Drought Stress Research Articles

Exploring the usefulness of drought tolerance indices in screening of maize inter-racial derivatives

Abstract Among all the abiotic factors affecting maize yield, drought stress is the most destructive one. Since drought tolerance is a complicated trait that is difficult to quantify, screening for stress involves measuring the effects of stress on several traits, most notably plant yield. Selection using the drought tolerance indices is an easy way to identify the stable and tolerant genotypes based on yield performances alone. The current study aims to identify suitable maize hybrids with high drought tolerance. A total of 30 maize-teosinte hybrids and 3 checks were raised under optimal and water-stressed environments and were screened using twelve different drought tolerance indices. It was observed that the inter-racial hybrids viz., G24, G27, and G29 were better than the drought tolerant Zea mays ssp. mays check C3 for yield and most of the indices. The indices STI, TOL, GMP, MP, YI, DI, SSPI, K1STI, and K2STI were observed to be significantly correlated with yield under stress and optimal environments. Based on the yield both environments, the genotypes were classified under four groups, with Group A consisting of genotypes with high yields under both environments. The indices Stress Tolerance Index (STI), Geometric Mean Productivity (GMP), Yield Index (YI), and Modified Stress Tolerance Index (K2STI)were identified for their ability to discriminate Group A from the other genotypes and these indices could be utilized to screen for drought tolerance with high yield.Component Analysis revealed two principal components contributing up to 98.15 percent of the cumulative variation. The PCA biplot identified the hybrids viz., G24, G27, G14, G19, and G25 as tolerant ones. Based on the index scores, the hybrids viz., G27, G29, G17, G20,and G24were identified as the top-ranking genotypes, with high and more stable yields under both stress and optimal environments. Keywords: Drought index, maize, 3D plot, inter-racial hybrids, teosinte

Unveiling the Hidden Responses: Metagenomic Insights into Dwarf Bamboo (Fargesia denudata) Rhizosphere under Drought and Nitrogen Challenges.

Dwarf bamboo (Fargesia denudata) is a crucial food source for the giant pandas. With its shallow root system and rapid growth, dwarf bamboo is highly sensitive to drought stress and nitrogen deposition, both major concerns of global climate change affecting plant growth and rhizosphere environments. However, few reports address the response mechanisms of the dwarf bamboo rhizosphere environment to these two factors. Therefore, this study investigated the effects of drought stress and nitrogen deposition on the physicochemical properties and microbial community composition of the arrow bamboo rhizosphere soil, using metagenomic sequencing to analyze functional genes involved in carbon and nitrogen cycles. Both drought stress and nitrogen deposition significantly altered the soil nutrient content, but their combination had no significant impact on these indicators. Nitrogen deposition increased the relative abundance of the microbial functional gene nrfA, while decreasing the abundances of nirK, nosZ, norB, and nifH. Drought stress inhibited the functional genes of key microbial enzymes involved in starch and sucrose metabolism, but promoted those involved in galactose metabolism, inositol phosphate metabolism, and hemicellulose degradation. NO3--N showed the highest correlation with N-cycling functional genes (p < 0.01). Total C and total N had the greatest impact on the relative abundance of key enzyme functional genes involved in carbon degradation. This research provides theoretical and technical references for the sustainable management and conservation of dwarf bamboo forests in giant panda habitats under global climate change.

Response of cool‐season turfgrass monocultures and two‐way mixtures to sequential acute drought periods

AbstractTurfgrass seeds are often sold as mixtures of several species to increase the probability of positive responses toward abiotic and biotic stresses, a response to drought being one of these. Several species of turfgrass are already thought to be better suited for drought, such as hard fescue (Festuca brevipila Tracey) and tall fescue [Schedonorus arundinaceus (Schreb.) Dumort]. However, little is known about the benefit of these species in mixtures with drought‐intolerant and/or drought‐avoiding species during drought. Understanding species mixture composition during establishment, before and after drought stress periods, could help develop more resilient mixtures for this stress condition. We compared monocultures and mixtures of hard fescue, Kentucky bluegrass (Poa pratensis L.), and perennial ryegrass (Lolium perenne L.) during sequential short drought and recovery periods in controlled conditions. We observed that the composition of most mixtures remained similar during drought and recovery periods; however, perennial ryegrass was often less prevalent after drought stress. We found that hard fescue monocultures had better green leaf coverage than Kentucky bluegrass and perennial ryegrass during drought stress. However, the presence of hard fescue in mixtures was not an indicator of greater drought tolerance, and variable fluorescence to maximal fluorescence data indicated that hard fescue was just as physiologically stressed as perennial ryegrass and Kentucky bluegrass during the drought periods. These results indicate that while hard fescue seems visually drought tolerant, it is still physiologically stressed and improved drought tolerance could be achieved through focusing on physiological indicators of stress in this species rather than visual indicators.

Genome-wide investigation of WRKY gene family in Lavandula angustifolia and potential role of LaWRKY57 and LaWRKY75 in the regulation of terpenoid biosynthesis.

The WRKY transcription factors are integral to plant biology, serving essential functions in growth, development, stress responses, and the control of secondary metabolism. Through the use of bioinformatics techniques, this research has effectively characterized 207 members of the WRKY family (LaWRKY) present in the entire genome of Lavandula angustifolia. Phylogenetic analysis classified LaWRKYs into three distinct categories based on conserved domains. Collinearity analysis revealed tandem repeats, segmental duplications, and whole genome duplications in LaWRKYs, especially for segmental duplication playing a significant role in gene family expansion. LaWRKYs displayed distinct tissue-specific expression profiles across six different tissues of L. angustifolia. Particularly noteworthy were 12 genes exhibiting high expression in flower buds and calyx, the primary sites of volatile terpenoid production, indicating their potential role in terpenoid biosynthesis in L. angustifolia. RT-qPCR analysis revealed a notable increase in the expression levels of most examined LaWRKY genes in flower buds in response to both intense light and low-temperature conditions, whereas the majority of these genes in leaves were primarily induced by drought stress. However, all genes exhibited downregulation following GA treatment in both flower buds and leaves. Overexpression of LaWRKY57 (La13G01665) and LaWRKY75 (La16G00030) in tobacco led to a reduction in the density of glandular trichomes on leaf surfaces, resulting in changes to the volatile terpenoid composition in the leaves. Specifically, the content of Neophytadiene was significantly elevated compared to wild-type tobacco, while compounds such as eucalyptol, cis-3-Hexenyl iso-butyrate, and D-Limonene were produced, which were absent in the wild type. These findings provide a valuable reference for future investigations into the biological functions of the WRKY gene family in L. angustifolia.

Genetic Analysis for Seed Yield and Yield‐Related Traits in Tepary Bean (Phaseolus acutifolius A. Gray) Under Drought‐Stress and Non‐stress Conditions

ABSTRACTTepary bean (Phaseolus acutifolius A. Gray) is an under‐utilized genetic resource with significant potential for food security and stress tolerance breeding. Expanding its cultivation in southern Africa requires high‐yielding, locally adapted and drought‐tolerant varieties. This study determined the combining ability and genetic components for seed yield and related traits in tepary bean genotypes under non‐stress (NS) and drought‐stress (DS) conditions. Seven parents were selected through rigorous phenotyping and crossed using a half‐diallel design. The 7 parents and 21 F2 progenies were evaluated in 2021/2022 season at Kasinthula and Bunda sites in Malawi under NS and DS conditions using a 4 × 7 lattice design with three replications. The specific combining ability (SCA) × location interaction effect was significant (p &lt; 0.05) for DTF, NPP, and SY, suggesting that the genetic effects of crosses were influenced by the test locations. General combining ability (GCA) and SCA mean squares were significant for the number of seeds per pod (NSP) and SY under DS conditions, indicating both additive and non‐additive gene effects. Baker's ratio (BR) &gt; 0.50 for NPP and NSP under DS conditions suggested a preponderance of additive gene effects. G40145, G40148 and G40150 parental lines were good combiners for NPP and SY. The F2 families from crosses such as Zimbabwe landrace/G40138, Zimbabwe landrace/G40150, G40059/G40145, G40059/G40148, G40138/G40150 and G40145/G40150 were identified as best specific combiners, with enhanced SY of 1.67 t/ha under DS conditions. The study recommends advancing high‐performing early‐generation families for selection across representative environments to facilitate variety release and commercialization.

Contrasted agronomical and physiological responses of five Coffea arabica genotypes under soil water deficit in field conditions.

Breeding programs have developed high-yielding Coffea arabica F1-hybrids as an adaptation against adverse conditions associated with climate change. However, theresponse to drought of coffee F1 hybrids has seldom been assessed. A trial was established with five C. arabica genotypes (2 pure lines: Catimor and Marsellesa and 3 F1 hybrids: Starmaya, Centroamericano and Mundo Maya) planted under the leguminous tree species Leuceana leucocephala. Coffee growth, yield and physiological responses were assessed under a rain-fed (control: CON) and a rainfall reduction treatment (RR) for 2 years. The RR treatment created a long-term rainfall deficit in a region with suboptimal temperature similar to those predicted by climate change scenarios. Moreover, the RR treatment reduced soil water content by 14% over 2 successive years of production and increased hydric stress of the three F1-hybrids (leaf water potentials averaged -0.8 MPa under RR compared with -0.4 MPa under CON). Under RR, coffee yields were reduced from 16 to 75% compared to CON. Mundo Maya F1 hybrid was the sole high-yielding genotype apable of sustaining its yield under RR conditions. Our results suggested that its significant increase in fine root density (CON = 300 and RR = 910 root.m-2) and its maintenance of photosynthetic rate (2.5 - 3.5 mmol CO2 m-2 s-1) at high evaporative demand might explain why this genotype maintained high yield under RR condition. This work highlights a possible drought tolerance mechanism in fruit bearing adult coffee trees where the plant fine root number increases to intake more water in order to preserve turgor and sustainphotosynthesis at high ETo and therefore conserves high yield in dry conditions.

Evaluating Ecological Drought Vulnerability from Ecosystem Service Value Perspectives in North China

Existing studies on the vulnerability assessment of ecological drought often focus on analyzing vegetation phenotypic characteristics, overlooking the impact of drought on ecosystem services. This study proposes an ecosystem vulnerability assessment method under ecological drought stress from the perspective of ecosystem service value (ESV), considering the characteristics and interactions of hazard-causing factors and hazard-bearing bodies. The spatiotemporal evolution of ecological drought, the spatial characteristics of ecosystem vulnerability, and the vulnerability characteristics of different ecosystem types in the North China region from 1991 to 2021 were evaluated. The results showed that: (1) ecological drought exhibited a trend of intensification followed by alleviation, with the most severe droughts occurring between 2002 and 2011, affecting up to 64.3% of the region; (2) ESV was mainly influenced by vegetation cover and precipitation gradients, displaying a spatial pattern of high values in the southeast and low values in the northwest, with total ESV averaging CNY 18.23 trillion; (3) grasslands exhibited higher sensitivity to drought compared to forests, and the sensitivity was higher in summer and autumn than in winter and spring. This method assessed the vulnerability of ecological drought from the perspective of ecosystem services, providing a new approach for a more comprehensive understanding of the impact of drought on ecosystem service functions.

Arbuscular Mycorrhizal Fungi Enhance Tolerance to Drought Stress by Altering the Physiological and Biochemical Characteristics of Sugar Beet

Arbuscular Mycorrhizal Fungi Enhance Tolerance to Drought Stress by Altering the Physiological and Biochemical Characteristics of Sugar Beet

TaCDPK1-5A positively regulates drought response through modulating osmotic stress responsive-associated processes in wheat (Triticum aestivum).

Wheat TaCDPK1-5A plays critical roles in mediating drought tolerance through regulating osmotic stress-associated physiological processes. Calcium (Ca2+) acts as an essential second messenger in plant signaling pathways and impacts plant abiotic stress responses. This study reported the function of TaCDPK1-5A, a calcium-dependent protein kinase (CDPK) gene in T. aestivum, in mediating drought tolerance. TaCDPK1-5A sensitively responded to drought and exogenous abscisic acid (ABA) signaling, displaying induced transcripts in plants under drought and ABA treatments. Yeast two-hybrid and co-immunoprecipitation assays revealed that TaCDPK1-5A interacts with the mitogen-activated protein kinase TaMAPK4-7D whereas the latter with ABF transcription factor TaABF1-3A, suggesting that TaCDPK1-5A constitutes a signaling module with above partners to transduce signals initiated by drought/ABA stressors. Overexpression of TaCDPK1-5A, TaMAPK4-7D and TaABF1-3A enhanced plant drought adaptation by modulating the osmotic stress-related physiological indices, including increased osmolyte contents, enlarged root morphology, and promoted stomata closure. Yeast one-hybrid assays indicated the binding ability of TaABF1-3A with promoters of TaP5CS1-1B, TaPIN3-5A, and TaSLAC1-3-2A, the genes encoding P5CS enzyme, PIN-FORMED protein, and slow anion channel, respectively. ChIP-PCR and transcriptional activation assays confirmed that TaABF1-3A regulates these genes at transcriptional level. Moreover, transgene analysis indicated that these stress-responsive genes positively regulated proline biosynthesis (TaP5CS1-1B), root morphology (TaPIN3-5A), and stomata closing (TaSLAC1-3-2A) upon drought signaling. Positive correlations were observed between yield and the transcripts of TaCDPK1-5A signaling partners in wheat cultivars under drought condition, with haplotype TaCDPK1-5A-Hap1 contributing to improved drought tolerance. Our study concluded that TaCDPK1-5A positively regulates drought adaptation and is a valuable target for molecular breeding the drought-tolerant cultivars in T. aestivum.

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

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

Potato E3 Ubiquitin Ligase StXERICO1 Positively Regulates Drought Resistance by Enhancing ABA Accumulation in Potato and Tobacco and Interacts with the miRNA Novel-miR1730-3p and Proteins StUBC and StTLP

Potato (Solanum tuberosum L.) is sensitive to drought, which severely impacts tuber yield and quality. In this study, we characterized a XERICO gene, encoding a RING-H2 type E3 ubiquitin ligase, StXERICO1, from a diploid potato, investigated its role in enhancing drought resistance and ABA accumulation, and identified its interaction with the miRNA novel-miR1730-3p, as well as its protein interactions with StUBC and StTLP. StXERICO1, with a complete Open Reading Frame (ORF) of 459 bp encoding 152 amino acids, was highly responsive to drought, ABA treatment, and abiotic stresses in potato plants. Overexpression of the StXERICO1 significantly enhanced drought resistance and ABA accumulation in transgenic potato and tobacco plants and exhibited greater sensitivity to ABA treatment, which was associated with the upregulation of expression of ABA biosynthetic genes NCED and CYP707A. Furthermore, our results revealed that StXERICO1 and its encoding protein interacted with miRNAs and other proteins. 5′ RLM-RACE (cDNA terminal rapid amplification) experiment showed that the miRNA novel-miR1730-3p targets 5′ UTR region of the StXERICO1 gene. Dual luciferase assay and virus-based miRNA silencing experiment showed that the novel-miR1730-3p negatively regulates StXERICO1 expression. Moreover, yeast two-hybrid assay indicated that StXERICO1 interacts with StUBC (an E2 ubiquitin ligase) and StTLP (a Tubby-like protein), suggesting that StXERICO1 might function on ABA homeostasis at the post-translational level. These findings elucidate the molecular mechanisms by which StXERICO1, a RING-H2 type E3 ubiquitin ligase, enhances drought resistance through increased ABA accumulation, how its expression is regulated by miRNA, and how it exerts its function through interactions with other proteins. The results also provide a potential candidate gene for subsequent precision molecular breeding aimed at improving crop drought resistance.

Genotype-specific responses to in vitro drought stress in myrtle (Myrtus communis L.): integrating machine learning techniques.

Myrtle (Myrtus communis L.), native to the Mediterranean region of Türkiye, is a valuable plant with applications in traditional medicine, pharmaceuticals, and culinary practices. Understanding how myrtle responds to water stress is essential for sustainable cultivation as climate change exacerbates drought conditions. This study investigated the performance of selected myrtle genotypes under in vitro drought stress by employing tissue culture techniques, rooting trials, and acclimatization processes. Genotypes were tested under varying polyethylene glycol (PEG) concentrations (1%, 2%, 4%, and 6%). Machine learning (ML) algorithms, including Gaussian process (GP), support vector machine (SVM), Random Forest (RF), and Extreme Gradient Boosting (XGBoost), were utilized to model and predict micropropagation and rooting efficiency. The research revealed a genotype-dependent response to drought stress. Black-fruited genotypes exhibited higher micropropagation rates compared to white-fruited ones under stress conditions. The application of ML models successfully predicted micropropagation and rooting efficiency, providing insights into genotype performance. The findings suggest that selecting drought-tolerant genotypes is crucial for enhancing myrtle cultivation. The results underscore the importance of genotype selection and optimization of cultivation practices to address climate change impacts. Future research should explore the molecular mechanisms of stress responses to refine breeding strategies and improve resilience in myrtle and similar economically important crops.

Effects of Salicylic Acid on Physiological Responses of Pepper Plants Pre-Subjected to Drought under Rehydration Conditions.

Capsicum annuum L. has worldwide distribution, but drought has limited its production. There is a lack of research to better understand how this species copes with drought stress, whether it is reversible, and the effects of mitigating agents such as salicylic acid (SA). Therefore, this study aimed to understand the mechanisms of action of SA and rehydration on the physiology of pepper plants grown under drought conditions. The factorial scheme adopted was 3 × 4, with three water regimes (irrigation, drought, and rehydration) and four SA concentrations, namely: 0 (control), 0.5, 1, and 1.5 mM. This study evaluated leaf water percentage, water potential of shoots, chlorophylls (a and b), carotenoids, stomatal conductance, chlorophyll a fluorescence, and hydrogen peroxide (H2O2) concentration at different times of day, water conditions (irrigation, drought, and rehydration), and SA applications (without the addition of a regulator (0) and with the addition of SA at concentrations equal to 0.5, 1, and 1.5 mM). In general, exogenous SA application increased stomatal conductance (gs) responses and modified the fluorescence parameters (ΦPSII, qP, ETR, NPQ, D, and E) of sweet pepper plants subjected to drought followed by rehydration. It was found that the use of SA, especially at concentrations of 1 mM in combination with rehydration, modulates gs, which is reflected in a higher electron transport rate. This, along with the production of photosynthetic pigments, suggests that H2O2 did not cause membrane damage, thereby mitigating the water deficit in pepper plants. Plants under drought conditions and rehydration with foliar SA application at concentrations of 1 mM demonstrated protection against damage resulting from water stress. Focusing on sustainable productivity, foliar SA application of 1 mM could be recommended as a technique to overcome the adverse effects of water stress on pepper plants cultivated in arid and semi-arid regions.

Harnessing the potential of copper-based nanoparticles in mitigating abiotic and biotic stresses in crops.

The demand for crops production continues to intensify with the rapid increase in population. Agricultural crops continue to encounter abiotic and biotic stresses, which can substantially hamper their productivity. Numerous strategies have been focused to tackle the abiotic and biotic stress factors in various plants. Nanotechnology has displayed great potential to minimize the phytotoxic impacts of these environmental constraints. Copper (Cu)-based nanoparticles (NPs) have displayed beneficial effects on plant growth and stress tolerance. Cu-based NPs alone or in combination with plant growth hormones or microorganisms have been documented to induce plant tolerance and mitigate abiotic or biotic stresses in different plants. In this review, we have comprehensively discussed the uptake and translocation of Cu-based NPs in plants, and beneficial roles in improving the plant growth and development at various growth stages. Moreover, we have discussed how Cu-based NPs mechanistically modulate the physiological, biochemical, metabolic, cellular, and metabolic functions to enhance plant tolerance against both biotic (viruses, bacterial and fungal diseases, etc.) and abiotic stresses (heavy metals or metalloids, salt, and drought stress, etc.). We elucidated recent advancements, knowledge gaps, and recommendations for future research. This review would help plant and soil scientists to adapt Cu-based novel strategies such as nanofertilizers and nanopesticides to detoxify the abiotic or biotic stresses. These outcomes may contribute to the promotion of healthy food production and food security, thus providing new avenues for sustainable agriculture production.

Chitosan Priming Ameliorates Protein and Amino Acid Profiles in Red Kidney Bean under Drought Stress

Chitosan Priming Ameliorates Protein and Amino Acid Profiles in Red Kidney Bean under Drought Stress

Impact of Plant Growth Promoting Endophytic Bacterial Consortia on Biochemical Parameters of Maize under Moisture Stress Conditions in In vitro

Mitigation strategies based on plant–microbe interactions to increase the performance of plants under water-deficit conditions are well documented. However, little is known about a suitable consortium of bacterial inoculants and underlying physiological and enzymatic events to improve drought tolerance in maize. This study aimed to investigate the synergistic interactions among plant growth-promoting bacteria to alleviate drought-induced damages in maize. In pot culture experiment endophytic bacterial consortium inoculated treatments imposed with moisture stress (75% water holding capacity) with full dose (T9) and 75% recommended dose of fertilizers (T8) were found to excel in many plant biochemical properties when compared to un-inoculated control. For instance chlorophyll stability index T9 (138.67%) T8 (133.33%), relative water content T9 (95.20%), The N, P and K uptake was found significantly higher in T9 with 13.98 g plant-1, 3.38 g plant-1 and 17.29 g plant-1 respectively. Thus, the current research advocates the use of endophytic microbial consortium to mitigate moisture stress and to improve plant biochemical properties which ultimately enhances the plant health and yield.

Reexploring Rice Germplasm: Enlightening a New Path Towards Abiotic Stress-resilient Crop

Oryza sativa, the commonly cultivated rice, is one of the most important crops for human consumption, but is also a crop whose production system is increasingly threatened by the current climate changes. Due to its intensive water requirement rice faces a lot of challenges due to abiotic stresses like drought, heat stress, salinity, flooding etc. Drought is the major abiotic stress to rice grain production under unpredictable and changing environmental conditions. Traits supporting drought resistance are limited in cultivars, while wild rice species like O. glaberrima, O. longistaminata, O. rufipogon and O. meridonalis represent an important reservoir of useful genes for this trait which can be exploited to develop varieties tolerant to drought. Similarly O. australiensis, O. coarctata and O. rufipogon serve as an important sources for salinity-tolerant genes. O. rufipogon, O. meridonalis, O. australiensis comprise a collection of accessions that are reservoirs for heat-tolerant genes. Although many efforts have resulted in breeding rice varieties that are relatively tolerant to their local environments; climate change and population growth are expected to soon require a new, rapid generation of stress-tolerant rice germplasm. Diversity studies suggest that the current diversity within rice varieties may not be sufficient for generation of highly resistant or tolerant varieties for the unfavorable growing conditions. All the efforts to design an ideotype to increase production and productivity has been attempted previously, rice self-sufficiency can be attained only if high production and productivity is coupled with a high degree of tolerance and resistance to biotic and abiotic stress factors. Since it has been found that wild rice relatives serve as a hub for many desirable genes conferring tolerance or resistance to specific stresses, the present article is focused on provide an overview of different wild ancestors of rice which can be exploited to identify suitable donors for gene of interest, their ecological and genomic diversity and the variation observed in wild Oryza species for different stress tolerance traits. Such identified traits can be incorporated in modern day breeding programmes through marker assisted breeding to develop cultivable varieties with desired tolerance to abiotic stresses or transfer such traits to modern day cultivars through backcross breeding.

A WUSCHEL-related homeobox transcription factor, SlWOX4, negatively regulates drought tolerance in tomato.

CRISPR/Cas9-mediated knockout of SlWOX4 gene in tomato enhances tolerance to drought stress. Drought stress is one of the major abiotic factors that seriously affects plant growth and crop yield. WUSCHEL-related homeobox (WOX) transcription factors are involved in plant growth, development and stress response. However, little is known about the role of WOX genes in drought tolerance in tomato. Here, SlWOX4, a member of the WOX family in tomato, was functionally characterized in mediating drought tolerance. SlWOX4 was homologous to Nicotiana tabacum NtWOX4 with a conserved HD domain, and was localized in the nucleus. SlWOX4 was significantly down-regulated by drought and abscisic acid (ABA) treatments. The loss-of-functionmutations of SlWOX4 produced using the CRISPR-Cas9 system in tomato improved drought tolerance by reducing water loss rate and enhancing stomatal closure. In addition, the wox4 lines exhibited reduced accumulation of reactive oxygen species (ROS) and malondialdehyde (MDA), increased antioxidant enzyme activity, proline contents and ABA contents under drought stress. Moreover, gene editing of SlWOX4 in tomato enhanced drought tolerance by regulating the expression of genes encoding antioxidants and ABA signaling molecules. In summary, SlWOX4 gene might negatively regulate drought stress tolerance in tomato and has great potential as a drought-resistant crop-breeding target genes.

Rice homolog of Arabidopsis Xylem NAC domain 1 (OsXND1), a NAC transcription factor regulates drought stress responsive root system architecture in indica rice.

Rice yield is greatly constrained by drought stress. In Arabidopsis, XYLEM NAC DOMAIN 1 (XND1) gene regulates the xylem formation, efficiency of water transport, and the delicate equilibrium between drought tolerance and resistance to pathogens. However, diversity and the role of rice homologs of OsXND1 is not reported so far. This study hypothesized that the rice homolog of OsXND1 also regulates drought stress tolerance through modulation of root architecture. Initially, phylogenetic analysis identified two OsXND1 homologs (Os02g0555300 and Os04g0437000) in rice. Further, 14 haplotypes were identified in the OsXND1 of which Hap1 and Hap3 were major haplotypes. The association analysis of OsXND1 with 16 different traits, including 10 root traits, showed three SNPs (Chr02:20972728-Promoter variant; Chr02:20972791-5' UTR variant, and Chr02:20973745-3' UTR variant) were significantly associated with root area, root surface area, total root length, and convex hull area only under drought stress in indica rice. Besides, the superior haplotype of OsXND1 increased the root area, root surface area, total root length, and convex hull area by 46%, 40%, 38%, and 42%, respectively, under drought stress conditions. Therefore, the identified superior haplotype of OsXND1 can be utilized in haplotype breeding programs for the improvement of drought tolerance in rice.

Screening of Ecotypes and Construction of Evaluation System for Drought Resistance during Seed Germination in Kudouzi (Sophora alopecuroides)

Drought is a major limiting factor in the cultivation of Sophora alopecuroides in China’s arid and semi-arid regions. This study aimed to identify drought-resistant S. alopecuroides ecotypes and explore key drought tolerance indicators during germination by simulating drought conditions with a 10% PEG-6000 solution, using pure water as a control. Determination of seven germination indicators for S. alopecuroides, including germination rate (GR), germination energy (GE), germination index (GI), vigor index (VI), promptness index (PI), fresh weight (FW), and dry weight (DW), was conducted. Principal component analysis (PCA), membership function, cluster analysis, and linear regression were employed to comprehensively evaluate the drought resistance of thirty-five S. alopecuroides ecotypes. The results showed that drought stress caused reductions in six of the seven indicators across all ecotypes, except for DW, compared to the control. Correlation analysis revealed varying relationships among the indicators, with most showing significant or highly significant correlations. PCA reduced the seven indicators to two independent comprehensive factors, with a cumulative contribution rate of 83.99%. Based on the D-value and cluster analysis, the thirty-five ecotypes were ranked for drought resistance and classified into four categories. The top five drought-tolerant genotypes during the germination stage were identified as Yutian, Alar, Jinghe, Baoding, and Guyuan. Moreover, the stepwise regression model was established and demonstrated that GR, GE, PI, FW, and DW are key indicators for screening and identifying drought-resistant S. alopecuroides ecotypes. This study offers a comprehensive and reliable method for evaluating drought resistance in S. alopecuroides ecotypes and provides a reference for selecting ecotypes for artificial cultivation in Northwestern China.