on these results, a preliminary study with different water availability scenarios and growth conditions was designed with two cultivars, Pavon 76 and Yecora Rojo. The duration of drought and water level significantly affected the root/shoot biomass allocation patterns. However, the responses of the two cultivars were quite different, suggesting that the point of diminishing returns in increasing root biomass may be different for different wheats, reinforcing the need to breed wheats for specific environmental challenges.

Plants are sensitive to changes projected in climates, such as elevated carbon dioxide (eCO2), high temperature (T), and drought stress (DS), which affect crop growth, development, and yield. These stresses, either alone or in combination, affect all aspects of sweetpotato plant growth and development, including storage root development and yield. We tested three sweetpotato cultivars (Beauregard, Hatteras, and LA1188) responses to eight treatments (Control, DS, T, eCO2, DS + T, T + eCO2, DS + eCO2, DS + T + eCO2). All treatments were imposed 36 days after transplanting (DAP) and continued for 47 days. Treatments substantially affected gas exchange, photosynthetic pigments, growth, and storage root components. Cultivars differed considerably for many of the measured parameters. The most significant negative impact of DS was recorded for the shoot and root weights. The combination of DS + T had a significant negative effect on storage root parameters. eCO2 alleviated some of the damaging effects of DS and high T in sweetpotato. For instance, eCO2 alone or combined with DS increased the storage root weights by 22% or 42% across all three cultivars, respectively. Based on the stress response index, cultivar “Hatteras” was most tolerant to individual and interactive stresses, and “LA 1188” was sensitive. Our findings suggest that eCO2 negates the negative impact of T or DS on the growth and yield of sweetpotato. We identified a set of individual and interactive stress-tolerant traits that can help select stress cultivars or breed new lines for future environments.

Plants are sensitive to changes projected in climates, such as elevated carbon dioxide (eCO2), high temperature (T), and drought stress (DS), which affect crop growth, development, and yield. These stresses, either alone or in combination, affect all aspects of sweetpotato plant growth and development, including storage root development and yield. We tested three sweetpotato cultivars (Beauregard, Hatteras, and LA1188) responses to eight treatments (Control, DS, T, eCO2, DS + T, T + eCO2, DS + eCO2, DS + T + eCO2). All treatments were imposed 36 days after transplanting (DAP) and continued for 47 days. Treatments substantially affected gas exchange, photosynthetic pigments, growth, and storage root components. Cultivars differed considerably for many of the measured parameters. The most significant negative impact of DS was recorded for the shoot and root weights. The combination of DS + T had a significant negative effect on storage root parameters. eCO2 alleviated some of the damaging effects of DS and high T in sweetpotato. For instance, eCO2 alone or combined with DS increased the storage root weights by 22% or 42% across all three cultivars, respectively. Based on the stress response index, cultivar “Hatteras” was most tolerant to individual and interactive stresses, and “LA 1188” was sensitive. Our findings suggest that eCO2 negates the negative impact of T or DS on the growth and yield of sweetpotato. We identified a set of individual and interactive stress-tolerant traits that can help select stress cultivars or breed new lines for future environments.

Drought stress is a major problem for potato production and will be of grave importance due to climate change and the resulting temperature peaks along with drought periods in the vegetative growth phase of potato. Plants, as sessile organisms, adapt to their environment morphologically as well as biochemically. To cope better with abiotic stresses like drought, plants developed strategies like reactive oxygen species (ROS) detoxification and fast reacting stomatal closure, as well as signalling cascades leading to a quick response to stress. This study aimed at analysing eight genes of interest, derived from a former proteomic study, and determining their suitability for detection of commencing drought stress in early growth stages of potato. For this aim, six starch potato genotypes, which differed in stress response in previous studies, were examined for plant growth and physiological parameters in two experiments in an open greenhouse after seven and 14 days of stress. Besides lower shoot biomass after drought stress, which was already visible after seven days and became stronger after 14 days, weaker root growth was also detected after 14 days. The observed differences between the experiments can presumably be explained by temperature peaks and high radiation prior to and during the first experiment, which took place earlier in the year. The expression of the eight genes was studied in young leaves of four genotypes after 7 days of water withdrawal. Gene expression patterns were dependent on the studied genes. Three genes, cell wall/vacuolar inhibitor of fructosidase (INH1), peroxidase 51-like (POD) and subtilase family protein (SBT1.7) showed consistent changes in gene expression after seven days of stress between all genotypes. The INH1 gene was found to be upregulated in all genotypes in two independent experiments after drought stress. This correlates with the results at the protein level, where INH1 was also found to be higher abundant in two genotypes of

Salicylic acid (SA) and proline exhibit protective effects against a wide range of stresses. However, the combined impact of SA and proline on rice under drought stress is still unknown. Therefore, we investigated the protective roles of SA and/or proline in conferring drought tolerance in rice. There were eight treatments comprising the control (T1; 95-100% FC), 1.5 mM SA (T2), 2 mM proline (T3), 0.75 mM SA + 1 mM proline (T4), 45-50% FC (T5, drought stress), T5 + 1.5 mM SA (T6), T5 + 2 mM proline (T7), and T5 + 0.75 mM SA + 1 mM proline (T8), and two rice varieties: BRRI dhan66 and BRRI dhan75. Drought stress significantly decreased the plant growth, biomass, yield attributes, photosynthetic rate (Pn), stomatal conductance (gs), transpiration rate (Tr), photosynthetic pigments (chlorophyll and carotenoids content), relative water content (RWC), membrane stability index (MSI), soluble sugar and starch content, and uptake of N, P and K+ in roots and shoots. Drought-induced oxidative stress in the form of increased hydrogen peroxide (H2O2) production and lipid peroxidation (MDA) was observed. The combined application of SA (0.75 mM) + proline (1 mM) was found to be more effective than the single application of either for drought stress mitigation in rice. A combined dose of SA + proline alleviated oxidative stress through boosting antioxidant enzymatic activity in contrast to their separate application. The application of SA + proline also enhanced proline, soluble sugar and starch content, which resulted in the amelioration of osmotic stress. Consequently, the combined application of SA and proline significantly increased the gas exchange characteristics, photosynthetic pigments, RWC, MSI, nutrient uptake, plant growth, biomass and yield of rice. Therefore, the combined application of SA and proline alleviated the detrimental impacts of drought stress more pronouncedly than their separate application did by increasing osmoprotectants, improving nutrient transport, u

Climate change and the resulting increase in the frequency and severity of drought can have significant impacts on plant production. The use of drought-tolerant crop varieties can significantly improve plant production under drought conditions. Therefore, the goal of this research was to evaluate the drought tolerance of different wheat genotypes using stress resistance indicators. An experiment was conducted with sixteen wheat genotypes in Novi Bečej (Vojvodina) in different growing seasons. The spike weight was used as a phenotypic marker of the effect of drought stress on the plant. Selection based on resistance indicators such as stress tolerance index (STI), mean productivity (MP), and geometric mean productivity (GMP) favors the selection of genotypes Dunavka, Skopjanka, and Fundulea 4, which were characterized by the highest average values of spike weight, especially in favorable growing conditions. However, genotype Fundulea 4 is characterized by the highest stress susceptibility index (SSI) and the lowest yield stability index (YSI), which makes this genotype undesirable for growing under drought conditions. The parameters SSI and YSI favor the selection of the genotype Pitoma, which showed the highest value of spike weight in drought conditions as well as the least reduction in value caused by stress. Genotypes Pitoma, Dunavka, and Skopjanka, characterized by a high yield index (YI), are suitable for cultivation in drought conditions, where they achieved above-average trait values. The most suitable stress resistance indicators for selecting drought-tolerant wheat genotypes are SSI, YSI, and YI.

A two-year study was conducted on 16 wheat genotypes with the aim of examining the reaction of genotypes to different environmental conditions. Grain weight per spike is a quantitative trait, which phenotypic expression is determined by the influence of a number of minor genes and environmental factors. Therefore, this trait is a suitable phenotypic marker of influence of environmental factors on the plant. The year factor had the largest share in the variation of grain weight per spike (67.82%), while the share of the genotype and the genotype x year interaction was significantly smaller (14.98 and 10.95% respectively). Drought conditions, which characterized the 2016/2017 growing season, affected the reduction of grain weight per spike by 41.7%. The greatest reduction in the value of trait under stress conditions was recorded in Fundulea 4 genotype (63.14%), which achieved the highest value in favorable environmental conditions (3.5 g), while in drought conditions it had a below-average value (1.29 g). Also, Dunavka genotype made good use of favorable environmental conditions to achieve a high value of grain weight per spike (3.14 g), so it can be recommended for breeding in favorable climatic conditions. On the other hand, the highest tolerance to drought was exhibited by the Pitoma genotype, which recorded a 15.67% decrease in grain weight per spike. The high tolerance of the mentioned genotype results from the highest value of the trait achieved in the dry growing season (1.83 g), which makes this genotype a good genetic resource for breeding for drought tolerance.

Raising temperatures and climate variability have intensified extreme weather events worldwide. These extremes can enhance and trigger possible pest outbreaks. Bark beetle attacks have become a major concern in regions with extensive spruce forest areas. Southeastern Sweden has faced repeated outbreaks resulting in widespread tree loss. By observing historic climate data for the main counties of Southeastern Sweden we can notice that the temperature is progressively raising. Rainfall do not manifest a clear pattern but it follows a descending trend. Water shortage can lead to drought events for the specific area. The main triggering factors for a bark beetle outbreak are a storm damage or a drought stress. In this study we used data and try to model an outbreak that was triggered by drought stress in 2018. This study focused on proactive risk management. Data from 2018 and 2019,2020 were combined to create two main datasets. One from 2018 which was considered a drought year and one that emerge from the years 2019 and 2020 which were considered more “normal” year from a meteorological perspective. The model used overlay analysis in ArcGIS environment between attacked trees and predisposing factors like soil moisture, topography and landcover data. Th goal was to investigate intervals of risk factors that could raise the potential risk. These factors could in some cases attribute higher danger in specific regions. Furthermore, a risk map was created by utilizing a weighted overlay model. All the abovementioned parameters were considered of equal weight. Some final things to consider about improving the specific model. Firstly, the unique type of the dataset that contained attacked trees. This dataset was collected by harvester machines which were equipped with GNSS devices. The attacked tree was attributed the coordinates of the body of harvester or the crane. This could result in a different landcover classification than the actual and it is an uncertainty i, Pop Abstract In recent years, bark beetle outbreaks have intensified causing damage to forests in many parts of the world. Forest ecosystems of Northern Hemisphere are considered more vulnerable because of their tree composition. Vast areas are covered by spruce forests which is a favorable type for the specific pest. Forest ecosystems provide many services and secure the wellbeing of wildlife and citizens. Protecting their structure and functionality is of the utmost importance. Other factors may contribute to the damages caused to forest ecosystems like outdated forest management policies. Furthermore, land use systems and guidelines that are not adjusted to the specific characteristics of a region. Another factor to consider is the percent of privately-owned forests, in some cases, which makes it difficult to communicate the hazards and follow some harmonized standards. Physical characteristics of a region and topography are parameters that can enhance the potential risk if other factors coexist as well. An event like a storm damage or a drought stress is usually the triggering factor for the beginning of the outbreak. The predisposing factors contribute to the rapid spatial propagation of the outbreak among with favorable climate conditions like temperature and drought. Southeastern Sweden is a region considered to fit the abovementioned description. Extreme events initialize a bark beetle outbreak which results in greater damages due to higher number of bark beetle. Climate crisis favors the breading process of bark beetle which results in higher number of bark beetle during their lifecycle. In this study, we focused on the environmental perspective of the bark beetle outbreaks. GIS techniques were used to analyze the risk factors associated with bark beetle outbreaks. By mapping trees that were attacked by bark beetles, we were able to identify patterns and trends in the risk factors. Data about attacked trees were provided by Skogsstyrelsen (Swedish Forest Ag

Phytohormones play an important role in regulating the plant behavior to drought. In previous studies, NIBER® pepper rootstock showed tolerance to drought in terms of production and fruit quality compared to ungrafted plants. In this study, our hypothesis was that short-term exposure to water stress in young, grafted pepper plants would shed light on tolerance to drought in terms of modulation of the hormonal balance. To validate this hypothesis, fresh weight, water use efficiency (WUE) and the main hormone classes were analyzed in self-grafted pepper plants (variety onto variety, V/V) and variety grafted onto NIBER® (V/N) at 4, 24, and 48h after severe water stress was induced by PEG addition. After 48h, WUE in V/N was higher than in V/V, due to major stomata closure to maintain water retention in the leaves. This can be explained by the higher abscisic acid (ABA) levels observed in the leaves of V/N plants. Despite the interaction between ABA and the ethylene precursor, 1-aminocyclopropane-1-carboxylic acid (ACC), in relation to stomata closure is controversial, we observed an important increase of ACC at the end of the experiment in V/N plants coinciding with an important rise of the WUE and ABA. The maximum concentration of jasmonic acid and salicylic acid after 48h was found in the leaves of V/N, associated with their role in abiotic stress signaling and tolerance. Respect to auxins and cytokinins, the highest concentrations were linked to water stress and NIBER®, but this effect did not occur for gibberellins. These results show that hormone balance was affected by water stress and rootstock genotype, where NIBER® rootstock displayed a better ability to overcome short-term water stress

Maintaining plant health is one of the most difficult but crucial challenges in crop production to realize plants’ full genetic potential. It is lowered by a variety of abiotic and biotic stresses that are becoming more severe and unpredictable due to climate change and its consequences. In addition, the use of chemical synthetic pesticides is increasingly criticized for endangering sensitive natural resources and possible pesticide residues in food and environment. Avoiding or reducing the use of chemical synthetic plant protection products makes the control of phytopathogenic pests even more difficult. Therefore, in addition to optimizing various management measures such as tillage, sowing time, row spacing or crop rotation, mineral nitrogen (N) fertilization and the targeted application of N forms must be utilized to reduce abiotic stress factors and the infestation pressure of certain pests to ensure high yield performance. Consequently, several experiments were conducted to better understand how mineral nitrogen fertilization and forms can improve plant health by increasing plant resistance to abiotic stressors, particularly repeated drought stress and nutrient (P) deficiency, and to biotic stressors, such as relevant phytopathogenic fungi. It was found that with respect to repeated drought stress, maize plants receiving supplemental nitrogen during the recovery period after an early drought stress were better able to cope with late drought stress. In this context, N fertilization could help the plant to maintain its photosynthetic activity under drought stress. Additionally, plants repeatedly exposed to drought stress recovered faster with N fertilization due to transiently higher antioxidant levels and higher production of reactive oxygen species. A further experiment revealed that depending on the maize genotype, ammonium as a form of nitrogen has a positive effect on the availability and uptake of phosphorus compared to nitrate, depending on the maize genot, Die Erhaltung der Pflanzengesundheit ist eine der schwierigsten, aber wichtigsten Herausforderungen im Pflanzenbau, um das volle genetische Potenzial von Pflanzen auszuschöpfen. Diese wird durch eine Vielzahl von abiotischen und biotischen Stressfaktoren beeinträchtigt, die aufgrund des Klimawandels und seiner Folgen immer gravierender und unvorhersehbarer werden. Darüber hinaus wird der Einsatz von chemisch-synthetischen Pestiziden zunehmend kritisiert, weil empfindliche natürliche Ressourcen gefährdet und Pestizidrückstände in Lebensmitteln und der Umwelt hinterlassen werden. Der Verzicht oder die Reduzierung des Einsatzes chemisch-synthetischer Pflanzenschutzmittel erschwert die Bekämpfung phytopathogener Schädlinge zusätzlich. Neben der Optimierung verschiedener Bewirtschaftungsmaßnahmen wie Bodenbearbeitung, Aussaatzeitpunkt, Reihenabstand oder Fruchtfolge muss daher die mineralische Stickstoffdüngung (N Düngung) und der gezielte Einsatz von N Formen genutzt werden, um abiotische Stressfaktoren und den Befallsdruck bestimmter Schädlinge zu reduzieren und eine hohe Ertragsleistung sicherzustellen. Daher wurden mehrere Versuche durchgeführt, um besser zu verstehen, wie mineralische Stickstoffdüngung und -formen die Pflanzengesundheit verbessern können, indem sie die Widerstandsfähigkeit der Pflanzen gegenüber abiotischen Stressfaktoren, insbesondere wiederholtem Trockenstress und Nährstoff (P)-Mangel, und gegenüber biotischen Stressfaktoren, wie wichtige phytopathogene Pilze, erhöhen. In Bezug auf wiederholten Trockenstress wurde festgestellt, dass Maispflanzen, die während der Erholungsphase nach einem frühen Trockenstress zusätzlichen Stickstoff erhielten, besser in der Lage waren, einen späteren Trockenstress zu bewältigen. Diese zusätzliche Stickstoffdüngung konnte der Pflanze unter anderem helfen ihre photosynthetische Aktivität unter Trockenstress aufrechtzuerhalten. Darüber hinaus wiesen Pflanzen, die wiederholt Trockenstress ausgesetzt waren, vorübergehen

Creating xeric landscapes in lawns and prairies is a significant challenge and practical need in arid urban environments. This study examined the drought resistance of some C4 grass species for constructing urban lawns and prairies. A factorial experiment based on randomized complete block designs with four replications was conducted. Experimental treatments were two irrigation levels (100% and 50% Field Capacity (FC)) and five warm-season grass species (Andropogon gerardii Vitman, Sorghastrum nutans (L.) Nash, Panicum virgatum L., Schizachyrium scoparium (Michx.) Nash, and Bouteloua curtipendula (Michx.) Torr.). The effects of drought on physiological, morphological, and qualitative characteristics of the grass species were analyzed. Drought conditions induced a decrease in all the measured traits. However, fewer physiological, morphological, and qualitative characteristics were affected by drought stress on Andropogon gerardii, Schizachyrium scoparium, and Bouteloua curtipendula, compared to the other two species. Overall, warm-season grasses of Andropogon gerardii, Schizachyrium scoparium, and Bouteloua curtipendula, had greater adaptability to drought stress, making them promising C4 grass species for prairie or lawn landscaping in arid urban environments. Landscape professionals and decision-makers should consider using Andropogon gerardii, Schizachyrium scoparium, and Bouteloua curtipendula, as these were the most resilient grass species for drought-tolerant prairie landscaping schemes. Sorghastrum nutans and Panicum virgatum may be used as a second priority if a more diverse variety of grasses is required for drought-resilient prairie or lawn landscaping in arid cities.

U dvogodišnjem istraživanju, sprovedenom na ritskoj crnici, analiziran je uticaj genotipa, vegetacione sezone i njihove interakcije na varijaciju prinosa zrna po biljci i mase 1000 zrna kod 16 genotipova pšenice. Uslovi povećane suše su značajno uticali na smanjenje ispitivanih osobina kod svih analiziranih genotipova. Faktor interakcije je imao najveći doprinos fenotipskoj ekspresiji prinosa zrna (47,74%), dok je faktor godina imao najveći udeo u varijaciji mase 1000 zrna (79,77%). Najveći prinos zrna u obe vegetacione sezone je ostvario genotip Skopjanka. Genotipovi Dukat i Iskra se karakterišu najslabijom reakcijom na stres, uz postignut visok prinos zrna u uslovima suše. Genotip Iskra se izdvaja najvećom vrednošću mase 1000 zrna u uslovima stresa suše, dok je genotip Dunavka postigao najveću vrednost mase 1000 zrna u povoljnim uslovima sredine., A two-year study on the humogley examined the effects of genotype, vegetation season, and their interaction on the variation in grain yield per plant and thousand grain weight in 16 wheat genotypes. Increased drought had a significant impact on the reduction of both investigated traits. The interaction of factors had the largest contribution to the phenotypic expression of grain yield per plant (47.74%), while the factor of vegetation season had the largest share in the variation of thousand grain weight (79.77%). Genotype Skopjanka achieved the highest grain yield per plant in both growing seasons. Genotypes Dukat and Iskra are characterized by the weakest reaction to stress and a high grain yield achieved under drought conditions. Genotype Iskra is distinguished by having the highest thousand grain weight under drought stress, while genotype Dunavka achieved the highest thousand grain weight under favorable environmental conditions.

Maintaining plant health is one of the most difficult but crucial challenges in crop production to realize plants’ full genetic potential. It is lowered by a variety of abiotic and biotic stresses that are becoming more severe and unpredictable due to climate change and its consequences. In addition, the use of chemical synthetic pesticides is increasingly criticized for endangering sensitive natural resources and possible pesticide residues in food and environment. Avoiding or reducing the use of chemical synthetic plant protection products makes the control of phytopathogenic pests even more difficult. Therefore, in addition to optimizing various management measures such as tillage, sowing time, row spacing or crop rotation, mineral nitrogen (N) fertilization and the targeted application of N forms must be utilized to reduce abiotic stress factors and the infestation pressure of certain pests to ensure high yield performance. Consequently, several experiments were conducted to better understand how mineral nitrogen fertilization and forms can improve plant health by increasing plant resistance to abiotic stressors, particularly repeated drought stress and nutrient (P) deficiency, and to biotic stressors, such as relevant phytopathogenic fungi. It was found that with respect to repeated drought stress, maize plants receiving supplemental nitrogen during the recovery period after an early drought stress were better able to cope with late drought stress. In this context, N fertilization could help the plant to maintain its photosynthetic activity under drought stress. Additionally, plants repeatedly exposed to drought stress recovered faster with N fertilization due to transiently higher antioxidant levels and higher production of reactive oxygen species. A further experiment revealed that depending on the maize genotype, ammonium as a form of nitrogen has a positive effect on the availability and uptake of phosphorus compared to nitrate, depending on the maize genot, Die Erhaltung der Pflanzengesundheit ist eine der schwierigsten, aber wichtigsten Herausforderungen im Pflanzenbau, um das volle genetische Potenzial von Pflanzen auszuschöpfen. Diese wird durch eine Vielzahl von abiotischen und biotischen Stressfaktoren beeinträchtigt, die aufgrund des Klimawandels und seiner Folgen immer gravierender und unvorhersehbarer werden. Darüber hinaus wird der Einsatz von chemisch-synthetischen Pestiziden zunehmend kritisiert, weil empfindliche natürliche Ressourcen gefährdet und Pestizidrückstände in Lebensmitteln und der Umwelt hinterlassen werden. Der Verzicht oder die Reduzierung des Einsatzes chemisch-synthetischer Pflanzenschutzmittel erschwert die Bekämpfung phytopathogener Schädlinge zusätzlich. Neben der Optimierung verschiedener Bewirtschaftungsmaßnahmen wie Bodenbearbeitung, Aussaatzeitpunkt, Reihenabstand oder Fruchtfolge muss daher die mineralische Stickstoffdüngung (N Düngung) und der gezielte Einsatz von N Formen genutzt werden, um abiotische Stressfaktoren und den Befallsdruck bestimmter Schädlinge zu reduzieren und eine hohe Ertragsleistung sicherzustellen. Daher wurden mehrere Versuche durchgeführt, um besser zu verstehen, wie mineralische Stickstoffdüngung und -formen die Pflanzengesundheit verbessern können, indem sie die Widerstandsfähigkeit der Pflanzen gegenüber abiotischen Stressfaktoren, insbesondere wiederholtem Trockenstress und Nährstoff (P)-Mangel, und gegenüber biotischen Stressfaktoren, wie wichtige phytopathogene Pilze, erhöhen. In Bezug auf wiederholten Trockenstress wurde festgestellt, dass Maispflanzen, die während der Erholungsphase nach einem frühen Trockenstress zusätzlichen Stickstoff erhielten, besser in der Lage waren, einen späteren Trockenstress zu bewältigen. Diese zusätzliche Stickstoffdüngung konnte der Pflanze unter anderem helfen ihre photosynthetische Aktivität unter Trockenstress aufrechtzuerhalten. Darüber hinaus wiesen Pflanzen, die wiederholt Trockenstress ausgesetzt waren, vorübergehen

Theoretically, the coexistence of diploids and related polyploids is constrained by reproductive and competitive mechanisms. Although niche differentiation can explain the commonly observed co-occurrence of cytotypes, the underlying ecophysiological differentiation among cytotypes has hardly been studied. We compared the leaf functional traits of the allotetraploid resurrection fern Oeosporangium tinaei (HHPP) and its diploid parents, O. hispanicum (HH) and O. pteridioides (PP), coexisting in the same location. Our experimental results showed that all three species can recover physiological status after severe leaf dehydration, which confirms their 'resurrection' ability. However, compared with PP, HH had much higher investment per unit area of light-capturing surface, lower carbon assimilation rate per unit mass for the same midday water potential, higher non-enzymatic antioxidant capacity, higher carbon content, and lower contents of nitrogen, phosphorus, and other macronutrients. These traits allow HH to live in microhabitats with less availability of water and nutrients (rock crevices) and to have a greater capacity for resurrection. The higher assimilation capacity and lower antioxidant capacity of PP explain its more humid and nutrient-rich microhabitats (shallow soils). HHPP traits were mostly intermediate between those of HH and PP, and they allow the allotetraploid to occupy the free niche space left by the diploids.

Mycorrhizal fungi can help plants to cope with drought, but research on the fungal communities that are more resistant to drought or alleviate drought stress of trees is still scarce. In this study, we investigated effects of drought on soil fungal communities and explored potential fungal traits related to drought resistance under greenhouse conditions. We manipulated water availability in pine seedlings belonging to three Spanish Pinus pinaster populations from geographical areas subjected to contrasting summer drought. A set of plant ecophysiological traits were quantified and soil fungi was quantified and profiled using ergosterol and Pacific Biosciences sequencing. Abundance of ectomycorrhizal (ECM) fungi in plants subjected to drought was lower than in well-watered plants. Most ECM taxa in plants surviving drought had long exploration types and were taxa typically forming rhizomorphs and hydrophobic mycelia. By contrast, ECM taxa in well-watered plants had wider range of distinct exploration types. No differences in fungal communities were found among P. pinaster populations. No associations between ECM fungi and plant ecophysiological traits were found, but significant interactions between drought treatments and belowground plant biomass were found for the relative abundances of ECM fungi, particularly ECM with long exploration types. Plants subjected to drought may benefit by associating to ECM taxa previously shown to transport water efficiently.

Functional symbiosis with fungal endophytes can help plants adapt to environmental stress. Diaporthe atlantica is one of the most abundant fungal taxa associated with roots of Festuca rubra subsp. pruinosa, a grass growing in sea cliffs. This study aimed to investigate the ability of a strain of this fungus to ameliorate the impact of drought stress on tomato plants. In a greenhouse experiment, tomato plants were inoculated with Diaporthe atlantica strain EB4 and exposed to two alternative water regimes: well-watered and drought stress. Several physiological and biochemical plant parameters were evaluated. Inoculation with Diaporthe promoted plant growth in both water treatments. A significant interactive effect of Diaporthe-inoculation and water-regime showed that symbiotic plants had higher photosynthetic capacity, water-use efficiency, nutrient uptake (N, P, K, Fe and Zn), and proline content under drought stress, but not under well-watered conditions. In addition, Diaporthe improved the enzymatic antioxidant response of plants under drought, through an induced mechanism, in which catalase activity was modulated and conferred protection against reactive oxygen species generation during stress. The results support that Diaporthe atlantica plays a positive role in the modulation of tomato plant responses to drought stress by combining various processes such as improving photosynthetic capacity, nutrient uptake, enzymatic antioxidant response and osmo-protectant accumulation. Thus, drought stress in tomato can be enhanced with symbiotic fungi

Three genotypes of wheat grown at two CO2 concentrations were used in a drought experiment, where water was withheld from the pots at anthesis until stomatal conductance (gs) dropped below 10% of the control and photosynthesis (A) approached zero. The genotypes had different leaf area (Gladius < LM19 < LM62) and while photosynthesis and shoot growth were boosted by elevated CO2, the water use and drying rate were more determined by canopy size than by stomatal density and conductance. The genotypes responded differently regarding number of fertile tillers, seeds per spike and 1000 kernel weight and, surprisingly, the largest genotype (LM62) with high water use showed the lowest relative decrease in grain yield. The maximum photochemical efficiency of photosystem II (Fv/Fm) was only affected on the last day of the drought when the stomata were almost closed although some variation in A was still seen between the genotypes. A close correlation was found between Fv/Fm and % loss of grain yield. It indicates that the precise final physiological stress level measured by Fv/Fm at anthesis/early kernel filling could effectively predict percentage final yield loss, and LM62 was slightly less stressed than the other genotypes, due to only a small discrepancy in finalising the drying period. Therefore, Fv/Fm can be used as a proxy for estimating the yield performance of wheat after severe drought at anthesis.

There is a controversy regarding when it is appropriate to apply the irrigation restriction in almond trees (Prunus dulcis Mill.) to save water without penalizing yield. We hypothesized that knowing when plants demand fewer photoassimilates would be a good indicator of less sensitivity of the crop to water deficit. One parameter that defines the photosynthetic capacity is the triose phosphate utilization (TPU). Due to its connection to the export of sugars from the leaves to other sink organs, it is a good candidate for being such an indicator. The objective was to analyze the seasonal evolution of the photosynthetic capacity of three almond cultivars (cvs Guara, Marta and Lauranne) subjected to water stress during vegetative, kernel-filling and postharvest stages. Two sustained deficit irrigation (SDI) treatments (SDI75 and SDI65 with water reductions of 25 and 35%, respectively) and a control treatment (FI) consisting of fully irrigated trees were applied. The response of curves A(N)-Ci was analyzed to assess the maximum carboxylation rate (V-cmax), maximum rate of electron transport (J(max)), TPU and mesophyll conductance to CO2. In addition, leaf water potential and yield were measured. Our experimental findings showed any significant differences in the variables analyzed among cultivars and irrigation treatments. However, consistent differences arose when the results were compared among the phenological stages. During the kernel-filling and the postharvest stages, a progressive limitation by TPU was measured, suggesting that the demand for photoassimilates by the plant was reduced. This result was supported by the correlation found between TPU and fruit growth rate. As a consequence, a downregulation in J(max) and V-cmax was also measured. This study confirms that the kernel-filling stage might be a good time to apply a reduction in the irrigation and suggests a method to detect the best moments to apply a regulated deficit irrigation in almond trees.

Three genotypes of wheat grown at two CO2 concentrations were used in a drought experiment, where water was withheld from the pots at anthesis until stomatal conductance (gs) dropped below 10% of the control and photosynthesis (A) approached zero. The genotypes had different leaf area (Gladius < LM19 < LM62) and while photosynthesis and shoot growth were boosted by elevated CO2, the water use and drying rate were more determined by canopy size than by stomatal density and conductance. The genotypes responded differently regarding number of fertile tillers, seeds per spike and 1000 kernel weight and, surprisingly, the largest genotype (LM62) with high water use showed the lowest relative decrease in grain yield. The maximum photochemical efficiency of photosystem II (Fv/Fm) was only affected on the last day of the drought when the stomata were almost closed although some variation in A was still seen between the genotypes. A close correlation was found between Fv/Fm and % loss of grain yield. It indicates that the precise final physiological stress level measured by Fv/Fm at anthesis/early kernel filling could effectively predict percentage final yield loss, and LM62 was slightly less stressed than the other genotypes, due to only a small discrepancy in finalising the drying period. Therefore, Fv/Fm can be used as a proxy for estimating the yield performance of wheat after severe drought at anthesis.

Drought is increasingly frequent in the context of climate change and is considered a major constraint for crop yield. Water scarcity can impair growth, disturb plant water relations and reduce water use efficiency. Pea (Pisum sativum) is a temperate grain legume rich in protein, fibre, micronutrients and bioactive compounds that can benefit human health. In reducing pea yield because of drought, the intensity and duration of stress are critical. This review describes several drought resistance mechanisms in pea based on morphology, physiology and biochemical changes during/after the water deficit period. Drought tolerance of pea can be managed by adopting strategies such as screening, breeding and marker-assisted selection. Therefore, various biotechnological approaches have led to the development of drought-tolerant pea cultivars. Finally, the main objective of the current research is to point out some useful traits for drought tolerance in peas and also, mention the methods that can be useful for future studies and breeding programmes.

Editorial on the Research Topic: Forests under pressure: The need for interdisciplinary approaches to address forest vulnerability to tree mortality in response to drought

The two-source energy balance model estimates canopy transpiration (Tr) and soil evaporation (E) traditionally from satellite partitions of remotely sensed land surface temperature (LST) and the Priestley-Taylor equation (TSEB-PT) at seasonal time with limited accuracy. The high spatial–temporal resolution spectral data collected by unmanned aerial vehicles (UAVs) provide valuable opportunity to estimate Tr and E precisely, improve the understanding of the seasonal and the diurnal cycle of evapotranspiration (ET), and timely detect agricultural drought. The UAV data vary in spatial resolution and the uncertainty imposed on the TSEB-PT outcome has thus far not being considered. To address these challenges and prospects, a new energy flux modelling framework based on TSEB-PT for high spatial resolution thermal and multispectral UAV data is proposed in this paper. Diurnal variations of LST in agricultural fields were recorded with a thermal infrared camera installed on an UAV during drought in 2018 and 2019. Observing potato as a test crop, LST, plant biophysical parameters derived from corresponding UAV multispectral data, and meteorological forcing variables were employed as input variables to TSEB-PT. All analyses were conducted at different pixelation of the UAV data to quantify the effect of spatial resolution on the performance. The 1 m spatial resolution produced the highest correlation between Tr modelled by TSEB-PT and measured by sap flow sensors (R2 = 0.80), which was comparable to the 0.06, 0.1, 0.5 and 2 m pixel sizes (R2 = 0.76–0.78) and markedly higher than the lower resolutions of 2 to 24 m (R2 = 0.30–0.72). Modelled Tr was highly and significantly correlated with measured leaf water potential (R2 = 0.81) and stomatal conductance (R2 = 0.74). The computed irrigation requirements (IRs) reflected the field irrigation treatments, ET and conventional irrigation practices in the area with high accuracy. It was also found that using a net primary production m

The CALCINEURIN B-LIKE PROTEIN family genes (CBLs) encode a group of plant-specific calcium sensor proteins that play critical roles in plant development and stress response. Although genome-wide analysis of CBL family genes has been conducted in several diploid plant species, less is known about their functions in allopolyploid plant species. This study conducted a detailed analysis of tobacco CBL family genes. Of the 24 NtCBL genes identified, 14 were derived from the maternal genome donor N. sylvestris, and 10 were from the paternal genome donor N. tomentosiformis. Phylogenetic analysis revealed that NtCBLs could be clustered into three different groups with distinct N-terminal characteristics. All NtCBLs contain EF-hand motifs, but amino acid substitutions and configuration changes may be responsible for variations in their Ca2+-binding abilities. Alternative splicing is common for NtCBL gene transcripts, which may contribute to variations in translation efficiency or protein interaction preferences. Several NtCBL genes exhibited shoot- or root-predominant expression patterns, and some were responsive to salt and/or drought stress. NtCBL4A-1, an ortholog of Arabidopsis thaliana AtCBL4 (SOS3), was predominantly expressed in roots and exhibited a lower gene expression level under salt stress. Further functional analysis showed that overexpression of NtCBL4A-1 increased the sensitivity of transgenic tobacco to Na+-induced salt stress, which is inconsistent with the role of AtCBL4 in contributing to salt tolerance. This study provides data for identifying CBL gene functions and selecting candidate stress-tolerant genes in N. tabacum. Additionally, the results may aid gene function studies in other allopolyploid plant species.

Extreme weather including heat waves and drought episodes are expected to increase in intensity and duration due to climate change. Wheat, being a major crop is under extreme threat to these stresses especially at the reproductive stage. This review addresses the potential of diverse wheat germplasm (originated from landraces and synthetic derivatives) to cope with drought and heat stress at the flowering stage. Here, important marker-trait associations were reported for sustainable grain production under drought and heat stress at anthesis. Likewise, the mechanisms of drought and heat resilience including gene expression and physiological traits (activities of carbohydrate metabolic and antioxidant enzymes, and endogenous hormonal responses) were explored. These studies helped to understand the genetic and physiological basis of drought and heat tolerance and certain pre-breeding traits related to osmotic adjustment, phytohormonal regulation, antioxidant metabolism, and the expression of novel genes were identified. Moreover, identified pre-breeding traits and genotypes can be utilized in breeding wheat cultivars resilient to future adverse environments.

Extreme weather including heat waves and drought episodes are expected to increase in intensity and duration due to climate change. Wheat, being a major crop is under extreme threat to these stresses especially at the reproductive stage. This review addresses the potential of diverse wheat germplasm (originated from landraces and synthetic derivatives) to cope with drought and heat stress at the flowering stage. Here, important marker-trait associations were reported for sustainable grain production under drought and heat stress at anthesis. Likewise, the mechanisms of drought and heat resilience including gene expression and physiological traits (activities of carbohydrate metabolic and antioxidant enzymes, and endogenous hormonal responses) were explored. These studies helped to understand the genetic and physiological basis of drought and heat tolerance and certain pre-breeding traits related to osmotic adjustment, phytohormonal regulation, antioxidant metabolism, and the expression of novel genes were identified. Moreover, identified pre-breeding traits and genotypes can be utilized in breeding wheat cultivars resilient to future adverse environments.

Producción Científica, Future climate predictions for the Mediterranean area include prolonged droughts and an increase in the frequency of extreme events. Silvicultural modification of stand density can buffer the response of tree growth to changes in climate by enhancing soil water availability. We analyzed the stem growth dynamics of Pinus halepensis, including the days of the year when 25%, 50% and 75% of the intra-annual basal growth was achieved, considering two different social statuses (suppressed and dominant) under four different thinning intensities (15%, 30% and 45% removal of the basal area) for 8 years, based on biweekly band dendrometer recordings. The moment the trees reached 25% of the intra-annual basal growth was significantly influenced by the amount of precipitation accumulated during the previous winter. On the other hand, the moment the trees reached 75% of the intra-annual basal growth was significantly influenced by water availability in a shorter term, which also affected the length of the growing period. Modification of competition through thinning showed a significantly positive impact on growth, causing a delayed attainment of 50% of the intra-annual basal growth. These results imply valuable information about forest dynamics that will support forest managers’ decisions dealing with low water-availability in forests., European Union’s Horizon 2020 and Innovation Program Marie Skłodowska-Curie - (Grant 778322), Junta de Castilla y León y Fondo Europeo de Desarrollo Regional (FEDER) - (project CLU-2019-01-iuFOR)

Altres ajuts: Acord transformatiu CRUE-CSIC, Intensification of droughts may aggravate the generally low capacity of Mediterranean soils to store C and nutrients and induce soil C:N:P stoichiometric imbalances through its impact on soil microbial biomass and activity. Soil microbes may nonetheless have different responses to seasonal and chronic drought, but very few studies investigate long-term drought periods under field conditions. This study compares the effects of seasonal drought versus the impacts of 16 years of chronic experimental drought on microbial biomass and nutrients and assess the implications for soil nutrient availability and biogeochemical functioning in a Mediterranean forest. The chronic drought treatment reduced substantially and persistently microbial biomass C, N and particularly P, probably due to P-sparing community shifts or microbial adaptations. The smaller microbial N pool and lower mineralization activity contributed to the accumulation of C- and N-rich organic compounds in the soil and to a lower availability of mineralized forms of N during the vegetation growing season. As a result, chronic drought conditions may increase the risks of N losses from the plant-soil system in Mediterranean ecosystems. Microbial C:N ratios remained unaltered under chronic drought compared to control, likely associated with the equivalent accumulation of C- and N-rich osmolytes by microbial communities. In contrast, microbial biomass increased its C content relative to N content in response to seasonal drought, but also reduced considerably its N and P pool. Therefore, while microbial P was more sensitive to chronic water stress, microbial N and C were more closely coupled to the seasonal fluctuations of water availability.

The increased demand for soybean (Glycine max (L.) Merrill) for human and animal consumption, vegetable oil extraction, and soil fertility improvement through biological nitrogen fixation has led to the expansion of its production to even marginal areas under rainfed farming systems. Production in dryland areas is constrained by drought, among other challenges. This study, therefore, sought to assess the performance of selected soybean varieties that were sourced locally and regionally and grown in Kalahari sands under different watering regimes before flowering. Seven soybean varieties (Kabanyolo 1, Maksoy 1N, Maksoy 4M, Namsoy 3N, Nam 1, Solitaire, and UG5) were studied for growth and yield performance under various watering regimes. The study was conducted at Lupane State University experimental plots. Soybean plants were grown in 9 l buckets arranged following a randomized complete block design with seven varieties in three blocks. Three irrigation regimes were used (soil saturation capacity, 50% soil saturation capacity, and 25% soil saturation capacity) up to flowering, after which the plants were sufficiently rainfed and supplemented through irrigation up to physiological maturity. Data were collected at physiological maturity (stem height, pod length, pods per plant, number of seeds per pod, nonviable pod percentage, 100-seed weight, and total grain weight per plant). Irrigation regimes and variety independently influenced most parameters that were assessed in soybeans. All the variables were significantly affected except for the % nonviable pod under the three irrigation regimes. Maksoy 4M, Nam 1, and Namsoy 3N performed better than the other varieties, while UG5 and Solitaire were the least performers in most of the variables measured. Irrigating to 50% soil saturation capacity and below suppressed growth and yield. Varieties that outperformed others can be used by breeders to improve their tolerance to pre-flowering drought stress

The increased demand for soybean (Glycine max (L.) Merrill) for human and animal consumption, vegetable oil extraction, and soil fertility improvement through biological nitrogen fixation has led to the expansion of its production to even marginal areas under rainfed farming systems. Production in dryland areas is constrained by drought, among other challenges. This study, therefore, sought to assess the performance of selected soybean varieties that were sourced locally and regionally and grown in Kalahari sands under different watering regimes before flowering. Seven soybean varieties (Kabanyolo 1, Maksoy 1N, Maksoy 4M, Namsoy 3N, Nam 1, Solitaire, and UG5) were studied for growth and yield performance under various watering regimes. The study was conducted at Lupane State University experimental plots. Soybean plants were grown in 9 l buckets arranged following a randomized complete block design with seven varieties in three blocks. Three irrigation regimes were used (soil saturation capacity, 50% soil saturation capacity, and 25% soil saturation capacity) up to flowering, after which the plants were sufficiently rainfed and supplemented through irrigation up to physiological maturity. Data were collected at physiological maturity (stem height, pod length, pods per plant, number of seeds per pod, nonviable pod percentage, 100-seed weight, and total grain weight per plant). Irrigation regimes and variety independently influenced most parameters that were assessed in soybeans. All the variables were significantly affected except for the % nonviable pod under the three irrigation regimes. Maksoy 4M, Nam 1, and Namsoy 3N performed better than the other varieties, while UG5 and Solitaire were the least performers in most of the variables measured. Irrigating to 50% soil saturation capacity and below suppressed growth and yield. Varieties that outperformed others can be used by breeders to improve their tolerance to pre-flowering drought stress

The current study investigated the effects of Pseudomonas putida strain KT2440 on the drought tolerance of tomato plants during fruit maturation. Plants at the ripening stage of the mature-green were not watered for 20 days to promote drought stress. Concentrations of photosynthetic pigments were determined. Bacteria-soaked tomato plants (BSS) had higher levels of chlorophyll and carotenoids than non-soaked plants (DWS) under stress conditions. Compared to the DWS, stomatal conductance, lipid peroxidation, and hydrogen peroxide content in the BSS plants decreased under drought stress. The ascorbate peroxidase (APX), catalase (CAT), and peroxidase (POD) activities increased in BSS plants compared to DWS under drought stress. Furthermore, the number and weight of fruits in both DWS and BSS plants was reduced by the stress, but the reduction in BSS plants was lower than in DWS plants. These results showed that bacteria treatment conferred tolerance to drought stress in tomato plants by reducing the peroxidation extent of polar lipids (PLs), increasing photosynthetic pigment content, and activities of the antioxidant enzymes in the leaves. Therefore, P. putida KT2440 has supported high fruit yield under drought stress as a biotic tolerance elicitor for this plant stress, El estudio investigó los efectos de la cepa KT2440 de Pseudomonas putida sobre la tolerancia a la sequía de plantas de tomate durante la maduración de la fruta. Las plantas en etapa de fruta verde madura no se regaron durante 20 días para promover el estrés por sequía. Se determinaron los contenidos de pigmentos fotosintéticos. Las plantas que recibieron la bacteria (PCB) tuvieron mayor cantidad de clorofila y carotenoides que las plantas sin la bacteria (PSB) en condiciones de estrés. En comparación con las PSB, la sequía indujo menor conductancia estomática, peroxidación de lípidos y peróxido de hidrógeno, y mayor actividad de ascorbato peroxidasa (APX), catalasa (CAT) y peroxidasa (POD) en las PCB. El número y peso de los frutos en las PCB y PSB se redujo por el estrés por sequía, pero la reducción fue menor en las PCB. Estos resultados indican que el tratamiento con bacterias confirió tolerancia al estrés por sequía en plantas de tomate al reducir el grado de peroxidación de los lípidos polares (PLs), aumentar el contenido de pigmentos fotosintéticos y las actividades de las enzimas antioxidantes en las hojas. Se concluye que P. putida KT2440 facilitó un alto rendimiento de frutos bajo estrés por sequía como un inductor biótico de tolerancia a este tipo de estrés.

Allium mongolicum Regel is a desert plant that shows great resistance to wind erosion, drought, and low temperatures and is widely distributed in the desert lands of China. Understanding the molecular mechanisms underlying its drought resistance is essential for uncovering drought resistance genes and improving its beneficial traits. Here, a de novo RNA-Seq assembly analysis was conducted using the roots of 1-month-old seedlings under drought stress. Using pairwise comparisons of untreated plants (CK), 48-hour drought plants (G48h), and 96- hour drought plants (G96h), in total, 2,211 differentially expressed unigenes (DEGs) were obtained. Furthermore, using functional annotation, these DEGs were mainly involved in the plasma membrane, photosynthesis, and secondary carbohydrate metabolism. Moreover, genes involved in the ABA-mediated signaling pathway and secondary metabolism were upregulated in the roots. These results suggest that desert plants may use signaling and secondary metabolic pathways as adaptive responses to drought stress. Collectively, this work could help elucidate the molecular mechanisms underlying the ability of A. mongolicum Regel to respond to drought stress and aid in the selection of novel drought tolerance genes.

The expansion and modernization of the cocoa area under new strategies, such as the use of adapted genetic material and the establishment of Agroforestry Systems with cocoa, under criteria of competitiveness and sustainability, require selecting sites with adequate biophysical conditions, which facilitate the optimization of resources for production. In this sense, we conducted a study in the Estación Agraria Cotové, of the Universidad Nacional de Colombia, located in a tropical dry forest life zone (TDF), at 540 meters of elevation, with an average temperature of 27 ºC, average annual precipitation annual of 1,031 mm and relative humidity less than 70 %. The yield components and productive potential of four cocoa clones, ICS 95, TSH565, CCN 51, and ICS 60, were evaluated. The cocoa clones were planted under two controlled sunlight habitats, generated by the timber species Gmelina arborea Roxb. (single-row and double-row arrangement), and two different canopy management of the cocoa plants (plagiotropic and orthotropic growth stimulus). The clones TSH 565 and CCN 51 showed the highest yields in the two harvest years. ICS 95 showed the lowest bean index. Regarding the pod index, no differences were observed between the cocoa clones. Clones TSH 565 and CCN 51 stood out as the earliest and most productive clones., La ampliación y modernización del área cacaotera, bajo nuevas estrategias, como la utilización de material genético sobresaliente y el establecimiento de Sistemas Agroforestales con cacao, bajo criterios de competitividad y sostenibilidad exigen la selección de sitios con adecuadas condiciones biofísicas, que faciliten la optimización de los recursos para la producción. Esta investigación se desarrolló en la Estación Agraria Cotové, de la Universidad Nacional de Colombia, ubicada en una zona de vida de bosque seco tropical (bs-T), a una altitud aproximada de 540 msnm., con temperatura promedio de 27ºC, precipitación media anual de 1.031 mm y humedad relativa menor al 70 %. Se evaluaron los componentes del rendimiento y potencial productivo de cuatro materiales genéticos de cacao (ICS 95, TSH565, CCN 51, ICS 60) dispuestos bajo dos hábitats lumínicos de la especie maderable Gmelina arborea Roxb. (hilera simple o hilera doble), sometidos a dos manejos diferentes de la copa del cacao (modificación de su arquitectura mediante el estímulo del crecimiento plagiotrópico u ortotrópico). Los clones de cacao TSH 565 y CCN 51 fueron los que presentaron los mayores rendimientos en los dos años de cosecha. ICS 95 mostró el índice de grano más bajo. En cuanto al índice de mazorca, no se observaron diferencias entre los clones de cacao. Los clones TSH 565 y CCN 51 se destacaron como clones precoces y de mayor producción

Drought in heavy metal polluted arid and semiarid regions severely inhibits the plant growth and phytoremediation potential by affecting photosynthesis, antioxidant defense mechanism, and other biochemical processes. In the present study, we explored the role of plant growth-promoting bacteria (PGPB) on Zea mays growth and phytoremediation efficiency in Chromium (Cr) contaminated soils under drought stress by assessing plant stress tolerance, photosynthetic gas exchange activities, chlorophyll fluorescence, and Cr accumulation. Two efficient Cr and drought resistant PGPB with the potential to reduce Cr(VI) to Cr(III) and produce plant growth-promoting metabolites even under Cr, drought, or Cr+drought stress conditions were isolated and identified as Providencia sp. (TCR05) and Proteus mirabilis (TCR20). In pot experiments, the inoculation of TCR05 and TCR20 increased the plant growth, pigments, protein, phenolics, and relative water content and decreased the lipid peroxidation, proline, and superoxide dismutase activity under Cr, drought, or Cr+drought conditions. Irrespective of stress treatment, TCR05 and TCR20 also improved plant photosynthetic efficiency by increasing the CO2 assimilation rate, stomatal conductance to water vapor, transpiration rate, maximum quantum efficiency of PSII, actual quantum efficiency of PSII, electron transport rate, photochemical quenching, reducing the internal CO2 concentration and non-photochemical quenching. Besides, the PGPB decreased the translocation of Cr through immobilization of Cr in root. These results denoted that strains TCR05 and TCR20 could be a capable bio-inoculant for improving plant growth and phytostabilization practices in Cr contaminated sites even under water-limited conditions. © 2021 The Authors.

Species abundance often determines the extent of influence of a species to ecosystem function and processes. Typically, the abundance of a species is constrained by environmental factors within its habitat. However, there are instances where native species becomes prolific and the shift in abundance greatly impacts the ecosystem. Such is the case when a flammable species becomes prolific within its range and alters the flammability of the ecosystem. This is a concern with climate change, as conditions might be tipped in favour of such species. Hence, it is crucial to understand the drivers of abundance to understand how native species can be released from environmental constraints of abundance to become prolific within their own range, and to predict the potential effect of changing environmental conditions on their abundance. Thus, the overarching aim of this thesis was to understand how a flammable native species can become prolific within its own range. This is achieved using a case study species – forest wiregrass Tetrarrhena juncea R.Br. (hereafter wiregrass) – an understorey native species that is of high importance to flammability in the eucalypts forests of south-eastern Australia and grows prolifically under certain conditions. The overarching aim of the thesis was addressed using a mix of research methods to identify the key drivers of wiregrass distribution and abundance. Firstly, a database of the current distribution for wiregrass were analysed using species distribution modelling to identify highly suitable habitat for wiregrass (Chapter 2). Temperature seasonality, precipitation of the driest month, rainfall seasonality, annual mean temperature, the minimum temperature of the coldest month and soil pH were strongly associated with the suitable habitat of wiregrass. The high importance of climatic factors indicates the distribution of wiregrass may be sensitive to climate change. Highly suitable habitats do not necessarily harbor abundant wiregrass bec

Background and aims Impact of drought on crop growth depends on soil and root hydraulic properties that determine the access of plant roots to soil water. Root hairs may increase the accessible water pool but their effect depends on soil hydraulic properties and adaptions of root systems to drought. These adaptions are difficult to investigate in pot experiments that focus on juvenile plants. Methods A wild-type and its root hairless mutant maize (Zea mays) were grown in the field in loam and sand substrates during two growing seasons with a large precipitation deficit. A comprehensive dataset of soil and plant properties and monitored variables were collected and interpreted using simulations with a mechanistic root water uptake model. Results Total crop water use was similar in both soils and for both genotypes whereas shoot biomass was larger for the wild type than for the hairless mutant and did not differ between soils. Total final root length was larger in sand than in loam but did not differ between genotypes. Simulations showed that root systems of both genotypes and in both soils extracted all plant available soil water, which was similar for sand and loam, at a potential rate. Leaf water potentials were overestimated by the model, especially for the hairless mutant in sand substrate because the water potential drop in the rhizosphere was not considered. Conclusions A direct effect of root hairs on water uptake was not observed but root hairs might influence leaf water potential dependent growth.