Salt-tolerant Genotypes Research Articles

Screening and evaluation of reliable traits of upland cotton (Gossypium hirsutum L.) genotypes for salt tolerance at the seedling growth stage

BackgroundSalt stress significantly inhibits the growth, development, and productivity of cotton because of osmotic, ionic, and oxidative stresses. Therefore, the screening and development of salt tolerant cotton cultivars is a key issue towards sustainable agriculture. This study subjected 11 upland cotton genotypes at the seedling growth stage to five different salt concentrations and evaluated their salt tolerance and reliable traits.ResultsSeveral morpho-physiological traits were measured after 10 days of salinity treatment and the salt tolerance performance varied significantly among the tested cotton genotypes. The optimal NaCl concentration for the evaluation of salt tolerance was 200 mmol·L− 1. Membership function value and salt tolerance index were used to identify the most consistent salt tolerance traits. Leaf relative water content and photosynthesis were identified as reliable indicators for salt tolerance at the seedling stage. All considered traits related to salt tolerance indices were significantly and positively correlated with each other except for malondialdehyde. Cluster heat map analysis based on the morpho-physiological salt tolerance-indices clearly discriminated the 11 cotton genotypes into three different salt tolerance clusters. Cluster I represented the salt-tolerant genotypes (Z9807, Z0228, and Z7526) whereas clusters II (Z0710, Z7514, Z1910, and Z7516) and III (Z0102, Z7780, Z9648, and Z9612) represented moderately salt-tolerant and salt-sensitive genotypes, respectively.ConclusionsA hydroponic screening system was established. Leaf relative water content and photosynthesis were identified as two reliable traits that adequately represented the salt tolerance of cotton genotypes at the seedling growth stage. Furthermore, three salt-tolerant genotypes were identified, which might be used as genetic resources for the salt-tolerance breeding of cotton.

Assessment of Marker Based Genotype Diversity of Saltol QTL in Relation to Seedling Stage Salinity Tolerance in Selected Rice Genotypes

Salinity stress is one of the major soil problems in relation to rice production in Sri Lanka. Development of salinity tolerant rice through rice breeding is a key solution for salinity problem. Saltol is the major Quantitative Trait Loci (QTL) responsible for salt tolerance at the seedling stage of the rice plants which is mapped on chromosome one of the rice genome. To select most salt tolerant rice genotypes for future breeding programmes and test the usefulness of the Microsatellite (SSR) markers associated with Saltol QTL, 18 rice varieties were screened using electrical conductivity 12 dSm-1 nutrient solution for salt tolerance at the seedling stage using a visual score of 1-9 scale. Six polymorphic SSR markers linked to the Saltol QTL were used to determine the impact of these markers associated with salt tolerance in rice. Results of the phenotypic screening of 18 rice genotypes showed different responses for salt stress at the seedling stage. Based on the phenotypic screening rice genotypes were categorized into four groups, and Pokkali accessions were the most tolerant genotypes for salinity stress which can be useful as donor parents for future rice breeding programs. Microsatellite marker RM10843 showed highest allelic number while RM140 and RM10748 showed lowest allelic number. Polymorphism information content (PIC) value varied from 0.1780 for RM10748 to 0.7659 for marker alleles. Based on the six SSR markers, 18 rice genotypes were clustered into two groups and salinity tolerant Pokkali accessions were grouped in a separate cluster. Salinity tolerant and susceptible genotypes were clearly discriminated by RM10852 marker in 3% agarose gel and positively associated with the result of the phenotypic screening. Therefore, the marker will be useful in Marker Assisted Selection (MAS) in rice breeding programmes for salinity tolerance.

Transcriptome analysis uncovers the gene expression profile of salt-stressed potato (Solanum tuberosum L.)

Potato (Solanum tuberosum L.) is an important staple food worldwide. However, its growth has been heavily suppressed by salt stress. The molecular mechanisms of salt tolerance in potato remain unclear. It has been shown that the tetraploid potato Longshu No. 5 is a salt-tolerant genotype. Therefore, in this study we conducted research to identify salt stress response genes in Longshu No. 5 using a NaCl treatment and time-course RNA sequencing. The total number of differentially expressed genes (DEGs) in response to salt stress was 5508. Based on Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis, it was found that DEGs were significantly enriched in the categories of nucleic acid binding, transporter activity, ion or molecule transport, ion binding, kinase activity and oxidative phosphorylation. Particularly, the significant differential expression of encoding ion transport signaling genes suggests that this signaling pathway plays a vital role in salt stress response in potato. Finally, the DEGs in the salt response pathway were verified by Quantitative real-time PCR (qRT-PCR). These results provide valuable information on the salt tolerance of molecular mechanisms in potatoes, and establish a basis for breeding salt-tolerant cultivars.

Tissue Tolerance Coupled With Ionic Discrimination Can Potentially Minimize the Energy Cost of Salinity Tolerance in Rice.

Salinity is one of the major constraints in rice production. To date, development of salt-tolerant rice cultivar is primarily focused on salt-exclusion strategies, which incur greater energy cost. The present study aimed to evaluate a balancing strategy of ionic discrimination vis-à-vis tissue tolerance, which could potentially minimize the energy cost of salt tolerance in rice. Four rice genotypes, viz., FL478, IR29, Kamini, and AC847, were grown hydroponically and subjected to salt stress equivalent to 12 dS m–1 at early vegetative stage. Different physiological observations (leaf chlorophyll content, chlorophyll fluorescence traits, and tissue Na+ and K+ content) and visual scoring suggested a superior Na+-partitioning strategy operating in FL478. A very low tissue Na+/K+ ratio in the leaves of FL478 after 7 days of stress hinted the existence of selective ion transport mechanism in this genotype. On the contrary, Kamini, an equally salt-tolerant genotype, was found to possess a higher leaf Na+/K+ ratio than does FL478 under similar stress condition. Salt-induced expression of different Na+ and K+ transporters indicated significant upregulation of SOS, HKT, NHX, and HAK groups of transporters in both leaves and roots of FL478, followed by Kamini. The expression of plasma membrane and vacuolar H+ pumps (OsAHA1, OsAHA7, and OsV-ATPase) were also upregulated in these two genotypes. On the other hand, IR29 and AC847 showed greater salt susceptibility owing to excess upward transport of Na+ and eventually died within a few days of stress imposition. But in the “leaf clip” assay, it was found that both IR29 and Kamini had high tissue-tolerance and chlorophyll-retention abilities. On the contrary, FL478, although having higher ionic-discrimination ability, showed the least degree of tissue tolerance as evident from the LC50 score (amount of Na+ required to reduce the initial chlorophyll content to half) of 336 mmol g–1 as against 459 and 424 mmol g–1 for IR29 and Kamini, respectively. Overall, the present study indicated that two components (ionic selectivity and tissue tolerance) of salt tolerance mechanism are distinct in rice. Unique genotypes like Kamini could effectively balance both of these strategies to achieve considerable salt tolerance, perhaps with lesser energy cost.

Morphological and Genetic Diversity within Salt Tolerance Detection in Eighteen Wheat Genotypes.

Salinity is a major obstacle to wheat production worldwide. Salt-affected soils could be used by improving salt-tolerant genotypes depending upon the genetic variation and salt stress response of adapted and donor wheat germplasm. We used a comprehensive set of morpho-physiological and biochemical parameters and simple sequence repeat (SSR) marker technique with multivariate analysis to accurately demonstrate the phenotypic and genetic variation of 18 wheat genotypes under salinity stress. All genotypes were evaluated without NaCl as a control and with 150 mM NaCl, until the onset of symptoms of death in the sensitive plant (after 43 days of salinity treatment). The results showed that the relative change of the genetic variation was high for all parameters, heritability (>60%), and genetic gain (>20%). Stepwise regression analysis, noting the importance of the root dry matter, relative turgidity, and their respective contributions to the shoot dry matter, indicated their relevance in improving and evaluating the salt-tolerant genotypes of breeding programs. The relative change of the genotypes in terms of the relative turgidity and shoot dry matter during salt stress was verified using clustering methods. For cluster analysis, the genotypes were classified into three groups: tolerant, intermediate, and sensitive, representing five, six, and seven genotypes, respectively. The morphological and genetic distances were significantly correlated based on the Mantel test. Of the 23 SSR markers that showed polymorphism, 17 were associated with almost all examined parameters. Therefore, based on the observed molecular marker-phenotypic trait association, the markers were highly useful in detecting tolerant and sensitive genotypes. Thus, it considers a helpful tool for salt tolerance through marker-assisted selection.

Biochemical traits associated with growing sorghum genotypes with saline water in the field

This study was aimed to determine biochemical traits related to higher phytomass production in sorghum genotypes irrigated with saline water. It was also attempted to consider whether or not forage yield production under non-saline conditions could be used as an index for for the selection of high yielding genotypes of sorghum under saline conditions. Forty-five sorghum genotypes were grown under field conditions using saline water or normal irrigation water in two growing seasons in Yazd, Iran. It appeared that salinity tolerance in sorghum genotypes, in addition to local adaption, was highly related to forage yield as well as some biochemical traits as carotenoid concentration, catalase activity, and K+/Na+ ratio. The screening method based on biochemical traits appeared to be applicable for identification of the salt-tolerant genotypes.

Bacterial endophyte mediated plant tolerance to salinity: growth responses and mechanisms of action.

Salinity stress is one of the key constraints for sustainable crop production. It has gained immense importance in the backdrop of climate change induced imbalanced terrestrial water budgets. The traditional agronomic approaches and breeding salt-tolerant genotypes have often proved insufficient to alleviate salinity stress. Newer approaches like the use of bacterial endophytes associated with agricultural crops have occupied center place recently, owing to their advantageous role in improving crop growth, health and yield. Research evidences have revealed that bacterial endophytes can promote plant growth by accelerating availability of mineral nutrients, helping in production of phytohormones, siderophores, and enzymes, and also by activating systemic resistance against insect pest and pathogens in plants. These research developments have opened an innovative boulevard in agriculture for capitalizing bacterial endophytes, single species or consortium, to enhance plant salt tolerance capabilities, and ultimately lead to translational refinement of crop-production business under salty environments. This article reviews the latest research progress on the identification and functional characterization of salt tolerant endophytic bacteria and illustrates various mechanisms triggered by them for plant growth promotion under saline environment.

Pistacia vera L. genotypes; a potential rival for UCB-1 rootstock for cultivating under salt stress conditions

Abstract UCB-1(P. integerrima ×P. atlantica) is considered as a high tolerant hybrid rootstock to salt stress from Pistacia genus that widely used as rootstock for pistachio cultivars. This study was conducted to compare the response of five P. vera salt-tolerant genotypes with UCB-1 under salt stress. The experiment was carried out as a completely randomized design with factorial arrangement and four replications. Eight months old pistachio genotypes namely Akbari, Ahmad-Aghaee, Italiyayi, Ghazvini, Badami, and UCB-1 were subjected to salinity stress at three salinity levels (0.5 (control), 12 and 18 dS m−1) for 75 days. In order to select the most tolerant genotypes, some physiological and biochemical factors were measured. Leaf water potential, chlorophyll, and K content decreased while leaf total proline, phenolic content, lipid peroxidation, antioxidant enzyme activities, and Na leaf content increased with raising salinity levels regardless of genotypes. Comparison between genotypes indicated that for most of the measured factors, UCB-1 and Akbari showed better performance comparing to others. However, there was no significant difference between Akbari and UCB-1 regarding salt tolerance that shows the high potential of P. vera genotypes to be used instead of UCB-1. Furthermore, there was no significant difference between Akbari, Ahmad-Aghaee, and UCB-1 in malondialdehyde (MDA) and total phenolic content as well as ascorbate peroxidase (APX) activity. In conclusion, the studied rootstocks can be ordered based on their tolerance to salinity as the following: UCB-1 = Akbari > Ahmad-Aghaee > Italiyayi > Ghazvini > Badami.

The Apoplastic and Symplastic Antioxidant System in Onion: Response to Long-Term Salt Stress.

The response of apoplastic antioxidant systems in root and leaf tissues from two onion genotypes (‘Texas 502’, salt-sensitive and ‘Granex 429’, salt-resistant) in response to salinity was studied. Electrolyte leakage data indicated the membrane integrity impairing by the effect of salts, especially in ‘Texas 502’. We detected superoxide dismutase (SOD) and peroxidase (POX) activity in the root and leaf apoplastic fractions from onion plants. Salinity increased SOD activity in the root symplast of ‘Texas 502’ and in ‘Granex 429’ leaves. In contrast, salinity reduced SOD activity in the leaf and root apoplastic fractions from ‘Texas 502’. In ‘Granex 429’, salt-stress increased leaf apoplastic POX activity and symplastic catalase (CAT) activity of both organs, but a decline in root apoplastic POX from ‘Texas 502’ took place. Salt-stress increased monodehydroascorbate reductase (MDHAR) in root and leaf symplast and in root glutathione reductase GR, mainly in ‘Granex 429’, but only in this genotype, leaf dehydroascorbate reductase (DHAR) activity increased. In contrast, a decline in leaf GR was produced only in ‘Texas 502’. Salinity increased leaf ASC levels, and no accumulation of dehydroascorbate (DHA) was observed in roots in both cases. These responses increased the redox state of ascorbate, especially in roots. In contrast, salinity declined reduced glutathione (GSH), but oxidised glutathione (GSSG) was accumulated in leaves, decreasing the redox state of glutathione. Salinity slightly increased root GSH concentration in the salt-tolerant genotype and was unchanged in the salt-sensitive genotype, but no accumulation of GSSG was produced, favoring the rise and/or maintenance of the redox state of the glutathione. These results suggest that the lower sensitivity to salt in ‘Granex 429’ could be related to a better performance of the antioxidant machinery under salinity conditions.

Study of Relative Antioxidant Potential of Induced Variants of Catharanthus roseus (L.) G. Don in Salt Stress Condition for the Effective Selection of Salt Tolerant Variant

Objectives: Catharanthus roseus (L.) G. Don is an important plant documented for variety of medicinal uses and salt tolerant potential. During genetic improvement programme an attempt of induced mutagenesis was made for isolation of improved genotype of C. roseus var. Nirmal (CIMAP 0865) and nine EMS induced variants were isolated. Present study was made for the assessment of relative antioxidative potential of these variants and identification/selection of salt tolerant genotype. Methods: For the assessment of relative antioxidative potential under glass house condition one month old seedlings of all variants exposed to salt stress condition and the activities of antioxidant enzymes viz., superoxide dismutase, peroxidase and catalase were estimated in leaf tissue at 4th day and 8th day of NaCl supply while proline and total alkaloid contents were estimated at 8th day of NaCl supply. Results: In general, NaCl imposition causes increase in activity of earlier two enzymes, decrease in catalase activity and stimulatory effect on proline and total alkaloid content. Values for these parameters varied with type of variants. Variants V2, V3 and V7 exhibited higher activity of antioxidant enzymes and had high accumulation of proline and total alkaloids. Conclusion: The variants V2, V3 and V7, having higher estimates for these parameters than that of parental variety which indicates their better survival/adaptive potential against salt stress condition and in context of salt tolerant may be utilized in genetic improvement programme of C. roseus.

Physiological and biochemical markers for screening salt tolerant quinoa genotypes at early seedling stage

ABSTRACT The present study was conducted to determine the predictive screening parameters of quinoa salt tolerance that can be applied at early development stages, based on physiological and biochemical approaches. Four quinoa varieties (Tumeko, Red Faro, Kcoito and UDEC-5) were cultivated using hydroponic system, and treated for 2 weeks with different NaCl concentrations (0, 100, 300 and 500 mM). Salt treatment induced a decrease of plant growth depending on NaCl concentrations, plant organs and varieties. Red Faro and UDEC-5 exhibited low level of Na+ accumulation and high K/Na selectivity. UDEC-5 showed high stomatal conductance leading to high net photosynthesis, even at 500 mM NaCl. Red Faro and UDEC-5 exhibited low level of lipid peroxidation, high antioxidant activities and high proline accumulation, as an indicator of ROS defense and osmotic adjustment. This study suggested that these physiological and biochemical traits could be used as screening criteria for selecting salt tolerant genotype.

Screening Rice (<i>Oryza sativa. L.</i>) for Salinity Tolerance for Yield and Yield Components in Saline Stressed Environment

Rice is one of the most important staple crops consumed by a large part of the human population but the issue of salinity is one of the limiting factors affecting its productivity. The objective of this study was to identify salt tolerant genotype for deployment into salt stressed regions and also for population improvement for salinity breeding programme. Material and Methods: the study was a potted experiment using 8 korean lines and UPIA1 and UPIA2 as check in a randomized complete block design with four levels of sodium chloride concentration (0, 2, 3 and 6 dS/m) replicated three times at the University of Port Harcourt Teaching and Research Farm. Result: most of the genotype showed differential response to salinity stress. Varieties like UPN 509, UPN 216, constantly showed high mean value for Leaf Area Index, 1000 grain weight, plant height and tillering ability across the salinity concentration gradient in salinity tolerance index. Principle Component 1 and 2 contributed 46.17% and 15.17% respectively of the total variation. Total grain yield showed strong positive significant correlation with plant height, grain weight per panicle leaf area index and 1000 grain weight. In conclusion, UPN 509 which showed the highest yielding capacity and UPN 216 which showed the highest tillering ability and tolerance to salinity stress at the highest concentration level maybe promising genotypes for deployment into saline stressed environment.

In vitro screening for salt stress tolerance of native and exotic potato genotypes by morphological and physiological parameters

This study was performed on in vitro bioassay screening for salt tolerance of ten native and six exotic potato genotypes in Bangladesh. Single node was used to evaluate salinity tolerance especially on biomass production. Five different concentrations of NaCl (0 = control, 100, 150, 200 and 250 mM) were used in addition to MS medium and evaluated salt tolerant and sensitive genotype by various morphological and physiological parameters e.g. shoot and root length and its thickness, number of leaves and roots, fresh and dry weight of whole plant and water contents. The ANOVA, DMRT and correlation coefficient were found highly significant at p<0.01 among the genotypes. With salt stress condition highly positive correlation, co-efficient were found between stem length and internodal distance, leaves number, roots number, root length, dry weight of whole plant and fresh weight of whole plant. A dendrogram based on relative values of 10 morphological and physiological parameters of growth under salt conditions were led to clustering into four distinct group’s i.e. tolerant, moderately tolerant, sensitive and very sensitive. On the basis of stress tolerance trait indices (STTIs), Arun (92.78) and Ausha (80.27) showed as a highest salt tolerant, Jamalu (56.33) and Chollisha (57.03) showed the most salt sensitive potato cultivars. From this finding it may be concluded that in vitro screening with bioassay are relatively simple, rapid and convenient and these methods can be used for further advance biotechnological research on potato improvement.
 J. bio-sci. 28: 21-32, 2020

Ionomic and transcriptomic analyses of two cotton cultivars (Gossypium hirsutum L.) provide insights into the ion balance mechanism of cotton under salt stress.

Soil salinity is a major abiotic stress factor that limits cotton production worldwide. To improve salt tolerance in cotton, an in-depth understanding of ionic balance is needed. In this study, a pot experiment using three levels of soil salinity (0%, 0.2%, and 0.4%, represented as CK, SL, and SH, respectively) and two cotton genotypes (salt-tolerant genotype: L24; salt-sensitive genotype: X45) was employed to investigate how sodium chloride (NaCl) stress effects cotton growth, ion distribution, and transport, as well as to explore the related mechanism. The results showed that SL treatment mainly inhibited shoot growth, while SH treatment caused more extensive impairment to roots and shoots. The growth inhibition ratio of NaCl stress on X45 was more marked than that of L24. Under NaCl stress, the Na concentration in the roots, stems and leaves significantly increased, whereas the K, Cu, B, and Mo concentration in roots, as well as Mg and S concentrations in the leaves, significantly decreased. Under salt stress conditions, salt-tolerant cotton plants can store Na in the leaves, and as a result, a larger amount of minerals (e.g., Cu, Mo, Si, P, and B) tend to transport to the leaves. By contrast, salt-sensitive varieties tend to accumulate certain minerals (e.g., Ca, P, Mg, S, Mn, Fe, Cu, B, Mo, and Si) in the roots. Most genes related to ion transport and homeostasis were upregulated in L24, but not in X45. The expression level of GhSOS1 in X45 was higher than L24, but GhNHX1 in L24 was higher than X45. Our findings suggest that the two varieties response to salt stress differently; for X45 (salt-sensitive), the response is predominantly governed by Na+ efflux, whereas for L24 (salt-tolerant), vacuolar sequestration of Na+ is the major mechanism. The expression changes of the genes encoding the ion transporters may partially explain the genotypic difference in leaf ion accumulation under salt stress conditions.

RNA-seq Analysis of Salt-Stressed Versus Non Salt-Stressed Transcriptomes of Chenopodium quinoa Landrace R49.

Quinoa (Chenopodium quinoa Willd.), a model halophytic crop species, was used to shed light on salt tolerance mechanisms at the transcriptomic level. An RNA-sequencing analysis of genotype R49 at an early vegetative stage was performed by Illumina paired-ends method comparing high salinity and control conditions in a time-course pot experiment. Genome-wide transcriptional salt-induced changes and expression profiling of relevant salt-responsive genes in plants treated or not with 300 mM NaCl were analyzed after 1 h and 5 days. We obtained up to 49 million pairs of short reads with an average length of 101 bp, identifying a total of 2416 differentially expressed genes (DEGs) based on the treatment and time of sampling. In salt-treated vs. control plants, the total number of up-regulated and down-regulated genes was 945 and 1471, respectively. The number of DEGs was higher at 5 days than at 1 h after salt treatment, as reflected in the number of transcription factors, which increased with time. We report a strong transcriptional reprogramming of genes involved in biological processes like oxidation-reduction, response to stress and response to abscisic acid (ABA), and cell wall organization. Transcript analyses by real-time RT- qPCR supported the RNA-seq results and shed light on the contribution of roots and shoots to the overall transcriptional response. In addition, it revealed a time-dependent response in the expression of the analyzed DEGs, including a quick (within 1 h) response for some genes, suggesting a “stress-anticipatory preparedness” in this highly salt-tolerant genotype.

Salt-tolerance diversity in diploid and polyploid cotton (Gossypium) species.

The development of salt-tolerant genotypes is pivotal for the effective utilization of salinized land and to increase global crop productivity. Several cotton species comprise the most important source of textile fibers globally, and these are increasingly grown on marginal or increasingly saline agroecosystems. The allopolyploid cotton species also provide a model system for polyploid research, of relevance here because polyploidy was suggested to be associated with increased adaptation to stress. To evaluate the genetic variation of salt tolerance among cotton species, 17 diverse accessions of allopolyploid (AD-genome) and diploid (A- and D-genome) Gossypium were evaluated for a total of 29 morphological and physiological traits associated with salt tolerance. For most morphological and physiological traits, cotton accessions showed highly variable responses to 2weeks of exposure to moderate (50mm NaCl) and high (100mm NaCl) hydroponic salinity treatments. Our results showed that the most salt-tolerant species were the allopolyploid Gossypium mustelinum from north-east Brazil, the D-genome diploid Gossypium klotzschianum from the Galapagos Islands, followed by the A-genome diploids of Africa and Asia. Generally, A-genome accessions outperformed D-genome cottons under salinity conditions. Allopolyploid accessions from either diploid genomic group did not show significant differences in salt tolerance, but they were more similar to one of the two progenitor lineages. Our findings demonstrate that allopolyploidy in itself need not be associated with increased salinity stress tolerance and provide information for using the secondary Gossypium gene pool to breed for improved salt tolerance.

Expression levels of vacuolar ion homeostasis-related genes, Na+ enrichment, and their physiological responses to salt stress in sugarcane genotypes.

Sugarcane is a sugar-producing crop widely grown in tropical regions in over 120 countries of the world. Salt-affected soil is one of the most significant abiotic constraints that inhibit growth and crop productivity, and, consequently, reduce sucrose concentration in the stalk. The present study investigated vacuolar ion homeostasis, Na+ accumulation, and physiological and morphological adaptations under salt stress in two different sugarcane genotypes (salt-tolerant K88-92 and salt-sensitive K92-80) under greenhouse conditions. Na+ was rapidly absorbed by the root tissues of both sugarcane genotypes within 3-7 days of 150 mM NaCl treatment, as confirmed by the results of CoroNa Green fluorescence staining. In addition, the rate of Na+ translocation from roots to shoots was evidently reduced, leading to lower amount of Na+ in the leaf tissues. At the cellular level, expression of ShNHX1 (vacuolar Na+/H+ antiporter), ShV-PPase (vacuolar H+-pyrophosphatase), and ShV-ATPase (vacuolar H+-ATPase) was upregulated in salt-stressed plants for the compartmentation of Na+ into the vacuoles of root cells. Interestingly, sucrose, glucose, and fructose in root tissues of salt-stressed sugarcane cv. K88-92 were increased by 10.61, 5.58, and 1.81 folds, respectively, over the control. Total soluble sugars in the roots and free proline in the leaves of sugarcane cv. K88-92 (salt-tolerant) were enriched by 3.08 and 1.99 folds, respectively, when plants were exposed to 150 mM NaCl, leading to maintain better photosynthetic abilities, net photosynthetic rate (Pn), stomatal conductance (gs), transpiration rate (E), and water use efficiency (WUE) in sugarcane cv. K88-92 than those in cv. K92-80. The study concludes that Na+ compartmentation in the root tissue acts as a major defense mechanism in sugarcane, especially in salt-tolerant genotype.

Change in physiological and biochemical parameters under drought stress in salt-tolerant and salt-susceptible eggplant genotypes

This study was carried out to determine the changes in chlorophyll and ion contents, lipid peroxidation level, and antioxidative enzyme activities of 4 eggplant genotypes (Mardin Kiziltepe (MK), Burdur Merkez (BM), Artvin Hopa (AH), and Kemer (K)) with different salt tolerance levels under drought stress. Experiments were conducted in a greenhouse with controlled climatic conditions. When the plants reached the 3-4 leaves stage, 3 different treatments were applied to create the drought levels. The first condition in the study was obtained through control application treatment (D0), which was depletion of 40% of the available water holding capacity. The second application (D1) was depletion of 90% of the available water holding capacity. The third application (D2) was no applied irrigation water. Plants were analyzed with regards to chlorophyll and ion contents, lipid peroxidation levels, and antioxidative enzyme activities. Significant differences were observed among interactions of genotypes and levels of drought stress in chlorophyll and ion (K+, Ca2+, Zn2+, Mn2+, and Fe2+) contents, lipid peroxidation levels, and activities of antioxidant enzymes (superoxide dismutase-SOD, catalase-CAT, glutathione reductase-GR, and ascorbate peroxidase-APX). The chlorophyll and ion contents of eggplant genotypes under drought stress decreased. However, different levels of lipid peroxidation and antioxidative enzyme activities were observed. The situation changed depending on genotypes. Lipid peroxidation levels increased under drought stress, especially in salt-sensitive genotypes (AH and K). On the other hand, the activities of antioxidative enzymes in the salt tolerant MK and BM genotypes significantly increased. With regard to the investigated traits, salt-tolerant genotypes were also found to be quite tolerant against drought stress.

Genotypic difference in secondary metabolism-related enzyme activities and their relative gene expression patterns, osmolyte and plant hormones in wheat.

Salinity and drought are the two most important and frequently co-occurring abiotic factors. A greenhouse pot experiment was carried out on two contrasting wheat genotypes (Jimai22, salt tolerant; Yangmai20, salt sensitive) to analyze the effect of drought (4% soil moisture content, D) and salinity (100 mM NaCl, S) either individually or combined on secondary metabolism-related enzyme activities and osmolytes. Results showed that drought, salinity and their combination (D + S) caused increases in phenylalanine ammonialyase (PAL, EC 4.3.1.24) activities compared with controls with a greater enhancement in Jimai22 than Yangmai20. Polyphenol peroxidase (PPO, EC 1.14.18.1) and shikimate dehydrogenase (SKDH, EC 1.1.1.25) activities increased more in Jimai22 both under salinity alone and D + S stresses. The D + S combination increased cinnamyl alcohol dehydrogenase (CAD, EC 1.1.1.195) activity and glycine betaine (GB) under both 10 and 4% soil moisture contents (SMC), and elevated abscisic acid (ABA), indole-3-acetic acid (IAA) and flavonoid contents at 4% SMC in Jimai22, contents of the compounds remained unchanged in Yangmai20. The treatment with salinity alone at both SMCs significantly increased callose and flavonoid contents in Jimai22 more than in Yangmai20, as compared to controls. In addition, the total phenol content at 4% SMC increased in the salt-tolerant genotype more. Moreover, total tocopherol under salinity alone and D + S at 4% SMC and chitinase activity under salinity at both SMC remarkably increased in Jimai22 while non-significant change observed in Yangmai20. Also, the expression of genes related to secondary metabolism (PAL, PPO, CAD, SKDH, and GB) was more induced in Jimai22 than Yangmai20 under D + S, and lower accumulation of H2 O2 and O2 - also occurred. Our findings suggest that high tolerance to D + S stress in Jimai22 was closely related to enhanced secondary metabolism-related enzyme activities and osmolytes such as PAL, CAD, PPO, SKDH, GB, total tocopherol, callose, plant hormones and their transcript level, which may beneficial to lower the reactive oxygen species (ROS) accumulation.

Water and Salt Stress Metabolomics for Wheat Genotypes of India

Shoots of ten day old seedlings of nineteen wheat genotypes were evaluated for proline metabolism, H2O2, thiobarbituric acid reactive substances (TBARS) and 2,2 diphenyl-picrylhydrazyl (DPPH) radical scavenging activity under water deficit, water withholding and salinity stress conditions. Principle component analysis demarcated four groups: i.e. drought tolerant (Excalibar, Krichauff, Babax, Drysdale, Gladius and C306), salt tolerant (Kharchia, Type11, Krl 1-4 and Krl 19), low stress tolerant (C273, C518 and C591) and susceptible (HD2967, PBW621, WH1105, HD3086, PBW660 and PBW175). Salt stress treatment affected the length, fresh weight and dry weight of seedlings of all studied genotypes in comparison to water deficit and water withholding condition which may be due to higher contents of TBARS. Shoots of salt and drought tolerant genotypes possessed higher proline content and DPPH radical scavenging activity alongwith reduced content of TBARS in parallel with decreased H2O2 content under water stress conditions. The activities of proline synthesizing enzymes i.e. pyrroline-5-carboxylate synthetase (P5CS) and pyrroline-5-carboxylate reductase (P5CR) were significantly higher than proline degrading enzyme viz. proline dehydrogenase (PDH) under water stress as compared to salinity stress conditions. Overall, results indicated that P5CS, P5CR and PDH activities led to higher build up of proline under water stress, which might play a significant role in improving membrane stability by increasing radical scavenging activity and finally imparting stress tolerance in specific wheat genotypes.