Improve Stress Tolerance Research Articles

Comparative Genomics of Three Aspergillus Strains Reveals Insights into Endophytic Lifestyle and Endophyte-Induced Plant Growth Promotion.

Aspergillus includes both plant pathogenic and beneficial fungi. Although endophytes beneficial to plants have high potential for plant growth promotion and improving stress tolerance, studies on endophytic lifestyles and endophyte-plant interactions are still limited. Here, three endophytes belonging to Aspergillus, AS31, AS33, and AS42, were isolated. They could successfully colonize rice roots and significantly improved rice growth. The genomes of strains AS31, AS33, and AS42 were sequenced and compared with other Aspergillus species covering both pathogens and endophytes. The genomes of AS31, AS33, and AS42 were 36.8, 34.8, and 35.3 Mb, respectively. The endophytic genomes had more genes encoding carbohydrate-active enzymes (CAZymes) and small secreted proteins (SSPs) and secondary metabolism gene clusters involved in indole metabolism than the pathogens. In addition, these endophytes were able to improve Pi (phosphorus) accumulation and transport in rice by inducing the expression of Pi transport genes in rice. Specifically, inoculation with endophytes significantly increased Pi contents in roots at the early stage, while the Pi contents in inoculated shoots were significantly increased at the late stage. Our results not only provide important insights into endophyte-plant interactions but also provide strain and genome resources, paving the way for the agricultural application of Aspergillus endophytes.

Characteristics and Regulating Roles of Wheat TaHsfA2-13 in Abiotic Stresses.

Heat shock transcription factor (Hsf) exists widely in eukaryotes and responds to various abiotic stresses by regulating the expression of downstream transcription factors, functional enzymes, and molecular chaperones. In this study, TaHsfA2-13, a heat shock transcription factor belonging to A2 subclass, was cloned from wheat (Triticum aestivum) and its function was analyzed. TaHsfA2-13 encodes a protein containing 368 amino acids and has the basic characteristics of Hsfs. Multiple sequence alignment analysis showed that TaHsfA2-13 protein had the highest similarity with TdHsfA2c-like protein from Triticum dicoccoides, which reached 100%. The analysis of tissue expression characteristics revealed that TaHsfA2-13 was highly expressed in root, shoot, and leaf during the seedling stage of wheat. The expression of TaHsfA2-13 could be upregulated by heat stress, low temperature, H2O2, mannitol, salinity and multiple phytohormones. The TaHsfA2-13 protein was located in the nucleus under the normal growth conditions and showed a transcriptional activation activity in yeast. Further studies found that overexpression of TaHsfA2-13 in Arabidopsis thaliana Col-0 or athsfa2 mutant results in improved tolerance to heat stress, H2O2, SA and mannitol by regulating the expression of multiple heat shock protein (Hsp) genes. In summary, our study identified TaHsfA2-13 from wheat, revealed its regulatory function in varieties of abiotic stresses, and will provide a new target gene to improve stress tolerance for wheat breeding.

Tyrosine or lysine priming modulated phenolic metabolism and improved cadmium stress tolerance in mung bean (Vigna radiata L.)

Cadmium stress deleteriously affects plant growth and yield with disturbed plant metabolism. Phenylpropanoid pathway (PePP) is an important component of plant secondary metabolism known to produce nutraceutical antioxidants. We hypothesized that tyrosine (Tyr) and lysine (Lys) vary in their metabolic entry into PePP pathway and modulate it differently. Hence, a completely randomized experiment was planned with four replicates; 12 hours primed (control, hydroprimed, 0.2% Tyr, and 0.2% lysine) mungbean seeds with two stress levels (0 and 0.22 mM CdCl2). Harvests were planned at vegetative and fully mature stages of growth. Attributes like total soluble proteins, total phenolic contents, flavonoids, membrane damage characteristics, and phenolic profile were used to compare the efficacy of applications. Cadmium (0.22 mM) reduced growth in terms of leaf dry weight, leaf area, germination percentage, root vigor, shoot vigor, number of pods, and soluble proteins. Enhanced levels of malondialdehyde (MDA) and relative Root Electrolyte Leakage indicated oxidative damage in stressed plants. Other parameters of growth and yield remained ineffective with increased accumulation of phenolics and flavonoids indicative of moderate cadmium tolerance. Lys and Tyr priming improved root fresh weight, shoot length, leaf dry weight, germination percentage, root and shoot vigor, number of pods, soluble proteins, phenolics and flavonoids with reduction of MDA and root electrolyte leakage. Activity of PAL, leaf number and leaf area were exclusively increased in Tyr primed stressed plants. Tyr directly and Lys indirectly affected products of PePP with improved stress tolerance in mung bean.

Knockdown of PagSAP11 Confers Drought Resistance and Promotes Lateral Shoot Growth in Hybrid Poplar (Populus alba × Populus tremula var. glandulosa)

Plants have evolved defense mechanisms to overcome unfavorable climatic conditions. The growth and development of plants are regulated in response to environmental stress. In this study, we investigated the molecular and physiological characteristics of a novel gene PagSAP11 in hybrid poplar (Populus alba × Populus tremula var. glandulosa) under drought stress. PagSAP11, a stress-associated protein (SAP) family gene, encodes a putative protein containing an A20 and AN1 zinc-finger domain at its N- and C-termini, respectively. Knockdown of PagSAP11 transgenic poplars (SAP11-Ri) enhanced their tolerance to drought stress compared with wild type plants. Moreover, the RNAi lines showed increased branching of lateral shoots that led to a gain in fresh weight, even when grown in the living modified organism (LMO) field. In SAP11-Ri transgenic plants, the expression levels of genes involved in axillary bud outgrowth and cell proliferation such as DML10, CYP707A and RAX were increased while the DRM gene which involved in bud dormancy was down-regulated. Taken together, these results indicate that PagSAP11 represents a promising candidate gene for engineering trees with improved stress tolerance and growth during unfavorable conditions.

Changes in epigenetic features in legumes under abiotic stresses.

Legume crops are rich in nutritional value for human and livestock consumption. With global climate change, developing stress-resilient crops is crucial for ensuring global food security. Because of their nitrogen-fixing ability, legumes are also important for sustainable agriculture. Various abiotic stresses, such as salt, drought, and elevated temperatures, are known to adversely affect legume production. The responses of plants to abiotic stresses involve complicated cellular processes including stress hormone signaling, metabolic adjustments, and transcriptional regulations. Epigenetic mechanisms play a key role in regulating gene expressions at both transcriptional and posttranscriptional levels. Increasing evidence suggests the importance of epigenetic regulations of abiotic stress responses in legumes, and recent investigations have extended the scope to the epigenomic level using next-generation sequencing technologies. In this review, the current knowledge on the involvement of epigenetic features, including DNA methylation, histone modification, and noncoding RNAs, in abiotic stress responses in legumes is summarized and discussed. Since most of the available information focuses on a single aspect of these epigenetic features, integrative analyses involving omics data in multiple layers are needed for a better understanding of the dynamic chromatin statuses and their roles in transcriptional regulation. The inheritability of epigenetic modifications should also be assessed in future studies for their applications in improving stress tolerance in legumes through the stable epigenetic optimization of gene expressions.

Improved pathogen and stress tolerance in tomato mutants of SET domain histone 3 lysine methyltransferases.

Histone lysine methylations (HLMs) are implicated in control of gene expression in different eukaryotes. However, the role of HLMs in regulating desirable crop traits and the enzymes involved in these modifications are poorly understood. We studied the functions of tomato histone H3 lysine methyltransferases SET Domain Group 33 (SDG33) and SDG34 in biotic and abiotic stress responses. SDG33 and SDG34 gene edited mutants were altered in H3K36 and H3K4 methylations, and expression of genes involved in diverse processes and responses to biotic and abiotic stimuli. The double but not the single mutants show resistance to the fungal pathogen Botrytis cinerea. Interestingly, single mutants were tolerant to drought and the double mutant showed superior tolerance and plant growth consistent with independent and additive functions. Mutants maintained higher water status during drought and improved recovery and survival after lapse of drought. Notably, diminution of H3K4 and H3K36 trimethylation and expression of negative regulators in challenged plants contributes to stress tolerance of the mutants. Mutations in SDG33 and SDG34 are likely to remove predisposition to biotic and abiotic stress by disrupting permissive transcriptional context promoting expression of negative regulatory factors. These allows improvement of stress and pathogen tolerance, without growth trade-offs, through modification of histone epigenetic marks.

Genome Editing Targets for Improving Nutrient Use Efficiency and Nutrient Stress Adaptation.

In recent years, the development of RNA-guided genome editing (CRISPR-Cas9 technology) has revolutionized plant genome editing. Under nutrient deficiency conditions, different transcription factors and regulatory gene networks work together to maintain nutrient homeostasis. Improvement in the use efficiency of nitrogen (N), phosphorus (P) and potassium (K) is essential to ensure sustainable yield with enhanced quality and tolerance to stresses. This review outlines potential targets suitable for genome editing for understanding and improving nutrient use (NtUE) efficiency and nutrient stress tolerance. The different genome editing strategies for employing crucial negative and positive regulators are also described. Negative regulators of nutrient signalling are the potential targets for genome editing, that may improve nutrient uptake and stress signalling under resource-poor conditions. The promoter engineering by CRISPR/dead (d) Cas9 (dCas9) cytosine and adenine base editing and prime editing is a successful strategy to generate precise changes. CRISPR/dCas9 system also offers the added advantage of exploiting transcriptional activators/repressors for overexpression of genes of interest in a targeted manner. CRISPR activation (CRISPRa) and CRISPR interference (CRISPRi) are variants of CRISPR in which a dCas9 dependent transcription activation or interference is achieved. dCas9-SunTag system can be employed to engineer targeted gene activation and DNA methylation in plants. The development of nutrient use efficient plants through CRISPR-Cas technology will enhance the pace of genetic improvement for nutrient stress tolerance of crops and improve the sustainability of agriculture.

Over-Expression of Dehydroascorbate Reductase Improves Salt Tolerance, Environmental Adaptability and Productivity in Oryza sativa.

Abiotic stress induces reactive oxygen species (ROS) generation in plants, and high ROS levels can cause partial or severe oxidative damage to cellular components that regulate the redox status. Here, we developed salt-tolerant transgenic rice plants that overexpressed the dehydroascorbate reductase gene (OsDHAR1) under the control of a stress-inducible sweet potato promoter (SWPA2). OsDHAR1-expressing transgenic plants exhibited improved environmental adaptability compared to wild-type plants, owing to enhanced ascorbate levels, redox homeostasis, photosynthetic ability, and membrane stability through cross-activation of ascorbate-glutathione cycle enzymes under paddy-field conditions, which enhanced various agronomic traits, including root development, panicle number, spikelet number per panicle, and total grain yield. dhar2-knockdown plants were susceptible to salt stress, and owing to poor seed maturation, exhibited reduced biomass (root growth) and grain yield under paddy field conditions. Microarray revealed that transgenic plants highly expressed genes associated with cell growth, plant growth, leaf senescence, root development, ROS and heavy metal detoxification systems, lipid metabolism, isoflavone and ascorbate recycling, and photosynthesis. We identified the genetic source of functional genomics-based molecular breeding in crop plants and provided new insights into the physiological processes underlying environmental adaptability, which will enable improvement of stress tolerance and crop species productivity in response to climate change.

Genome-Wide Identification and Functional Differentiation of Fatty Acid Desaturase Genes in Olea europaea L.

Olive (Olea europaea L.) is a world-famous woody oil tree and popular for redundant unsaturated fatty acids. Fatty acid desaturase (FAD) genes are responsible for fatty acid desaturation and stress regulation but have not yet been identified in olive at the whole genome level. This study identified 40 and 27 FAD genes in the cultivated olive O. europaea cv. Farga and the wild olive O. europaea var. Sylvestris, respectively. Phylogenetic analysis showed that all the FAD genes could be classified into the soluble FAB2/SAD clade and membrane-bound clade, including ADS/FAD5, DES, FAD4, SLD, ω-6 and ω-3, with the high consistency of subcellular localization, motif composition and exon-intron organization in each group. FAD genes in olive showed the diverse functional differentiation in morphology of different tissues, fruit development and stress responses. Among them, OeFAB2.8 and OeFAD2.3 were up-regulated and OeADS.1, OeFAD4.1 and OeFAD8.2 were down-regulated under the wound, Verticillium dahliae and cold stresses. This study presents a comprehensive analysis of the FAD genes at the whole-genome level in olives and will provide guidance for the improvement of oil quality or stress tolerance of olive trees.

Genetic Improvement of Heat Stress Tolerance in Cereal Crops

Crop heat stress is a threat to food supply, with heatwaves expected to increase in frequency and intensity globally. In addition to yield loss, heat stress dramatically reduces fertility and seed-setting rate, grain quality and weight, and seed germination and growth. Genetic variability for heat stress tolerance can be used in breeding programs to develop tolerant genotypes. The availability of genome assemblies with high-confidence sequences for many cereal crops, including rice, maize, wheat and barley, now allows the identification of heat stress tolerance-associated genes and gene networks. This review focuses on synthesizing current advances in understanding the detrimental effects of heat stress on cereal crop production at the physiological and genetic levels. It provides an account of available genomic resources, genetic variation, candidate genes, and molecular markers for heat stress tolerance. Lastly, this review offers insight into crop genetic improvement for heat stress tolerance, including germplasm screening in glasshouse and field trials, marker-assisted selection, mapping genomic loci and identification of candidate genes, and genomic-assisted breeding.

Priming with Small Molecule-Based Biostimulants to Improve Abiotic Stress Tolerance in Arabidopsis thaliana

Biostimulants became a hotspot in the fight to alleviate the consequences of abiotic stresses in crops. Due to their complex nature, it is challenging to obtain stable and reproducible final products and more challenging to define their mechanism of action. As an alternative, small molecule-based biostimulants, such as polyamines have promoted plant growth and improved stress tolerance. However, profound research about their mechanisms of action is still missing. To go further, we tested the effect of putrescine (Put) and its precursor ornithine (Orn) and degradation product 1,3-diaminopropane (DAP) at two different concentrations (0.1 and 1 mM) as a seed priming on in vitro Arabidopsis seedlings grown under optimal growth conditions, osmotic or salt stress. None of the primings affected the growth of the seedlings in optimal conditions but altered the metabolism of the plants. Under stress conditions, almost all primed plants grew better and improved their greenness. Only Orn-primed plants showed different plant responses. Interestingly, the metabolic analysis revealed the implication of the N- acetylornithine and Orn and polyamine conjugation as the leading player regulating growth and development under control and stress conditions. We corroborated polyamines as very powerful small molecule-based biostimulants to alleviate the adverse abiotic stress effects.

Use of endophytic fungi in turfgrasses: Difficulties in delivery to the market

AbstractThe agronomic benefits of endophytic Epichloë fungi for the performance of ryegrass (Lolium spp.) and fescue (Festuca spp.) species were first reported in the 1980s. Various Epichloë endophyte species and strains have been shown to produce a series of different alkaloids with considerable impact on insect pests and grazing animals, some effects on nematodes and diseases, and improvements in plant stress tolerance. However, the impact of these alkaloids on plant performance and turf resilience varies across environments, and often relates to specific insect pressures and stressful summer conditions. Over 40 insect pests and diseases have been documented as responding to endophyte infection.As many Epichloë fungi are seed transmitted, endophyte transmission to the seed is controlled by the levels found in the parent plants and how well the endophyte is maintained during seed production. Endophyte viability in seed lots can drop during storage and transport, especially when stored under high temperatures and humidity. Endophyte growth into seed during seed production can be influenced by the weather, use of fungicides and growth regulators, and the timing of combining after swathing. In the United States, the endophyte infection levels in breeders’ seed of the cultivars used in the National Turfgrass Evaluation Program trials have been reported but currently, no standards exist for labeling cultivars delivered with high endophyte levels. Without suitable protocols and standards, challenges exist in delivering high endophyte infection levels to tall fescue (Festuca arundinacea Schreb.), ryegrass, and fine fescues.

Characteristics of Bacterial Microbiota in Different Intestinal Segments of Aohan Fine-Wool Sheep.

The microbial community performs vital functions in the intestinal system of animals. Modulation of the gut microbiota structure can indirectly or directly affect gut health and host metabolism. Aohan fine-wool sheep grow in semi-desert grasslands in China and show excellent stress tolerance. In this study, we amplified 16S rRNA gene to investigate the dynamic distribution and adaptability of the gut microbiome in the duodenum, jejunum, ileum, cecum, colon, and rectum of seven Aohan fine-wool sheep at 12 months. The results showed that the microbial composition and diversity of the ileum and the large intestine (collectively termed the hindgut) were close together, and the genetic distance and functional projections between them were similar. Meanwhile, the diversity index results revealed that the bacterial richness and diversity of the hindgut were significantly higher than those of the foregut. We found that from the foregut to the hindgut, the dominant bacteria changed from Proteobacteria to Bacteroidetes. In LEfSe analysis, Succiniclasticum was found to be significantly abundant bacteria in the foregut and was involved in succinic acid metabolism. Ruminococcaceae and Caldicoprobacteraceae were significantly abundant in hindgut, which can degrade cellulose polysaccharides in the large intestine and produce beneficial metabolites. Moreover, Coriobacteriaceae and Eggthellaceae are involved in flavonoid metabolism and polyphenol production. Interestingly, these unique bacteria have not been reported in Mongolian sheep or other sheep breeds. Collectively, the gut microbiota of Aohan fine-wool sheep is one of the keys to adapting to the semi-desert grassland environment. Our results provide new insights into the role of gut microbiota in improving stress tolerance and gut health in sheep.

Editorial: Biostimulants as an Avenue of Abiotic Stress Tolerance Improvement in Crops

Plants are sessile organisms that are continuously exposed to changing climatic conditions. To provide 27 food security for the increasing global population, agricultural produce must double by 2050. Increases 28 agricultural productivity have been provided using chemical fertilizers. However, such gains in 29 productivity using this non-sustainable, synthetic chemistry have been shown repeatedly to pose threats 30 to the ecosystem and human health. Additionally, the prices of these inputs continuously increase as 31 their sources are non-renewable. Thus, there is an immediate need for the development of more 32 sustainable agricultural production systems (Castiglione et al., 2021)

Development and Characterization of Chromosome Segment Substitution Lines Derived from Oryza rufipogon in the Background of the Oryza sativa indica Restorer Line R974

Dongxiang wild rice (DXWR) (O. rufipogon Griff.), which has the northernmost worldwide distribution of a wild rice species, is a valuable genetic resource with respect to improving stress tolerance in cultivated rice (Oryza sativa L.). In the three-line hybrid rice breeding system, restorer lines play important roles in enhancing the tolerance of hybrid rice. However, restorer lines have yet to be used as a genomic background for development of substitution lines carrying DXWR chromosome segments. We developed a set of 84 chromosome segment substitution lines (CSSLs) from a donor parent DXWR × recurrent parent restorer line R974 (Oryza sativa indica) cross. On average, each CSSL carried 6.27 introgressed homozygous segments, with 93.37% total genome coverage. Using these CSSLs, we identified a single QTL, qDYST-1, associated with salt stress tolerance on chromosome 3. Furthermore, five CSSLs showing strong salt stress tolerance were subjected to whole-genome single-nucleotide polymorphism chip analyses, during which we detected a common substitution segment containing qDYST-1 in all five CSSLs, thereby implying the validity and efficacy of qDYST-1. These novel CSSLs could make a significant contribution to detecting valuable DXWR QTLs, and provide important germplasm resources for breeding novel restorer lines for use in hybrid rice breeding systems.

Potassium deficiency stress tolerance in peanut (Arachis hypogaea) through ion homeostasis, activation of antioxidant defense, and metabolic dynamics: Alleviatory role of silicon supplementation

Potassium (K) scarcity of arable land is one of the important factors that hamper the growth of the plants and reduce yield worldwide. In the current study, we examine the physiological, biochemical, and metabolome response of Arachis hypogaea (GG7 genotype: fast-growing, tall, early maturing, and high yielding) under low K either solitary or in combination with Si to elucidate the ameliorative role of Si. The reduced fresh and dry biomass of peanut and photosynthetic pigments content was significantly alleviated by Si. Si application did not affect the leaf and stem K+, although it enhanced root K+ in K-limitation, which is probably due to up-regulated expression of genes responsible for K uptake. Si improves the potassium use efficiency in K-limitation as compared to control. K-deficiency increased MDA, O2•−, and H2O2 levels in leaf and root of peanut. Si improved/maintained the activity of antioxidative enzymes, which significantly lowered the ROS accumulation in K-limitation. The AsA/DHA and GSH/GSSG ratio was approximately unaffected in both leaf and root, suggesting the maintained cellular redox potential in K-starved peanut. Si promotes accumulation of sugars and sugar alcohols, phytohormones indicating their probable involvement in signal transduction, osmotic regulation, and improvement of stress tolerance. Down-regulation of aspartic acid and glutamic acid while up-regulation of lysine, histidine, and arginine could maintain charge balance in K-deprived peanut. The significant accumulation of polyphenols under K limitation supplemented with Si suggests the role of polyphenols for ROS scavenging. Our results demonstrated that Si as a beneficial element can mitigate K-nutrient toxicity and improve KUE of peanut under K-limitation conditions. Moreover, our results demonstrate that Si application can improve crop yield, quality, and nutrient use efficiency under nutrient limitation conditions.

Biostimulants to Improved Tree Physiology and Fruit Quality: A Review with Special Focus on Sweet Cherry

Due to the increasing global population and the continued need to sustainably increase agricultural production, the agricultural sector requires innovative strategies to increase productivity and efficiency in the use of resources. Biostimulants have emerged as new, promising, and environmentally friendly products to promote the overall sustainability of production systems. Humic and fulvic acids, protein hydrolysates, seaweed extracts, chitosan and other biopolymers, inorganic compounds, beneficial fungi, and bacteria are widely accepted categories of biostimulants, with proven potential in improving plant growth, increasing crop production, and quality of the final product. Some of them also have the capacity to enhance nutrient uptake and improve stress tolerance of the crop. Sweet cherry is a highly appreciated fruit, with a significant economic value, linked to production yield and quality attributes influencing consumer acceptability. However, this fruit presents several undesirable characteristics, such as physiological disorders (e.g., fruit cracking) and a short shelf-life. Several approaches are used to enhance not only sweet cherry production, but also cherry quality, with the latest efforts being placed in biostimulants. The present review focuses on the most recent findings on the use of biostimulants in sweet cherry production.

Melatonin Application Alleviates Stress-Induced Photosynthetic Inhibition and Oxidative Damage by Regulating Antioxidant Defense System of Maize: A Meta-Analysis.

Melatonin is effective in modulating metabolism and regulating growth and development in many plants under biotic and abiotic stress. However, there is no systematic quantification of melatonin effects on maize growth, gas exchange, chlorophyll content, and the antioxidant defense system. A meta-analysis was conducted on thirty-two currently available published articles to evaluate the effect of stress types, study types, and maize varieties on response ratio (lnRR++) of “melatonin” to “control (no melatonin)” on plant growth, enzyme activities, gas exchange parameters, and photosynthetic pigments. Our findings revealed that melatonin application overall increased plant height, leaf area, root length, fresh and dry root weight and shoot weight, superoxide dismutase (SOD), peroxide (POD), catalase (CAT), ascorbate peroxidase (APX), soluble sugar and protein, photosynthetic rate, stomatal conductance, transpiration rate, chlorophyll, and carotenoid in maize leaf under stress conditions. In contrast, melatonin application decreased the levels of hydrogen peroxide (H2O2), superoxide anion (O2−), malondialdehyde (MDA), and electrolyte leakage. The categorical meta-analysis demonstrated that melatonin application to chilling stress resulted in higher SOD activity followed by salt stress. Melatonin application to all stress types resulted in higher POD, CAT and APX activities, except Cd stress, which had no effect on POD and decreased CAT by 38% compared to control. Compared to control, melatonin resulted in lower reactive oxygen species (ROS) and electrolyte leakage under no stress, Cd, drought, salt, lead, heat, and chilling stress in all study types (pot, growth chamber, hydroponic, and field), except O2 content which was not affected in pot and growth chamber studies. It was concluded that melatonin alleviates oxidative damage by improving stress tolerance, regulating the antioxidant defense system, and increasing leaf chlorophyll content compared to control.

NGHIÊN CỨU MỨC ĐỘ BIỂU HIỆN CỦA CÁC GEN LẶP TRONG HỌ NHÂN TỐ PHIÊN MÃ NAC LIÊN QUAN ĐẾN ĐÁP ỨNG HẠN Ở CÂY LẠC (Arachis hypogaea)

NAC has been considered one of the largest transcription factor families in plant species. In peanut (Arachis hypogaea), 29 members of the AhNAC gene family have been identified and characterized. However, the information of their functions related to the mechanism of the stress response has been reported. In this study, a total of seven duplication events, which occurred from the segmental duplication, has been predicted in the AhNAC gene family in peanuts. The Ka\Ks ratios revealed that natural selection prevented the presence of the point mutations in the most duplicated genes, consequently, maintaining their structure and function during evolution. Based on the unrooted phylogenetic tree between AhNAC proteins in peanuts and 23 drought-responsive CaNAC in chickpea (Cicer arietinum), we proposed 12 members of the AhNAC that potentially share similar functions with well-characterized NAC in chickpea. Furthermore, various hormone- and drought-responsive cis-regulatory elements have been found in the promoter regions of these candidate genes. Re-analysis of the previous RNA-Seq demonstrated that the majority of the candidate AhNAC genes were responsive to the osmotic stress. Taken together, our study could provide an important foundation for further functional characterization towards the improvement of stress tolerance in peanuts.

Approaches Involved in the Vegetable Crops Salt Stress Tolerance Improvement: Present Status and Way Ahead.

Salt stress is one of the most important abiotic stresses as it persists throughout the plant life cycle. The productivity of crops is prominently affected by soil salinization due to faulty agricultural practices, increasing human activities, and natural processes. Approximately 10% of the total land area (950 Mha) and 50% of the total irrigated area (230 Mha) in the world are under salt stress. As a consequence, an annual loss of 12 billion US$ is estimated because of reduction in agriculture production inflicted by salt stress. The severity of salt stress will increase in the upcoming years with the increasing world population, and hence the forced use of poor-quality soil and irrigation water. Unfortunately, majority of the vegetable crops, such as bean, carrot, celery, eggplant, lettuce, muskmelon, okra, pea, pepper, potato, spinach, and tomato, have very low salinity threshold (ECt, which ranged from 1 to 2.5 dS m–1 in saturated soil). These crops used almost every part of the world and lakes’ novel salt tolerance gene within their gene pool. Salt stress severely affects the yield and quality of these crops. To resolve this issue, novel genes governing salt tolerance under extreme salt stress were identified and transferred to the vegetable crops. The vegetable improvement for salt tolerance will require not only the yield influencing trait but also target those characters or traits that directly influence the salt stress to the crop developmental stage. Genetic engineering and grafting is the potential tool which can improve salt tolerance in vegetable crop regardless of species barriers. In the present review, an updated detail of the various physio-biochemical and molecular aspects involved in salt stress have been explored.