Degree Of Salinity Tolerance Research Articles

Salinity Tolerance in a Synthetic Allotetraploid Wheat (SlSlAA) Is Similar to Its Higher Tolerant Parent Aegilops longissima (SlSl) and Linked to Flavonoids Metabolism.

Allotetraploidization between A and S (closely related to B) genome species led to the speciation of allotetraploid wheat (genome BBAA). However, the immediate metabolic outcomes and adaptive changes caused by the allotetraploidization event are poorly understood. Here, we investigated how allotetraploidization affected salinity tolerance using a synthetic allotetraploid wheat line (genome SlSlAA, labeled as 4x), its Aegilops longissima (genome SlSl, labeled as SlSl) and Triticum urartu (AA genome, labeled as AA) parents. We found that the degree of salinity tolerance of 4x was similar to its SlSl parent, and both were substantially more tolerant to salinity stress than AA. This suggests that the SlSl subgenome exerts a dominant effect for this trait in 4x. Compared with SlSl and 4x, the salinity-stressed AA plants did not accumulate a higher concentration of Na+ in leaves, but showed severe membrane peroxidation and accumulated a higher concentration of ROS (H2O2 and O2⋅⁣–) and a lesser concentration of flavonoids, indicating that ROS metabolism plays a key role in saline sensitivity. Exogenous flavonoid application to roots of AA plants significantly relieved salinity-caused injury. Our results suggest that the higher accumulation of flavonoids in SlSl may contribute to ROS scavenging and salinity tolerance, and these physiological properties were stably inherited by the nascent allotetraploid SlSlAA.

Identification of novel source of salt tolerance in local bread wheat germplasm using morpho-physiological and biochemical attributes

Salt tolerant wheat cultivars may be used as genetic resource for wheat breeding to ensure yield stability in future. The study was aimed to select salt tolerant cultivar(s) to identify novel source of salt tolerance in local wheat germplasm. Initially, 40 local wheat cultivars were screened at 150 mM NaCl stress at seedling stage. Selected salt-tolerant (three; S-24, LU-26S and Pasban-90) and salt-sensitive (four; MH-97, Kohistan-97, Inqilab-91 and Iqbal-2000) wheat cultivars were further evaluated using growth, yield, biochemical and physiological attributes. Growth and yield of selected cultivars were reduced under salt stress due to decline in plant water status, limited uptake of macronutrients (N, P and K), reduced K+/Na+ ratio, photosynthetic pigments and quantum yield of PSII. Wheat plants tried to acclimate salt stress by osmotic adjustment (accumulation of total soluble sugars, proline and free amino acids). Degree of salinity tolerance in cvs. S-24 and LU-26S found to be associated with maintenance of K+/Na+ ratio, osmo-protectant and photosynthetic activity and can be used as donor for salt tolerance in wheat breeding program at least in Pakistan. These cultivars can be further characterized using molecular techniques to identify QTLs/genes for salt exclusion, osmo-protectant and photosynthetic activity for molecular breeding.

Effects of salinity on potassium absorption and expression of K+transporter genes at different concentrations of potassium in Grape (Vitis vinifera L.)

Grapevine is classified as a moderately sensitive plant to salinity. Hydroponically three grape genotypes (Vitis vinifera L.) were treated with different concentrations of KCl (0.1, 0.3, 0.5, 1, 5, 10 mM KCl) and NaCl (0, 25, 50,100 mM NaCl). Cl- and Na+ contents were significantly increased in different plant organs of all the genotypes under salinity. In this study, sensitive ('GhezelUzum'), tolerant ('Gharashani') and semi-resistant ('Chawga') grape genotypes were selected based on screening experiments under salinity. 'Gharashani' accumulated higher Na+ and Cl- in roots compared to the sensitive one. 'Chawga' accumulated high K+ similar to Na+ in root and shoot even at high salinity. Km calculation for K+ and Na+ uptake in root and shoot of 'Chawga' showed that K+ and Na+ compete to enter the plant through roots. Two KUP/KT/HAK-type potassium transporters are expressed highly in the grapevine during stress. VvK1.1 could play a major role in K+ loading into grape tissues. The expression of VvKUP1 and VvKUP2 transporters and VvK1.1 channel in roots of 'Chawga' genotype increased significantly (P < 0.05) at different KCl concentrations under salinity stress. Our results showed a significant difference between tolerant and sensitive genotypes and highlighted a strong relationship between the accumulation of specific transcripts and the degree of salinity tolerance.

Sodium Chloride Induced Stress Responses of Antioxidative Activities in Leaves and Roots of Pistachio Rootstock.

Salinity substantially affects plant growth and crop productivity worldwide. Plants adopt several biochemical mechanisms including regulation of antioxidant biosynthesis to protect themselves against the toxic effects induced by the stress. One-year-old pistachio rootstock exhibiting different degrees of salinity tolerance were subjected to sodium chloride induced stress to identify genetic diversity among cultivated pistachio rootstock for their antioxidant responses, and to determine the correlation of these enzymes to salinity stress. Leaves and roots were harvested following NaCl-induced stress. The results showed that a higher concentration of NaCl treatment induced oxidative stress in the leaf tissue and to a lesser extent in the roots. Both tissues showed an increase in ascorbate peroxidase, superoxide dismutase, catalase, glutathione reductase, peroxidase, and malondialdehyde. Responses of antioxidant enzymes were cultivar dependent, as well as temporal and dependent on the salinity level. Linear and quadratic regression model analysis revealed significant correlation of enzyme activities to salinity treatment in both tissues. The variation in salinity tolerance reflected their capabilities in orchestrating antioxidant enzymes at the roots and harmonized across the cell membranes of the leaves. This study provides a better understanding of root and leaf coordination in regulating the antioxidant enzymes to NaCl induced oxidative stress.

Characterization of OglDREB2A gene from African rice (Oryza glaberrima), comparative analysis and its transcriptional regulation under salinity stress.

In this study, AP2 DNA-binding domain-containing transcription factor, OglDREB2A, was cloned from the African rice (Oryza glaberrima) and compared with 3000 rice genotypes. Further, the phylogenetic and various structural analysis was performed using in silico approaches. Further, to understand its allelic variation in rice, SNPs and indels were detected among the 3000 rice genotypes which indicated that while coding region is highly conserved, yet noncoding regions such as UTR and intron contained most of the variation. Phylogenetic analysis of the OglDREB2A sequence in different Oryza as well as in diverse eudicot species revealed that DREB from various Oryza species were diversed much earlier than other genes. Further, structural features and in silico analyses provided insights into different properties of OglDREB2A protein. The neutrality test on the coding region of OglDREB2A from different genotypes of O. glaberrima showed the lack of selection in this gene. Among the different developmental stages, it was upregulated at tillering and flag leaf under salinity treatment indicating its positive role in seedling and reproductive stage tolerance. Real-time PCR analysis also indicated the conserve expression pattern of this gene under salinity stress across the three different Oryza species having different degree of salinity tolerance.

Salinity effects on expression of some important genes in sensitiveand tolerant grape genotypes

The effects of NaCl on expression of some genes related to salinity tolerance in grape (Vitis L.) were investigated. According to our screening study on eighteen grape genotypes, H6 and Gharashani (tolerant) and Shirazi and GhezelUzum (sensitive) were selected for molecular analysis. Our tolerant genotypes showed a higher water potential and a lower MDA content compared to other genotypes. Plants were treated with 50 mM NaCl as a critical concentration that is not lethal for grape. The expression profile of VvNHL1 in leaves of all genotypes and in roots of tolerant genotypes was similar to that of VvEDS1; these genes probably associated in defense responses. VvP450 and VvCPN21 transcripts were expected only in leaves, but they were also detected in roots. VvChS and VvPAL transcripts accumulated significantly (P < 0.05) in leaves of tolerant genotypes under salinity. Our results showed a significant difference between tolerant and sensitive genotypes and highlighted a strong relationship between the accumulation of specific transcripts and the degree of salinity tolerance.

Effect of salt stress on some sweet corn (Zea mays L. var. saccharata) genotypes

An experiment was carried out hydroponically under laboratory conditions to investigate the effect of salt stress on several physiological and biochemical parameters of three sweet corn (Zea mays L. var. saccharata) genotypes: lines 6-13, C-6 (pollen source) and their heterotic F1 hybrid ?Zaharina?. The degree of salinity tolerance among these genotypes was evaluated at three different sodium chloride (NaCl) concentrations: 0 mM, 100 mM, 125 mM and 150 mM. Seed germination, plant growth and biochemical stress determining parameters such as malondialdehyde (MDA), proline content and hydrogen peroxide (H2O2) levels were compared between seedlings of lines and hybrid. The obtained results indicated that both lines and hybrid have similar responses at different salinity levels for all examined traits. All the seedlings? growth parameters, such as germination percentage, root length, shoot length, root and shoot fresh and dry weight, decreased with increasing salinity level. MDA, proline and H2O2 increased at different saline conditions in comparison to the control. Based on the results, of the three genotypes examined, the hybrid Zaharina, followed by line C-6, was more salt-sensitive than line 6-13 in salt stress condition.

Genotypic differences in salt tolerance from germination to seedling stage in peanut

Aims In the present study, the degree of salt tolerance in different peanut varieties/lines was investigated from emergence to seedling stage. Methods The seeds of peanut varieties/lines were planted in pots with salt levels of 0, 0.15%, 0.30%, and 0.45% NaCl in soils. The degree of salinity tolerance was systematically evaluated according to ten indices reflecting emergence, morphology, and biomass accumulation, etc. Important findings Statistic analysis for the 10 indices, including the relative emergence time, relative plant height, relative stem height, relative taproot length, relative shoot fresh mass, relative root fresh mass, relative shoot dry mass, relative root dry mass, and relative plant dry mass, showed large variations among the 107 varie- ties/lines; each index displayed a normal distribution under different salt stresses. Using the principal component analysis, the ten indices could be categorized into several independent factors. According to the total score, the 107 varieties/lines were divided into four groups, i.e., highly salt tolerant, salt tolerant, salt susceptible, and highly salt susceptible, by cluster analysis at salt level of 0.15%, 0.30%, and 0.45%, respectively. The 107 varieties/lines accounted for 29.0%, 39.0%, 27.5%, and 4.5%, respectively under salt level of 0.15%, and 5.5%, 34.5%, 23.5%, and 29.0%, respectively under salt level of 0.30%, in the highly salt tolerant, salt tolerant, salt susceptible, and highly salt susceptible groups. The salt tolerance in some varieties/lines varied with the level of salt stresses; some varieties/lines showed tolerance under low salt stress but susceptible under high salt stress. The number of varie- ties/lines showed the same tolerance or susceptibility under different salt stresses was 1 ('Fuhua 11'), 7 ('Huayu 28', 'Z11', 'Huayu 39', 'Huayu 32', 'HLN2', 'Yueyou 26', and 'XE019'), 0 and 1 ('D1035'), respectively, in the highly salt tolerant, salt tolerant, salt susceptible, and highly salt susceptible groups. The 10 indices reflecting emergence, morphology, and biomass accumulation, etc., differed significantly or highly significantly among the varieties/lines in the four groups. Compared to the salt tolerant groups, the salt susceptible groups had prolonged

English

Generation, screening and isolating mutants for any developmental and adaptive traits plays a major role in plant functional genomics research. Identification and exploitation of mutants possessing contrasting root growth behavior and salinity tolerance in rice will help us to identify key genes controlling these traits and in turn will be useful for manipulating abiotic stress tolerance through tilling and genetic engineering in rice. In this study, we have screened about 1500 mutants (M 2 generation) generated by treating an upland drought tolerant genotype Nagina 22 with Ethyl Methane Sulfonate (EMS), for their root growth behavior and salinity tolerance under hydroponic conditions. Six independent mutant lines possessing significantly shorter roots and three mutant lines exhibiting greater degree of salinity tolerance than the wild type plants were identified. The identified mutant lines were advanced to M 5 generation to allow the mutants to reach homozygosity, and the fixed mutants were confirmed for their phenotype. One mutant namely N22-C-241-5-6 was found to possess significantly shorter roots than wild type N22, and it was also noticed that the mutant was devoid of root cap. Among the three salinity tolerant mutant lines identified, N22-C-334-3 was found to possess a greater degree of tolerance upto 250 mM Nacl stress at germination stage. These identified mutant lines can be used for further physiological, biochemical and molecular biology experiments to identify candidate gene(s) controlling root growth behavior and salinity tolerance in rice. Keywords : Rice, mutation, EMS, altered rood growth and salinity tolerant mutant African Journal of Biotechnology Vol. 12(40), pp. 5852-5859

Salt Stress Induced Variation in DNA Methylation Pattern and Its Influence on Gene Expression in Contrasting Rice Genotypes

BackgroundSalinity is a major environmental factor limiting productivity of crop plants including rice in which wide range of natural variability exists. Although recent evidences implicate epigenetic mechanisms for modulating the gene expression in plants under environmental stresses, epigenetic changes and their functional consequences under salinity stress in rice are underexplored. DNA methylation is one of the epigenetic mechanisms regulating gene expression in plant’s responses to environmental stresses. Better understanding of epigenetic regulation of plant growth and response to environmental stresses may create novel heritable variation for crop improvement.Methodology/Principal FindingsMethylation sensitive amplification polymorphism (MSAP) technique was used to assess the effect of salt stress on extent and patterns of DNA methylation in four genotypes of rice differing in the degree of salinity tolerance. Overall, the amount of DNA methylation was more in shoot compared to root and the contribution of fully methylated loci was always more than hemi-methylated loci. Sequencing of ten randomly selected MSAP fragments indicated gene-body specific DNA methylation of retrotransposons, stress responsive genes, and chromatin modification genes, distributed on different rice chromosomes. Bisulphite sequencing and quantitative RT-PCR analysis of selected MSAP loci showed that cytosine methylation changes under salinity as well as gene expression varied with genotypes and tissue types irrespective of the level of salinity tolerance of rice genotypes.Conclusions/SignificanceThe gene body methylation may have an important role in regulating gene expression in organ and genotype specific manner under salinity stress. Association between salt tolerance and methylation changes observed in some cases suggested that many methylation changes are not “directed”. The natural genetic variation for salt tolerance observed in rice germplasm may be independent of the extent and pattern of DNA methylation which may have been induced by abiotic stress followed by accumulation through the natural selection process.

Análise multivariada da divergência genética de genótipos de arroz sob estresse salino durante a fase vegetativa

Soil salinity is a limiting factor for rice cultivation, especially in the early stages of development and the flowering period. The use of sources of poor quality water for irrigation results in the accumulation of salts in the soil, causing major toxicity in culture. A solution to the problem would be the introduction of varieties with tolerance to high salinity. Hus the aim of this work is to evaluate genetic divergence among rice genotypes, aiming at the selection of genotypes tolerant to salinity during the vegetative phase. Seeds of 10 rice genotypes were grown in vitro on MS medium supplemented with 0 and 136 mM NaCl. After 21 days, six morphological characters were evaluated and the results subjected to multivariate analysis. The methods of Tocher, based on Mahalanobis distance, and graphic dispersion of canonic variables followed the same pattern of clustering structure, forming six groups. The characteristic of shoot fresh weight was the largest contributor to the genetic dissimilarity between genotypes by the method of Singh, while the other two canonic variables were sufficient to account for 91.27% of observed variation. Under the experimental conditions tested, the genotypes showed different degrees of salinity tolerance, while Colossus BRS, BRS Bojuru and BR IRGA 410, belonging to the groups three and four, were those who were more tolerant genotype and Moti, belonging to two what was more sensitive to salt stress.

Effects of salt stress on germination of some maize ( Zea mays L .) cultivars

This study was conducted to investigate the effects of salt stress on germination of six maize (Zea mays L.) cultivars (ADA-523, Bora, C-955, PR 3394, Progen 1150 and Trebbia). The degrees of salinity tolerance among these cultivars were evaluated at seed germination stage at six different salt concentrations (0, 50, 100, 150, 200 and 250 mM NaCl). The results showed that in all cultivars as the salt concentration increased, both germination percentage and germination index decreased significantly. Responses of cultivars to salt stress indicated differences. For all salt concentrations, C-955 had the highest germination percentage and germination index. Salt concentration decreased shoot and root dry weight. Bora and C-955 had the lowest reduction of shoot and root dry weight, respectively. Progen-1550 had the highest reduction of shoot and root dry weight. On the other hand, C-955 showed better results than the other cultivars in respect of salt tolerance index. The results showed that C-955 is the cultivar to be recommended for saline soils. Progen-1550 was more sensitive to salinity in this study.

Salinity tolerance of Great Lakes invaders

Summary1. The Laurentian Great Lakes are among the most invaded freshwater ecosystems in the world. Historically, the major vector for the introduction of non‐indigenous species (NIS) has been the release of contaminated ballast water via transoceanic ships. Despite regulations implemented in 1993, requiring vessels carrying fresh ballast water to exchange this water with saline ocean water, new reports of invasions have continued.2. NIS often have a wide environmental tolerance allowing them to adapt to and invade a variety of habitats. It has been hypothesized that NIS with broad salinity tolerance may be able to survive ballast water exchange (BWE) and continue to pose an invasion risk to the Great Lakes.3. We tested the short‐term salinity tolerance of eight recent invaders to the Great Lakes, specifically three cladocera (Bosmina coregoni, Bythotrephes longimanus, Cercopagis pengoi), two molluscs (Dreissena polymorpha, Dreissena rostriformis bugensis), and one species each of the families Gammaridae, Mysidae and Gobidae (Echinogammarus ischnus, Hemimysis anomala, Neogobius melanostomus) to determine if they could have survived salinities associated with BWE.4. Overall, short‐term exposure to highly saline water dramatically reduced survival of all species. Two different methods of BWE tested, simultaneous and sequential, were equally effective in reducing survival. Species that survived the longest in highly saline water either possess behavioural characteristics that reduce exposure to adverse environments (valve closure; both Dreissena species) or are reported to have some degree of salinity tolerance in their native region (Echinogammarus). Given that exposure in our trials lasted a maximum of 48 h, and that species in ballast tanks would typically be exposed to saline water for c. 5 days, it appears that BWE is an effective method to reduce the survival of these NIS. These results provide impetus for tightening policy and monitoring of BWE, in particular for ships entering the Great Lakes from freshwater ports.

Freshwater invertebrate fauna of the Tristan da Cunha islands (South Atlantic Ocean), with new records for Inaccessible and Nightingale Islands

As part of a multidisciplinary floristic-faunistic study, a three week survey of the invertebrate fauna of Inaccessible Island (South Atlantic Ocean) was carried out in October/November 1989. In addition, one day of collecting was done on Nightingale Island. This paper deals only with the fauna associated with freshwater ecosystems from these islands, some of which are usually associated with marine or brackish conditions. On Inaccessible Island, five distinct types of freshwater body were identified—pH neutral streams, acidic streams (pH 5), an open pool of standing water (pH 6), areas of acidic bog, and seepages down rock faces. The survey, the most comprehensive for Inaccessible Island to date, has resulted in the discovery of 19 aquatic invertebrate species previously unrecorded on Inaccessible Island, two new to Nightingale Island, and 14 of which are new to the Tristan da Cunha archipelago. Many of the species are known from other parts of the world, indicating a low degree of endemicity within the freshwater invertebrate community. Recolonisation from the source populations, preventing an isolated gene pool, may account for the low endemicity. Several of the species have a degree of salinity tolerance, enabling them to withstand transportation across tracts of ocean, and others have marine origins.

Salinity tolerance of the larvae and first juveniles of a semiterrestrial grapsid crab, Armases miersii (Rathbun)

The tropical crab Armases miersii breeds in supratidal rock pools, where great salinity variations occur. In laboratory experiments, all larval stages (zoea I–III, megalopa) and the first juvenile were studied as to their tolerance of acute salinity changes (5–55%., intervals of 10%.) after preceding adaptation to ambient sea water (32–33%.). Our observations suggest that some osmoregulatory capability exists from hatching. Survival was frequently higher and development faster at 15–25%. than in sea water (35%.), possibly indicating a phylogenetic adaptation of A. miersii to brackish water. Extremely low and high salinities (5, 45–55%.) caused prolonged development durations and increased mortality rates. Tolerance of very low salinity, but not that of hypersaline conditions tended to increase during development. This suggests that late stages attain an increasing capability for hyper-osmoregulation in dilute media, but probably remain poor regulators in concentrated media. The megalopa and crab I were, in some experiments, less affected by chronic than by acute exposure to unfavourable salinities, suggesting that non-genetic resistance adaptation (acclimatization) had taken place during earlier development. During continual exposure to extreme salinities, however, effects of severe osmotic stress outweighed those of acclimatization. The range which allowed for successful development through metamorphosis widened with consecutively later change of salinity: 15–35%. (exposure from hatching), 15–45%. (from zoea II), 5–45%. (from zoea III), 5–55%. (from megalopa or crab I). It is concluded that tolerance of variable, predominantly low salinities in larval and early juvenile A. miersii has evolved as an adaptation to breeding in a physically unstable environment, where rapidly decreasing or continually low salinities are more likely to occur than hypersaline conditions. The degree of salinity tolerance in its early life-cycle stages shows that this species has reached, within the Grapsidae, a phylogenetically intermediate stage of adaptation to conditions in freshwater and terrestrial environments.

Salinity Tolerance of an Aphanomyces Isolate (Oomycetes) and Its Possible Relationship to Ulcerative Mycosis (UM) of Atlantic Menhaden

An Aphanomyces sp. recovered from and thought to be a pathogen of Atlantic menhaden was subjected to salinity stress to see if its behavior suggested that it was a salt-resistant isolate. Respiration during prolonged salinity exposure as well as hyphal morphology suggested a degree of salinity tolerance generally greater than previously reported for this or other saprolegniaceous fungi. Furthermore, zoo? spores were shown to germinate during salinity stress if exogenous nutrients are present. In vitro studies of salinity tolerance of saprolegniaceous fungi have demonstrated that some representatives exhibit substantial resistance to salt stress. Te Strake (1959) described vegetative growth of several species at salinities as high as 22.5 parts per thousand (ppt), while Harrison and Jones (1971) observed growth of Saprolegnia