Drought Susceptible Genotypes Research Articles

Early Detection of Drought Stress in Durum Wheat Using Hyperspectral Imaging and Photosystem Sensing

Wheat, being the third largest U.S. crop and the principal food grain, faces significant risks from climate extremes such as drought. This necessitates identifying and developing methods for early water-stress detection to prevent yield loss and improve water-use efficiency. This study investigates the potential of hyperspectral imaging to detect the early stages of drought stress in wheat. The goal is to utilize this technology as a tool for screening and selecting drought-tolerant wheat genotypes in breeding programs. Additionally, this research aims to systematically evaluate the effectiveness of various existing sensors and methods for detecting early stages of water stress. The experiment was conducted in a durum wheat experimental field trial in Maricopa, Arizona, in the spring of 2019 and included well-watered and water-limited treatments of a panel of 224 replicated durum wheat genotypes. Spectral indices derived from hyperspectral imagery were compared against other plant-level indicators of water stress such as Photosystem II (PSII) and relative water content (RWC) data derived from proximal sensors. Our findings showed a 12% drop in photosynthetic activity in the most affected genotypes when compared to the least affected. The Leaf Water Vegetation Index 1 (LWVI1) highlighted differences between drought-resistant and drought-susceptible genotypes. Drought-resistant genotypes retained 43.36% more water in leaves under well-watered conditions compared to water-limited conditions, while drought-susceptible genotypes retained only 15.69% more. The LWVI1 and LWVI2 indices, aligned with the RWC measurements, revealed a strong inverse correlation in the susceptible genotypes, underscoring their heightened sensitivity to water stress in earlier stages. Several genotypes previously classified based on their drought resistance showed spectral indices deviating from expectations. Results from this research can aid farmers in improving crop yields by informing early management practices. Moreover, this research offers wheat breeders insights into the selection of drought-tolerant genotypes, a requirement that is becoming increasingly important as weather patterns continue to change.

Transcriptome analysis provides insights into the stress response in cultivated peanut (Arachis hypogaea L.) subjected to drought-stress.

Peanut (Arachis hypogaea L.) is one of the valuable oilseed crops grown in drought-prone areas worldwide. Drought severely limits peanut production and productivity significantly. In order to decipher the drought tolerance mechanism in peanut under drought stress, RNA sequencing was performed in TAG - 24 (drought tolerant genotype) and JL-24 (drought susceptible genotype). Approximately 51million raw reads were generated from four different libraries of two genotypes subjected to drought stress exerted by 20% PEG 6000 stress and control conditions, of which ~ 41million (80.87%) filtered reads were mapped to the Arachis hypogaea L. reference genome. The transcriptome analysis detected 1,629 differentially expressed genes (DEGs), 186 genes encoding transcription factors (TFs) and 30,199 SSR among the identified DEGs. Among the differentially expressed TF encoding genes, the highest number of genes were WRKY followed by bZIP, C2H2, and MYB during drought stress. The comparative analysis between the two genotypes revealed that TAG-24 exhibits activation of certain key genes and transcriptional factors that are involved in essential biological processes. Specifically, TAG-24 showed activation of genes involved in the plant hormone signaling pathway such as PYL9, Auxin response receptor gene, and ABA. Additionally, genes related to water deprivation such as LEA protein and those involved in combating oxidative damage such as Glutathione reductase were also found to be activated in TAG-24. This genome-wide transcription map, therefore, provides a valuable tool for future transcript profiling under drought stress and enriches the genetic resources available for this important oilseed crop.

Comparative metabolomics of root-tips reveals distinct metabolic pathways conferring drought tolerance in contrasting genotypes of rice

BackgroundThe mechanisms underlying rice root responses to drought during the early developmental stages are yet unknown.ResultsThis study aimed to determine metabolic differences in IR64, a shallow-rooting, drought-susceptible genotype, and Azucena, a drought-tolerant and deep-rooting genotype under drought stress. The morphological evaluation revealed that Azucena might evade water stress by increasing the lateral root system growth, the root surface area, and length to access water. At the same time, IR64 may rely mainly on cell wall thickening to tolerate stress. Furthermore, significant differences were observed in 49 metabolites in IR64 and 80 metabolites in Azucena, for which most metabolites were implicated in secondary metabolism, amino acid metabolism, nucleotide acid metabolism and sugar and sugar alcohol metabolism. Among these metabolites, a significant positive correlation was found between allantoin, galactaric acid, gluconic acid, glucose, and drought tolerance. These metabolites may serve as markers of drought tolerance in genotype screening programs. Based on corresponding biological pathways analysis of the differentially abundant metabolites (DAMs), biosynthesis of alkaloid-derivatives of the shikimate pathway, fatty acid biosynthesis, purine metabolism, TCA cycle and amino acid biosynthesis were the most statistically enriched biological pathway in Azucena in drought response. However, in IR64, the differentially abundant metabolites of starch and sucrose metabolism were the most statistically enriched biological pathways.ConclusionMetabolic marker candidates for drought tolerance were identified in both genotypes. Thus, these markers that were experimentally determined in distinct metabolic pathways can be used for the development or selection of drought-tolerant rice genotypes.

Phenotyping for the Seedling Stage of the Drought Stress Tolerance in Rice (Oryza sativa L.)

The ever-increasing demand for rice raises the need to increase productivity by developing drought-tolerant rice varieties. Drought tolerance is a complex polygenic trait that largely depends upon plant developmental stages and showed genotype-specific variability. The experiment was conducted using drought tolerant (Binadhan-19, BRRI dhan83) and drought susceptible (BRRI dhan26, BRRI dhan48) rice genotypes at the glasshouse of Bangladesh Institute of Nuclear Agriculture (BINA), Mymensingh to characterize the seedling stage drought tolerance as well as disclose the variability of the genotypes for morphological and biochemical traits. A completely randomized design (CRD) with three replications and treatments (control and drought stress imposed by 20% PEG) was used for the experiment. Data on shoot length, root length, fresh root weight, fresh shoot weight, dry root weight, dry shoot weight, chlorophyll content (SPAD value), MDA, and H2O2 were recorded and analyzed through appropriate breeding tools. Significant variation (p<0.01) was observed for genotype, treatment, and genotype (G) × treatment (T) interactions viz., shoot length, root length, root fresh weight, shoot fresh weight, root dry weight, shoot dry weight, chlorophyll, H2O2, and MDA. Drought stress leads to a significant decrease in root and shoots growth whereas the level of H2O2 and MDA increased significantly. A greater decrease in root and shoot growth was observed in susceptible genotypes (BRRI dhan28, BRRI dhan48) compared to tolerant genotypes (BRRI dhan71, Binadhan-19). In contrast, a limited increase in H2O2 and MDA was recorded in tolerant genotypes compared to susceptible genotypes. H2O2 showed a significant positive correlation with root and shoot characteristics under control conditions, whereas H2O2 showed a significant negative correlation with chlorophyll content under drought conditions. MDA showed a significant negative correlation with most of the studied traits under well-watered conditions. Considering all of the traits at the seedling stage, the genotype Binadhan-19 is considered a drought-tolerant genotype both under well-watered and drought conditions, and this genotype was selected for further study under direct field conditions as well as for genetic improvement against drought stress.

EVALUATION OF COTTON GENOTYPES SEEDLINGS FOR DROUGHT STRESS TOLERANCE

The present studies clearly indicated that expressivity of some of the genes was changed due to the simulated drought conditions. The root increases in length in response to drought thus utilizes more photosynthates changing the sink and ultimately reducing the shoot growth. The shift due to drought indicated that the growth and morphological development of root system are under genetic control but may be modified by environmental influences. To screen out drought tolerant and drought susceptible genotypes on the basis of morphological seedling traits such as root characters and root / shoot length ratio. After screening, three drought tolerant genotypes namely BH-124,149-F and DPL-26 and three drought susceptible genotypes i.e. CIM-446, FH-945 and VH-28 were identified which may be used in further hybridization programme to develop drought tolerance varieties and hybrids.

Inoculation of Trichoderma asperelloides NT33 causes minor transcriptional changes in tomato plants under water deficit stress conditions.

Abstract The growth-promoting fungi Trichoderma are reported to have a positive effect on the morphological and physio-chemical properties of plants under water deficit stress conditions. In the present study, transcriptomic analysis was conducted to understand the key molecular mechanisms and candidate genes involved in water deficit response in drought susceptible tomato genotype 'Jaune Flamme' when colonized by Trichoderma asperelloides NT33. The data showed that gene expression differences between irrigation treatments were more pronounced than those due to Trichoderma inoculation. Specifically, we found that more than 16,000 genes were differentially expressed between water deficit stress and irrigated plants, while only 28 genes were differentially expressed between NT33 inoculated and non-inoculated treatments under water stress conditions. Nevertheless, nine of these 28 genes have important roles in stress tolerance mechanisms. The transcriptomic study showed that the metabolic pathways involved in secondary metabolite production are one of the main mechanisms adopted by NT33 inoculated plants for maintenance of homeostasis balance under water deficit stress conditions compared to non-inoculated control plants. Among genes upregulated in inoculated (versus non-inoculated) plants under water deficit stress conditions, gene ontology categories involved in regulation of secondary metabolite biosynthetic processes, anthocyanin biosynthetic processes, phospholipase activity, cellular responses to stress, lipid catabolic processes, and regulation of stomata development were overrepresented. On the other hand, genes downregulated in NT33 inoculated samples were involved in the induction of defense response and signaling such as pathogenesis-related proteins, polyphenol oxidase, and chitinase, compared to non-inoculated control samples under water deficit stress. Overall, this study identified key molecular mechanisms involved in water deficit tolerance in the drought susceptible tomato, 'Jaune Flamme', using a novel Trichoderma asperelloides NT33.

Chronic Drought Differentially Alters the Belowground Microbiome of Drought-Tolerant and Drought-Susceptible Genotypes of Populus trichocarpa

Populus trichocarpa is an ecologically important tree species and economically important biofeedstock. Belowground, P. trichocarpa interacts with diverse microorganisms in the rhizosphere and root endosphere. These plant–microbe interactions can bolster a variety of plant processes, ranging from pathogen suppression to drought tolerance, yet we know little about the impact of chronic drought stress on P. trichocarpa’s belowground microbiomes. To investigate the interactive effect of chronic drought on belowground microbial communities across genetically different P. trichocarpa hosts, we assessed archaeal/bacterial and fungal communities within the root endosphere, rhizosphere, and surrounding bulk soil of selected genotypes in a long-term drought experiment in Boardman, OR, U.S.A. We sequenced the 16S ribosomal RNA and internal transcribed spacer 2 gene region on samples collected from 16 distinct P. trichocarpa genotypes in plots with full or reduced irrigation. Eight of these genotypes have been previously identified as drought tolerant while the other eight genotypes were drought susceptible. Although reduced irrigation influenced the composition of every archaeal or bacterial microbiome compartment, fungal communities were only affected in the rhizosphere and bulk soil compartments. Drought-tolerant bacteria such as Actinobacteria were differentially abundant in reduced irrigation across all belowground microbiomes. Host drought tolerance influenced plant-associated microbiome compartments but had little impact on the bulk soil compartment. Drought-tolerant trees were enriched for potential growth-promoting microorganisms in the root endosphere and rhizosphere, including Sphingomonas bacteria and ectomycorrhizal fungi. Overall, associations of growth-promoting microbes in drought-resistant P. trichocarpa genotypes can be leveraged to improve biofeedstock productivity in regions prone to periodic drought.

Comparative and expression analysis of MYB transcription factor genes in groundnut (Arachis hypogaea L.)

ABSTRACT The myeloblastosis (MYB) superfamily is one of the largest transcription factor families in the plant kingdom, and has diverse functions in plants, including regulating biotic and abiotic stresses. In this study, a total of 108 MYB protein sequences were identified and characterized through an insilico approach. We confirmed that the MYB proteins had three conserved repeats (R1, R2, and R3). The putative functions of AhyMYB genes were predicted on the basis of 31 functional groups formed from a comparative phylogenetic analysis. Important cisregulatory motifs, such as ABRE, TGA, ARE, LTR and TATA were present in the upstream regions of AhyMYB genes, and also some post-translational modifications were identified in the present study. Drought- stress was induced in five elite groundnut genotypes (Dh 256, Dh 257, GPBD 4, TMV 2, and JL 24) at flowering and peg initiation stages, and the expression patterns of five selected AhyMYB genes were investigated in these genotypes. In the drought-tolerant genotypes (Dh 256 and Dh 257), at the peg initiation stage, five drought-related transcription MYB factor genes showed greater up-regulation compared with the drought-susceptible genotypes. Among the five genes used in the study, AhyMYB17 gene showed higher expression in JL 24 (moderately drought resistant) compared to untreated control plants at the peg initiation stage. These results indicated the possible involvement of MYB transcription factor genes in regulating the drought stress conditions in groundnut. In-silico analysis, along with the expression studies of AhyMYB genes will definitely help in understanding the stress-response mechanism in groundnut.

Metabolic and Enzymatic Evaluation of Lentil (Lens culinaris M.) Seedlings under Drought Stress

Background: In the agricultural context, drought is a period of deficient water conditions, resulting in negative effects on crop growth and yield. A continuous increase in global temperature, leading to warmer climatic conditions, is expected to further increase the severity and frequency of drought. Methods: The experiments were carried out during 2018-2019 under laboratory conditions to study the effects of PEG-6000 on seedling growth in eight genotypes of lentil (Lens culinaris Medik.). Result: Our research work evaluated the effect of PEG-6000 induced drought stress on metabolite and enzymatic activity of eight genotypes of lentil (Lens culinaris Medik.) (PL-4, L-4147, L-4594, L-4596 belonging to microsperma subspecies and K-75, L-4076, DPL-15, DPL-62 belonging to macrosperma subspecies). Drought stress significantly increased metabolite content i.e., protein, proline and carbohydrate and enzyme activity i.e., acid phosphatase, invertase in drought tolerant genotypes (PL-4, L-4594, DPL-15 and DPL-62) and reduced amount of these metabolites and enzymes was observed in drought susceptible genotypes (L-4147, L-4596, K-75, L-4076).

Estimation of Water Use Efficiency and Osmolyte accumulation to Evaluate Drought Stress Tolerance in Mulberry

The present study was under taken to assess the drought stress tolerance in four mulberry genotypes and three varieties. Four months old mulberry plants were subjected to three water regimes viz., 100% PC, 50% PC, 25% PC for 30 days. Chlorophyll Stability Index, intrinsic Water Use Efficiency and osmolyte accumulation (proline content) were estimated before imposing drought stress and 30 days after drought stress. WUEi and proline accumulation was increased, while CSI, carbohydrate and protein contents were found to be decreased as severity of drought stress progressed. Mulberry genotype, MI-0425 was found to be drought tolerant with higher WUEi (4.13 mmol CO2 mol-1 H2O) and proline accumulation (8.54 μg g-1). This line also showed lesser protein degradation at severe drought stress. The genotype MI-0613 recorded lower WUEi (3.18 mmol CO2 mol-1 H2O) and proline content (5.87 μg g-1) under severe drought stress. It also recorded severe reduction in yield (45.96%) under stress. Hence, MI-0613 was identified as a drought susceptible genotype. Variety V1 recorded higher CSI (77.68%) and carbohydrate (29.03 mg/g) and yield (95.48 g/plant) under both in moderate and intense water stress treatments. Hence, V1 was found to mitigate drought stress by maintaining higher CSI and carbohydrate content.

Physiochemical Changes of Mung Bean [Vigna radiata (L.) R. Wilczek] in Responses to Varying Irrigation Regimes

Mungbean is one of the most powerful pulses providing substantial protein for human diets and fixing N to the soil, improving nutritional food security and agricultural sustainability. The production of summer mungbean in the tropics and subtropics is adversely affected by drought due to water scarcity caused by various factors as well as lack of rainfall. Irrigation at different growth phases is not a suitable solution. An environmentally friendly and economically viable answer is a convenient irrigation management option that will be available to farmers together with drought-tolerant genotypes. The study considered to determine the effect of differences between drought-tolerant and drought susceptible genotypes on water productivity response and physiological traits in mung beans. To quantify seed yield-related to irrigation at different growth stages eventually to quickly determine the most appropriate irrigation stage. One water stress tolerant mung bean genotype (BMX-08010-2) and one sensitive genotype (BARI Mung-1) were grown in the field with four different irrigation schedules along with water stress conditions (no irrigation) under rain shelter at Regional Agricultural Research Station, BARI, Ishwardi, Pabna, Bangladesh. The experiment was laid out in split plots with three replications, with irrigation schedules assigned in the main plot and mung bean genotypes assigned in the side plots. Water use efficiency ranged from 3.79 to 4.68 kg ha−1 mm−1 depending on irrigation regime, and mung bean seed yield of mung bean Water stress decreased plant water status, photosynthetic pigment and membrane stability index, and increased proline soluble sugar content. Treatments that received irrigation during two or three phases (I3 or I4) gave significantly higher yields than those that received irrigation during only one stage (I1 and I2) with the lowest yield. While the yield obtained ranged between 1145.44 kg ha−1 with seasonal irrigation of 277 mm (I4) and 555.14 kg ha−1 without irrigation (I0). The flowering stage (I3) was recorded as the most sensitive growth stage with an 18.15% yield reduction compared to the treatment with triple irrigation (I4). Also, depending on the irrigation sources, at least two irrigation phases should be provided at the triple leaf stage (I2, i.e., 20 DAS) and at the flowering stage (I3, i.e., 35 DAS) to achieve the highest yield. Genotypes that maintained the higher performance of physicochemical traits under water stress provided higher seed yield and promoted drought tolerance. Therefore, these parameters can be used as physiological and biochemical markers to identify and develop superior genotypes suitable for drought-prone environments.

Contribution of Ascorbate and Glutathione in Endobacteria Bacillus subtilis-Mediated Drought Tolerance in Two Triticum aestivum L. Genotypes Contrasting in Drought Sensitivity.

We evaluated the effect of endobacteria Bacillus subtilis (strain 10–4) as a co-inoculant for promoting plant growth and redox metabolism in two contrasting genotypes of Triticum aestivum L. (wheat): Ekada70 (drought tolerant (DT)) and Salavat Yulaev (drought susceptible (DS)) in early stages of adaptation to drought (12% PEG–6000). Results revealed that drought reduced growth and dramatically augmented oxidative stress markers, i.e., hydrogen peroxide (H2O2) and lipid peroxidation (MDA). Furthermore, the depletion of ascorbate (AsA) and glutathione (GSH), accompanied by a significant activation of ascorbate peroxidase (APX) and glutathione reductase (GR), in both stressed wheat cultivars (which was more pronounced in DS genotype) was found. B. subtilis had a protective effect on growth and antioxidant status, wherein the stabilization of AsA and GSH levels was revealed. This was accompanied by a decrease of drought-caused APX and GR activation in DS plants, while in DT plants additional antioxidant accumulation and GR activation were observed. H2O2 and MDA were considerably reduced in both drought-stressed wheat genotypes because of the application of B. subtilis. Thus, the findings suggest the key roles in B. subtilis-mediated drought tolerance in DS cv. Salavat Yulaev and DT cv. Ekada70 played are AsA and GSH, respectively; which, in both cases, resulted in reduced cell oxidative damage and improved growth in seedlings under drought.

Multi-Environment Screening of Durum Wheat Genotypes for Drought Tolerance in Changing Climatic Events

Durum wheat is the most widely grown cereal in Tunisia, but its production is threatened by drought, which is exacerbated by climate change. This study aimed to identify drought-tolerant durum wheat genotypes from five modern varieties and six landraces in a multi-environment trial at two sites (Kef and Siliana, Tunisia) during three growing seasons under rainfed and irrigated conditions. Six drought tolerance indices (mean productivity (MP), geometric mean productivity (GMP), stress susceptibility index (SSI), tolerance index (TOL), stress tolerance index (STI), and yield stability index (YSI)) were used to evaluate the 11 genotypes. The environment was the dominant source of variation for grain yield (GY; 94.27%), followed by the environment × genotype interaction (4.06%) and genotype (1.65%). Cluster analysis based on GY identified four environment-based groups with distinct water treatments, extreme minimum/maximum temperatures, and rainfall. Principal component analysis and a correlation matrix revealed that drought tolerance indices significantly correlated with GY in non-stressed and stressed conditions and could be separated into four groups. Based on STI, MP, and GMP, G6 and G8 (landraces) were the most drought-tolerant genotypes attaining high GY in both conditions. TOL was able to discriminate G1, G3, and G5 (modern varieties) as well as drought-susceptible genotypes, all of which were suitable for irrigation. Genotypes G7, G9, G10, and G11 (landraces), which had high SSI and lowest STI, MP, GMP, and YSI values, were susceptible to drought and were thus not suitable for cultivation in both conditions. Finally, G2 and G4 (modern varieties), which had an intermediate rank for different indices, were classified as semi-tolerant or sensitive genotypes. Drought tolerance indices and genotype ranks were helpful tools to screen drought-tolerant genotypes with a large adaptation to a range of environments, namely irrigated and rainfed conditions (landraces G6 and G8), or genotypes with the ability to adapt (modern varieties G1, G3, and G5) to irrigated conditions.

ACCESSING POTENTIAL OF SEEDLING TRAITS FOR SCREENING OF WHEAT GENOTYPES UNDER DROUGHT CONDITIONS

Drought stress causes considerable decrease in wheat yield especially in developing countries like Pakistan. In current study, seedling traits i.e., root length, shoot length, shoot fresh weight, shoot dry weight and root to shoot (length) ratio were selected to find their effectiveness in evaluating drought tolerance of wheat genotypes. It was found that different genotypes showed different response under normal and drought conditions as mean squares for genotypes were significant. When plant is exposed to stress, it tries to overcome the stress by adopting different strategies like extending root system to reach the deep soil water. Increase in stress causes reduction in both root and shoot length. Genotypes named Faisalabad-08, Sehar-06, 9633, 9507 and lasani-08 showed maximum and high root length under normal conditions but their root length decreased drastically when exposed to drought environment. Because of their behavior they are tagged as drought susceptible genotypes. Genotypes Chakwal-86, Ass-11, Manthar-2003, Miraj 2008, Chakwal-50, 9488, 9805, 9859, 9512 and 9637 showed high values for root length under drought condition and while comparing their performance under both the environments i.e., normal and drought, their root length decreased non-significantly. So these genotypes are tagged as drought tolerant genotypes.

Proline, Total Antioxidant Capacity, and OsP5CS Gene Activity in Radical and Plumule of Rice are Efficient Drought Tolerance Indicator Traits

The success of a plant breeding program is linked with the rapid screening of crop germplasm. In the following study, the germination stage of rice seeds has been examined for the rapid screening of drought-tolerant genotypes. The rice genotypes (10 drought tolerant, 5 moderately drought tolerant, and 5 drought susceptible) were sown in Petri dishes under control and osmotic stress of 15% PEG6000. Data were recorded after four days of sowing for the osmotic stress-induced change in imbibition rate, speed of germination, radical and plumule length, radical and plumule total fresh and dry weight, proline contents, total antioxidant capacity, and malondialdehyde level in radical and plumule of seeds. Moreover, the change in expression of OsP5CS gene was also recorded in one of each drought tolerant, moderately drought tolerant, and drought susceptible genotypes. Under osmotic stress, the level of proline, total antioxidant capacity, and the expression of OsP5CS were increased in drought-tolerant genotypes as compared to moderately drought tolerant and drought susceptible genotypes. While, the change in imbibition rate, speed of germination, radical and plumule length, and fresh and dry weight were not symmetrical in drought tolerant, moderately drought tolerant, and drought susceptible genotypes. In short, the symmetrical change in proline, total antioxidant capacity, and expression of OsP5CS gene within radical and plumule of drought tolerant, moderately drought tolerant, and drought susceptible genotypes can help rapid screening of drought-tolerant rice genotypes.

Screening of mungbean for drought tolerance and transcriptome profiling between drought-tolerant and susceptible genotype in response to drought stress

Mungbean, is a widely cultivated pulse crop in India, experiences severe drought stress during the cultivation period. The mechanism of drought tolerance in mungbean is not well understood. In this presents study we screened 7 widely cultivated mungbean genotypes towards their drought sensitivity at seedling stage and transcriptome sequencing of drought-tolerant and susceptible genotype to understand the drought tolerance mechanism. Our physiological data such as increase in root length, shoot length, fresh weight, dry weight, relative water content (RWC), proline content, MDA content and molecular data in terms of quantitative expression of drought stress responsive genes under 3-d drought stress in mungbean suggests that, K851 seems to be most drought tolerant and PDM-139 as drought susceptible genotype. The transcriptomic study between K-851 and PDM-139 revealed 22,882 differentially expressed genes (DEGs) which were identified under drought stress, and they were mainly mapped to phytohormone signal transduction, carbon metabolism and flavonoid biosynthesis. Out of these, 10,235 genes were up-regulated and 12,647 genes were down-regulated. Furthermore, we found that, the DEGs related to, phytohormone signal transduction, carbon metabolism and flavonoid biosynthesis and they were more induced in K-851. Our data suggested that, the drought tolerant genotype K-851, scavenges the damage of drought stress by producing more amount of osmolytes, ROS scavengers and sugar biosynthesis.

Morpho-physiological and molecular evaluation of drought tolerance in cassava (Manihot esculenta Crantz)

Abstract Understanding drought tolerance mechanisms of cassava is a pre-requisite to improve the performance of the crop in water-scarce regions. Several hypotheses have been formulated to suggest how cassava can withstand a prolonged period of drought. We performed field trials under drought conditions with a selection of 37 cassava genotypes to identify phenotypic and molecular patterns associated with drought tolerance. Plant morphologies varied significantly between cassava genotypes under drought conditions in Kenya, which indicates a strong genetic basis for phenotypic differences. Drought stress reduced yield by 59%, the number of edible storage roots by 43% and leaf retention by 50% on average. Over three years and in two experimental field sites, the most drought tolerant genotype bulked 7.1 (±2.1) t/ha yield while the most drought susceptible genotype yielded 3.3 (±1.4) t/ha under drought conditions. The significant positive correlation of yield under irrigated and non-irrigated conditions suggests that selection of genotypes with high yield performance under well-watered or control conditions should be prioritized to identify genotypes with superior performance under drought stress. The positive correlation between yield and leaf retention provided further evidence that leaf longevity positively contributes to yield in water-deficit conditions. Yield differences could be attributed in part to variation in stomatal conductance (gs) because selected drought tolerant genotypes maintained higher gs and delayed stomatal closure as compared to drought susceptible genotypes. Further analysis revealed that genetic or molecular differences for gs between drought tolerant and susceptible genotypes could be detected at early stages of water deficit. These differences likely involve both abscisic acid (ABA)-dependent and ABA-independent molecular pathways.

Conferring drought-tolerant wheat genotypes through morpho-physiological and chlorophyll indices at seedling stage.

The decrease in water resources due to the excessive use of water for irrigation purpose and climatic changes represents a serious world-wide threat to food security. In this regards, 50 wheat accessions were analyzed, using completely random factorial design at the seedlings stage under normal and drought stress conditions. Significant variation was detected among all accessions under both conditions. All characters studied showed variations in the mean values in water deficit environments in studied gemplasm at seedling stage. As seedling fresh weight, dry weight, relative water content, cell membrane thermo-stability, chlorophyll a & b were positively associated among themselves under drought conditions which showed the significance of these attribute for water deficit areas in future wheat breeding programs. Based on their performance, five accessions namely Aas-11, Chakwal-86, Pasban-90, Chakwal-97 and Kohistan-97 were selected as drought tolerant and three accessions namely Mairaj-08, Lasani-2008 and Gomal-2008 were selected as drought susceptible genotypes. The choice of wheat accessions based on the characteristics of the seedlings is informal, low-priced and less hassle. Likewise, the seedlings attributes exhibit moderate to high variation with an additive genetics effects on the environments. Best performance accessions under water deficit environment will be beneficial in future wheat breeding schemes and early screening for the attributes suggested in current experiment will be useful for producing best-yielded and drought-tolerance wheat genotypes to sustainable food security.

Transcriptome and metabolome analysis reveals regulatory networks and key genes controlling barley malting quality in responses to drought stress

Malting quality will be greatly deteriorated when barley plants suffer from post-anthesis drought stress, however there is a marked difference among barley genotypes in the responses of malting quality to drought stress, and the molecular mechanisms underlying the genotypic difference remain unclear. We made transcriptome and metabolome analysis on the developing grains of two barley genotypes differing in the responses to drought stress. Post-anthesis drought treatments led to decreased grain weight and β-glucan content, increased grain protein content and β-amylase activity. Drought stress enhanced H2O2 and heat-shock protein accumulation in the two barley genotypes, with the drought-tolerant genotype showing higher capacity of scavenging H2O2 and reducing misfolded protein accumulation than the drought-susceptible genotype. Moreover, the drought-tolerant genotype was more efficient in redistributing assimilates stored in the vegetative tissues into the developing grains. After re-watering to relieve drought stress, the drought-tolerant genotype can further modify auxin transport and ethylene signaling, enhancing redistribution of assimilates into grains. Transcriptome comparisons and weighted correlation network analysis (WGCNA) identified some key genes regulating the responses of malting quality traits to drought stress, such as RLK-LRR, β-glucosidase and HSP . In conclusion, less change of main malting quality traits in the drought-tolerant genotype under post-anthesis drought stress is attributed to its higher capacity of alleviating the stress injury through scavenging ROS and redistributing the metabolites stored in the vegetative organs into the developing grains.

Chlorophyll α Fluorescence Parameters as an Indicator to Identify Drought Susceptibility in Common Bush Bean

The common bean is susceptible to drought conditions and the evaluation of plant responses to low water availability can be difficult. The quantification of chlorophyll fluorescence as a sensitive trait to environmental stresses is an important alternative in the characterization of drought-susceptible genotypes. The objective of this study was to evaluate mainly the use of chlorophyll α fluorescence (maximum efficiency of PSII (Fv/Fm), photochemical quenching (qP), non-photochemical quenching (NPQ)) and rapid light-response curves (RLCs) (initial slope of the curve (α), minimum saturation irradiance (Ik) and maximum relative electron transport rate (ETRmax)) parameters as tools for the identification of susceptible or tolerant bush bean cultivars to water deficit stress conditions in two different phenological stages. Using a randomized block design in a factorial arrangement, five bush bean cultivars (Cerinza, Bachue, NUA35, Bacata and Bianca) were evaluated under water deficit conditions by the suspension of irrigation for 15 days from 40 to 55 Days after Emergence (DAE) (vegetative stage) or 50 to 65 DAE (reproductive stage). The results showed that Fv/Fm and NPQ recorded the highest variation due to water deficit conditions, especially in the vegetative stage. The greatest reductions in Fv/Fm (0.67) and NPQ (0.71) were evidenced in cultivar NUA35 compared to its control plants (0.78 and 1.07, respectively). The parameters obtained from RLCs showed that cultivar Bacata registered the lowest α (0.17) and Ik (838.19 μmol∙m−2∙s−1) values compared to its control plants (α 0.23; Ik 769.99 μmol∙m−2∙s−1). Differences were only obtained in ETRmax in the reproductive stage (50–65 DAE) in which cultivar NUA35 reached values of 158.5 in stressed plants compared to control plants (251.22). In conclusion, the parameters derived from RLCs such as α and Ik can be used as tools to identify drought susceptibility in the vegetative stage, whereas ETRmax can be used in the reproductive stage. In addition, PSII photochemistry (Fv/Fm and NPQ) can also help to understand the agronomic responses of common bush bean cultivars to drought conditions.