Assessment of molecular markers and marker-assisted selection for drought tolerance in barley(Hordeum vulgare L.)

This review updates the present status of the field of molecular markers and marker-assisted selection(MAS),using the example of drought tolerance in barley.The accuracy of selected quantitative trait loci(QTLs),candidate genes and suggested markers was assessed in the barley genome cv.Morex.Six common strategies are described for molecular marker development,candidate gene identification and verification,and their possible applications in MAS to improve the grain yield and yield components in barley under drought stress.These strategies are based on the following five principles:(1)Molecular markers are designated as genomic‘tags’,and their‘prediction’is strongly dependent on their distance from a candidate gene on genetic or physical maps;(2)plants react differently under favourable and stressful conditions or depending on their stage of development;(3)each candidate gene must be verified by confirming its expression in the relevant conditions,e.g.,drought;(4)the molecular marker identified must be validated for MAS for tolerance to drought stress and improved grain yield;and(5)the small number of molecular markers realized for MAS in breeding,from among the many studies targeting candidate genes,can be explained by the complex nature of drought stress,and multiple stress-responsive genes in each barley genotype that are expressed differentially depending on many other factors.

Screening and identification of salt tolerance soybean varieties and germplasms

Soil salinization is a globally prevalent abiotic environmental stress.The imbalance of ions caused by high concentrations of sodium chloride results in a 40%reduction in soybean yield.Soybean,as an important crop for soil quality improvement,necessitates the identification of salt-tolerant varieties and germplasms to effectively utilize and enhance saline-alkali land.In this study,we assessed the salt tolerance of 435 soybean varieties and germplasms during the seedling stage.Among them,Qihuang34,You2104,Hongzhudou,Pamanheidou,and Osage exhibited grade 1 salt tolerance rates surpassing other tested materials.Furthermore,Hongzhudou and Qihuang34 demonstrated higher salt tolerance during germination and emergence stages based on their elevated rates of emergence,salt tolerance index,chlorophyll content,and shoot fresh weights.Overall findings provide valuable resources for molecular breeding efforts aimed at developing salt-tolerant soybean varieties suitable for cultivation in saline-alkali soils.

Multidimensional evaluation of salt tolerance in groundnut genotypes through biochemical responses

The manuscript explores the complex interplay between groundnut genotypes,salt tolerance and hormonal influence,shedding light on the dynamic responses of three specific groundnut genotypes,KDG-128,TG-37 A and GG-20,to salt treatments and gibberellic acid(GA3).The study encompasses germination,plant growth,total protein content and oil content as key parameters.Through comprehensive analysis,it identifies TG-37 A and KDG-128 as salt-tolerant genotypes,and GG-20 as salt-susceptible genotypes,which highlighting the potential for targeted breeding efforts to develop more resilient groundnut varieties.Moreover,the quantification of protein and oil content under different treatments provides vital data for optimizing nutritional profiles in groundnut cultivars.Principal Component Analysis(PCA) underscores the significance of the first principal component(PC1)in explaining the majority of variance,capturing primary trends and differences in plant length.Analysis of Variance(ANOVA) and hierarchical analysis confirm the presence of statistically significant differences in protein and oil content among the genotypes.Pearson's correlation coefficient matrix analysis reveals strong positive correlations between plant length and protein content,plant length and oil content,and a moderately positive correlation between protein content and oil content.These findings provide valuable insights into groundnut physiology,salt tolerance,and nutritional composition,with implications for future research in sustainable agriculture and crop improvement.

Gamma Irradiation of Embryogenic Callus Cultures and In vitro Selection for Salt Tolerance in Sugarcane (Saccharum officinarum L.)

Radiation induced mutagenesis followed by in vitro selection was employed for salt tolerance in popular Indian sugarcane （Saccharum officinarum L.） cv. CoC-671. Embryogenic calli were gamma irradiated and exposed to different levels of NaCl （42.8, 85.6, 128.3, 171.1,213.9, 256.7, 299.5, or 342.2 mM）. The relative growth rate （RGR） decreased progressively with increasing salt stress and was the least with a salt stress of 256.7 mM （0.25±0.009）, almost 10 fold lesser than the control. The RGR was significantly lower in 85.6 mM and higher salt stressed calli than the control. The survival percent also decreased, with an increase in NaCl concentration. In case of 10 and 20 Gy irradiated calli, regeneration was observed up to 85.6 mM NaCl selection, medium, whereas, higher treatments （128.3 mM and beyond） exhibited browning initially. However, in the subsequent subcultures, regeneration was obtained in the case of 10 and 20 Gy irradiated calli on 128.3 and 171.1 mM NaCl selections. Higher dose of gamma irradiation （40 Gy） also showed regeneration, but only with 85.6 mM NaCI selection. The unirradiated calli regenerated the highest number of plantlets followed by 10 and 20 Gy irradiated calli on salt selection. A total of 147 plantlets were selected from different salt levels. The salt selected plants are being tested for their field performance.

Breeding and Selection of Some Lines of Bread Wheat for Salt Tolerance

The aim of this experimental work is to select wheat progenies tolerant high levels of salinity. Studies were conducted to determine the realized response in salt tolerance of some selected progeny （F3） through one cycle of screening and selection and the extent of variability for salt tolerance among selected progeny （F3） of wheat. All the selected progeny （F3） derived from （F2） populations after exposure are to high salinity level, were tested for salt tolerance during all growth stages in sand cultures salinized with 0, 100, 175 mM NaCI as compared with the unselected progeny （F2）. Results showed that the selected progeny （F3） were in all cases except one, superior in yield at maturity and in most cases significantly so, both at 100 and 175 mM NaCl, to the yield of the unselected progeny （F2） controls. In this study, some selected progeny exhibited more than twice the seed yield compared with that obtained from unselected progeny at 175 mM NaCl, and their seed yield was also significantly higher than that at 0 mM NaCl. Results also indicated that the highest value percentage of realized response in salt tolerance was in （F3AS1） and （F3AS2） at 175 mM NaCI. It is important to bear in mind that the significant improvement in selected progeny was achieved just in a single cycle of selection. There is then a strong possibility that further increases in tolerance may be obtained through further cycles of selection till reaching F6 or F7 where would show genetics stability.

Cloning of cDNA Encoding Choline Monooxygenase from Suaeda liaotungensis and Salt Tolerance of Transgenic Tobacco

Betaine is a very effective osmoprotectant found in many organisms. In high plants, betaine is synthesized by oxidation of choline in two sequential steps: choline-->betaine aldehyde-->betaine. The first step is catalyzed by choline monooxygenase (CMO). In this study, the full-length CMO cDNA (1 820 bp) was cloned from halophyte Suaeda liaotungensis Kitag by RT-PCR and RACE. It included a 123 bp 5' UTR, a 368 bp 3' UTR and a 1 329 bp open reading frame encoding a 442-amino-acid polypeptide with 77%, 72% and 74% sequence identity compared to CMOs from spinach, sugar beet and Atriplex hortensis, respectively. The CMO open reading frame (ORF) was cloned and the plant expression vector pBI121-CMO was constructed. It was transferred into tobacco ( Nicotiana tabacum L. ev. 89) via Agrobacterium mediation. PCR and Southern blotting analysis showed that the CMO gene was integrated into tobacco genome. Transgenic tobacco plants contained higher amount of betaine than that of control plants and were able to survive on MS medium containing 250 mmol/L NaCl. Relative electronic conductivity demonstrated less membrane damage in transgenic plants as in the wild type.

Relationship Between Polyamine Metabolism in Roots and Salt Tolerance of Barley Seedlings

Plant growth rate (GR), contents of free polyamines (fPAs) and bound polyamines (bPAs) and activities of some key enzymes involved in polyamine (PA) metabolism in the roots of two barley (Hordeum valgare L.) cultivars differing in salt sensitivity were investigated with 0-300 mmol/L NaCl treatments. With 0-200 mmol/L NaCl treatments, activities of arginine decarboxylase (ADC) and transglutaminase (TGase) and PA oxidase (PAO) in the roots of barley seedlings all increased, while TGase and PAO activities decreased slightly at 300 mmol/L NaCl. As a result, free Put (fPut) content increased continuously with increasing concentrations of NaCl, while levels of free Spd (fSpd) and an unknown PA (fPAx) and bPAs (bPut, bSpd and bPAx), as well as (fSpd + fPAx)/fPut ratio rose at 50-200 mmol/L NaCl and reduced at 300 mmol/L NaCl. However, no significant change in the tetra-amine spermine (Spin) content was observed. Statistical analysis showed that GR was very significantly positively correlated with (fSpd + fPAx)/fPut ratios and the contents of bPAs, whereas a significant inverse correlation existed between GR and the ratios of fPA contents to bPA levels. These results showed that, under salt stress, the balance between fSpd, fPAx and fPut levels and an equipoise between fPA and bPA contents in roots were important to salt tolerance of barley seedlings.

Effects of Adaptation to Elevated Salinity on Some Enzymes' Salt_tolerance in Vitro and Physiological Changes of Eelgrass

The eelgrass ( Zostera marina L.) was treated with artificial seawater (ASW) of different salinities ( 100%, 150% and 200% seawater) for 5 d. The activities of two enzymes extracted from the plant leaves were determined under a salinity grade in vitro So were the photosynthesis rates of the plants from the three treatments in the media with different salinities 100%, 150%, 200%, 300% ASW) and Some physiological data. The data showed that under increased salinities (concentrated seawater), Na+, Cl-, MDA (malon dialdehyde) and glucose contents and the osmotic potentials ( absolute value) in the leaves increased with the salinity elevation in the medium (ASW), but both K+ and free amino acid (mainly proline) contents decreased. Malate dehydrogenase (MDH) from the plant leaves under a salinity grade showed its activities (A) as follows: A(100%) (ASW) > A(150%) (ASW) > A(200%) (ASW). Phosphoenolpyruvate carboxylase (PEPC) extracted from the 100% ASW- and 200% ASW-treated plants showed similar activities (both insensitive to salinities) under the salinity grade in vitro, but the activities of PEPC from plants treated with 150% ASW were dependent oil salinity. Whether the plant is stressed at 150% ASW and can stand higher salinity than seawater needs to be studied further. Meantime, die data do not agree with the opinion that the adaptation of the eelgrass to seawater salinity is partly fulfilled by its insensitiveness to salinities in Some metabolic enzymes. It can be inferred that the lack of transpiration may be an important aspect of tire plant's tolerance to seawater salinity.

Application of Fuzzy Comprehensive Evaluation Method Based on Entropy Weight Theory in Evaluation of Salt Tolerance of Cotton

[Objective] The aim was to propose a new entropy weight fuzzy compre- hensive evaluation method for assessing cotton salt tolerance, realizing the objective, accurate and comprehensive evaluation of salt tolerance of cotton. [Method] A sand culture experiment under salt stress of 150 mmol/L of NaCI was designed. The in- dicator weight was determined with the entropy weight fuzzy comprehensive evalu- ation method, based on the salt injury index of indicators. The salt tolerance of cotton was evaluated comprehensively. [Result] At the germination stage, the entropy and weight of salt injury index of germination energy, vigor index, hypocotyl length and fresh weight were highest, followed by germination rate and germination index, and of root length were lowest. At the seedling stage, the entropy and weight of salt injury index of plasma membrane permeability, root vigor and leaf expansion rate were highest, followed by plant height and net photosynthetic rate, and of shoot dry weight and root dry weight were lowest. The salt tolerance of cotton differed a- mong growth stages and cultivars. Among the 11 cultivars, CCRI-44 and CCRI-75 were steadily salt-tolerant at both germination and seedling stages; CCRI-17, Sumi- an 22, Sumian 15 and Dexiamianl had a stable moderate salt tolerance; while Sumian 12 and Simian 3 were steadily salt-sensitive. [Conclusion] The evaluated result was objective and exact, which indicated that this method could be used in comprehensive evaluation of salt tolerance of cotton.

Winter Wheat Salt Tolerance Appraisal Indices with Varied Mineral Content of Saline Water

[Objective] The aim was to study wheat salt resistance appraisal indicators under the condition of saline water irrigation.[Method] A trial was conducted with five varieties irrigated with saline water at 1,2,4,6,and 8 g/L during 2009-2010 and 2010-2011 in the research station of Dry-land Farming Institute of Hebei Academy of Agricultural and Forestry Sciences.With standardized indicators for measuring treatment,the response relations among different salt stress levels and winter wheat growth index were analyzed in this study.[Result] Under the condition of different salinity of irrigation,relative plant height after jointing stage,relative leaf area index,relative dry matter weight,relative ear number per unit area showed significant differences among treatments and yield showed significant correlation,which can be taken as salt-resistance examination index of wheat.[Conclusion] The results showed that the relative height after jointing stage was recommended as the most practical salt-tolerance appraisal indices,because it was easy to be observed and sensitive to salt stress.

The Waterlogging Tolerance of Cut Rose by Field Observation and Variety Selection in Sanya

[Objective] The aim was to master waterlogging tolerance of cut rose vari-eties, and provided technical reference for promoting cut rose largely. [Method] Based on natural rainfal information from July to October in Sanya, comprehensive performance of 22 varieties were observed in two consecutive years to analyze wa-terlogging tolerance ability of cut rose at waterlogging disaster. [Result] The mortality rates of Diana, Black Magic, Eric Red and Vendela were over 15%, and Diana ’s was 25.7%. Carola, Rouge Meil and, Perfume white, Lovers ’ Meeting, Choice, Tineke, Vendela, Marina, Samantha, Golden Emblem, Asagumo, Pink Fan and Dou-ble Delight grew better and recovered quickly after the disaster, with waterlogging tolerance. [Conclusion] The waterlogging tolerance of Carola, Rouge Meil and, My Choice, Tineke, Vendela, Marina, Samantha, Golden Emblem, Asagumo, Pink Fan and Double Delight was the best, which is also true for their comprehensive perfor-mances. But the waterlogging tolerance of other major cultivars such as Black Magic, Movie Star, Tineke and Vendela was poorer.

On the Identification and Evaluation of Salt Tolerance of Peanut Germplasm

For screening out salt tolerance germplasm and providing materials for ge- netic research of peanut, based on the indexes including relative germination poten- tial, relative germination rate, relative germination index and salt-injury rate, 128 peanut germplasms were selected for salt-tolerant identification and estimation under 2.5% NaCI. We found significant but various depressing levels of germination rate under salt stress among different germplasms, and only 5% of 128 germplasms were highly resistant to salinity. We also found that the relative germination index was a useful evaluation index for salt tolerance besides salt damage rate and rela- tive germination rate. After all, we comprehensively screened out 7 materials （JS011, JS024, JS125, JS491, JS523, JS524 and JS525） as salt tolerance germplasms for further research. Key

Mechanism of Salt Tolerance in Rice

Shaheen Basma ti was evolved as a salt tolerant fine rice va riety by the Soil Salinity Research Institute,Pindi Bhattian, Pakistan. Water culture studies were conducted to investigate the physiological mechanismexercised by this variety in particular and rice plant in general to face the saline environment. Performanceof this rice variety and the concentration and uptake of ions were studied under stress of three salinity levels(30, 60 and 90 mmol L-1) created with NaCl. Recorded data indicated that shoot dry matter was notsignificantly affected by all the three levels of salinity. However, NaCl levels of 60 and 90 mmol L-1 affectedthe root dry matter significantly. Sodium concentration and uptake was enhanced significantly in root andshoot at the first level of salinity (30 mmol L-1) but thereafter the differences were non-significant, indicatingthe preferential absorption of this cation. The K concentration decreased significantly in shoots at all thelevels. The impact was less pronounced in roots as far as K absorption was concerned. The effect on Ca andMg concentrations was not significant. The values of K:Na, Ca:Na and (Ca+Mg):Na ratios in shoot and rootwere comparatively low under stress conditions, indicating that selective ion absorption may be the principalsalt tolerance mechanism of variety Shaheen Basmati when grown in a saline medium.

Overexpression of GmDREB1 improves salt tolerance in transgenic wheat and leaf protein response to high salinity

The transcription factor dehydration-responsive element binding protein(DREB)is able to improve tolerance to abiotic stress in plants by regulating the expression of downstream genes involved in environmental stress resistance.The objectives of this study were to evaluate the salt tolerance of GmDREB1 transgenic wheat(Triticum aestivum L.)and to evaluate its physiological and protein responses to salt stress.Compared with the wild type,the transgenic lines overexpressing GmDREB1 showed longer coleoptiles and radicles and a greater radicle number at the germination stage,as well as greater root length,fresh weight,and tiller number per plant at the seedling stage.The yield-related traits of transgenic lines were also improved compared with the wild type,indicating enhanced salt tolerance in transgenic lines overexpressing GmDREB1.Proteomics analysis revealed that osmotic-and oxidative-stressrelated proteins were up-regulated in transgenic wheat leaves under salt stress conditions.Transgenic wheat had higher levels of proline and betaine and lower levels of malondialdehyde and relative electrolyte leakage than the wild type.These results suggest that GmDREB1 regulates the expression of osmotic-and oxidative-stress-related proteins that reduce the occurrence of cell injury caused by high salinity,thus improving the salt tolerance of transgenic wheat.

The landscape of molecular mechanisms for salt tolerance in wheat

Wheat is one of the most important food crops, and its yield is seriously restricted by high salinity and other abiotic stresses. Many attempts have been made to elucidate the major physiological processes associated with salt tolerance and to identify the genes controlling the processes. In this review, the major role of high-affinity potassium transporter(HKT)genes in enhancing the salt tolerance of wheat is summarized. The link between maintenance of reactive oxygen species(ROS) homeostasis and salt tolerance through a comprehensive study of a wheat introgression line is examined, and the contribution of a set of genes involved in this process is depicted. New research strategies to uncover the mechanisms underlying salt tolerance in wheat based on recent advances in omics will be discussed.

Mapping and validation of a dominant salt tolerance gene in the cultivated soybean(Glycine max) variety Tiefeng 8

Salt is an abiotic stress factor that strongly affects soybean growth and production. A single dominant gene has been shown to confer salt tolerance in the soybean cultivar Tiefeng 8.The objective of the present study was to genetically map the salt-tolerance gene in an F2:3population and a recombinant inbred line(RIL) population derived from a cross between two cultivated soybeans, Tiefeng 8(tolerant) and 85-140(sensitive). The F2:3families and RILs were treated with 200 mmol L-1Na Cl to evaluate salt tolerance. The F2:3population showed 1(42 tolerant): 2(132 segregating): 1(65 sensitive) segregation, indicating a single dominant gene for salt tolerance in Tiefeng 8. A sequence-characterized amplified region(SCAR) marker from a previously identified random amplified polymorphic DNA(RAPD)marker and four insertion/deletion polymorphism(In Del) markers were developed within the mapping region. Using these markers along with SSR markers, the salt-tolerance gene was mapped within 209 kb flanked by SCAR marker QS08064 and SSR marker Barcsoyssr_3_1301 on chromosome 3. Three markers that cosegregated with the salt tolerance gene and SCAR marker QS08064 were used to genotype 35 tolerant and 23 sensitive soybean accessions. These markers showed selection efficiencies of 76.2% to94.2%. The results indicate that these markers will be useful for marker-assisted breeding and facilitating map-based cloning of the salt tolerance gene in soybean.

Cloning and Characterization of a Salt Tolerance-Associated Gene Encoding Trehalose-6-Phosphate Synthase in Sweetpotato

Trehalose plays an important role in metabolic regulation and abiotic stress tolerance in a variety of organisms. In plants, its biosynthesis is catalyzed by two key enzymes： trehalose-6-phosphate synthase（TPS） and trehalose-6-phosphate phosphatase（TPP）. In the present study, a TPS gene, named IbTPS, was first isolated from sweetpotato（Ipomoea batatas（L.） Lam.） cv. Lushu 3 by rapid amplification of cDNA ends（RACE）. The open reading frame（ORF） contained 2 580 nucleotides encoding 859 amino acids with a molecular weight of 97.433 kDa and an isoelectric point（pI） of 5.7. The deduced amino acid sequence showed high identities with TPS of other plants. Real-time quantitative PCR analysis revealed that the expression level of IbTPS gene was significantly higher in stems of Lushu 3 than in its leaves and roots. Subcellular localization analysis in onion epidermal cells indicated that IbTPS gene was located in the nucleus. Transgenic tobacco（cv. Wisconsin 38） plants over-expressing IbTPS gene exhibited significantly higher salt tolerance compared with the control plant. Trehalose and proline content was found to be significantly more accumulated in transgenic tobacco plants than in the wild-type and several stress tolerance related genes were up-regulated. These results suggest that IbTPS gene may enhance salt tolerance of plants by increasing the amount of treahalose and proline and regulating the expression of stress tolerance related genes.

Molecular Cloning and Functional Characterization of a Salt Tolerance-Associated Gene IbNFU1 from Sweetpotato

Iron-sulfur cluster biosynthesis involving the nitrogen fixation（Nif） proteins has been proposed as a general mechanism acting in various organisms.NifU-like protein may play an important role in protecting plants against abiotic and biotic stresses.Based on the EST sequence selected from salt-stressed suppression subtractive hybridization（SSH） cDNA library constructed with a salt-tolerant mutant LM79,a NFU gene,termed IbNFU1,was cloned from sweetpotato（Ipomoea batatas（L.） Lam.） via rapid amplification of cDNA ends（RACE）.The cDNA sequence of 1 117 bp contained an 846 bp open reading frame encoding a 281 amino acids polypeptide with a molecular weight of 30.5 kDa and an isoelectric point（pI） of 5.12.IbNFU1 gene contained a conserved Cys-X-X-Cys motif in C-terminal of the iron-sulfur cluster domain.The deduced amino acid sequence had 66.08 to 71.99% sequence identity to NFU genes reported in Arabidopsis thaliana,Eucalyptus grandis and Vitis vinifera.Real-time quantitative PCR analysis revealed that the expression level of IbNFU1 gene was significantly higher in the roots of the mutant LM79 compared to the wild-type Lizixiang.Transgenic tobacco（cv.Wisconsin 38） plants expressing IbNFU1 gene exhibited significantly higher salt tolerance compared to the untransformed control plants.It is proposed that IbNFU1 gene has an important function for salt tolerance of plants.

Overexpression of SOS Genes Enhanced Salt Tolerance in Sweetpotato

The production of transgenic sweetpotato （cv.Xushu 18） plants exhibiting enhanced salt tolerance using salt overly sensitive （SOS） genes was achieved through Agrobacterium tumefaciens-mediated transformation.A.tumefaciens strain EHA105 harbors a binary vector pCAMBIA3301 with SOS genes （SOS1,SOS2 and SOS3） and bar gene.Selection culture was conducted using 0.3 mg L^-1 phosphinothricin （PPT）.A total of 40 plants were produced from the inoculated 170 cell aggregates via somatic embryogenesis.PCR analysis showed that 37 of the 40 regenerated plants were transgenic plants.The in vitro assay demonstrated that superoxide dismutase （SOD） and proline were significantly more accumulated and malonaldehyde （MDA） was significantly less accumulated in 21 transgenic plants than in control plants when they were exposed to 86 mmol L^-1 NaCl.Salt tolerance of these 21 plants was further evaluated with Hoagland solution containing 0,51,86,and 120 mmol L^-1 NaCl in the greenhouse.The results indicated that 6 of them had significantly better growth and rooting ability than the remaining 15 transgenic plants and control plants.Expression of SOS genes in the 6 salt-tolerant transgenic plants was demonstrated by RT-PCR analysis.This study provides an alternative approach for improving salt tolerance of sweetpotato.

The osmolyte-producing endophyte Streptomyces albidoflavus OsiLf-2 induces drought and salt tolerance in rice via a multi-level mechanism

Drought and salinity are major environmental stresses that impair crop growth and productivity worldwide. Improving drought and salt tolerance of crops with microbial mutualists is an effective and environmentally sound strategy to meet the demands of the ever-growing world population. In the present study, we found that the Streptomyces albidoflavus Osi Lf-2, a moderately salt-tolerant endophytic actinomycete, produced abundant osmolytes, including proline, polysaccharides, and ectoine. Inoculation with Osi Lf-2 increased the osmotic-adjustment ability of the rice host by increasing the proline content(by250.3% and 49.4%) and soluble sugar(by 20.9% and 49.4%) in rice under drought and salt conditions, relative to the uninoculated control. Osi Lf-2 increased stress responses in the rice host at the physiological and biochemical levels(photosynthesis efficiency, osmolytes and antioxidant content), and the gene level(osmolytes synthesis, stress-responsive and ion-transport related genes), raising rice yields under both greenhouse and saline–alkaline soil conditions. The use of endophytic actinomycetes offers a promising biotechnological approach to developing stress-tolerant plants.