Polyethylene Glycol-induced Drought Stress Research Articles

Elucidating Drought Tolerance Potential of Maize (Zea mays L.) Inbred Lines through Polyethylene Glycol Induced Drought Stress

Drought is one of the most distressing environmental stresses restraining the crop production . Drought undermines the plant growth from seedling to maturity and the studies have unveiled that the harmful impact of drought results in crops due to the damages perceived during crucial stages of development namely, germination, seedling development and flowering stages. Biometric elements and indices at an early growth stage could be employed in designing the selection criteria to figure out the drought tolerant genotypes. Breeding for drought-prone environments is constrained by lack of suitable selection indices of drought stress resistance. The present study was conducted to determine the reliability of in-vitro screening method for initiating drought breeding programme. Poly ethylene glycol (PEG) has been used often as abiotic stress inducer in many studies to screen drought tolerant germplasm. The present investigation was carried out to reveal the drought tolerance potential of 103 maize inbred lines by in-vitro screening under three levels of PEG levels viz., 0% as control, 10% and 20% and evaluating their effect on the root parameters like primary root length, number of seminals roots , number of lateral roots and root biomass. The seedlings exhibited a significant variation for all the traits analyzed. All the root parameters had highest value under control and had significant decline with increasing PEG concentrations (0% < 10% < 20%). The inbreds showing the best level of drought tolerance at all levels of PEG induced stress can be used as a source of drought tolerance for the improvement of drought tolerant hybrids . The variation among maize inbreds for these traits was found to be an ideal indicator to screen the drought tolerant genotypes at early growth stages.

ACC deaminase producing bacteria alleviate the polyethylene glycol induced drought stress in black gram (Vigna mungo L.) by enhancing nutrient uptake and soil respiration activity

The present study aimed to exploit ACC deaminase (ACCD) producing drought-tolerant bacteria to mitigate drought stress (PEG stress) and simultaneous enhancement of the essential nutrients (N and P), relative water content (RWC), and chlorophyll pigment. In this study, 80 previously isolated ACCD-producing bacteria were screened for drought tolerance, and the results showed that 13.75 % (11isolates) were tolerant to up to -0.73 MPa. Further, screening of these drought tolerant ACCD producers revealed that the 11 isolates produced siderophore (96.82–99.67 %), indole-3-acetic acid like substances (15.15–70.55 µg/mL), and phosphate solubilization (39.33–142.67 µg/mL). Furthermore, pot studies (2000 ppm PEG stress) revealed an enhanced root (40.97–174.24 %) and shoot length (14.06–194.86 %) in inoculated plants compared to the control plants. In addition, inoculated plants also enhanced the uptake of nitrogen (35.10–42.61 mg/g) and phosphorus (2.67–3.68 mg/g), relative water content (55.26–83.33 %), chlorophyll (15.83–47.25 mg/g) and ACCD production in the soils (2.03–5.51 µmol/mL). The inoculated bacteria also enhanced the soil respiration activity such as dehydrogenase enzyme (65.31–144.48 µg/g), fluorescein diacetate hydrolysis (19.27–55.25 µg/g), and alkaline phosphatase (611.53–1011.53 µg/g). In conclusion, IPTS 7 (Rhodococcus kroppenstedtii) and CWN 5 (Bacillus altitudinis) can be used to mitigate drought stress and mobilize essential nutrients (N and P).

Anti-stress effects of melatonin pre-treatment on germination indicators in tomato (Lycopersicon esculentum L.) under polyethylene glycol induced drought stress

Tomato is a commercially grown vegetable crop that is susceptible to drought stress, which can be improved by understanding the tolerance mechanism. This study aims to evaluate the impact of melatonin pretreatment on alleviating PEG-induced drought stress on tomato. Initially, screening was performed with different polyethylene glycol (PEG) concentrations (-0.1, -0.2, -0.3, and -0.4 MPa), along with a control. The seeds treated with -0.3 MPa PEG exhibited lower germination percentage, seedling growth, and vigour index, while no germination was observed at -0.4 MPa. Therefore, -0.3 Mpa was selected as the sublethal osmotic concentration to assess the effect of melatonin to alleviate the osmotic stress. The seeds treated with various melatonin concentrations (20, 40, 60, 80, 100, and 120 µM) and untreated stress control were subjected to -0.3 MPa osmotic concentration, and absolute control was maintained. Seed germination parameters viz., germination indicators, shoot and root length indicators, biomass indicators, stress indices, and germination speed, were recorded. The results showed that the germination parameters were significantly reduced in stress control; however, notable improvements were observed in melatonin pre-treated seeds. Pretreatment with 100 µM melatonin led to an increase in germination percentage (61%), germination index (150.5), vigour index (1010.1), promptness index (65), shoot length (6.28 cm), root length (7.38 cm), fresh weight (0.66 mg), dry weight (0.07 mg), shoot length stress index (86), root length stress index (112), dry matter stress index (87), rate of germination (1.5% per day), germination rate index (15.1% per day), and coefficient of the velocity of germination (20.6) under drought stress. The study evidenced that melatonin pretreatment could effectively enhance seed germination under PEG-induced drought stress in tomato, which, therefore, can be recommended for further research.

Impact of water stress on morpho-physiological and biochemical traits in rice genotypes

Laboratory and field screening were performed in nine rice genotypes i.e., TM 12061, TM 12077, TM 12012, TM 14035, TM 16017, Senthuram, Vandhana, TKM 12 and Anna (R) 4 to assess their drought tolerant potential. For laboratory screening, the effect of different levels of Poly Ethylene Glycol (PEG) concentration viz., -0.2, -0.4, -0.6 and -1.0 MPa on germination, shoot length and root length were studied. There was a considerable decrease in the germination potential among all the genotypes with increase in PEG concentration. The TM 12077 showed higher level of tolerance to PEG induced drought stress showing 30.8 % germination with 3.2 cm and 8.85 cm shoot and root length, respectively at higher level of concentration (1.0 MPa). In the field screening under managed stress condition, TM 12077 and TM 12012 showed higher accumulation of proline (4.15 mg/g). Chlorophyll stability index was more than 80 % in the genotypes TM 12012, TM 12077 and TM 12061. The genotype TM 14035, the varieties Anna (R) 4 and Vandhana matured early in 115 days. Number of tillers per plant, number of panicles/sqm and yield/hectare were maximum in TM 12077. While considering both laboratory and field screening, the genotypes TM 12077, TM 12012 and TM 12061 were found promising for water stress environment and can be utilized as donors in the drought tolerance breeding programs. High heritability coupled with moderate to high GA as per cent of mean recorded for plant height, tillers per plant, chlorophyll stability Index and total chlorophyll content indicates the presence of additive gene effects and their improvement through direct selection. Bangladesh J. Bot. 52(4): 1041-1046, 2023 (December)

Polyethylene glycol-induced drought stress screening of selected Philippine high-yielding sugarcane varieties

A greenhouse study was conducted to characterize the drought response of eight high-yielding sugarcane varieties at tillering stage using polyethylene glycol 6000 (PEG6000) induced drought conditions. Plant height, stalk diameter, dry matter accumulation, root characteristics, stomatal conductance, chlorophyll fluorescence, SPAD, normalized difference vegetation index (NDVI), and canopy temperature were evaluated at 2.5 months after planting after four weeks of induced drought conditions. The study aimed to determine whether 1.0% PEG treatment would be able to produce significant differences among test genotypes and use it as a basis to determine drought-tolerant and susceptible varieties. Significant differences were observed among genotypes in PEG stress treatments. PEG stress resulted in significant reductions relative to non-PEG treatment in plant height (32.1%), leaf dry matter (31.6%), and stalk dry matter (49.5%) while total root length (11.8%), root surface area (7.8%) and root volume (19.6%) have generally increased. Reduced plant height, stalk diameter, and dry matter accumulation were observed in susceptible genotypes, while potential tolerant lines maintained or exhibited less reduction in these traits. Moreover, principal component analysis suggests that stalk dry matter, stomatal conductance, chlorophyll fluorescence plant height, SPAD, canopy temperature, and NDVI, highly contributed to the overall variation in the data (41.5%). With this, vars. 2289, 1011, 2569, and 1899 were identified to be potential drought-tolerant varieties while vars. 1763 and 2155 were potential drought susceptible varieties. Screening for drought tolerance under controlled conditions using PEG-induced drought stress offers a promising approach for sugarcane breeding especially when focusing on specific drought responses during important formative stages such as tillering stage. Being able to select genotypes of interest as early as the tillering stage would significantly hasten breeding cycles and will highly benefit the efforts towards drought stress tolerance in sugarcane.

Water uptake, anatomical, and biochemical changes of sorghum genotypes subjected to polyethylene glycol-induced drought stress

Absract To investigate the water uptake, anatomical and biochemical changes of sorghum, three genotypes including grain sorghum [Sorghum bicolor (L.) Moench subsp. bicolor], Sudan grass [Sorghum bicolor (L.) Moench subsp. drummondii (Steud.) de Wet ex Davidse] and Johnson grass [Sorghum halepense (L.) Pers.] were subjected to polyethylene glycol (PEG 60000)-induced drought stress (PEG 60000) at 0, −0.15, and −0.3 MPa levels, hydroponically. In all genotypes, stele diameter decreased as osmotic potential of the medium decreased and the largest stele diameter (247 µm) was observed in Johnson grass at control and declined to 196 µm under −0.3 MPa PEG. Drought affected the diameter of peripheral metaxylem (PMX) and central metaxylem (CMX), negatively. The number of PMX and CMX in Johnson grass was 36 and 200% more than in grain sorghum under −0.3 MPa PEG, respectively. In all genotypes, chlorophyll a and b declined under drought, but in Johnson grass, it only decreased 25 and 29%, respectively. Johnson grass had the highest total chlorophyll content, while carotenoid content was stable under drought stress in this genotype. Drought stress increased catalase and peroxidase activities but decreased relative water content (RWC) and hydraulic conductivity (hc). Under drought, the higher seedling dry weight and root to shoot ratio in Johnson grass might be related to higher hc, total chlorophyll content, and RWC. Moreover, Johnson grass showed less water loss and more efficiency in water uptake under induced drought stress; and it could be attributed to the larger stele diameter, number, and diameter of PMX, substantiating their roles in drought adaptation.

Molecular mechanism of Cu metal and drought stress resistance triggered by Porostereum spadiceum AGH786 in Solanum lycopersicum L.

Rapid industrialization and global warming have threatened the plants with multiple abiotic stresses, such as heavy metals and drought stress. For crop cultivation, the conventional approach of cleaning the soils by excavation is very costly and not feasible for large scale. Establishing toxin-free and drought-resistant crops is a major challenge in the environment under natural and anthropogenic pressure. In the past decades, copper contamination of agricultural land has become an emerging concern. For dry land reclamation, several new strategies, including bioremediation (phytoremediation and microbial remediation), have been used. Owing to the potential of Cu hyperaccumulators, the current project aims to enhance the drought tolerance and the phytoremediation potential of Solanum lycopersicum L. with the inoculation of copper and 12% polyethylene glycol (PEG)-induced drought stress-tolerant endophytic fungus Porostereum spadiceum AGH786 under the combined stress of copper heavy metal and PEG-induced drought stress. When S. lycopersicum L. was watered with individual stress of copper (Cu) concentration (400 ppm) in the form of copper sulfate (CuSO4.5H2O), 12% PEG-induced drought stress and the combined stress of both negatively affected the growth attributes, hormonal, metabolic, and antioxidant potential, compared with control. However, the multistress-resistant AGH786 endophytic fungus ameliorated the multistress tolerance response in S. lycopersicum L. by positively affecting the growth attributes, hormonal, metabolic, and antioxidant potential, and by restricting the root-to-shoot translocation of Cu and inducing its sequestration in the root tissues of affected plants. AGH786-associated plants exhibited a reduction in the severity of copper (Cu) and drought stress, with higher levels of SlCOPT (Cu transporters) and SlMT (metallothionine) gene expressions in root and shoot tissues, indicating that AGH786 contributed to resistance to copper metal toxicity and drought stress in the host S. lycopersicum L.

Mechanistic Insights into Potassium-Conferred Drought Stress Tolerance in Cultivated and Tibetan Wild Barley: Differential Osmoregulation, Nutrient Retention, Secondary Metabolism and Antioxidative Defense Capacity.

Keeping the significance of potassium (K) nutrition in focus, this study explores the genotypic responses of two wild Tibetan barley genotypes (drought tolerant XZ5 and drought sensitive XZ54) and one drought tolerant barley cv. Tadmor, under the exposure of polyethylene glycol-induced drought stress. The results revealed that drought and K deprivation attenuated overall plant growth in all the tested genotypes; however, XZ5 was least affected due to its ability to retain K in its tissues which could be attributed to the smallest reductions of photosynthetic parameters, relative chlorophyll contents and the lowest Na+/K+ ratios in all treatments. Our results also indicate that higher H+/K+-ATPase activity (enhancement of 1.6 and 1.3-fold for shoot; 1.4 and 2.5-fold for root), higher shoot K+ (2 and 2.3-fold) and Ca2+ content (1.5 and 1.7-fold), better maintenance of turgor pressure by osmolyte accumulation and enhanced antioxidative performance to scavenge ROS, ultimately suppress lipid peroxidation (in shoots: 4% and 35%; in roots 4% and 20% less) and bestow higher tolerance to XZ5 against drought stress in comparison with Tadmor and XZ54, respectively. Conclusively, this study adds further evidence to support the concept that Tibetan wild barley genotypes that utilize K efficiently could serve as a valuable genetic resource for the provision of genes for improved K metabolism in addition to those for combating drought stress, thereby enabling the development of elite barley lines better tolerant of abiotic stresses.

Effect of PEG Induced Drought Stress on Seed Germination and Seedling Growth of Greengram Genotypes

Greengram (Vigna radiata L. Wilczek) is the third most important pulse crop and drought is the most severe constraint to greengram growth and productivity. The present study was conducted to identify the drought tolerant greengram genotypes. Four greengram varieties used for standarization of drought stress using Polyethyleneglycol (PEG) 6000. The effect of water stress caused by different concentration of PEG 6000 are control (0 MPa), -0.4MPa, -0.5 MPa, -0.6MPa and -0.7 MPa. Increasing PEG concentration decrease the germination percentage, root length, shoot length, fresh weigh and dry weight of seedlings. At -0.5 MPa shows 50% seedling mortality , So control and -0.5 MPa level of drought stress was used for screening the greengram genotypes. Under PEG induced drought situations, parameters such as germination percentage, growth indices and proline content were recorded in all greengram genotypes. Compared to control, PEG induced drought stress (-0.5MPa) decrease all these parameters studied, where as drought has increased the proline content in all greengram genotypes screened. Among the greengram genotypes VGG17019 and VGG17004 posses higher germination percentage, GSI and proline content indicates high level of tolerance to drought stress.

Physiological and biochemical studies of black gram (Vigna mungo (L.) Hepper) under polyethylene glycol induced drought stress

Black gram (Vigna mungo L. Hepper) is an important nutritious legume plant, the loess plateau with strong drought tolerance and broad adaptability. To understand the adaptation mechanism of black gram under simulatedlevels of drought (5, 10 and 20% PEG) stress, and the growth characteristics, physiological parameters including levels of chlorophyll content, reactive oxygen species, and antioxidant enzymes were measured and the changes were compared with control. The result showed the root and shoot length, chlorophyll content, relative water content, stomatal activity, electrolyte leakage, antioxidant, and histochemical activity were carried out for treated and control plants. Experimentally, the drought-induced black gram seedlings of fresh weight, dry weight, and relative water contents found to be decreased with increasing concentrations of PEG. However, the electrolyte leakage and biochemical components (MDA content), antioxidant enzymes (SOD, CAT, POX), isozyme band patterns and histochemical detection of ROS accumulation (H2O2 and O2•–) level also enhanced under drought stress. The electrolyte leakage and MDA content were raised at 60% and 20% of severe PEG treatment. ROS accumulation was increased in the PEG treatment when compared to control. Overall, the rapid, accurate, and strong physiological observations from the electrolyte leakage and histochemical detection suggest that modification or enhancement of the biochemical and antioxidant contents would be determine the growth of black gram under PEG induced drought stress.

Evaluation of sodium nitroprusside and putrescine on polyethylene glycol induced drought stress in Stevia rebaudiana Bertoni under in vitro condition

The present work aimed to regenerate Stevia rebaudiana Bertoni under in vitro drought condition induced by different concentrations (0%, 5%, 10 % and 15 %) of polyethylene glycol (PEG) 6000, and to investigate the mitigating effect of sodium nitroprusside (SNP; nitric oxide donor) and putrescine in relation to efficient multiplication. Varying concentrations of SNP (50, 100, 250 and 500 μM) and putrescine (0.05, 0.1, 0.3 and 0.5 mM), used singly or in combination in the MS medium, along with best selected concentration of plant growth regulator (kinetin 0.2 mg l−1) under in vitro drought imposed by 10 % PEG were taken for studies at 20, 40 and 60 days after inoculation (DAI). The best response with maximum values on the basis of morphological parameters was recorded; number of shoot and number of leaves were observed in half strength MS media supplemented with combination of both SNP and putrescine treatment i.e. SNP 100 μM + putrescine 0.05 mM followed by other treatments as compared to remaining treatments as well as control (10 % PEG only). On the basis of present investigation, it is concluded that in vitro drought stress significantly reduced the number of shoot, length of shoot (cm), number of leaves, number of roots, length of root (cm) and survival percentage. However, treatment with SNP and putrescine, alone or in combination, alleviated the negative impacts of drought stress up to a great extent. The production of more number of stevia leaves even under drought condition as a result of ameliorative treatment with SNP and putrescine has implication in R&D industries to target for production of maximum content of stevioside and rebaudioside, key principles in treating diabetes, if there is an increase in their content.

Deciphering drought tolerance potential of sweet corn genotypes through polyethylene glycol induced drought stress

Drought is a restraining factor for the major dependent factors like yield. Pertaining to this issue, analyzing the drought potential of the sweet corn is a major concern. The present investigation was carried out to reveal the drought tolerant potential of sweet corn genotypes by invitro screening under four levels of osmotic stress (0, -2, -4 and -6 bar) using PEG. The material used for the study included six lines and five testers and their corresponding thirty hybrids synthesized in a line x tester mating design. The seedlings exhibited a significant variation for all the traits and indices analyzed. Under high stress, SVI of the selected entries were found to be higher because of increase in germination percentage and seedling length which would ultimately lead to better field emergence. Performance of the hybrids WNC12039-1× 45503, WNC12039-1×45678 and SC11-2×45679 excelled over the commercial check i.e. Misthi when subjected to lower water potential. Based on the preliminary study, the identified inbreds WNC 12069-2, SC 11-2 and the hybrids WNC12039-1×45503, WNC12039-1×45678 and SC11-2×45679 could be further evaluated in the field.

Physiological and Transcriptome Profiling Analyses Reveal Important Roles of Coronatine in Improving Drought Tolerance of Tobacco

Coronatine (COR) is a phytotoxin produced by Pseudomonas syringae and is a functional analogue of the bioactive hormone JA-Ile, which is widely involved in plant defence responses. In this study, we explored the effects of exogenous applications of COR on tobacco plants under polyethylene glycol-induced drought stress. Compared with control (CK), COR-treated tobacco plants exhibited higher leaf relative water content and better photosynthetic performance under drought exposure. Ultrastructural examination revealed that drought led to stomatal closure and disorganization of granum stacking in the chloroplasts (with obvious accumulation of plastoglobuli), and mitochondria in the CK samples presented injured cristae. In the leaf tissue of the COR-treated plants, regularly stacked granum thylakoids, few plastoglobuli and intact mitochondrial membranes and cristae were observed. Totals of 1803 and 6207 differentially expressed genes (DEGs) were identified between the samples from the COR-treated and CK plants under well-watered and drought conditions. Functional annotation analysis revealed that these DEGs were involved mainly in plant hormone signal transduction, cellular carbohydrate metabolic processes and photosynthesis processes. Six hundred forty transcription factor genes were also identified among the DEGs. This study provides a global view of COR-induced drought stress tolerance in tobacco from both physiological and transcriptional aspects.

Polyethylene glycol induced drought stress strongly influences seed germination, root morphology and cytoplasm of different kenaf genotypes

Plants are sessile and therefore continuously confronted to drought stress. Therefore, a better understanding of different kenaf genotypes is essential. The objective of this study was to assess seed germination, root morphology and cytoplasmic effects of four types of kenaf cytoplasms i.e., C1, C2, C3, C4 under different concentration of polyethylene glycol (PEG). Results showed that seed germination was increased under 10% PEG treatment compared with control and 20% PEG treatment. Among the genotypes, the hybrids C2/992, C3/992, C4/992 resulted in better germination compared with P3B and FH992. The C2 cytoplasm had the most positive cytoplasmic effects on seed vigor at germination stage. Root growth was significantly inhibited under 10% PEG and 20% PEG at seedling stage. C3/992, P3A, and P3B had improved root growth compared with other treatments at seedling stage. Under 20% PEG conditions, C1, C2, C3, and C4 cytoplasms had inhibitory effect on root growth traits except C3 cytoplasm had a positive effect on root growth. Correlation analysis showed that hundred-grain weight (HGW) was significantly correlated to seed germination performance (P < 0.01) and root dry weight (P < 0.05) under 20% PEG conditions. In particular, the CMS line P3A was the most beneficial in terms of higher germination rate and better root morphological characteristics. This indicating that P3A had the potential to withstand under drought conditions and could be used for drought resistant breeding of three-line system of kenaf crop with heavy hundred-grain weight of restorer line.

Genome-wide characterization of drought stress responsive long non-coding RNAs in Tibetan wild barley

Drought is the most common and frequently occurring abiotic stress limiting crop yield and quality. Long non-coding RNAs (lncRNA) play crucial roles in regulating expression of genes in plants under various abiotic stress. The participation of lncRNAs in plant drought tolerance in barley is largely unknown. Here, we compared the lncRNA transcriptome in roots of two Tibetan wild barley genotypes XZ5 (drought-tolerant) and XZ54 (drought-sensitive), and one drought tolerant cv. Tadmor in response to polyethylene glycol-induced drought stress. In total, 23,651 novel lncRNAs were identified, among which 535 were characterized as drought responsive according to their different expression profile among XZ5, and XZ54 and Tadmor in response to drought stress. LncRNA target prediction revealed 1279 potential lncRNA-messenger RNA (mRNA) pairs, among which 503 pairs function in cis-acting mode and 776 in trans. Functional enrichment analysis showed that the targets were significantly enriched in molecular functions related to plant hormone signal transduction, diterpenoid biosynthesis, and ascorbate/aldarate metabolism. Multiple promising targets of drought-responsive lncRNAs were discovered, including the SPL3, BRI1 gene. Further analysis of genotypic difference in transcriptome we identified 10 drought-tolerance associated lncRNAs in XZ5, being exclusively induced by drought stress in XZ5 among the three genotypes, and sequencing data were confirmed by RT-qPCR. The lncRNA-mRNA interaction-based functional role showed these lncRNAs mediated the regulation of kinase mediated signal transduction, a serine/threonine-protein kinase SMG1 is likely responsible for drought tolerance in XZ5. These findings extend our knowledge of lncRNAs as important regulators in drought tolerance.

Effect of PEG Induced Drought Stress on Germination and Seedling Traits of Maize (Zea mays L.) Lines

Maize is the staple food&#x0D; crop in hilly areas of Nepal. Drought stress is one of the most important crop&#x0D; growth limiting factors leading to lower crop productivity in these areas.&#x0D; Maize seedlings are susceptible to drought stress. Nine lines (Arun-2, NML-1,&#x0D; Rampur Composite, RL-100, RL-105, Rl-106, RL-197, RML-18 and RML-8) of maize&#x0D; obtained from National Maize Research Program, Rampur, Chitwan, Nepal to study&#x0D; their tolerance to drought stress. An experiment was designed to study their&#x0D; drought tolerance by subjecting to four levels of osmotic potential (0, -5, -10&#x0D; and -15 bar) induced by polyethylene glycol (PEG) 6000 in two factor completely&#x0D; randomized design with three replication at Biotechnology Division, National&#x0D; Agricultural Research Institute, Khumaltar, Lalitpur, Nepal. Effects of&#x0D; different levels of PEG 6000 were found significant on all traits studied viz.&#x0D; Germination rate (%), Speed of germination, Root length, Shoot length, Root&#x0D; Shoot ratio, Seedling length, Seedling fresh weight, Seedling dry weight and&#x0D; Vigor index. Line Arun-2 was recorded as best performer followed by Rampur&#x0D; Composite and RL-105 for all the traits analyzed. Lines RL-100, RL-106, RL-197,&#x0D; RML-18 and RML-8 showed poor performance under the same levels of PEG induced&#x0D; drought stress. Furthermore, the results also showed that maize manifests&#x0D; better genetic expression such as drought tolerance under severe moisture&#x0D; stress conditions in soil. Therefore, Lines Arun-2, Rampur Composite and RL-&#x0D; 105 are suggested for varietal improvement program for drought stress conditions.

The effect of polyethylene glycol-induced drought stress on photosynthesis, carbohydrates and cell membrane in Stevia rebaudiana grown in greenhouse

Drought stress is one of the major environmental stresses that limit crop production in arid regions. A greenhouse culture experiment was conducted to evaluate the response of an agronomically and economically important sweet medical herb (Stevia rebaudiana) to polyethylene glycol (PEG 6000)-induced drought stress (5, 10, and 15% (w/v) PEG, equivalent to leaf water potentials of − 0.49, − 1.40 and − 2.93 MPa, respectively) for 1 month. Plant mass, a major determinant of Stevia yield, showed a reduction after PEG treatments. PEG-reduced photosynthesis traits included the maximal quantum yield of photosystem II (Fv/Fm), efficiency of photosystems I and II (PIabs), intercellular CO2, net photosynthesis, chlorophylls, carotenoids and water use efficiency, followed by the reduction of carbohydrates. Under PEG treatment, the reactive oxygen species (ROS) accumulation occurred and plants exhibited an increase in H2O2 generation. Consequently, an increase in malondialdehyde and electrolyte leakage was evident in PEG treatment, indicating membrane lipid peroxidation. In PEG-treated plants, the ROS accumulation was accompanied by an increase in activity of some enzymatic and non-enzymatic antioxidants. Leaf extracts of PEG-treated plants showed lower superoxide anion, hydroxyl and nitric oxide radical scavenging activity than control plants. Drought stress also caused the accumulation of the compatible solutes proline and glycine betaine. Collectively, the results demonstrated that PEG-induced oxidative stress, due to insufficient antioxidant mechanisms, provoked damages to cell membrane and photosynthetic apparatus, with consequently reduced carbohydrates and plant growth. These results are of basic importance as vegetative growth is the major determining criterion for Stevia crops and adequate irrigation is crucial for obtaining higher yield.

Identification of quantitative trait loci associated with drought tolerance traits in rice (Oryza sativa L.) under PEG and field drought stress

Two recombinant inbred line F10 rice populations (IAPAR-9/Akihikari and IAPAR-9/Liaoyan241) were used to identify quantitative trait loci (QTLs) for ten drought tolerance traits at the budding and early seedling stage under polyethylene glycol-induced drought stress, and two traits of leaf rolling index (LRI) and leaf withering degree (LWD) under field drought stress. The results showed that the drought-tolerance capacity of IAPAR-9 was stronger than that of Akihikari and Liaoyan241. Thirty-four QTLs for 12 drought tolerance traits were detected, and among them, in the IAPAR-9/Akihikari population, qLRI9-1 and qLRI10-1 for LRI were repeatedly detected in RM3600-RM553 on chromosome 9 and in RM6100-RM3773 on chromosome 10, respectively, at two times points of July 31 and August 13 in 2014. The two QTLs are stable against the environmental impact, and qLRI9-1 and qLRI10-1 explained 6.77–13.66% and 5.01–8.32% of the phenotypic variance, respectively, at the two times points. qLWD9-2 for LWD in the IAPAR-9/Liaoyan241 population contributed 8.73% of variation was detected in the same marker interval with the qLRI9-1, and qLRI1-1 for LRI and qLWD1-1 for LWD were located in the same marker interval RM11054-RM5646 on chromosome 1, which contributed 18.82 and 5.78% of phenotype variation respectively. qGV3 for germination vigor and qRGV3 for relative germination vigor at the budding stage were detected in the same marker interval RM426-RM570 on chromosome 3, which explained 14.98 and 16.30% of the observed phenotypic variation respectively, representing major QTLs. The above-mentioned stable or major QTLs regions could be useful for molecular marker assisted selection breeding, fine mapping, and cloning.

Potential toxicity of nano-graphene oxide on callus cell of Plantago major L. under polyethylene glycol-induced dehydration

Graphene-based nanomaterials have shown a great potential towards improving plant performance in various contexts. However, their increased application over the last few years has raised concerns about their potential biological and environmental risks, warranting optimization and safety assessment considerations. The current study was performed to explore the potential impacts of nano-garphene oxide (NGO) at various concentrations (100–800µgmL−1) on morphological, physiological and biochemical responses of Plantago major L. calli cultures under normal and polyethylene glycol-induced drought stress conditions. Leaf-derived calli on the ½ MS-treated medium with polyethylene glycol showed a decrease in relative growth rate (78.5%), osmotic potential value (48.2%) and an increase in dry matter (35.1%) and H2O2 (54.2%) contents at the highest employed NGO concentration compared with control (p < 0.05). The engineered NGO affected secondary metabolites and amino acid contents under normal water availability as well: at 800µgmL−1, NGO significantly increased total phenolic (40.9%) and flavonoid (35.3%) contents, but significantly reduced proline (26.9%) content compared to the respective control. The integrated biological marker (IBR/n) index for antioxidant enzymes (SOD, CAT, POD, and APX) activities was differentially influenced by the experimental treatments. Overall, the results demonstrated that NGO can positively affect the performance of P. major L. calli cells when applied at specific concentrations, and provide useful inputs into the further studies on phytotoxicity assessment of NGO.

Genome-wide in silico identification, characterization and transcriptional analysis of the family of growth-regulating factors in common bean (Phaseolus vulgaris L.) subjected to polyethylene glycol-induced drought stress

According to most recent findings, growth regulating factors (GRFs) are plant-specific transcription factors (TFs) that play important roles in many processes, including abiotic and biotic stress response mechanisms. Completion of the common bean (Phaseolus vulgaris) genome project has provided researchers with the opportunity to identify all GRF genes in this species. With this aim, a genome-wide in silico study was performed and 10 GRF proteins (called PhvGRFs) were identified in the common bean genome. Conserved and mandatory motifs (QLQ and WRC) were confirmed in all identified PhvGRFs and two segmental duplication events were determined. Most of the PhvGRFs were found to be more similar to Arabidopsis thaliana GRFs than to Zea mays GRFs in a phylogenetic tree. According to the expression analysis of 10 PhvGRFs, inversely related expression patterns were observed in the roots of Yakutiye and Zulbiye cultivars based on their capacity to adopt to drought stress. After drought treatment of the Zulbiye cultivar, a drought-sensitive common bean cultivar, PhvGRF1, PhvGRF2, PhvGRF3, PhvGRF5, PhvGRF6, PhvGRF9 and PhvGRF10 genes were upregulated 2- to 4-fold in root tissues, as compared to the untreated control. The trend of PhvGRF1, PhvGRF2, PhvGRF3, PhvGRF5, PhvGRF6, PhvGRF7, PhvGRF9 and PhvGRF10 genes showed a consistent decline of 2- to 6-fold in root tissues of the drought-tolerant Yakutiye cultivar subjected to 24 h of drought stress. We demonstrated that the expression patterns of the identified PhvGRFs correlated with the drought-stress response in a cultivar-specific manner in the common bean. We suggest that members of the GRF family can also be used for genetic engineering applications in the common bean.