Salt-tolerant Genotypes Research Articles

Salt tolerance of cowpea genotypes during seed germination and seedling growth

Cowpea (Vigna unguiculata (L.) Walp.) is one of the most important grain legumes worldwide and its production is affected by increasing soil salinity due to global climate change. An experiment was conducted at the Plant Physiology Laboratory of the Department of Crop Botany, Bangladesh Agricultural University, Mymensingh to evaluate the germination capability of seven cowpea genotypes under salt stress. The germination test was carried out in Petri dishes following two factorial CRD with three replications. Seven cowpea genotypes viz, Red Pine, Green Super, Hai Jiang San Hao, Kegornatki, Kegornatki Green, Kegornatki HYV & Kegornatki Red; and three salt levels viz, 0, 6 & 12 dSm-1, were used as experimental treatments. The germination percentage (GP), mean germination time (MGT), radicle and plumule length, radicle and plumule fresh and dry weight and different stress tolerance indices were recorded to screen the genotypes for salt tolerance. The study highlighted that salt concentrations drastically reduced seed germination and significantly delayed the process in all genotypes. The GP, length and biomass of radicle and plumule and salt tolerance indices were significantly decreased while the MGT was significantly increased with increasing salt stress in all cowpea genotypes. A significant variation among the genotypes in response to salt stress was also observed. Among the seven cowpea genotypes, Hai Jiang San Hao and Green Super showed higher salt tolerance in comparison to the other genotypes based on the measured traits; these genotypes can be used for further breeding program and/or cultivation in coastal saline prone areas with further investigation. J. Bangladesh Agril. Univ. 17(1): 39–44, March 2019

Insights into Salt Stress-Induced Biochemical, Molecular and Epigenetic Regulation of Spatial Responses in Pigeonpea (Cajanus cajan L.)

Pigeonpea (Cajanus cajan L.) is a rich source of nutritionally good quality proteins, carbohydrates, minerals, and vitamins. However, environmental stresses adversely affect its productivity. Only limited reports are available on biochemical/physiological responses of pigeonpea under salt stress. The objectives of the present study were to screen pigeonpea germplasm accessions for salt stress tolerance, followed by understanding their biochemical, epigenetic and molecular responses. Based on germination, growth, and vigor of seedlings under salt stress, the most contrasting pair of salt-responsive genotypes (ICP1071- most salt-sensitive, and ICP7- most salt-tolerant) were selected. Three-week-old seedlings subjected to 250 mM NaCl stress for 7 days showed a significant increase in proline and reducing sugar contents in the case of ICP7, whereas a considerable increase in cell wall-degrading enzyme activity and protein oxidation was observed in ICP1071. Superoxide dismutase, peroxidase, and glutathione reductase activity increased considerably in shoots of ICP7. We observed the CcCYP gene to be upregulated in root, whereas CcCDR was upregulated in shoots of the salt-tolerant genotype to provide protection against the stress. The extent of DNA hypomethylation in the contrasting pigeonpea genotypes under salt stress was correlated with their salt tolerance level. Bisulfite sequencing of CcCDR revealed that methylation of three cytosine residues in CHH context in shoots of the ICP7 genotype due to salt stress results in 2.6-fold upregulated expression of the gene. With a 6.8% increase in methylation of the coding region of CcCDR, its expression level increased by 22%. To the best of our knowledge, this is the first report on a comprehensive study of salt-induced biochemical, epigenetic and molecular responses of pigeonpea, which might be useful in the development of improved salt-tolerant variety.

Screening Oryza Sativa L. for Salinity Tolerance During Vegetative Stage for the Coastal Region of Niger-Delta Nigeria

Background and Objective: The coastal region of Niger Delta of Nigeria is favourable for rice production because of the swampy nature, but rice productivity is very low due high level of salinity in the soil. The objectives of this study was to identify promising salt tolerant genotypes for the deployment into this salt stressed region and also for population improvement for salt breeding programme. Materials and Methods: Two potted experiments comprise the same twenty genotypes were established concurrently in coastal soil and controlled sterilized top soil in two replications in a randomized complete block design at the University of Port Harcourt teaching and research farm. Results: Most of the genotypes showed differential response to salinity stress, the protocol used for the screening could be effective as significant difference was observed based on t-test for the two experiments. Salinity scores showed significan negetative association with number of tillers and leaf area index (LAI). Principal component 1 contributed 44.21% and 38.44% of the total variation in the control and coastal soil experiments, respectively. Conclusion: Genotypes IR 84105-5-B-1-B-3 and IR 84105-5-B-1-B-2 maybe promising for deployment into this salinity stressed region. The leave area index and tillering ability of the rice crop are major yield components, their high weight and factor loading values indicate that they are purtative traits for salinity tolerant, which could be used for population development in salinity breeding programme.

Nitrogen Application Improved Photosynthetic Productivity, Chlorophyll Fluorescence, Yield and Yield Components of Two Oat Genotypes under Saline Conditions

: Understanding the interaction between salinity and nitrogen (N) nutrition is of great economic importance to improve plant growth and grain yield for oat plants. The objective of this study was to investigate whether N application could alleviate the negative effect of salinity (NaCl) stress on oat physiological parameters and yield performance. Two oat genotypes with contrasting salt tolerance response (6-SA120097, a salt-tolerant genotype SA and 153-ND121147, salt-sensitive ND) were grown under four N rates (0, 100, 200, and 400 mg N pot−1) in non-saline and saline (100 mM NaCl) conditions. The results showed that salinity, N fertilization and their interaction significantly affected the photosynthetic rate, transpiration rate, agronomic nitrogen use efficiency (aNUE), physiological nitrogen efficiency (pNUE) and apparent nitrogen recovery (ANR), seed number, and grain yield. Saline stress reduced gas exchange rate, nitrogen use efficiency (NUE), grain yield, and yield components. N fertilization increased photosynthetic productivity and chlorophyll fluorescence, resulting in improved grain yields and yield components for both genotypes. On average, the photosynthetic rate was increased by 38.7%, 74.1%, and 98.8% for SA and by 49.8%, 77.6%, and 110% for ND, respectively, under the N rates of 100, 200, and 400 mg N pot−1, as compared with non-fertilized treatment. In addition, grain yield was increased by 80.6% for genotype SA and 88.7% for genotype ND under higher N application rate (200 mg N pot−1) in comparison with the non-nitrogen treatment. Our experimental results showed that an increase of N supply can alleviate the negative effects induced by salinity stress and improved plant growth and yield by maintaining the integrity of the photosynthesis and chlorophyll fluorescence processes of oat plants, which provides a valuable agronomic strategy for improving oat production in salt-affected soils.

Adaptation of sugarcane plants to saline soil

Sugarcane is an important crop in tropical regions of the world, often being exposed to environments with high salinity, but little is known of genetic variation in salt tolerance. The aim of this work was to compare the performance of two genetically diverse cultivars of sugarcane under different concentrations of salinity (0, 40, 80 and 160 mM NaCl) over a period of 30 days. SP 81–3250 was more salt-tolerant and maintained its rate of biomass production, photosynthesis and leaf area up to 160 mM NaCl, whereas IAC 87–3396 was sensitive to 80 mM NaCl. SP 81–3250 maintained very low concentrations of Na+ in both leaves and roots with increasing time and salinity, whereas in IAC 87–3396 the Na+ concentrations were 2–5 times higher. SP 81–3250 ha d a greater accumulation of proline, and lower lipid peroxidation, whereas glycine betaine and sucrose concentrations were similar in the two cultivars. This suggests that the tolerance of SP 81–3250 to high salinity was due to its ability to exclude Na+ while taking up water from the soil, and that measurements of Na+ concentration in leaves could be used to select salt-tolerant genotypes for saline areas.

Seedling salt tolerance for above ground-related traits in cowpea (Vigna unguiculata (L.) Walp)

With poor quality of irrigation water, salt concentrations in cultivated areas keep increasing, hence preventing cowpea from being cultivated for optimal growth and development. Effects of salinity on crops are severe in semi-arid and arid regions where low rainfall does not allow salt compounds to be leached from soils. Seedling stage is one the most vulnerable stages in plant growth and development. However, to date, few if any salt-tolerant cowpea cultivars have been reported worldwide. Therefore, the objective of this study was to evaluate cowpea genotypes for salt tolerance based on the reduction of above ground-related traits. A total of 155 cowpea genotypes was phenotyped for salt tolerance at seedling stage. Salt treatments were 0 mM and 200 mM NaCl. The experiment design was completely randomized (CRD) with three replications per genotype and salt treatment combination, and organized in a split-plot manner. Salt stress was imposed for 2 weeks and a total of 19 parameters were used for salt tolerance evaluation. Results revealed that: (1) a large variation in salt tolerance was found among the 155 cowpea genotypes; (2) salt stress significantly reduced plant height and fresh shoot biomass, but slightly increased chlorophyll content; (3) a relatively high correlation was found between plant height and fresh biomass-related parameters; (4) chlorophyll content had low correlation with plant height and fresh shoot biomass reductions, respectively; and (5) PI354686, PI353270, PI354666, and PI354842 were salt-tolerant based on the decrease in plant height and fresh shoot biomass, and PI548785, PI582466, PI339599, and 09-697 were the top performers based on chlorophyll content. These results can be used for advancing breeding programs for salt tolerance in cowpea.

Omeprazole treatment elicits contrasting responses to salt stress in two basil genotypes

Omeprazole (OP) has been shown to act as a plant growth regulator and enhances tolerance to salt stress. In this study, two Ocimum basilicum genotypes were tested for their responses to OP under salt stress. The two genotypes, Napoletano (NAP) a salt sensitive genotype, and Genovese (GEN) a salt tolerant genotype, had contrasting responses to OP treatment. NAP demonstrated increases in terms of growth (+36%) and salt tolerance (+19%) upon treatment while GEN had a growth increase (+35%) and OP enhanced sensitivity to salt stress (−13%). OP treatment also had an effect on the post‐harvest behaviour of these two genotypes by increasing NAP shelf life while decreasing GEN shelf life. The contrasting responses to OP in these two genotypes has provided insight into the role of this molecule in mediating growth and adaptation to stress and, more importantly, into the complexity of the mechanisms mediating these processes.

Transcriptome and metabolome analyses of two contrasting sesame genotypes reveal the crucial biological pathways involved in rapid adaptive response to salt stress

BackgroundSoil salinity is one of the major serious factors that affect agricultural productivity of almost all crops worldwide, including the important oilseed crop sesame. In order to improve salinity resistance in sesame, it is crucial to understand the molecular mechanisms underlying the adaptive response to salinity stress.ResultsIn the present study, two contrasting sesame genotypes differing in salt tolerance were used to decipher the adaptive responses to salt stress based on morphological, transcriptome and metabolome characterizations. Morphological results indicated that under salt stress, the salt-tolerant (ST) genotype has enhanced capacity to withstand salinity stress, higher seed germination rate and plant survival rate, as well as better growth rate than the salt-sensitive genotype. Transcriptome analysis revealed strongly induced salt-responsive genes in sesame mainly related to amino acid metabolism, carbohydrate metabolism, biosynthesis of secondary metabolites, plant hormone signal transduction, and oxidation-reduction process. Especially, several pathways were preferably enriched with differentially expressed genes in ST genotype, including alanine, aspartate and glutamate metabolism, carotenoid biosynthesis, galactose metabolism, glycolysis/gluconeogenesis, glyoxylate and dicarboxylate metabolism, porphyrin and chlorophyll metabolism. Metabolome profiling under salt stress showed a higher accumulation degree of metabolites involved in stress tolerance in ST, and further highlighted that the amino acid metabolism, and sucrose and raffinose family oligosaccharides metabolism were enhanced in ST.ConclusionsThese findings suggest that the candidate genes and metabolites involved in crucial biological pathways may regulate salt tolerance of sesame, and increase our understanding of the molecular mechanisms underlying the adaptation of sesame to salt stress.

Evaluation of Salt Tolerance and Its Relationship with Carbon Isotope Discrimination and Physiological Parameters of Barley Genotypes

ABSTRACTSoil management through the cultivation of salt-tolerant plants is a practical approach to combat soil salinization. In this study, salt tolerance of 35 barley (Hordeum vulgare L.) genotypes was tested at four salinity levels (0, 100, 200, and 300 mM NaCl in Hoagland nutrient solution) at two growth stages (germination and vegetative). The relationship between salinity tolerance and carbon isotope discrimination (CID) was also accessed. Results of the study carried out under laboratory conditions showed that a negative linear relationship was observed between salt concentration and germination as well as other growth parameters. Some genotypes showed good salt tolerance at germination but failed to survive at seedling stage. However, five genotypes, namely, Jau-83, Pk-30109, Pk-30118, 57/2D, and Akermanns Bavaria showed better tolerance to salinity (200 mM) both at germination and at vegetative growth stage. The salt tolerance of these barley genotypes was significantly correlated with minimum decrease in K+:Na+ ratio in plant tissue with increase in the root zone salinity. However, the case was reversed in sensitive genotypes. CID was decreased linearly with increase in root zone salinity. However, salt-tolerant genotypes maintained their turgor by osmotic adjustment and by minimum increase in diffusive resistance and showed minimum reduction in CID (Δ) with gradual increase in rooting medium salt concentration. Results suggested that the tolerant genotypes make osmotic adjustments by selective uptake of K+ and by maintaining a higher K+:Na+ ratio in leaves. Moreover, CID technique can also be good criteria for screening of salt-tolerant germplasm.

Meta-Analysis of Quantitative Trait Loci Associated with Seedling-Stage Salt Tolerance in Rice (Oryza sativa L.).

Soil and water salinity is one of the major abiotic stresses that reduce growth and productivity in major food crops including rice. The lack of congruence of salt tolerance quantitative trait loci (QTLs) in multiple genetic backgrounds and multiple environments is a major hindrance for undertaking marker-assisted selection (MAS). A genome-wide meta-analysis of QTLs controlling seedling-stage salt tolerance was conducted in rice using QTL information from 12 studies. Using a consensus map, 11 meta-QTLs for three traits with smaller confidence intervals were localized on chromosomes 1 and 2. The phenotypic variance of 3 meta-QTLs was ≥20%. Based on phenotyping of 56 diverse genotypes and breeding lines, six salt-tolerant genotypes (Bharathy, I Kung Ban 4-2 Mutant, Langmanbi, Fatehpur 3, CT-329, and IARI 5823) were identified. The perusal of the meta-QTL regions revealed several candidate genes associated with salt-tolerance attributes. The lack of association between meta-QTL linked markers and the level of salt tolerance could be due to the low resolution of meta-QTL regions and the genetic complexity of salt tolerance. The meta-QTLs identified in this study will be useful not only for MAS and pyramiding, but will also accelerate the fine mapping and cloning of candidate genes associated with salt-tolerance mechanisms in rice.

ITRAQ-Based Protein Profiling and Biochemical Analysis of Two Contrasting Rice Genotypes Revealed Their Differential Responses to Salt Stress.

Salt stress is one of the key abiotic stresses causing huge productivity losses in rice. In addition, the differential sensitivity to salinity of different rice genotypes during different growth stages is a major issue in mitigating salt stress in rice. Further, information on quantitative proteomics in rice addressing such an issue is scarce. In the present study, an isobaric tags for relative and absolute quantitation (iTRAQ)-based comparative protein quantification was carried out to investigate the salinity-responsive proteins and related biochemical features of two contrasting rice genotypes—Nipponbare (NPBA, japonica) and Liangyoupeijiu (LYP9, indica), at the maximum tillering stage. The rice genotypes were exposed to four levels of salinity: 0 (control; CK), 1.5 (low salt stress; LS), 4.5 (moderate salt stress; MS), and 7.5 g of NaCl/kg dry soil (high salt stress, HS). The iTRAQ protein profiling under different salinity conditions identified a total of 5340 proteins with 1% FDR in both rice genotypes. In LYP9, comparisons of LS, MS, and HS compared with CK revealed the up-regulation of 28, 368, and 491 proteins, respectively. On the other hand, in NPBA, 239 and 337 proteins were differentially upregulated in LS and MS compared with CK, respectively. Functional characterization by KEGG and COG, along with the GO enrichment results, suggests that the differentially expressed proteins are mainly involved in regulation of salt stress responses, oxidation-reduction responses, photosynthesis, and carbohydrate metabolism. Biochemical analysis of the rice genotypes revealed that the Na+ and Cl− uptake from soil to the leaves via the roots was increased with increasing salt stress levels in both rice genotypes. Further, increasing the salinity levels resulted in increased cell membrane injury in both rice cultivars, however more severely in NPBA. Moreover, the rice root activity was found to be higher in LYP9 roots compared with NPBA under salt stress conditions, suggesting the positive role of rice root activity in mitigating salinity. Overall, the results from the study add further insights into the differential proteome dynamics in two contrasting rice genotypes with respect to salt tolerance, and imply the candidature of LYP9 to be a greater salt tolerant genotype over NPBA.

Evaluation and clustering on salt-tolerant ability in rice genotypes (Oryza sativa L. subsp. indica) using multivariate physiological indices.

Salinity is a major abiotic stress that affects plant growth and development, especially in rice crop as it is a salt susceptible crop. Therefore, a wide range of rice genetic resources are screened in the germplasm banks to identify salt tolerant cultivars. The objective of this investigation was to develop effective indices for the classification of salt tolerant rice genotypes among Pathumthani 1, Khao Dawk Mali 105 (KDML 105), RD31, RD41, Suphanburi 1, RD43, RD49 and Riceberry. Rice seedlings were hydroponically grown with 10dSm-1 NaCl treatment or without NaCl treatment (to serve as control) (WP; 2dSm-1). Standard evaluation system peaked at a score of 9 in Pathumthani 1 and KDML 105, after 21days of salt treatment, leading to leaf chlorosis, leaf burns and plant death. Chlorophyll a, chlorophyll b and total carotenoids were maintained better in the salt-stressed leaves of rice cvs. Riceberry and RD43, as compared to other cultivars. Salt stress induced a remarkable increase in the free proline accumulation (by 8.38 folds) in cv. Riceberry. Overall growth performance in rice cv. Riceberry was retained, whereas it declined in other cultivars. After 21days of NaCl treatment at a concentration of 10dSm-1, eight rice cultivars were classified into 3 groups based on multivariate physio-morphological indices, Group I: salt-tolerant rice, including cv. Riceberry; Group II: moderately salt tolerant, consisting of RD31, RD41, Suphanburi 1, RD43 and RD49 cultivars; Group III: salt-sensitive cultivars, namely Pathumthani 1 and KDML 105.

Comparative proteomic analysis of salt-responsive proteins in canola roots by 2-DE and MALDI-TOF MS

Salinity stress is a major abiotic stress that affects plant growth and limits crop production. Roots are the primary site of salinity perception, and salt sensitivity in roots limits the productivity of the entire plant. To better understand salt stress responses in canola, we performed a comparative proteomic analysis of roots from the salt-tolerant genotype Safi-7 and the salt-sensitive genotype Zafar. Plants were exposed to 0, 150, and 300 mM NaCl. Our physiological and morphological observations confirmed that Safi-7 was more salt-tolerant than Zafar. The root proteins were separated by two-dimensional gel electrophoresis and MALDI-TOF mass spectrometry was applied to identify proteins regulated in response to salt stress. We identified 36 and 25 protein spots whose abundance was significantly affected by salt stress in roots of plants from the tolerant and susceptible genotype, respectively. Functional classification analysis revealed that the differentially expressed proteins from the tolerant genotype could be assigned to 14 functional categories, while those from the susceptible genotype could be classified into 9 functional categories. The most significant differences concerned proteins involved in glycolysis (Glyceraldehyde-3-phosphate dehydrogenase, Fructose-bisphosphate aldolase, Phosphoglycerate kinase 3), stress (heat shock proteins), Redox regulation (Glutathione S-transferase DHAR1, L-ascorbate peroxidase), energy metabolism (ATP synthase subunit B), and transport (V-type proton ATPase subunit B1) which were increased only in the tolerant line under salt stress. Our results provide the basis for further elucidating the molecular mechanisms of salt-tolerance and will be helpful for breeding salt-tolerant canola cultivars.

Mass screening for salinity tolerance in rice (Oryza sativa. L) genotypes at early seedling stage by hydroponics

Salinity is a major abiotic factor that affects rice cultivation in the world along the coastal areas. The salt affected areas in India is estimated to be around 8 to 10 million hectares that causes significant reduction in rice growth and yield. In order to improve the rice cultivars for salt tolerance, selection of the suitable genotypes is necessitated. Hence, in this experiment ninety seven rice genotypes including traditional landraces were collected and subjected to screening under salt stress by hydroponics system on Yoshida nutrient solution of EC 8 dSm−1and 12 dSm−1 with 4 replications. The genotypes were scored on 15th day after sowing based on standard evaluation scoring system of IRRI. Among the 97 rice genotypes scored, 5% were tolerant, 21% were moderately tolerant, 54% genotypes were susceptible and 18% were highly susceptible. The rice genotypes viz., Pokkali, FL478, Kuliyadichan, Gurukot and IR12L-107 revealed significant level of tolerance to salt stress. The rice genotypes, Pokkali and FL478 showed no symptoms at 8 dSm−1 and leaf rolling alone at 12dSm−1. Kuliyadichan, Gurukot and IR12L-107 showed leaf rolling at 8dSm−1 and leaf rolling and leaf tip burning at 12dSm−1. Screening of the rice genotypes for salinity tolerance only by visual symptoms is not reliable and hence the selected rice genotypes will further be characterized based on the morphological and biochemical parameters under salt stress in order to select elite salt tolerant rice genotypes for use in developing salinity tolerant somaclones by in vitro culture.

Genetic variability for seedling stage salinity tolerance in barnyard millet [Echinochloa frumentaceae (Roxb.) Link

Barnyard millet (Echinochloa frumentaceae) has a potential to withstand salinity. The existing genetic variability for salinity tolerance in 32 barnyard millet accessions was assessed based on the morpho-physiological parameters governing salt tolerance viz., germination percentage, relative germination rate, root length, shoot length, seedling length, vigour index, relative salt injury rate and relative water content. Under gradual increase in the intensity of salt stress, decrease in germination percentage, relative germination rate, root length, shoot length, seedling length, vigour index, relative water content and increase in relative salt injury rate was observed. The antioxidant assay also revealed that catalase and peroxidase activity increased with rise in salt level in tolerant genotypes (ACM161, ACM295, ACM335, GECH10, IEc167) but the enzyme activity in the salt sensitive genotypes (IEc134, IEc348, IEc607) declined with increase in salt concentration, when compared to control. The salt tolerant genotypes maintained higher relative water content and enzyme activity under salt stress. Hence, this may be the underlying mechanism for salt tolerance.

Differential response of Indian mustard (Brassica juncea L., Czern and Coss) under salinity: photosynthetic traits and gene expression.

To explore the effect of salt stress on photosynthetic traits and gene expression in Indian mustard, four genotypes CS 54 (national check for salinity), CS 52-SPS-1-2012 (salt tolerant mutant), CS 614-4-1-4-100-13 (salt sensitive mutant) and Pusa bold (high yielding variety) were evaluated under irrigation water salinity (ECiw 12, and 15dSm-1). Results suggest genotype CS 52-SPS-1-2012 followed by CS 54 performed better under imposed salt stress due to differential regulation of Na+ accumulation in the roots and main stem, restriction of Na+ influx from root to shoot, maintaining higher net photosynthetic traits under saline stress compared to CS 614-4-1-4-100-13 and Pusa bold. Further, overexpression of antiporters (SOS1, SOS2, SOS3, ENH1 and NHX1) and antioxidant (APX1, APX4, DHAR1 and MDHAR) genes in salt tolerant genotypes CS 52-SPS-1-2012 and CS 54 demonstrated their significant role in imparting salt tolerance in Indian mustard.

Silicon-induced Salinity Tolerance Improves Photosynthesis, Leaf Water Status, Membrane Stability, and Growth in Pepper (Capsicum annuum L.)

Salt stress is a major problem worldwide because it decreases yields of many important agricultural crops. Silicon is the second-most abundant element in soil and has numerous beneficial effects on plants, particularly in alleviating stress-related impacts. Pepper is an important crop in the Mediterranean region, but pepper varieties differ in their salinity tolerances. The objective of this research was to test the ability of silicon to mitigate effects of salt stress in both salt-sensitive and salt-tolerant cultivars. Salt damage was evaluated by measuring biomass, photosynthetic-related variables, leaf water potential, and membrane damage. We found that the addition of silicon solute to a growth medium was highly effective in improving plant growth by enhancing photosynthesis, stomatal conductance (gS), leaf water status, and membrane stability, which in turn led to higher biomass production in salt-stressed pepper plants, especially in a salt-sensitive cultivar. From an agronomic viewpoint, application of Si may provide economically relevant productivity improvements for salt-sensitive pepper genotypes grown under moderate salinity conditions and for salt-tolerant genotype grown under higher-salinity conditions.

Gene expression analysis reveals diversified responsiveness to salt stress in rice genotypes

Salt stress is a major factor affecting rice (Oryza sativa) growth and productivity, limiting its distribution globally. Rice production is primarily gets affected due to its vulnerability to salinity stress at seedling stage, as well as reproductive stage leading to reduction in yield. We report the analysis of 12 diverse rice genotypes collected from different parts of coastal places of northern Andra Pradesh and southern Orissa in India for salt tolerance and categorized their tolerance levels on the basis of reduction in growth and transcript expression pattern. The analysis identified four contrasting salt tolerant genotypes and other eight genotypes exhibited moderate tolerance. Two tolerant and two sensitive genotypes were biochemically explored and used further for gene expression analysis. Proline content showed significant difference between salt tolerant and sensitive genotypes suggesting high tolerance level in tolerant CR1014 and Kudrat-5. The gene-expression analysis of selected CR1014 (salt-tolerant) and Kudrat-5 (salt-sensitive) genotypes differed at transcript expression levels for antioxidant specific A2YPX2/plant peroxidase—POX (19.03-fold) and SODCP/superoxide dismutase (SOD) copper/zinc binding (3.77-fold) in shoots of Kudrat-5 and CATA1/catalase (2.49-fold) and SODCP/SOD copper/zinc binding (4.83-fold) in CR1014 in stress conditions). The salt-stress responsive-specific transcripts HAK17/K+ potassium transporter, A2XMP7/heat shock protein DnaJ, cysteine-rich domain and Q10D68/serine hydroxymethyltransferase in CR1014 after treatment showed increased expression. Interestingly, the transcripts specific for methionine biosynthesis mainly A2Z9C9/Cys/Met metabolism, pyridoxal phosphate-dependent enzyme and B8AF89/spermine synthase induced their expression in Kudrat-5 under salinity stress, where the similar trend was not reflected in salt-tolerant genotype. Thus, the present study highlights on transcript expression pattern for salt-stress responsive candidate genes in two-contrasting rice genotypes selected from the pool of farmer’s cultivated varieties along the coastal belts of India.

Exogenously Applied Nitric Oxide Enhances Salt Tolerance in Rice (Oryza sativa L.) at Seedling Stage

Salinity is one of the major abiotic factors that limit rice production worldwide. Previous trends show that salt concentration in rivers is increasing consistently, posing potentially adverse threats in the near future. Thus, crops currently being cultivated, particularly in small-scale farming systems, are under high threat from salinity. In this study, we investigated the mitigating effect of nitric oxide (NO) on salt stress in rice based on the assessment of changes in the transcript levels of different genes and the phenotypic response of rice genotypes. We observed that exogenously applied NO increased the expression levels of OsHIPP38, OsGR1, and OsP5CS2 in the susceptible genotype of rice, whereas in the tolerant genotype, the effect of NO was mainly in counteracting the salt-induced gene expression that diverts cellular energy for defense. Moreover, seedlings that were pretreated with NO showed high biomass production under salt stress conditions, indicating the positive role of NO against salt-induced leaf chlorosis and early senescence. The effect of NO-mediated enhancement was more pronounced in the salt tolerant genotype. Therefore, the use of NO with the integration of tolerant genes or genotypes will enhance salt tolerance levels in rice.

Screening of wheat genotypes against salinity at early vegetative stage in pot culture

Experiment was carried out to investigate intraspecific variation for salt tolerance and to classify the wheat genotypes into different salt tolerant groups. Considerable variations among the genotypes in response to salinity were observed for shoot length under 16 dS/m NaCl salinity in the both seasons. Salt tolerant genotype was found to be less affected at high salinity and could be produced better total dry matter compared to other genotypes. Five and seven genotypes appeared as tolerance during 2008 - 09 and 2009 - 10, respectively based on relative total dry matter (RTDM). On the other hand, six and three genotypes exhibited tolerant during 2008 - 09 and 2009 - 10, respectively based on visual scoring. The distribution pattern of the genotypes into various salinity tolerant groups remained fairly constant under two methods. Three genotypes G24, G33 and G40 exhibited tolerant category. RTDM compared to the control would be very useful trait in salinity tolerant improvement programme. However, visual scoring provide guidelines for mass screening of salt tolerant genotypes.