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The performance of a soybean genotype under water deficit stress at an early vegetative stage might be related to its general tolerance to drought. To investigate the plasticity of root and shoot seedling traits in response to drought at an early vegetative stage, a set of 32 soybean genotypes adapted to southeast European growing conditions was grown under polyethylene glycol (PEG) 8000-induced drought stress and well-watered control conditions. Under drought, mean tap root length (RL), shoot length (SL), root fresh weight (RFW) and shoot fresh weight (SFW) decreased significantly by 11, 17, 38 and 34%, respectively, while root dry matter (RDM) and shoot dry matter (SDM) increased significantly by 13 and 11%, respectively. Of the four derived traits, the ratios of RL/SL, RL/RFW and SL/SFW increased significantly by 8, 45 and 28%, respectively, under drought, while the ratio of RFW/SFW decreased significantly by 4%. However, a wide variation between genotypes was observed for all 10 studied seedling traits under both control and drought conditions. Broad sense heritability ranged from 0.53 (RL) to 0.97 (SL) under control conditions and from 0.56 (RL/RFW) to 0.96 (SL) under drought conditions. The correlation coefficients between the traits were either weak or moderate, indicating that the studied traits can be modified independently by selection. [ABSTRACT FROM AUTHOR]

Climate change scenarios and water restrictions are key challenges for Mediterranean citriculture, requiring sustainable deficit irrigation (DI) strategies to ensure sustainable yields. Further research on the physiological pathways that regulate crop responses to water stress is necessary. This work describes the physiological limitations induced under drought conditions in young Navelina orange trees, including the crop's capability to recuperate its physiological status upon rewatering and after water withholding. A trial was conducted in two-year-old trees subjected to three irrigation treatments: a full irrigation treatment (FI) and two different DI strategies. The results show significant decreases in gas exchange rates for stem water potential (ΨStem) values below −1.5 MPa, evidencing diffusive limitations from drought stress. Additionally, there was evidence of increased osmolyte synthesis, a preventative response to oxidative damage. Significantly increased levels of proline (Pro) and malondialdehyde (MDA) were observed with higher levels of water stress (ΨStem < −1.8 MPa), which leads us to assume that this threshold signals the presence of oxidative damage with no capacity for subsequent recovery, probably affecting the final yield. [ABSTRACT FROM AUTHOR]

Background: Extreme weather events induced by climate change, particularly droughts, have detrimental consequences for crop yields and food security. Concurrently, these conditions provoke substantial changes in the soil bacterial microbiota and affect plant health. Early recognition of soil affected by drought enables farmers to implement appropriate agricultural management practices. In this context, interpretable machine learning holds immense potential for drought stress classification of soil based on marker taxa. Results: This study demonstrates that the 16S rRNA-based metagenomic approach of Differential Abundance Analysis methods and machine learning-based Shapley Additive Explanation values provide similar information. They exhibit their potential as complementary approaches for identifying marker taxa and investigating their enrichment or depletion under drought stress in grass lineages. Additionally, the Random Forest Classifier trained on a diverse range of relative abundance data from the soil bacterial micobiome of various plant species achieves a high accuracy of 92.3 % at the genus rank for drought stress prediction. It demonstrates its generalization capacity for the lineages tested. Conclusions: In the detection of drought stress in soil bacterial microbiota, this study emphasizes the potential of an optimized and generalized location-based ML classifier. By identifying marker taxa, this approach holds promising implications for microbe-assisted plant breeding programs and contributes to the development of sustainable agriculture practices. These findings are crucial for preserving global food security in the face of climate change. [ABSTRACT FROM AUTHOR]

Introduction: This study used Bacillus amyloliquefaciens DGL1 isolated from the arid sandy land of the Qinghai-Tibetan Plateau as the research strain and investigated the effects of DGL1 on the biomass, physiology, and metabolites of Medicago sativa under different intensities of drought stress to provide a high-quality bacterial source and a theoretical basis for the research and development of biological fertilizer suitable for arid areas. Methods: The exopolysaccharides (EPS), 1-Aminocyclopropane-1-carboxylate deaminase (ACC), and phosphorus solubilizing capacity of DGL1 were determined. The effects of a DGL1 suspension on alfalfa biomass, physiological indexes, degree of peroxidation of cell membranes, and activity of antioxidant enzymes were determined after irrigating roots under drought stress. The effects on soil physicochemical properties were also evaluated, and metabolomics analysis was performed to explore the effect of DGL1 on the metabolites of alfalfa under drought stress. Results: Strain DGL1 produced extracellular polysaccharide EPS and ACC deaminase and was capable of phosphorus solubilization. Treatment with DGL1 increased the biomass of alfalfa under different degrees of drought stress, significantly increased the activities of alfalfa antioxidant enzymes Super Oxide Dismutase (SOD), Peroxidase (POD), and catalase (CAT), reduced the content of MDA and H2O2, and increased the content of quick-acting phosphorus, quick-acting potassium, ammonium nitrogen, and nitrate nitrogen in the soil, thus improving soil fertility. Through metabolomics analysis, DGL1 was shown to affect amino acid metabolic pathways, such as arginine, leucine, glutamate, and tyrosine, as well as the levels of energy-providing polysaccharides and lipids, in alfalfa under 15% PEG-6000 drought stress, enhancing alfalfa's capacity to resist drought stress. Discussion: Strain DGL1 enhances the drought suitability of alfalfa and has the potential for dryland development as a biological agent. [ABSTRACT FROM AUTHOR]

Salvia miltiorrhiza is commonly used as a Chinese herbal medicine to treat different cardiovascular and cerebrovascular illnesses due to its active ingredients. Environmental conditions, especially drought stress, can affect the yield and quality of S. miltiorrhiza. However, moderate drought stress could improve the quality of S. miltiorrhiza without significantly reducing the yield, and the mechanism of this initial drought resistance is still unclear. In our study, transcriptome and metabolome analyses of S. miltiorrhiza under different drought treatment groups (CK, A, B, and C groups) were conducted to reveal the basis for its drought tolerance. We discovered that the leaves of S. miltiorrhiza under different drought treatment groups had no obvious shrinkage, and the malondialdehyde (MDA) contents as well as superoxide dismutase (SOD) and peroxidase (POD) activities dramatically increased, indicating that our drought treatment methods were moderate, and the leaves of S. miltiorrhiza began to initiate drought resistance. The morphology of root tissue had no significant change under different drought treatment groups, and the contents of four tanshinones significantly enhanced. In all, 5213, 6611, and 5241 differentially expressed genes (DEGs) were shared in the A, B, and C groups compared with the CK group, respectively. The results of KEGG and co-expression analysis showed that the DEGs involved in plant-pathogen interactions, the MAPK signaling pathway, phenylpropanoid biosynthesis, flavonoid biosynthesis, and plant hormone signal transduction responded to drought stress and were strongly correlated with tanshinone biosynthesis. Furthermore, the results of metabolism analysis indicated that 67, 72, and 92 differentially accumulated metabolites (DAMs), including fumarate, ferulic acid, xanthohumol, and phytocassanes, which were primarily involved in phenylpropanoid biosynthesis, flavonoid biosynthesis, and diterpenoid biosynthesis pathways, were detected in these groups. These discoveries provide valuable information on the molecular mechanisms by which S. miltiorrhiza responds to drought stress and will facilitate the development of drought-resistant and high-quality S. miltiorrhiza production. [ABSTRACT FROM AUTHOR]

Background: The mechanisms by which the apple MdPYL9 gene mediates the response to drought stress remain unclear. Here, transcriptome and metabolome analyses of apple plants under drought were used to investigate the mechanisms by which MdPYL9 regulates the response to drought stress in apple. MdPYL9-overexpressed transgenic and non-transgenic apple histoculture seedlings were rooted, transplanted, and subjected to drought treatments to clarify the mechanisms underlying the responses of apples to drought stress through phenotypic observations, physiological and biochemical index measurements, and transcriptomic and metabolomic analyses. Results: Under drought stress treatment, transgenic plants were less affected by drought stress than non-transgenic plants. Decreases in the net photosynthetic rate, stomatal conductance, and transpiration rate of transgenic apple plants were less pronounced in transgenic plants than in non-transgenic plants, and increases in the intercellular CO2 concentration were less pronounced in transgenic plants than in non-transgenic plants. The relative electrical conductivity and content of malondialdehyde, superoxide anion, and hydrogen peroxide were significantly lower in transgenic plants than in non-transgenic plants, and the chlorophyll content and activities of antioxidant enzymes (superoxide dismutase, peroxidase, and catalase) were significantly higher in transgenic plants than in non-transgenic plants. The number of differentially expressed genes (DEGs) involved in the response to drought stress was lower in transgenic plants than in non-transgenic plants, and the most significant and highly annotated DEGs in the transgenic plants were involved in the flavonoid biosynthesis pathway, and the most significant and highly annotated DEGs in control plants were involved in the phytohormone signal transduction pathway. The number of differentially accumulated metabolites involved in the response to drought stress was lower in transgenic plants than in non-transgenic plants, and up-regulated metabolites were significantly enriched in apigenin-7-O-glucoside in transgenic plants and in abscisic acid in non-transgenic plants. In the flavonoid biosynthetic pathway, the expression of genes encoding chalcone synthase (CHS) and chalcone isomerase (CHI) was more significantly down-regulated in non-transgenic plants than in transgenic plants, and the expression of the gene encoding 4-coumarate-CoA ligase (4CL) was more significantly up-regulated in transgenic plants than in non-transgenic plants, which resulted in the significant up-regulation of apigenin-7-O-glucoside in transgenic plants. Conclusions: The above results indicated that the over-expression of MdPYL9 increased the drought resistance of plants under drought stress by attenuating the down-regulation of the expression of genes encoding CHS and CHI and enhancing the up-regulated expression of the gene encoding 4CL, which enhanced the content of apigenin-7-O-glucoside. [ABSTRACT FROM AUTHOR]

The objective of this study was to develop a crop model for sunflower in Daisy. For this intent, the field experiment data of two full irrigation treatments for 2 years, 2012 and 2013, were used to develop the crop model. The average RMSE of the dry matter (DM), leaf area index (LAI), height of plant (H), and water content parameters in the treatments utilized for calibration was calculated 0.093 Ton/ha, 0.198 cm2/cm2, 2.25 cm, and 1.035%, respectively. The average RMSE of the parameters of DM, LAI, H, and water content in the treatments utilized for validation were estimated 0.207 Ton/ha, 0.272 cm2/cm2, 4.22 cm, and 1.123%, respectively. The results of the validation showed that the developed crop model had good accuracy making it useful for simulation of sunflower agroecology. It is suggested to use the developed crop model in the information library of Daisy and survey and calibrate it for other areas with different climates and sunflower varieties. [ABSTRACT FROM AUTHOR]

As global arid conditions worsen and groundwater resources diminish, drought stress has emerged as a critical impediment to plant growth and development globally, notably causing declines in crop yields and even the extinction of certain cultivated species. Numerous studies on drought resistance have demonstrated that DNA methylation dynamically interacts with plant responses to drought stress by modulating gene expression and developmental processes. However, the precise mechanisms underlying these interactions remain elusive. This article consolidates the latest research on the role of DNA methylation in plant responses to drought stress across various species, focusing on methods of methylation detection, mechanisms of methylation pattern alteration (including DNA de novo methylation, DNA maintenance methylation, and DNA demethylation), and overall responses to drought conditions. While many studies have observed significant shifts in genome-wide or gene promoter methylation levels in drought-stressed plants, the identification of specific genes and pathways involved remains limited. This review aims to furnish a reference for detailed research into plant responses to drought stress through epigenetic approaches, striving to identify drought resistance genes regulated by DNA methylation, specific signaling pathways, and their molecular mechanisms of action. [ABSTRACT FROM AUTHOR]

Bassia dasyphylla is a prevalent herbaceous plant that exhibits enhanced resilience to dryness and elevated temperatures. It is frequently found in dispersed or grouped formation on sandy soil within steppe, semi-desert, and desert regions. Herein, we conducted experiments to examine the growth and physiological traits of B. dasyphylla seeds originated from various regions in response to water scarcity. The study seeks to investigate the ability of these seeds to germinate under drought conditions and offer valuable insights for the development and breeding of high-quality germplasm resources in Inner Mongolia. The results demonstrated that B. dasyphylla originating from desert steppe (DS) exhibited a greater capacity to endure drought conditions in comparison to its counterparts from sandy land (SL). At a water potential of -0.30 MPa, the Seed germination rate from DS was 33.3%, while from SL it was 22.7%. With the increase in drought duration and intensity, germination rate, plumule length, both single-seed weight (SSW) and seed water content (SWC) of B. dasyphylla declined. The protective enzyme activity exhibited an initial increase, followed by a subsequent decline as the duration of the drought increased. Notably, we found that the protective enzyme activity from DS was higher than that from SL. During the initial and intermediate stages of dryness, the soluble sugar and protein of the plant from DS effectively inhibited the peroxidation of membrane lipids, whereas the osmoregulatory properties from SL did not have a significant impact. The findings suggest that the ability of B. dasyphylla to withstand drought conditions in DS can be attributed to its elevated amounts of protective enzymes and osmoregulatory factors, which serve to safeguard the cell membrane during periods of drought. [ABSTRACT FROM AUTHOR]

Background: Autofluorescence-based imaging has the potential to nondestructively characterize the biochemical and physiological properties of plants regulated by genotypes using optical properties of the tissue. A comparative study of stress tolerant and stress susceptible genotypes of Brassica rapa with respect to newly introduced stress-based phenotypes using machine learning techniques will contribute to the significant advancement of autofluorescence-based plant phenotyping research. Methods: Autofluorescence spectral images have been used to design a stress detection classifier with two classes, stressed and non-stressed, using machine learning algorithms. The benchmark dataset consisted of time-series image sequences from three Brassica rapa genotypes (CC, R500, and VT), extreme in their morphological and physiological traits captured at the high-throughput plant phenotyping facility at the University of Nebraska-Lincoln, USA. We developed a set of machine learning-based classification models to detect the percentage of stressed tissue derived from plant images and identified the best classifier. From the analysis of the autofluorescence images, two novel stressbased image phenotypes were computed to determine the temporal variation in stressed tissue under progressive drought across different genotypes, i.e., the average percentage stress and the moving average percentage stress. Results: The study demonstrated that both the computed phenotypes consistently discriminated against stressed versus non-stressed tissue, with oilseed type (R500) being less prone to drought stress relative to the other two Brassica rapa genotypes (CC and VT). Conclusion: Autofluorescence signals from the 365/400 nm excitation/emission combination were able to segregate genotypic variation during a progressive drought treatment under a controlled greenhouse environment, allowing for the exploration of other meaningful phenotypes using autofluorescence image sequences with significance in the context of plant science. [ABSTRACT FROM AUTHOR]

Glutathione (GSH) has been studied for its potential to enhance stress tolerance in plant systems, but the role of hydrogen sulfide (H2S) in GSH‐induced water stress tolerance in sweet pepper (Capsicum annuum L.) is still under investigation. This study explores how H2S and GSH modulate water stress tolerance in pepper plants, addressing a research gap. The joint effect of sodium hydrosulfide (NaHS), a donor of H2S, and GSH on water stress tolerance was determined through pre‐treatment with the H2S scavenger 0.1 mM hypotaurine (HT). Pepper seedlings were sprayed with 1.0 mM GSH or GSH + 0.2 mM NaHS once a week, with soil moisture content set at 80% and 40% for full irrigation and water stress conditions for a duration of 2 weeks. The results showed that water stress significantly reduced total plant dry weight, chlorophyll a and b content, Fv/Fm, leaf water potential, and relative water content by 50%, 56%, 33%, 27%, 52%, and 34%, while increasing hydrogen peroxide (H2O2), proline, and H2S levels by 152%, 134%, and77%, respectively. Treatment with GSH and NaHS reduced water stress‐induced H2O2 production and improved plant growth, photosynthetic traits, proline, and the activity of L‐cysteine desulfhydrase (L‐DES), leading to the generation of H2S content. GSH reduced NADPH oxidase (NOX), superoxide dismutase (SOD), and H2O2 but increased glutathione peroxidase (GPX) activities. The interaction of NaHS and GSH led to further reductions in NOX, SOD, and H2O2 values but increased GPX activity. The combined GSH and NaHS treatment increased nitric oxide (NO) production but decreased the activity of S‐nitrosoglutathione reductase (GSNOR), potentially accelerating S‐nitrosylation. Hypotaurine negated the positive impacts of GSH on water stress tolerance by reducing H2S concentration in pepper plants, but this was corrected by the concurrent application of NaHS and GSH + HT. Therefore, water stress tolerance requires H2S. [ABSTRACT FROM AUTHOR]

SET-domain group histone methyltransferases (SDGs) are known to play crucial roles in plant responses to abiotic stress. However, their specific function in cotton's response to drought stress has not been well understood. This study conducted a comprehensive analysis of the SDG gene family in Gossypium hirsutum, identifying a total of 82 SDG genes. An evolutionary analysis revealed that the SDG gene family can be divided into eight subgroups. The expression analysis shows that some GhSDG genes are preferentially expressed in specific tissues, indicating their involvement in cotton growth and development. The transcription level of some GhSDG genes is induced by PEG, with GhSDG59 showing significant upregulation upon polyethylene glycol (PEG) treatment. Quantitative polymerase chain reaction (qPCR) analysis showed that the accumulation of transcripts of the GhSDG59 gene was significantly upregulated under drought stress. Further functional studies using virus-induced gene silencing (VIGS) revealed that silencing GhSDG59 reduced cotton tolerance to drought stress. Under drought conditions, the proline content, superoxide dismutase (SOD) and peroxidase (POD) enzyme activities in the GhSDG59-silenced plants were significantly lower than in the control plants, while the malondialdehyde (MDA) content was significantly higher. Transcriptome sequencing showed that silencing the GhSDG59 gene led to significant changes in the expression levels of 1156 genes. The KEGG enrichment analysis revealed that these differentially expressed genes (DEGs) were mainly enriched in the carbon metabolism and the starch and sucrose metabolism pathways. The functional annotation analysis identified known drought-responsive genes, such as ERF, CIPK, and WRKY, among these DEGs. This indicates that GhSDG59 is involved in the drought-stress response in cotton by affecting the expression of genes related to the carbon metabolism and the starch and sucrose metabolism pathways, as well as known drought-responsive genes. This analysis provides valuable information for the functional genomic study of SDGs and highlights potential beneficial genes for genetic improvement and breeding in cotton. [ABSTRACT FROM AUTHOR]

Plant roots exert hydrotropism in response to moisture gradients to avoid drought stress. The regulatory mechanism underlying hydrotropism involves novel regulators such as MIZ1 and GNOM/MIZ2 as well as abscisic acid (ABA), reactive oxygen species (ROS), and Ca2+ signaling. ABA, ROS, and Ca2+ signaling are also involved in plant responses to drought stress. Although the mechanism of moisture gradient perception remains largely unknown, the sensory apparatus has been reported to reside in the root elongation zone rather than in the root cap. In Arabidopsis roots, hydrotropism is mediated by the action of MIZ1 and ABA in the cortex of the elongation zone, the accumulation of ROS at the root curvature, and the variation in the cytosolic Ca2+ concentration in the entire root tip including the root cap and stele of the elongation zone. Moreover, root exposure to moisture gradients has been proposed to cause asymmetric ABA distribution or Ca2+ signaling, leading to the induction of the hydrotropic response. A comprehensive and detailed analysis of hydrotropism regulators and their signaling network in relation to the tissues required for their function is apparently crucial for understanding the mechanisms unique to root hydrotropism. Here, referring to studies on plant responses to drought stress, we summarize the recent findings relating to the role of ABA, ROS, and Ca2+ signaling in hydrotropism, discuss their functional sites and plausible networks, and raise some questions that need to be answered in future studies. [ABSTRACT FROM AUTHOR]

Drought stress is the prime obstacle for worldwide agricultural production and necessitates innovative strategies for enhancing crop resilience. This study explores the efficacy of plant growth-promoting rhizobacteria (PGPR) and biochar (BC) as sustainable amendments for mitigating the effects of drought on wheat growth. Multiple experiments were carried out on isolated strains to assess their drought tolerance potential and multiple plant growth-promoting attributes. Experiments in the laboratory and natural environment were conducted to assess the impact of plant growth-promoting rhizobacteria, biochar, and their synergistic application on various growth parameters of wheat. The results revealed that the drought-tolerant PGPR strains (Bacillus subtilis and Bacillus tequilensis), alongside biochar (rice husk), alleviated the phytotoxic impact of drought by increasing the root length from 17.0% to 70.0% and shoot length from 30.0% to 82.0% as compared to un-inoculated stressed controls. The total chlorophyll and carotenoid contents of the plants were substantially increased to 477% and 423%, respectively, when biochar and PGPR were applied synergistically. Significant enhancements in membrane stability index, relative water content, proline, and sugar level were achieved by combining biochar and bacterial strains, resulting in increases of 19.5%, 37.9%, 219%, and 300%, respectively. The yield of wheat in terms of plant height, spike length, number of spikelets per spike, and number of grains per spike was enhanced from 26.7% to 44.6%, 23.5% to 62.7%, 91.5% to 154%, and 137% to 182%, respectively. It was concluded that the biochar-based application of PGPR induced drought tolerance in wheat under water deficit conditions, ultimately improving the production and yield of wheat. [ABSTRACT FROM AUTHOR]

Drought (water shortage) can substantially limit the yield and economic value of rose plants (Rosa spp.). Here, we characterized the effect of exogenous calcium (Ca2+) on the antioxidant system and photosynthesis-related properties of rose under polyethylene glycol 6000 (PEG6000)- induced drought stress. Chlorophyll levels, as well as leaf and root biomass, were significantly reduced by drought; drought also had a major effect on the enzymatic antioxidant system and increased concentrations of reactive oxygen species. Application of exogenous Ca2+ increased the net photosynthetic rate and stomatal conductance of leaves, enhanced water-use efficiency, and increased the length and width of stomata following exposure to drought. Organ-specific physiological responses were observed under different concentrations of Ca2+. Application of 5 mmol. L-1 Ca2+ promoted photosynthesis and antioxidant activity in the leaves, and application of 10 mmol. L-1 Ca2+ promoted antioxidant activity in the roots. Application of exogenous Ca2+ greatly enhanced the phenotype and photosynthetic capacity of potted rose plants following exposure to drought stress. Overall, our findings indicate that the application of exogenous Ca2+ enhances the drought resistance of roses by promoting physiological adaptation and that it could be used to aid the cultivation of rose plants. [ABSTRACT FROM AUTHOR]

The Arabidopsis Tóxicos en Levadura (ATL) protein is a subfamily of the E3 ubiquitin ligases, which exists widely in plants and is extensively involved in plant growth and development. Although the ATL family has been identified in other species, such as Arabidopsis, Oryza sativa, and grapevine, few reports on pear ATL gene families have been reported. In this study, 92 PbrATL genes were identified and analyzed from the Pyrus breschneideri genome. Motif analysis and phylogenetic tree generation divided them into nine subgroups, and chromosome localization analysis showed that the 92 PbrATL genes were distributed in 16 of 17 pear chromosomes. Transcriptome data and quantitative real-time polymerase chain reaction (qRT-PCR) experiments demonstrated that PbrATL18, PbrATL41, and PbrATL88 were involved in both pear drought resistance and Colletotrichum fructicola infection. In addition, Arabidopsis thaliana overexpressing PbrATL18 showed greater resistance to drought stress than the wild type (WT), and PbrATL18-silenced pear seedlings showed greater sensitivity to drought and C. fructicola infection than the controls. PbrATL18 regulated plant resistance by regulating chitinase (CHI), phenylalanine ammonia-lyase (PAL), polyphenol oxidase (PPO), catalase (CAT), peroxidase (POD), and superoxide dismutase (SOD) activities. This study provided a reference for further exploring the functions of the PbrATL gene in drought resistance and C. fructicola infection. [ABSTRACT FROM AUTHOR]

Abiotic stress reduces plant yield and quality. WRKY transcription factors play key roles in abiotic stress responses in plants, but the molecular mechanisms by which WRKY transcription factors mediate responses to drought and osmotic stresses in apple (Malus × domestica Borkh.) remain unclear. Here, we functionally characterized the apple Group III WRKY gene MdWRKY115. qRT-PCR analysis showed that MdWRKY115 expression was up-regulated by drought and osmotic stresses. GUS activity analysis revealed that the promoter activity of MdWRKY115 was enhanced under osmotic stress. Subcellular localization and transactivation assays indicated that MdWRKY115 was localized to the nucleus and had a transcriptional activity domain at the N-terminal region. Transgenic analysis revealed that the overexpression of MdWRKY115 in Arabidopsis plants and in apple callus markedly enhanced their tolerance to drought and osmotic stresses. DNA affinity purification sequencing showed that MdWRKY115 binds to the promoter of the stress-related gene MdRD22. This binding was further verified by an electrophoretic mobility shift assay. Collectively, these findings suggest that MdWRKY115 is an important regulator of osmotic and drought stress tolerance in apple. [ABSTRACT FROM AUTHOR]

In the current study, the effects of drought stress on the growth and phytochemical profile of Scolymus hispanicus L. (a.k.a. golden thistle) were evaluated. Plants were treated with three irrigation regimes, e.g., plants that received only rainwater (Control; C), deficit irrigation (I1; 50% of field capacity (FC)), and full irrigation (Ι2; 100% of FC). The fresh weight of the rosette of leaves was not negatively impacted by deficit irrigation, whereas root development was severely restrained compared to control and I2 treatments. Drought stress conditions had a positive effect on the nutritional properties of the golden thistle since the treatments of control and deficit irrigation showed the highest content of macronutrients and energy. Oxalic acid was the richest organic acid, especially under the I1 regime. Similarly, α-tocopherol was the only identified vitamin E isoform, whose content was also doubled in I1 treatment. Raffinose, glucose, and sucrose were the most abundant free sugars in amounts that varied among the irrigation treatments, while the total and distinct free sugar content was the highest for the I1 treatment. The most abundant detected fatty acid compounds were α-linolenic acid, followed by palmitic and linoleic acid, with the highest amount being detected in C, I1, and I2 treatments, respectively. Flavonoids were the only class of polyphenols detected in golden thistle leaves, including mostly kaempferol and quercetin derivatives. The greatest antioxidant potency was shown for the control and I1 treatments (for OxHLIA and TBARS methods, respectively). The evaluated leaf samples recorded a varied antimicrobial effect for the different bacterial strains and fungi, whereas no cytotoxic, hepatotoxic, and anti-inflammatory effects against the tested cell lines were recorded. Finally, the mineral content of leaves was significantly affected by the irrigation regime, with Ca, Mg, Cu, and Zn being the highest for the I1 treatment, while the I2 treatment had the highest content of K, Fe, and Mn and the lowest Na content. In conclusion, deficit irrigation showed promising results since it improved the phytochemical content without compromising the fresh weight of leaves, and thus it could be suggested as a sustainable agronomic practice for producing high-added value products without significant constraints in growth development and yield parameters of golden thistle. [ABSTRACT FROM AUTHOR]

Watermelons are one of the most important crop species, and they are enjoyed across the globe; however, the cultivation of watermelon commercial varieties in arid regions is challenging, as they are highly susceptible to water deficit. Conversely, their wild relatives and traditional landraces have shown a higher tolerance to water deficit, which makes them important study material. Therefore, this study was undertaken to evaluate the potential roles of two compatible osmolytes (citrulline and arginine) in the tolerance of local watermelon accessions to drought stress. Four commonly cultivated watermelon accessions were used in this study to evaluate their response when exposed to water deficit stress. The accessions were planted in stress boxes in the greenhouse and allowed to grow until the fourth leaf was fully open and then the water deficit stress was initiated by withholding water for a period of nine days, before rewatering for three days. Data and leaf samples were collected at three-day intervals. The common drought indicators that were assessed, like chlorophyll fluorescence, showed that Clm-08 (wild watermelon) had significantly different results when compared to the other accessions; the Fv/Fm values for days 3, 6, and 9 were significantly higher than those of the other accessions, while phiNPQ was higher in the Clm-08 with average values of 0.41 and 0.41 on days 6 and 9 of the drought stress, respectively. This suggests that the wild watermelon responded differently to drought stress when compared with the other accessions. Arginine and citrulline are important osmolytes that play an important role in stress tolerance, and the results of the current study correlate with the common physiological indicators. The expression pattern for both the biochemical and molecular analyses of the two compatible osmolytes was higher in Clm-08 in comparison with that of the other accessions. The gene expressions of the enzymes in the citrulline and arginine pathways were higher in Clm-08; Cla022915 (CPS) recorded a 6-fold increase on day 6 and Cla002611 (ASS) recorded an 11-fold increase. This suggests that citrulline and arginine play an important role in watermelon tolerance to drought stress. [ABSTRACT FROM AUTHOR]

The main production area of Camellia vietnamensis (C. vietnamensis) is in the low mountain and hilly areas of southern China. The low survival rate of seedlings caused by drought is one of the main obstacles restricting the development of the C. vietnamensis industry. An exploration of the key adaptation mechanism of C. vietnamensis to drought stress is important in order to improve its drought resistance. We conducted a study on the morphological, physiological, biochemical, and drought resistance-related genes of five C. vietnamensis cultivars grown in Hainan province under varying degrees of drought stress. The results indicate that drought stress can lead to a decrease in the relative water content and photosynthetic capacity of C. vietnamensis leaves. Compared with the control, the drought damage index, malondialdehyde, relative electrical conductivity, soluble protein, soluble sugar and proline contents of the five C. vietnamensis cultivars increased with drought-stress duration and degree. With increasing drought-stress intensity, the activity of antioxidant enzymes and the content of related metabolites (total polyphenols, total flavonoids, tea saponins) gradually increased, and the expression levels of phenylpropanoid pathway-related genes (Cv4CL1, CvCAD1, CvCAD2, CvPOX1, CvPOX2, CvPOX3) were upregulated. Based on the results of the drought tolerance coefficients, principal component analysis, and hierarchical cluster analysis, we classified five C. vietnamensis cultivars into drought-tolerant cultivars ('Haida 1'); moderately drought-tolerant cultivars ('Haida 4' and 'Wanhai 4'); and drought-sensitive cultivars ('Wanhai 3' and 'Wanhai 1'). The results of this study provide a theoretical basis for the promotion and cultivation of C. vietnamensis and the selection of drought-resistant cultivars. [ABSTRACT FROM AUTHOR]

Background: Drought stress severely impedes plant growth, and only a limited number of species exhibit long-term resistance to such conditions. Pinus sylvestris var. mongolica, a dominant tree species in arid and semi-arid regions of China, exhibits strong drought resistance and plays a crucial role in the local ecosystem. However, the molecular mechanisms underlying this resistance remain poorly understood. Results: Here, we conducted transcriptome sequence and physiological indicators analysis of needle samples during drought treatment and rehydration stages. De-novo assembly yielded approximately 114,152 unigenes with an N50 length of 1,363 bp. We identified 6,506 differentially expressed genes (DEGs), with the majority being concentrated in the heavy drought stage (4,529 DEGs). Functional annotation revealed enrichment of drought-related GO terms such as response to water (GO:0009415: enriched 108 genes) and response to water deprivation (GO:0009414: enriched 106 genes), as well as KEGG categories including MAPK signaling pathway (K04733: enriched 35 genes) and monoterpenoid biosynthesis (K21374: enriched 27 genes). Multiple transcription factor families and functional protein families were differentially expressed during drought treatment. Co-expression network analysis identified a potential drought regulatory network between cytochrome P450 genes (Unigene4122_c1_g1) and a core regulatory transcription factor Unigene9098_c3_g1 (PsNAC1) with highly significant expression differences. We validated PsNAC1 overexpression in Arabidopsis and demonstrated enhanced drought resistance. Conclusions: These findings provide insight into the molecular basis of drought resistance in P. sylvestris var. mongolica and lay the foundation for further exploration of its regulatory network. [ABSTRACT FROM AUTHOR]

Background: Morphological plasticity is one of the capacities of plants to modify their morphological appearance in response to external stimuli. A plant's morphology and physiology are constantly tuned to its variable surroundings by complex interactions between environmental stimuli and internal signals. In most of plant species,, such phenotypic and physiological expression varies among different varieties based on their levels of particular environmental stress conditions. However, the morphological and yield responses of common bean varieties to different environmental conditions are not well known. The purpose of the study was to evaluate morphological and yield response of common bean to soil moisture stress and to investigate the morphological mechanism by which common bean varieties tolerate fluctuations in moisture stress. Methods: A pot experiment was carried out to investigate the effects of different moisture levels on the phenotypic and yield responses of common bean varieties. A factorial combination of five common bean varieties (Hirna, kufanzik, Awash-1, Ado, and Chercher) and three moisture levels (control, waterlogging stress, and moisture deficit stress) was used in three replications. Moisture stress treatments were started 20 days after planting, at the trifoliate growth stage. To evaluate the response of each variety, morphological and yield data were collected at week intervals. Main results: The results indicated that moisture levels and varieties had a significant influence on all growth parameters. Crop phenology was significantly influenced by the interaction effect of moisture level and variety. Exposing Hirna variety to moisture stress led to extended flowering and pod setting by 23 and 24 days, respectively, compared to the other treatments. The results showed that the phenotypic responses to moisture deficit and waterlogging stress varied between varieties. Waterlogging stress had a stronger reduction effect on the fresh weight, dry weight and leaf area of common bean varieties than moisture deficit and the control. Pods per plant, seeds per plant, grain yield per plant, and harvest index were significantly influenced by the varieties, moisture stress levels and their interaction. Except for Chercher and Hirna. However, varieties Ado, kufanzik and Awasha-1 did not show significant differences on the time of flower initiation due to moisture level. Biomass and growth in leaf fresh weight, leaf dry weight, leaf area, leaf number and plant height were significantly influenced by moisture level. When moisture deficit and waterlogging stress occurred, Ado and Awash-1 were more responsive to moisture stress than Hirna, Chercher, and Kufanzik. Conclusion: Hence, Hirna and Kufanzik varieties were found to be tolerant because they produced higher yields than the Chercher, Awash-1, and Ado varieties. [ABSTRACT FROM AUTHOR]

Plant growth and development can be significantly impacted by drought stress. Plants will adjust the synthesis and accumulation of secondary metabolites to improve survival in times of water constraint. Simultaneously, drought stress can lead to modifications in the DNA methylation status of plants, and these modifications can directly impact gene expression and product synthesis by changing the DNA methylation status of functional genes involved in secondary metabolite synthesis. However, further research is needed to fully understand the extent to which DNA methylation modifies the content of secondary metabolites to mediate plants' responses to drought stress, as well as the underlying mechanisms involved. Our study found that in Eleutherococcus senticosus (E. senticosus), moderate water deprivation significantly decreased DNA methylation levels throughout the genome and at the promoters of EsFPS, EsSS, and EsSE. Transcription factors like EsMYB-r1, previously inhibited by DNA methylation, can re-bind to the EsFPS promotor region following DNA demethylation. This process promotes gene expression and, ultimately, saponin synthesis and accumulation. The increased saponin levels in E. senticosus acted as antioxidants, enhancing the plant's adaptability to drought stress. [ABSTRACT FROM AUTHOR]

As an essential crop that provides vegetable oil and protein, soybean (Glycine max (L.) Merr.) is widely planted all over the world. However, the scarcity of water resources worldwide has seriously impacted on the quality and yield of soybean. To address this, exploring excellent genes for improving drought resistance in soybean is crucial. In this study, we identified natural variations of GmFNSII-2 (flavone synthase II) significantly affect the drought resistance of soybeans. Through sequence analysis of GmFNSII-2 in 632 cultivated and 44 wild soybeans nine haplotypes were identified. The full-length allele GmFNSII-2C, but not the truncated allele GmFNSII-2A possessing a nonsense nucleotide variation, increased enzyme activity. Further research found that GmDREB3, known to increase soybean drought resistance, bound to the promoter region of GmFNSII-2C. GmDREB3 positively regulated the expression of GmFNSII-2C, increased flavone synthase abundance and improved the drought resistance. Furthermore, a singlebase mutation in the GmFNSII-2C promoter generated an additional drought response element (CCCCT), which had stronger interaction strength with GmDREB3 and increased its transcriptional activity under drought conditions. The frequency of drought-resistant soybean varieties with Hap 1 (Pro:GmFNSII-2C) has increased, suggesting that this haplotype may be selected during soybean breeding. In summary, GmFNSII-2C could be used for molecular breeding of drought-tolerant soybean. [ABSTRACT FROM AUTHOR]

Drought poses a significant challenge, restricting the productivity of medicinal and aromatic plants. The strain induced by drought can impede vital processes like respiration and photosynthesis, affecting various aspects of plants' growth and metabolism. In response to this adversity, medicinal plants employ mechanisms such as morphological and structural adjustments, modulation of drought-resistant genes, and augmented synthesis of secondary metabolites and osmotic regulatory substances to alleviate the stress. Extreme water scarcity can lead to leaf wilting and may ultimately result in plant death. The cultivation and management of medicinal plants under stress conditions often differ from those of other crops. This is because the main goal with medicinal plants is not only to increase the yield of the above-ground parts but also to enhance the production of active ingredients such as essential oils. To elucidate these mechanisms of drought resistance in medicinal and aromatic plants, the current review provides a summary of recent literature encompassing studies on the morphology, physiology, and biochemistry of medicinal and aromatic plants under drought conditions. [ABSTRACT FROM AUTHOR]

Background and Aims: Drought stress is one of the most common global factors of abiotic stress affecting plant growth and productivity world-wide. The present study aims to assess the effects of 1, 2, and 4 weeks of drought stress on the two endemic tree species, Quercus vulcanica and Q. aucheri Methods: After applying drought stress conditions, the study determines the physiological parameters, markers of oxidative damage, and levels of antioxidant enzymes in the leaves and stems of 6-month-old oak seedlings. Results: The dry and fresh weights were observed to decrease by at least 11.44%, as well as the chlorophyll levels by at least 14%, in both the Q. vulcanica and Q. aucheri that were subjected to 1, 2, and 4 weeks of drought stress. The carotenoid, proline, and anthocyanin levels also increased in the leaves of both Quercus species; however, the amount of ascorbic acid, reduced glutathione (GSH), and total soluble protein decreased in the leaves and stems of both Quercus species. As oxidative stress markers, the levels of hydrogen peroxide (H2O2) and lipid peroxidation were seen to elevate by at least 1.21 fold under drought stress conditions. This revealed some of the alterations in the activities of antioxidant enzymes in the leaves and stems of both Q. aucheri and Q. vulcanica. Conclusion: In conclusion, this study revealed increasing drought stress to have a substantial impact on the physiological parameters and oxidative and antioxidant responses in Q. vulcanica and Q. aucheri. This will contribute to understanding how oak species respond to drought stress and their adaptation strategies. [ABSTRACT FROM AUTHOR]

The mitogen-activated protein kinase (MAPK) cascades act as crucial signaling modules that regulate plant growth and development, response to biotic/abiotic stresses, and plant immunity. MAP3Ks can be activated through MAP4K phosphorylation in non-plant systems, but this has not been reported in plants to date. Here, we identified a total of 234 putative TaMAPK family members in wheat (Triticum aestivum L.). They included 48 MAPKs, 17 MAP2Ks, 144 MAP3Ks, and 25 MAP4Ks. We conducted systematic analyses of the evolution, domain conservation, interaction networks, and expression profiles of these TaMAPK–TaMAP4K (representing TaMAPK, TaMAP2K, TaMAP3K, and TaMAP4K) kinase family members. The 234 TaMAPK–TaMAP4Ks are distributed on 21 chromosomes and one unknown linkage group (Un). Notably, 25 of these TaMAP4K family members possessed the conserved motifs of MAP4K genes, including glycine-rich motif, invariant lysine (K) motif, HRD motif, DFG motif, and signature motif. TaMAPK3 and 6, and TaMAP4K10/24 were shown to be strongly expressed not only throughout the growth and development stages but also in response to drought or heat stress. The bioinformatics analyses and qRT-PCR results suggested that wheat may activate the MAP4K10–MEKK7–MAP2K11–MAPK6 pathway to increase drought resistance in wheat, and the MAP4K10–MAP3K8–MAP2K1/11-MAPK3 pathway may be involved in plant growth. In general, our work identified members of the MAPK–MAP4K cascade in wheat and profiled their potential roles during their response to abiotic stresses and plant growth based on their expression pattern. The characterized cascades might be good candidates for future crop improvement and molecular breeding. [ABSTRACT FROM AUTHOR]

Extreme drought weather has occurred frequently in recent years, resulting in serious yield loss in tea plantations. The study of drought in tea plantations is becoming more and more intensive, but there are fewer studies on drought-resistant measures applied in actual production. Therefore, in this study, we investigated the effect of exogenous tea polyphenols on the drought resistance of tea plant by pouring 100 mg·L−1 of exogenous tea polyphenols into the root under drought. The exogenous tea polyphenols were able to promote the closure of stomata and reduce water loss from leaves under drought stress. Drought-induced malondialdehyde (MDA) accumulation in tea leaves and roots was also significantly reduced by exogenous tea polyphenols. Combined transcriptomic and metabolomic analyses showed that exogenous tea polyphenols regulated the abnormal responses of photosynthetic and energy metabolism in leaves under drought conditions and alleviated sphingolipid metabolism, arginine metabolism, and glutathione metabolism in the root system, which enhanced the drought resistance of tea seedlings. Exogenous tea polyphenols induced jasmonic acid–isoleucine (JA-ILE) accumulation in the root system, and the jasmonic acid–isoleucine synthetase gene (TEA028623), jasmonic acid ZIM structural domain proteins (JAMs) synthesis genes (novel.22237, TEA001821), and the transcription factor MYC2 (TEA014288, TEA005840) were significantly up-regulated. Meanwhile, the flavonoid metabolic flow was significantly altered in the root; for example, the content of EGCG, ECG, and EGC was significantly increased. Thus, exogenous tea polyphenols enhance the drought resistance of tea plants through multiple pathways. [ABSTRACT FROM AUTHOR]

MAPKKs, as one of the main members of the mitogen-activated protein kinase (MAPK) cascade pathway, are located in the middle of the cascade and are involved in many physiological processes of plant growth and development, as well as stress tolerance. Previous studies have found that StMAPKK5 is responsive to drought and salt stress. To further investigate the function and regulatory mechanism of StMAPKK5 in potato stress response, potato variety 'Atlantic' was subjected to drought and NaCl treatments, and the expression of the StMAPKK5 gene was detected by qRT-PCR. StMAPKK5 overexpression and RNA interference-mediated StMAPKK5 knockdown potato plants were constructed. The relative water content, superoxide dismutase (SOD), catalase (CAT), and peroxidase (POD) activities, as well as proline (Pro) and malondialdehyde (MDA) contents of plant leaves, were also assayed under drought and NaCl stress. The StMAPKK5 interacting proteins were identified and validated by yeast two-hybrid (Y2H) and bimolecular fluorescence complementation (BiFC). The results showed that the expression of StMAPKK5 was significantly up-regulated under drought and NaCl stress conditions. The StMAPKK5 protein was localized in the nucleus, cytoplasm, and cell membrane. The expression of StMAPKK5 affected the relative water content, the enzymatic activities of SOD, CAT, and POD, and the proline and MDA contents of potatoes under drought and salt stress conditions. These results suggest that StMAPKK5 plays a significant role in regulating drought and salt tolerance in potato crop. Yeast two-hybrid (Y2H) screening identified four interacting proteins: StMYB19, StZFP8, StPUB-like, and StSKIP19. BiFC confirmed the authenticity of the interactions. These findings suggest that StMAPKK5 is crucial for potato growth, development, and response to adversity. [ABSTRACT FROM AUTHOR]

Drought is a major abiotic stress that affects the productivity of sugarcane worldwide. Water deficiency during sugarcane growth will lead to a reduction in leaf pigment content, such as chlorophyll, known as chlorosis. Although changes in spectral reflectance signature were identified a conspicuous sign of chlorophyll content changes caused by drought stress, the quantitative relationships between leaf chlorophyll content and spectral reflection signatures are still poorly explored. In this study, we present our contribution in systematically establishing a model for estimating leaf chlorophyll content in drought-affected sugarcane using VIS/NIR reflectance spectroscopy and characteristic band extraction techniques. Leaves of sugarcane plants at early elongation stage under different controlled irrigation conditions were used for spectra data collection, and the chlorophyll contents were collected with standard analytical methods. Different characteristic band extraction techniques and regression models were compared and discussed to obtain a chlorophyll content estimation model with the best performance. As the quantitative results, the combination of characteristic bands extracted by the successive projection algorithm (SPA) with a Stacking regression model achieved a high chlorophyll content estimation performance (R2 = 0.9834, RMSE = 0.0544 mg/cm2) with only 4.3% of original spectral variables as inputs. This study provides a theoretical basis for accurate and non-invasive drought stress level estimation in large-scale cultivation. [ABSTRACT FROM AUTHOR]

Introduction: Maize cultivation is rapidly expanding in the world due to its high adaptability to different weather conditions, and it is an exceptional product that can be effectively used as feed and forage products to meet the ever-increasing needs of livestock. Low irrigation is an approach to increase water productivity with the view of increasing production per unit of water consumption. The research results show that water stress has a significant effect on the quantity and quality of forage. Lack of water is one of the important factors in reducing the level of corn, so this experiment was conducted in order to check the possibility of saving water consumption by using low irrigation method and choosing the best hybrid in low irrigation conditions. Materials and methods: In order to investigate the effects of low irrigation and different maize hybrids on the quantitative and qualitative traits of maize forage in the Gorgan region, an experiment was conducted in split plots arranged in a randomized complete block design with three replications in the Iraqi station of the Gorgan. Low irrigation was implemented in four levels in the main plots (100, 75, 50% and 25% of water requirement) and subplots in four levels (including hybrids SC703, SC704, ZP548 and BK50). To determine the amount of water consumption three days after each irrigation, the amount of moisture was determined by sampling the soil and immediately after reaching 40 to 60% usable moisture, irrigation was done. Irrigation was done as a drip using tapes, the distance between the nozzles was 20 cm and the amount of water output per nozzle was 2 liters per hour. Harvesting was done from the two middle lines by removing half a meter at the beginning of the row and weighed separately (leaf, stem, cob) in a separate laboratory, and their fresh weight was recorded and then placed in an oven with a temperature of 65 degrees Celsius for 72 hours, Then the dry weight was calculated. The samples of dry forage were sent to the laboratory of Forests and Ranges Organization (Tehran) and the amount of protein, fiber and other quality attributes of forage were measured by infrared spectrometry with PertenInformatic 8620. The data were analyzed using SAS 9.1.3 statistical software and the means were compared with the LSD test at the 5% probability level. Results and discussion: The results of analysis of variance showed that low irrigation effect was significant on all studied traits. Also, the effect of the studied hybrids on all the traits was significant except for insoluble fibers in acidic detergent and water-soluble carbohydrates. Also, the interaction effect of hybrid × low irrigation was significant only on forage yield (Total biomass, ear fresh weight, stem and leaf fresh weight, and total dry weight). The results of means comparison showed that the highest biomass yield was observed in the 100% water demand treatment, which was 7.2, 49, and 79.7% higher than the 75, 50, and 25% irrigation treatments, respectively. However, the highest water consumption efficiency with a significant difference compared to other levels was observed in the treatment of 75% water requirement (5.99 kg m-3). Also, with the increase of irrigation levels, the amount of crude protein, crude fiber, water-soluble carbohydrates and insoluble fibers in the neutral environment increased significantly, and among the studied hybrids, the SC703 hybrid had the highest forage yield (43692.4 kg ha-1). Conclusion: Considering the shortage and high economic value of water, the reduction in rainfall and the occurrence of successive droughts in recent years, optimum use of water can allocate more land to irrigated cultivation in addition to achieving appropriate and economic performance. The results showed that the lack of water reduces all quantitative traits. Among the studied hybrids, SC703 had the highest forage yield per unit area. On the other hand, low irrigation treatment at the level of 75% of the total water requirement is recommended to achieve the highest water consumption efficiency in Gorgan region. [ABSTRACT FROM AUTHOR]

The increasing impact of global climate change has resulted in adversity stresses, like salt and drought, gradually becoming the main factors that limit crop growth. Hemp, which contains numerous medicinal active components and multiple bioactive functions, is widely used in the agricultural, industrial, and medical fields, hence promoting the rapid development of related industries. Arbuscular mycorrhizal fungi (AMF) can establish a symbiotic relationship with 80% of vascular plants. This symbiosis promotes host plant growth, regulates plant physiology and biochemistry, facilitates secondary metabolite synthesis, and enhances resistance to abiotic stresses. However, the effects of salt stress, drought stress, and AMF interaction in hemp are not well understood. In this study, to investigate this, we performed a study where we cultured hemp that was either inoculated or uninoculated with Funneliformis mosseae and determined changes in effective colonization rate, growth, soluble substances, photosynthesis, fluorescence, ions, and secondary metabolites by cultivating hemp under different concentrations of NaCl (0 mM, 100 mM, and 200 mM) and different soil moisture content (45%, 25%, and 15%). The results showed that salt, drought stress, or salt–drought interaction stress all inhibited colonization rate after stress, plant growth, mainly due to ion toxicity and oxidative damage. Inoculation with F. mosseae effectively alleviated plant growth inhibition under 100 mM NaCl salt stress, drought stress, and salt–drought interaction stress conditions. It also improved osmoregulation, photosynthetic properties, fluorescence properties, and ion homeostasis, and promoted the accumulation of secondary metabolites. However, under 200 mM NaCl salt stress conditions, inoculation with F. mosseae negatively affected plant physiology, biochemistry, and secondary metabolite synthesis, although it did alleviate growth inhibition. The results demonstrate that there are different effects of salt–drought interaction stress versus single stress (salt or drought stress) on plant growth physiology. In addition, we provide new insights about the positive effects of AMF on host plants under such stress conditions and the effects of AMF on plants under high salt stress. [ABSTRACT FROM AUTHOR]

IN EGYPT, water scarcity is the main problem the agricultural sector faces. Salicylic acid (SA) as a plant growth regulator may help mitigate the adverse effects of deficit irrigation water on pepper plants. Sweet pepper (cv. S702 F1) plants subjected to deficit irrigation (DI40%= 60% of crop evapotranspiration, ETc) regularly during growth stages produced decreases in plant height, total chlorophyll, fruit number per plant, fruit length, fruit diameter, fruit volume, fruit yield, fruit carotenoids, and total dry matter comparing with the full irrigation (FI= 100% of ETc). However, water use efficiency (WUE), proline, free amino acids, ascorbic acid, total sugars, total soluble solids (TSS), total phenols content (TPC), total flavonoids content (TFC), and nitrate content were enhanced under deficit irrigation conditions. The results showed that under FI or DI40% with foliar application of SA at 1.0 mM was more effective than 0.5 and 1.5 mM in improving vegetative growth and yield parameters. However, FI produced the highest significant values of plant height, total chlorophyll, fruit yield, carotenoids, and total dry matter. Conversely, the pepper plant's ability to withstand DI40% was enhanced by the 1.0 mM SA treatment, which resulted in the highest accumulation of ascorbic acid, total sugars, TSS, TPC, and TFC. Moreover, the application of SA significantly increased WUE and decreased fruit nitrate content. It could be concluded that the foliar application of SA can alleviate the detrimental effects of deficit irrigation on pepper plants. [ABSTRACT FROM AUTHOR]

Introduction and Objectives: Oilseed rape is one of the most important sources of vegetable oil in the world, and its seed contains more than 40% of oil, and the meal obtained from oil extraction has more than 35% of protein, and currently it ranks third among oil plants after soybean and oil palm. in the world. The existance of environmental stresses, such as drought stress, causes a significant decrease in oilseed rape yields. Therefore, breeding for drought tolerance is very important, and creating high yielding and early maturing or drought tolerant cultivars is one of the important goals of breeders. The purpose of this study was to determine the best general and specific combiners and the amount of heterosis compared to the superior parent in spring rapeseed using line×tester analysis in two conditions of normal irrigation and drought stress. Material and Methods: Seven high-yielding rapeseed lines were crossed with five testers with a range of early maturity in the 2018-2019. The first generation hybrids along with 12 parents (47 genotypes in total) were evaluated in the randomized complete block design with three replications in two conditions of normal irrigation and terminal drought stress (irrigation cut off at the beginning of podding stage) in the 2019-2020. The studied traits included physiological maturity date, plant height, number of pods per plant, pod length, number of grains per pod, height of the first pod from the ground, 1000-grain weight, seed yield, oil percentage and oil yield. Results: The results of analysis of variance in both normal irrigation and drought stress conditions showed a significant difference between hybrids for all investigated traits, which indicated a significant diversity between genotypes. In analyzing the effect of hybrids into the relevant components, the interaction effect of line × tester was significant for all the traits under normal irrigation conditions and also under drought stress conditions except for the height of the first pod from the ground, and oil yield. The effect of parents versus hybrids was significant in normal for all traits except the number of seeds per pod under normal irrigation conditions and except for plant height, pod length and number of seeds per pod in drought stress conditions, which indicates the existence of heterosis for these traits. For the trait of physiological maturing, among the lines, line 6 showed the highest negative general combining ability under normal irrigation and drought stress conditions, and tester 5 showed the highest negative general combining ability among the testers under normal irrigation and drought stress conditions. Tester 5 was contributed in early maturing T5×L3 hybrid under drought stress conditions. L1 and L5 in both conditions and T2, and L3 and L4 in normal irrigation conditions and T1 in drought stress conditions were identified as the best general positive and significant combiner for the number of pods per plant, and hybrids T5×L1, T1× L5, T2×L4, T4×L4, T1×L7, T1×L6, T2×L7, T3×L2, T5×L7, and T4×L3 were the best specific combiner to increase the number of pods per plant in both experiment conditions. T4 was the most significant positive general combiner under normal irrigation conditions and drought stress for the 1000-grain trait. Also, regarding the positive significant specific combining ability for this trait hybrids T2×L7, T3×L7 in both conditions, and in addition hybrids T1×L7 and T5×L4 under normal irrigation conditions and hybrids T1×L6 and T3×L5 under drought stress conditions showed the highest amount. The most significant positive general combining ability in grain yield was determined to T5 and L1 and L6 in both conditions. The best significant positive specific combining ability were T2×L7 and T3×L7 in both conditions. The highest positive and significant amount of general combining ability of the amount of oil, was given to T3 and T5 and L6 in both experimet conditions, and T4 and L7 in normal irrigation conditions and L5 in drought stress conditions. T1×L6, T5×L1, T2×L5, T3×L1, T5×L3 and T4×L4 were among the best hybrids in both conditions. In normal irrigation conditions, T2×L3, T4×L3, T5×L1, T4×L6, and T5×L3 and in drought stress, T5×L1, T2×L3, T2×L4, T4×L4, T4×L3, T4×L5 and T2×L7 had the highest amount of heterosis in the positive direction for the number of pods per plant. The trait of the number of grain per pods, T2×L3, T4×L3, T5×L1, and T2×L5 under normal irrigation conditions and T5×L6, T3×L6, and T5×L3 under drought stress condition had the highest amount of heterosis. Conclusion: The estimation of traits' combining ability showed that T5 and L1 and L6 were the best general combiners to increase grain yield. T3×L7 and T2×L7 hybrids were the best specific combiner for increasing grain yield under normal irrigation and drought stress conditions. Also for the 1000-seed trait, T3×L6, T4×L1, T5×L4 and T1×L1 hybrids under normal irrigation conditions and T3×L7, T1×L6, T2×L6 and T3×L3 hybrids under drought stress conditions have the highest amount of heterosis. The number of pods per plant and the number of grain per pods under normal irrigation conditions, T2×L3, T4×L3 and T5×L1 had significant positive heterosisTherefore, their parents can be suggested for hybrid varieties production programs. [ABSTRACT FROM AUTHOR]

Introduction and Objective: Yield under stress conditions has never been an accurate criterion for selecting drought-tolerant genotypes, and the goal of preparing drought-tolerant cultivars has always been to create cultivars that relatively tolerate stress better compared to other genotypes and in the same agricultural conditions, they show less yield loss. In most studies, only the seed yield is considered for the field selection of crops, while some researchers believe that in order to be more efficient in breeding compatible and superior cultivars in arid and semi-arid regions, the indicators that are effective in identifying the stability of cultivars under drought stress conditions should be identified and used them as selection index in addition to seed yield, therefore, the relative uield status of genotypes in drought stress conditions and water conditions is a starting point for identifying and selecting genotypes for improvement in dry environments. In semi-arid regions where the distribution of rainfall is not proportional, the yield potential in stress conditions is not considered the best criterion for drought tolerance, but in addition to yield stability, the comparison of yield in stress and optimal conditions is a more suitable criterion for the reaction of genotypes to moisture stress. Due to the fact that most of the studies related to indicators in crop species and especially wheat are done only in one place and one year and finally in a specific environment and the results are generalized to all environments and the variable effects of year and place are not taken into account in the calculation of indicators. In this regard, this research was carried out to evaluate the genotypes of autumn wheat in terms of drought tolerance, to select the best drought tolerance indices and to identify drought stress tolerant cultivars in different regions of the country's cold climate. Material and Methods: In this research project, 20 genotypes under normal irrigation and water deficit conditions in the form of randomized complete block design (RCBD) with three replications in the research stations of Karaj, Mashhad, Miandoab and Arak, in the crop years of 2017-2018 and 2018-2019 were investigated. In order to investigate the drought tolerance of the genotypes, different tolerance and stress sensitivity indices were determined for the genotypes under investigation and the genotypes were grouped based on the sensitivity and tolerance to drought by each of these indices. Principal component analyzing was also used in order to summarize the data and draw a diagram based on the first two components and identify the desired indicators. Finally, biplot analysis was used to group genotypes and indices based on drought tolerance criteria. Results: Stress decreased the Yield of genotypes, but the amount of reduction was different in different genotypes. The average grain yield for all genotypes under normal irrigation conditions and drought stress at the end of the season was 7.002 and 5.215 tons per hectare, respectively, which showed that the stress conditions caused a decrease of about 25% in grain yield compared to normal irrigation conditions. The environmental and agricultural conditions of different regions and the studied years caused differences in the estimated indices so that the ranking of genotypes changed based on different indices in different years and regions therefore, it is better to carry out studies on stress tolerance indices in several places and several years so that the process of functional changes of different cultivars and genotypes is correctly determined and as a result, there is more confidence in the calculated tolerance and sensitivity indices. Genotypes G4, G2, G16 and G5 showed higher yield in both conditions. STI, MP, GMP, MSTI1, MSTI2, YI, HM, and RR had a positive and significant correlation with grain yield under normal and stress conditions, and therefore, they can be used for more favorable selection of drought tolerant genotypes. Principal component analysis showed that indicators can be grouped using the first two components. The first principal component explained 53.16% of the changes in the total data and had a positive and significant correlation with yield in normal and stress conditions as well as MP, STI, GMP, YI, MSTI1, MSTI2, HM and RDY indicators. Due to the high correlation of this component with yield under normal and stress conditions, this component was named as the yield potential component under normal and stress conditions. The second estimated component justified 42.33% of the total data changes and showed a positive and significant correlation with yield in normal conditions and SSI, TOL, ATI, SSPI and RR indices. It seems that this component is able to identify genotypes that have high yield under stress conditions. Biplot analysis showed that HM, MP, STI, MSTI1, MSTI2, GMP, RDY, YI, and SNPI indices had a positive and high correlation with performance under stress and normal conditions. So that the sharp angles between these indices showed their positive and very high correlation with each other. RDI and YSI indices had a negative correlation with performance in normal conditions and RR, SSI, TOL and SSPI indices had a negative correlation with performance in stressful conditions. Conclusion: In order to achieve varieties resistant to drought stress by using indices, in order to prevent the mutual effects of the environment in the genotype, the experiments should be carried out in many years and places so that the effects of the environment in the calculated indices can be reduced and more reasonable results can be obtained. Finally, G4, G2, G16, G5 and G17 genotypes can be selected as genotypes with high performance under normal and stress conditions. [ABSTRACT FROM AUTHOR]

Roots play a key role in withstanding wheat abiotic stress. In this work, we phenotyped seedling root morphology of two semi-dwarf bread wheat cultivars, the Chinese cv Lankaodali and the Italian cv Rebelde, under the hypothesis that these two genotypes have contrasting root traits and could be used as donors in breeding programs. Root development was compared in a semi-hydroponic screening, where full-strength (FS) vs. half-strength (HS) complete Hoagland's solution represented high and moderate nutrient availability, and a screening comparing HS solution with tap water corresponding to a condition of nutrient starvation. Genotypes were further compared in soil under full watering (100% of field capacity) vs. drought stress (50% of field capacity). Lankaodali outperformed Rebelde by producing 50% more leaf mass and 70% more root mass in FS solution, 125% more leaf mass and 106% more root mass in HS solution, and 65% more leaf mass and 36% more root mass under nutrient starvation. This cv also showed a positive correlation between leaf mass and root length and mass (between r = 0.82–0.9 and r = 0.83–0.87, respectively, p < 0.05). In the soil screening experiment, Lankaodali produced more biomass than Rebelde regardless of water availability, 48% more leaf mass, 32% more root mass, and 31% more absolute rhizosheath mass (average across water availability treatments). Lankaodali proved to be more responsive than Rebelde to both water and nutrient availability. High values of broad-sense heritability—ranging between 0.80 for root mass and 0.90 for length in a hydroponic screen and 0.85 for rhizosheath size in soil—indicate that these traits could be useful for breeding. [ABSTRACT FROM AUTHOR]

Drought is a major obstacle to the development of naked oat industry. This work investigated mechanisms by which exogenous Streptomyces albidoflavus T4 and Streptomyces rochei D74 improved drought tolerance in naked oat (Avena nuda) seedlings. Results showed that in the seed germination experiment, germination rate, radicle and hypocotyl length of naked oat seeds treated with the fermentation filtrate of T4 or D74 under PEG induced drought stress increased significantly. In the hydroponic experiment, the shoot and root dry weights of oat seedlings increased significantly when treated with the T4 or D74 fermentation filtrate under the 15% PEG induced drought stress (S15). Simultaneously, the T4 treatment also significantly increased the surface area, volume, the number of tips and the root activity of oat seedlings. Both T4 and D74 treatments elicited significant increases in proline and soluble sugar contents, as well as the catalase and peroxidase activities in oat seedlings. The results of comprehensive drought resistance capacity (CDRC) calculation of oat plants showed that the drought resistance of oat seedlings under the T4 treatment was better than that under the D74 treatment, and the effect was better under higher drought stress (S15). Findings of this study may provide a novel and effective approach for enhancing plant defenses against drought stress. [ABSTRACT FROM AUTHOR]

The effect of drought stress on leaf physiology was studied in 10-month-old plants of Sindora siamensis. Plants were either placed in an open greenhouse (unhardening; UH) or in an open field (open field hardening; H) for 45 days. Both the UH and H plants stopped receiving water (D) until the initial drought injury and then rewatered (R) until complete recovery. Results showed necrosis in the leaves of UH + D, while H + D showed wilting at Day 7 after drought. A greater degree of necrosis was found in UH + D + R but made complete recovery in H + D + R at Day 4 after rewatering. Drought stress resulted in decreased leaf area in H, and reduced leaf and stem water status, PSII efficiency, net photosynthetic rate, stomatal conductance and transpiration rate in both UH and H. It also resulted in an increase in water use efficiency in both UH and H. Electrolyte leakage and malondialdehyde contents in UH were markedly increased due to drought stress. These results suggest that unhardened young plants of Sindora exposed to drought exhibited enhanced stomata behaviour by minimising open stomata and transpiration, resulting in high efficiency of water usage. However, there was still membrane damage from lipid peroxidation, which caused necrosis. Open field hardened plants exposed to drought demonstrated reduced open stomata and transpiration, thereby preserving leaf and soil water status and enhancing water use efficiency. This may be a reduction in lipid peroxidation though an oxidative scavenging mechanism that causes a slight alteration in membrane stability and a slight necrosis. [ABSTRACT FROM AUTHOR]

Pugionium cornutum is an annual or biennial xerophyte distributed in arid regions, with drought resistance properties. While previous studies have predominantly focused on the physiological changes of P. cornutum, the understanding of its metabolite variations remains limited. In this study, untargeted metabolomic technology was performed to analyse the change of metabolites in the roots of P. cornutum seedlings under drought stress. Our findings revealed that compared to the R1, the root water potential and the number of lateral roots increased, while the length of the tap root and fresh weight increased first and then decreased. In the R1–R2, a total of 45 differential metabolites (DMs) were identified, whereas in the R1–R3 82 DMs were observed. Subsequently, KEGG analysis revealed a significant enrichment of microbial metabolism in diverse environments and aminobenzoate degradation in the R1–R2, and phenylpropanoid biosynthesis, ubiquinone, and other terpenoid-quinone biosynthesis and isoquinoline alkaloid biosynthesis were significantly enriched in the R1–R3. The upregulation DMs, including L-arginosuccinate, L-tyrosine, p-coumarate, caffeate, ferulate, vanillin, coniferin, 5-aminopentanoate, 2-methylmaleate and 2-furoate in P. cornutum seedlings may play a crucial role in enhancing root growth and improving drought resistance. These findings provide a basis for future investigations into the underlying mechanisms of drought resistance in P. cornutum. [ABSTRACT FROM AUTHOR]

The soybean seeds were subjected to priming treatments using varying concentration of silicon dioxide (SiO2) nanoparticles in conjunction with water. The study assessed the effects of SiO2 nanoparticles on seed germination, seedling vigour, biochemical parameters, and osmotic adjustments in seeds that were primed with SiO2 nanoparticles, hydroprimed, and control seeds. These evaluations were conducted under conditions of moisture stress generated by PEG 6000 at -4 and -5 bars, as well as under non-drought stress condition. The findings of the study indicate that lower concentrations of SiO2 nanoparticles (NPs) had a positive impact on seed physiological and biochemical parameters. Conversely, higher concentrations of SiO2 NPs during priming resulted in reduced seed germination and antioxidant activity, both in drought stress and non stress conditions. Soybean seeds that were treated with silicon dioxide nanoparticles (SiO2 NPs) at a concentration of 500 mg/liter exhibited the highest rate of germination, germination percentage, and seedling vigour in non drought stress and in drought stress at -4 and -5 bars. The application of silicon dioxide nanoparticles (SiO2 NPs) at a concentration of 500 mg/liter during seed priming resulted in an enhancement in antioxidant enzyme activities, including catalase, peroxidase, and superoxide dismutase. Additionally, the seedlings exhibited increased levels of proline and relative water content, while experiencing a reduction in electrolyte leakage from the leaves under conditions of moisture stress generated by polyethylene glycol (PEG). [ABSTRACT FROM AUTHOR]