Salt-tolerant Genotypes Research Articles

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.

Cloning and characterization of a gene encoding MIZ1, a domain of unknown function protein and its role in salt and drought stress in rice.

Dwindling fresh water resources and climate change poses serious threats to rice production. Roots play crucial role in sensing water gradient and directing growth of the plant towards water through a mechanism called hydrotropism. Since very little information is available on root hydrotropism in major food crops, this study was carried out to clone and characterize an ortholog of Arabidopsis MIZU-KUSSEI1 (MIZ1) from rice. Contrasting rice genotypes for drought and salt tolerance were selected based on phenotyping for root traits. Nagina 22 and CR-262-4 were identified as most tolerant and Pusa Sugandh 5 and Pusa Basmati 1121 were identified as most susceptible varieties for both drought and salt stresses. Allele mining of MIZ1 in these varieties identified a 12 bp Indel but did not show specific allelic association with stress tolerance. Analysis of allelic variation of OsMIZ1 in 3024 rice genotypes of 3K genome lines using Rice SNP-Seek database revealed 49 InDels. Alleles with the 12bp deletions were significantly prevalent in indica group as compared to that of japonica group. Real-time RT-PCR analysis revealed that OsMIZ1 expression levels were upregulated significantly in tolerant cv. Nagina 22 and CR-262-4 under osmotic stress, while under salt stress, it was significantly upregulated only in CR-262-4 but maintained in Nagina 22 under salt stress. However, in the roots of susceptible genotypes, OsMIZ1 expression decreased under both the stresses. These results highlight the possible involvement of OsMIZ1 in drought and salt stress tolerance in rice. Furthermore, expression studies using publically available resources showed that enhanced expression of OsMIZ1 is regulated in response to disease infections, mineral deficiency, and heavy metal stresses and is also expressed in reproductive tissues in addition to roots. These findings indicate potential involvement of MIZ1 in developmental and stress response processes in rice.

Ameliorative effects of inoculation with Serratia marcescens and grafting on growth of eggplant seedlings under salt stress

Grafting on a moderate salt-tolerant rootstock (Vista-306) and bacteria (Serratia marcescens) inoculation were tested whether grafting and bacteria can alleviate salinity stress in eggplant. Two salt-tolerant eggplant genotypes (‘Mardin Kızıltepe’, ‘Burdur Merkez’) and two salt-sensitive eggplant genotypes (‘Artvin Hopa’, ‘Kemer’) were used as scions. Grafted and non-grafted seedlings with 4–5 true leaves were transferred to pots filled with a mixture of peat: perlite (2:1) in a controlled greenhouse and were cultivated under temperatures of 23–25 °C with approximately 50–55% relative humidity. After 10 days from planting, 20 mL bacteria solution (cell density of 3 × 108 cells mL−1) per plant was applied to the root region of the seedlings as inoculum. 200 mM NaCl solution was applied to plants for 20 days after 5 days from inoculation of the bacteria. The study was arranged in a randomized block factorial design with three replicates. The grafted seedlings induced salt tolerance registering lower foliar concentrations of Na+ and Cl–, the lower lipid peroxidation and higher antioxidative enzyme activities. Inoculation of the bacteria significantly counteracted the salt-induced adverse effects on growth characteristics, leaf Cl−, Na+ contents, and antioxidative enzyme activities. In conclusion, grafting and inoculation with Serratia marcescens are effective in improving growth and some key physiological processes in eggplant under salt stress.

Salt-Treated Roots of Oryza australiensis Seedlings are Enriched with Proteins Involved in Energetics and Transport.

Salinity is a major constraint on rice productivity worldwide. However, mechanisms of salt tolerance in wild rice relatives are unknown. Root microsomal proteins are extracted from two Oryza australiensis accessions contrasting in salt tolerance. Whole roots of 2-week-old seedlings are treated with 80mM NaCl for 30 days to induce salt stress. Proteins are quantified by tandem mass tags (TMT) and triple-stage Mass Spectrometry. More than 200 differentially expressed proteins between the salt-treated and control samples in the two accessions (p-value <0.05) are found. Gene Ontology (GO) analysis shows that proteins categorized as "metabolic process," "transport," and "transmembrane transporter" are highly responsive to salt treatment. In particular, mitochondrial ATPases and SNARE proteins are more abundant in roots of the salt-tolerant accession and responded strongly when roots are exposed to salinity. mRNA quantification validated the elevated protein abundances of a monosaccharide transporter and an antiporter observed in the salt-tolerant genotype. The importance of the upregulated monosaccharide transporter and a VAMP-like protein by measuring salinity responses of two yeast knockout mutants for genes homologous to those encoding these proteins in rice are confirmed. Potential new mechanisms of salt tolerance in rice, with implications for breeding of elite cultivars are also discussed.

Assessment of Cucumber Genotypes for Salt Tolerance Based on Germination and Physiological Indices

Soil salinity is one of the primary problem for agricultural crops which causes a great loss in crop production in Pakistan and worldwide. Various approaches have been implemented to overcome salinity problem. Assembly of crops for the enhancement of salt tolerance is a good strategy to achieve cost-effective yields. Cucumber is considered as one of the leading vegetable crop around the world for the nourishment of human being as source of nutrients, minerals, and vitamins. Screening of 12 cucumber genotypes using some physiological indices, that is, seedling germination stress tolerance index, plant height stress tolerance index, root length stress tolerance index, shoot and root dry weight stress tolerance index, and shoot and root fresh weight stress tolerance index were performed for the identification of salt tolerance. Using the above characteristics genotypes, Valley and HC-999 were categorized as tolerant, Safaa and Debra as medium tolerant, while Thamin-II identified as medium sensitive and NSC-CM1 and Akbar are classified as sensitive genotypes of cucumber. According to the current study findings, the screened cucumber genotypes for salinity tolerance can also be suggested to farmers for the improved production and yield of crop at saline soil.

Change in Chlorophyll Content Over Time Well-differentiated Salt-tolerant, Moderately Salt-tolerant, and Salt-susceptible Cowpea Genotypes

Previous investigations showed that accumulations of Na+ and Cl− in leaves resulted in reductions in chlorophyll content, thereby affecting photosynthesis. Understanding how chlorophyll content evolves over time will help plant breeders to select cowpea genotypes with better tolerance to salinity by allowing them to choose those with more stable chlorophyll content under salt stress. The objective of this study was to assess how the chlorophyll content of cowpea genotypes changed over the course of 24 d of salt stress at the seedling stage. A total of 24 cowpea genotypes with different salt responses were used in this study. The experiment used a split-plot design with salt treatment as the main plot and cowpea genotypes as the subplot. In the main plot, there were two salt treatments: 0 mm (ionized water) and 200 mm NaCl. In the subplot, the cowpea genotypes were arranged as a completely randomized design with three replicates per genotype. The results revealed that: a1) the time × genotype interaction was significant under conditions with and without salt; 2) chlorophyll content slowly decreased in the salt-tolerant genotypes; 3) chlorophyll content slightly increased on day 6 and day 9 of salt stress in both moderate and sensitive genotypes, but it decreased at a faster rate than in the salt-tolerant genotypes; and 4) salt-sensitive genotypes were completely dead on day 24 of salt stress, whereas the salt-tolerant genotypes were able to maintain a significant amount of chlorophyll content. These results can be used to advance breeding programs for salt tolerance in cowpea.

The effect of NaCl on some physiological and biochemical parameters in Triticum aestivum L. genotypes

Effects of salinity caused by different concentrations of NaCl (100 and 200 mM) have been studied in two genotypes of Triticum aestivum L. (salt tolerant Saratovskaya-29 and salt sensitive Gyrmyzygul-1) with contrasting salt tolerance. Stress caused by salinity influenced differently on the content of photosynthetic pigments (chlorophyll a, b and carotenoids) in 14 to 16-day-old seedlings. In plants exposed to 100 mM NaCl an increase in quantity of photosynthetic pigments was observed in leaves, while 200 mM concentration of NaCl caused a reduction of the pigment content in leaves. A slightly higher amount of photosynthetic pigments were observed in the salt tolerant genotype Saratovskaya-29 at 200 mM NaCl. Lipid peroxidation level was higher in the sensitive Gyrmyzygul-1 genotype compared with tolerant Saratovskaya-29. It was found that, salinity stress caused an accumulation of soluble sugars and secondary metabolites—phenolic compounds. The amounts of soluble sugars and phenolic compounds were high in the salt sensitive genotype exposed to salt stress.