جستجوی مقالات مرتبط با کلیدواژه « salinity tolerance » در نشریات گروه « زراعت »

Soil salinity, as one of the most important environmental stresses, is a serious threat to agricultural production. Currently, more than 20% of the agricultural lands, which includes 954 million hectares of the world's lands, is affected by soil salinity. Salinity is expanding daily and it is predicted that by 2050, more than 50% of the world's arable lands will be saline. The decrease in yield due to salinity stress in wheat is considerable and worrying, so that a 50% decrease in yield of durum wheat due to salinity of rainfed lands, and an 88% decrease in yield of bread wheat under irrigation with high salinity and and a 70% decrease in yield of bread wheat in sodic soils has been reported. The high levels of salt in soils and irrigation waters are worrying factors for agriculture, therefore it is necessary to develop the effective strategies to improve yield through salinity stress tolerance. The present study was carried out due to the importance of genetic accessions as sources of tolerance to biotic and abiotic stresses including salinity, and the existence of considerable genetic diversity in wheat germplasm to salinity stress tolerance. The objective of this experiment is to investigate the diversity of genetic accessions of bread wheat collection of Iran's National Plant Gene Bank, to compare the accessions with the tolerant control varieties, and to identify the new genetic resources for salinity tolerance.

To identify the genetic resources of salinity tolerance in wheat germplasm, 512 accessions from the bread wheat collection of the National Plant Gene Bank of Iran along with salinity tolerant varieties, Kavir, Roshan and Mahoti as controls, were investigated in two different augmented designs under normal and salinity stress conditions. The normal experiment was carried out at the research field of Yazd Research Center and the salt experiment was done at saline lands of Ardekan Research Station. The studied traits included spike length, spike density, 100-grain weight, number of tillers, plant height, number of spikelets per spike, number of florets per spikelet, number of grains per spike, days to heading, days to maturity, grain filling period and grain weight of five spikes,  which were recorded according to the international description. To perform data statistical analyses, descriptive statistical indices were first calculated and then the studied accessions were grouped using K-means cluster analysis. Discriminant function analysis based on principal components was used to investigate the differentiation between the groups resulting from cluster analysis. Statistical analyzes were performed by SPSS and R softwares.
 
 
Research

The results showed that grain weight of five spikes (with a minimum of 4.15 and a maximum of 12.26 g in normal conditions and a minimum of 2.19 and a maximum of 9.78 g in stress conditions) and the number of spikes (with a minimum of 3 and a maximum of 8 in normal conditions and a minimum of 3 and a maximum of 7 in stress conditions) had the highest coefficients of variation, while days to heading (with a minimum-maximum of 130-163 days and 126-168 days in normal and salinity stress conditions, respectively) and days to maturity (with a minimum-maximum of 173-189 days and 168-196 days in normal and salinity stress conditions, respectively) had the lowest coefficient of variation under both normal and salinity stress conditions. A large number of superior accessions were identified for various traits compared to the control cultivars under both normal and salinity stress conditions. The results of stepwise regression indicated the importance of three characteristics, 100-grain weight, number of grains per spike and number of florets per spikelet, in describing the variation of grain weight of five spikes. The investigated accessions were divided into five groups using K-means cluster analysis and the control cultivars were separated into different groups so that Roshan and Mahooti along with 70 accessions were grouped in the first cluster and Kavir along with 53 accessions in the fifth cluster.

The results of this experiment showed the presence of significant and valuable genetic diversity in traits related to salt stress tolerance in the studied bread wheat germplasm. The effect of salinity stress on different traits of the studied accessions was different. Among the studied traits, 100-grain weight, number of grains per spike and number of florets per spike were more important, so they can be used in breeding programs. A large number of accessions were also superior to control cultivars for various traits. Cluster analysis grouped the control cultivars into distinct clusters, which indicates different aspects of salt stress tolerance in these cultivars. The superior accessions identified in this research can be used to improve salt stress tolerance in bread wheat breeding programs.

Using plant tissue culture, including embryo culture, is one of the ways to increase genetic diversity to withstand environmental stresses, including salinity tolerance in plants. In this study, the reaction of 20 different durum wheat (Triticum turgidum var. durum Desf.) genotypes, including improved lines, native accessions, and two control cultivars, Zardak and Saji, were evaluated to the induction of callus formation and plant regeneration through mature embryo culture and comparison of callus response to salt stress condition. Murashige and Skoog (MS) medium was used for the mature embryo culture of durum wheat. For assessment of genotypes to salt stress, growing morphogenic calli were exposed to different concentrations of NaCl (0, 4, 8, 12, 16 and 20 dSm-1) added to the culture medium. The response of genotypes to in vitro NaCl stress was analyzed as a 20 × 6 factorial experiment based on a completely randomized design with three replications. Comparison of genotypes for callus induction from mature embryos was based on callus induction frequency, relative fresh weight growth of callus (RFWG), relative growth rate (RGR) and callus growth rate. The relative fresh weight growth of callus (RFWG), relative growth rate (RGR), callus growth rate and necrosis percent of callus were used for salt stress. The analysis of the correlation coefficients of the investigated traits in the conditions of callus induction showed that the callus induction percentage has a positive and significant correlation (P<0.01) with the callus growth rate. A positive and significant correlation (P<0.05) was also observed between the relative callus growth and the relative callus growth rate. Under salinity stress, relative callus growth showed a positive and significant correlation (P<0.01) with callus relative growth rate and a negative and significant correlation with callus chlorosis percentage. The results cluster analysis showed that genotypes 65-12-3-3, 75-5-3-5 and Zardak were classified in the same group of tolerant salt stress genotypes. Based on the results, Zardak variety and accessions 65-12-3-3 and 75-5-3-5 due to high relative growth rate and relative growth of callus and low chlorosis percentage in the saline environment were identified as tolerant genotypes to salinity under in vitro conditions. Genotype 25-25-1-5 had the highest response to adult embryo culture. The results showed a significant variation in the ability to callus induction in the genetic material under salinity stress conditions, which can be used in the durum wheat breeding program. It could be suggested to evaluate genotypes in field conditions and study the relationships between traits in vitro and in vivo. Selected cells and plants provide a tool to determine the mechanisms involved in salt stress tolerance. The laboratory screening method for tolerance to salinity stress of plant genotypes can provide a suitable path for developing salinity-tolerant lines in durum wheat.

Salinity as one of the major abiotic stresses influences plant growth and development. Rice with a salt tolerance threshold of 3 ds/m is regarded as a very sensitive crop, especially at seedling stage. Metabolite profiling is conducted by instruments such as GC-MS (Gas chromatography–mass spectrometry) and permits the study of plant responses to environmental stresses at the molecular level. The present study assessed the primary metabolite profiles related to high salinity stress in sensitive (IR28) and tolerant (CSR28) genotypes of rice seedlings in shoots and roots after 6h and 54 h salinity exposure.

The seeds of two rice (Oryza sativa L. ssp. Indica) genotypes with different salinity tolerance were obtained from International Rice Research Institute (IRRI) in Philippines. The plants were grown hydroponically in the greenhouse of Heinrich-Heine-University (HHU), Düsseldorf, Germany. The two-week old seedlings were exposed to 150 mM (15 ds/m) NaCl salinity. The topmost parts of the plants were harvested (in five replications of 10 seedlings each) at 6h and 54h post-treatment. Metabolite extraction was performed by GC-MS method. The experiment was conducted as factorial in a completely randomized design (CRD) and significance level was tested using ANOVA in SAS v9.2 software. R software was used for Principal Component Analysis (PCA) using metabolite z-score data

GC-MS analysis identified 37 primary metabolites including 18 amino acids (AAs), five sugars and sugar alcohols and 14 organic acids (OAs) in roots and shoots of the CSR28 and IR28 genotypes at 6h and 54h post-salt exposure. In response to salinity, amino acids and sugars accumulated and organic acids depleted in both genotypes. Long-term stress revealed pronounced differences between the two genotypes. The major osmolyte proline indicated maximum response to salinity in CSR28 shoots, while the stress marker GABA accumulated more in IR28 shoots. Under high salinity the osmoprotectants raffinose and myo-inositol increased in CSR28 roots. Principal Component Analysis (PCA) revealed amino acid accumulations in the long-term exposure of salt stress in roots are main contributors to differentiate the genotypes for salt tolerance.

Based on GC-MS analysis, 83.3% increase in amino acids and 61.8% decrease in organic acids were observed in response to salinity, indicating an increase in osmotic adjustment mechanisms and a decrease in photosynthetic reactions in the genotypes, respectively. The PCA demonstrated that amino acids play the most important role in separating the samples under salinity stress and control conditions in both organs. Further, the genotypes were differentiated due to metabolic changes in roots in response to salinity particularly in the long-term stress. Proline which is one of the most important osmolytes involved in abiotic stresses was significantly higher in the shoots of CSR28 under the long-term salinity compared to that of IR28. On the other hand, GABA which is a stress marker accumulated more in the shoots of the sensitive genotype. Some metabolites such as aspartate myo-inositol, citrate, glycerate, isocitrate and shikimate were specifically accumulated in roots. Finally, proline, GABA, etc. can be used as biomarkers for selecting salt tolerant lines. The present study highlights the contribution of metabolic adaptation to salinity tolerance.

Salinity limits production in the world and affects 19.5% of water lands. It is estimated that between 18 and 27 million hectares (10 to 15%) of Iran's land has salinity problems (Mahlooji et al., 2018); therefore, salinity of water and soil resources is one of the most important agricultural problems in Iran. Salinity is one of the major abiotic environmental stresses, which affects almost every aspect of plant life and significantly reduces crop yield and quality. Thus it is a serious threat to agricultural productivity, especially in arid and semi-arid regions. The response of plants to salinity depends on several factors such as growth and developmental stage, severity, duration of stress, and cultivar genetics (Seyed Sharifi et al., 2017). Nutrient availability is decreased in saline conditions because of high concentration of sodium, chloride and sometimes calcium ions in soil solution and plant nutrient balance is changed. These saline water sources reduce absorption, impair growth and deficiency of nutrients in the plant, including zinc. Recent studies have shown that the use of zinc sulfate and zinc nanoxide is effective due to the improvement of photosynthetic pigments and the plant's ability to tolerate salinity stress. Zinc micronutrients under salinity stress conditions increase the activity of antioxidant enzymes, proline accumulation and soluble sugars and chlorophyll content and play an essential role in improving plant growth. As a result, under these conditions, proper and adequate nutrition play an important role in maintaining nutrient balance and crop improvement (Ahmadi et al., 2006). In this regard, the aim of this research was to study the effects of zinc foliar application and saline water on growth indices and grain yield in barley (Hordeum vulgare L.) cultivars.

The experiment was conducted in a strip split block design with three replications at Esfahan (Rodasht) drainage and salinity research station in 2012-14. Three water irrigation quality treatments including W1=check, 1-2 dS/m (low salinity), W2=10 dS/m (a common salinity in the region), W3=18 dS/m (high salinity) were evaluated as vertical factor. The horizontal factors were foliar spraying including (Nano zinc-oxide, Chelated zinc, mixture of nano and chelated and water spraying as a check). Three different barley cultivars including (Moroco=moderate semi salt sensitive, Nosrat=moderate salt tolerant and Khatam= salttolerant) were spilted within the vertical factors. Data were analyzed using SAS software and the means were compared by Lsmeans test at 5% probability level.

The results showed that with increasing salinity of irrigation water, yield and grain yield components decreased. Foliar application of zinc chelate increased the number of spikes, 1000-kernel weight and grain yield. Khatam cultivar was the most salt tolerant, Nosrat cultivar was semi-tolerant to salinity and Morocco cultivar was more sensitive to salinity. Triple interaction (salinity * foliar application * cultivar) was significant on the all traits in the two years of the experiment (except for number of seeds per spike in the first year). That being the case, effects slicing was performed. With increasing salinity to moderate level (10 dS / m), the advantage of using a mixture of zinc oxide nanoparticles and zinc chelate (in the first year) and zinc chelate (in the second year) became apparent in which it had a positive effect on grain yield of barley cultivars. Under excessive salinity (18 dS / m), no foliar application (in the first year) and the foliar application of zinc chelate (in the second year) were found to be the most appropriate treatments.

It seems that the second year of research was closer to normal conditions (in terms of long-term annual meteorological data) and could be considered more representative of the real condition in the region where the foliar application of zinc fertilizer and the use of salt tolerant cultivar (Khatam) is recommended.

Numerous environmental factors affect the growth and development of crop plants. Salinity affects crop production through mineral imbalance (toxicity or deficiency of elements), osmotic and oxidative stresses. In this study, using real-time PCR technology, changes expression levels of SOS2, MYB-related and HD-ZIP genes were evaluated under different salinity stress conditions (2, 5, 8, 11 and 14 dS/m) in two different oil seed sunflower lines (AS5305 and 9CSA3). Leaf sampling was performed at 8-leaf stage at four times; 6, 12, 24 and 48 hours after salinity stress application. SOS2 involve in signal transduction and MYB-related and HD-ZIP act as transcription factors under abiotic stresses. According to the results, the expression pattern of all three genes is different in the studied lines in response to salinity stress. Comparison of the two lines shows that the major increase in expression occurred in line AS5305, and where an increase in expression in line 9CSA3 is seen, in comparison, the rate of increase in corresponding times and salinity is higher in line AS5305 (tolerant line) than that in line 9CSA3 (sensitive line). The results indicate the positive role of these genes in the mechanism of sunflower resistance to salinity stress. On the other hand, in this study, by confirming the resistance of AS5305 line to salinity stress at the molecular level, it is possible to potentially use this line in the production of salinity-resistant hybrid cultivars in plant breeding programs.

St John's wort is a valuable medicinal plant with treating depression and wound-healing. It’s belonging to the Hypericacea family that are rich in polyphenols. Hyperforin and Hypericin are two biological active substances of this species that have anticancer properties. In regard to the pharmaceutical properties of this plant, the demand for St John's wort products has been increased. Therefor it’s required to investigate plant adaption to different growing condition such as salinity. Scarcity of water resources, soil and water salinity are concern of 21st century. Salinity is the main widespread water quality problem for crop production. Population growth, rapid urbanization, climate changes and lowering of the rainfall are the main causes of salinization of water and land. One way to reduce adverse effects of salt in salt affected areas is using compounds such as antioxidant. Ascorbic acid (AA) is the most abundant and small antioxidant molecule. It has been participating in ROS scavenging and led to broad tolerance to salt. Understanding the physiological and biochemical mechanism of St John's wort to salinity will be crucial for growing plants on salt affected soils or irrigated with saline water in the big scale.

The pot experiment was done in factorial scheme in a completely randomized design with 3 replications during 2016 and 2017 spring season. In this experiment, St john’s wort plant (Hungarian variety) were treated by different saline water concentrations including 2 (control), 6 and10 dS/m and ascorbic acid foliar application (0 (control), 200, 400 mg/l). Treatments were started at 12 leaves stage (10 cm height). Foliar spray was carried out 2 times by 7 day interval. Salinity treatments were started 7 days after second spraying. The plants were harvested 30 days after the beginning of salinity treatments. Photosynthesis pigments of leaf, total phenols, hydrogen peroxide, cations (Na and K) and dry weight of shoot and root were measured.

Based on results, salinity decreased photosynthesis pigments, carotenoid, leaf phenol, root potassium, K/Na Ratio in both leaf and root as well as shoot and root dry weights. But with increasing NaCl, hydrogen peroxide and sodium in both leaf and root parts increased. One of the reasons for the reduction in chlorophyll and carotenoids content is oxygen radicals which degrade chlorophyll. Phenolic compounds can play a critical role during salinity stress by minimizing the ionic imbalance caused by the presence of salts which in turn has a positive role in water absorption and balance in the plant. They have strong antioxidant activities, therefore may be used in defense against ROS that produces under stress. No significant changes found in root phenol and leaf potassium compared to the control. Unchanged potassium content in the leaves showed the roots ability to retain potassium as an important salt tolerance mechanism. stomatal pore can be closed by the accumulation of sodium and chloride, reduced carbon dioxide fixation and plant growth reduction. Ascorbic acid application increased, Chl a, Total Chl, carotenoid, leaf phenol, leaf potassium and sodium, shoot and root dry weights compared to control and decreased leaf and root hydrogen peroxide. During stress condition, Abscisic acid increases hydrogen peroxide which induces stomatal closure; while application of ascorbic acid reversed this action. In plants that treated with ascorbic acid and salinity, Chl a, leaf phenol, leaf and root hydrogen peroxide, leaf potassium, root K/ Na ratio, shoot and root dry weights reduced less compared to the plants which only treated with salinity.

Based on the results of this experiment increase in phenolic compounds due to their antioxidants properties, maintaining leaf potassium are possible salt tolerance mechanisms. The highest concentration of ascorbic acid (400 mg/l) was more effective in minimizing negative effects of salinity.

Enlarged root systems that extend into the salt affected soil improve water and nutrient capture by plants and can increase plant productivity. In order to examine root system characteristics of four bread wheat cultivars contrasting in salt tolerance (Arg, Ofoq, Tajan and Morvarid) a greenhouse experiment was conducted with applying two salinity levels (0 and 150 mM NaCl) on plants grown in PVC tubes. Salinity led to decreases in total root length, seminal root length, shoot dry weight, root dry weight, shoot K+ and shoot K+/Na+ ratio and increases in shoot Na+, leaf temperature and chlorophyll content compared to control. Seminal root length was greater in salt tolerant cultivars (Arg and Ofoq) than salt sensitive ones, under saline conditions. Ofoq maintained a greater total root length and Arg indicated a greater reduction (64%) in root length, but total root length was not significantly different among all cultivars under salinity stress. Adverse effects of salinity on shoot dry weight was not notably different in salt tolerant (16%) and salt sensitive (18%) cultivars. There were no significant differences in leaf temperature and chlorophyll content between cultivars. Our results illustrate that initial roots growth reduction is mainly due to the osmotic effects of the salt in roots environment and the extent of salt-induced decreases were similar in salt sensitive and salt tolerant cultivars. Given the effects of salt stress on root system characteristics and root growth response to salinity, it seems that rooting attributes can be used as valuable indices for screening salinity tolerance. The comparison of roots and shoots response to salinity showed that regulation of rooting and nutrient uptake under salt stress conditions is more crucial to salt tolerance than regulation of stomatal conductance.

The understanding of salt tolerant mechanisms is crucial for development of varieties with high salinity tolerance. Crop growth is being limited by the osmotic effect of the salt around the root and the toxic effect of the salt within the plant. The osmotic stress has a greater effect on growth rate than the ionic stress. The osmotic stress immediately reduces stomatal conductance with the onset of salinity and is one of the initial causes of a decline in crop growth. As leaf temperature correlate with stomatal conductance, this can be used to asses osmotic stress tolerance in plants. Much of the recent experiment to improve the salt tolerance in wheat has focused on sodium exclusion in plant tissue as a criterion for salinity tolerance but in some work there was no significant relationship between sodium exclusion and salt tolerance. However, pattern of sodium accumulation in shoot is different in wheat cultivar through time. The aim of this study was to evaluate the potential use of leaf temperature in screening for salt tolerance and pattern of sodium accumulation through time and its relationship with some physiological characters and salt tolerance.

In this greenhouse experiment, two bread (Arg and Tajan) and a durum (Behrang) wheat cultivars were evaluated in terms of leaf temperature and patterns of Na+ accumulation under three salinity levels (Control, 100 and 200 mM NaCl). Treatments were imposed when the leaf 2 was fully expanded. Leaf temperature of plants were acquired in the greenhouse 6 days after imposing the salt treatments. Plants were harvested after salt treatment every 15 days for 60 days and sodium concentration was measured at each harvest. Chlorophyll content, K+ and Na+ root and shoot and shoot dry weight, 45 days after salt treatment, were measured.

Shoot and root Na+ concentration was increased in response to increasing salinity but in roots this increase was greater than shoots. Salt stress decreased shoot dry weight in bread wheat cultivars (32%) and durum wheat (63%). In the highest salinity level, after 45 days exposure to salt, shoot K+/Na+ ratio was reduced in all genotypes to a similar extent (about 60%) and in this level of salinity higher reduction in chlorophyll content occurred in Behrang (75%) cultivar. Shoot K+/Na+ ratio showed the most reaction to salinity. Differences in leaf Na+ concentration between two bread wheat cultivars was more obvious in 45 days after salt treatments but in other growth stages were less obvious. Results showed that differences between sodium concentrations in two bread wheat cultivar through time, was remarkable 45 days after treatments. At 200 mM NaCl, Arg showed the lowest and non significant increased in leaf temperature (0.87◦ C) but in Tajan (1.74◦ C) and Behrang (4.30◦ C) this increased were significant. Salt concentration of 100 mM NaCl had no effect on leaf temperature in cultivars.

Different patterns of Na+ accumulation may be exist in wheat cultivars through time. Differences in sodium transport rates from roots to shoots may cause different patterns of sodium accumulation through time in wheat. This preferential in early growth stages, stomatal factors is more important than chlorophyll content and as leaf temperature is largely a function of stomatal conductance, this can be used to assess osmotic stress tolerance. Thermography could be acquire accurate technique to distinguish differences in salt tolerance in wheat cultivars. The shoot K+/Na+ ratio, cannot be used as a reliable indicator of salt tolerance in wheat. Greater tissue tolerance in wheat cultivars was associated with prolonged retention of chlorophyll in leaves and this resulted in less reduction in shoot growth.

Salinity stress is the second major problem and limiting the rice production after drought. To investigate the effects of salinity stress on some important morphological and physiological characteristics of rice, 41 mutant lines from radiation of gama ray to four rice varieties (two Iranian local varieties, Hashemi and Tarom and two improved varieties, Khazar and Fajr) along with parental varieties and two control lines, FL478 (tolerant to salinity) and Teqing (sensitive to salinity) were studied under three salinity conditions (control, 6 and 12 dS.m-1). The experiment was carried out in factorial experiment based on completely randomized design with six replications. The variation among genotypes were also studied using twelve microsatellite (SSR) markers linked to SalTol, a major salinity tolerant QTL. The results of analysis of variance showed significant and considerable differences among the genotypes for all studied traits. The results of cluster analysis of morphological data grouped the studied genotypes into three clusters so that M1, M3, M7, M9, M35, M37 and M40 mutant lines together with the salinity tolerant line FL478 grouped into one cluster, while Hashemi and Fajr varieties and M47, M48, M49 and M56 mutant lines along with the salinity sensitive line Teqqing grouped into a similar cluster. The cluster analysis of molecular data also divided the studied genotypes into three main groups. Accordingly, the mutant lines M35, M37 and M40 together with the control variety FL478 were grouped as salinity tolerant and the mutant lines M36, M47, M48, M49, M54 and M56 together with the control variety Teqing as salinity sensitive genotypes. The Mantel test showed a high similarity of about 65%between two cluster analyses which was due to the use of tigh linked SSR markers to the SalTol, each of them were linked to the several traits studied in this research. As mentioned above, all three salinity tolerant lines identified in the molecular data analysis were also identified in cluster analysis of morphological traits and all four salinity sensitive lines identified in the morphological data analysis were also identified in molecular dataanalysis. Evaluating the microsatellite markers also showed that the AP3206, RM5, RM3412, RM140 markers were the most suitable and informative markers to assess the genetic variation of salinity tolarance in this research.

To investigate the effect of salicylic acid (SA) on salinity tolerance of two sugar beet cultivars, this experiment was conducted as split factorial based on a randomized complete block design with three replications during growing seasons of 2012 and 2013 in Research Farm of Shahid Chamran University. The studied factors were three levels of SA (0 mM, 0.5 mM and 1 mM), two levels of salinity (150 mm sodium chloride and control) and two sugar beet cultivars (Jolgeh and Shariff). SA was applied as foliar spray along with salinity in the 4-leaf stage. Results showed that foliar application of SA caused significant increase of leaf area (LA), chlorophyll, stomatal conductance, ФPSІІ, Fv/Fm, proline and total soluble sugars, and decrease membrane permeability compared to control under salt stress conditions. Salinity caused a significant decrease in LA, Chlorophyll, stomatal conductance, ФPSІІ and Fv/Fm, while increase proline, total soluble sugars and membrane permeability. Therefore, according to the results of this research, it seems, foliar application of salicylic acid could enhance sugarbeet growth and increases resistance to salt stress.

To determine salinity-tolerant genotypes among the citrus germplasm present in Kotra collection, a greenhouse experiment was carried out as factorial, completely randomized design with three replications, at four levels of NaCl (0, 2, 4 and 6 dS/m) and 10 unknown genotypes, for 16 weeks. Cleopatra mandarin and Swingle Citromelo, as tolerant (control) and sensitive cultivars, respectively, were used. After 6 months of seedlings growth in pots containing equal amounts of perlite, sand and garden soil, the irrigation water, containing different concentrations of sodium chloride was applied every 5 days (considering climatic conditions and plant requirements). At the end of the experiment, concentration of chloride and sodium in leaf and root, chlorophyll a and b and total chlorophyll content and concentration of soluble sugars in leaves were measured. Results showed that salinity increased chloride and sodium concentration in root and leaf. The lowest level of accumulation of chloride in leaf was related to genotype g9 and Cleopatra mandarin. Potassium concentration and chlorophyll a and b content decreased with salinity, while the interaction of genotype and salinity did not show significant difference in these characteristics. Genotypes were different in content of soluble sugars, in response to salinity. Based on the results, genotype g9, because of the lowest increase in leaf chloride content and also the lower decrease in total chlorophyll content, in comparison with most of the studied genotypes, can be considered as a tolerant genotype to salinity stress, and could be utilized in breeding programs of rootstocks.

Rice is moderately sensitive to salinity. Salinity affects virtually all aspects of rice growth in varying degree at all stages from germination through maturity. Tolerance to salinity is genetically and physiologically complicated and inherited quantitatively. Application of molecular-marker aided selection technique for improvement of salinity tolerance would accelerate breeding progress by increasing selection efficiency. In order to map the Quantitative Trait Loci (QTLs) for salinity tolerance in rice and determine the contribution of each QTL in phenotypic variation, 63 advanced backcross lines (BC2F5) derived from a cross between IR64 as recurrent parent and Tarom Molaii as donor parent, were used. The phenotypic traits under study included: Sodium(Na) and Potassium(K) concentration in root and shoot, dry and wet weight of root and shoot, Na+:K+ ratio in root and shoot. Polymorphism between the two parents was assesed using 235 SSR markers with uniform coverage on all 12 linkage groups, through which 114 markers showed polymorphism and assigned for genotyping. The map length was 1692.6 cM with an average interval size of 16.3 cM. Transgressive segregation was observed for all traits. We found QTLs with additive effects for K+ in shoot, dry weight of root and shoot, Na+:K+ ratio in root and shoot. At least one QTL was mapped for Na+:K+ ratio in root, on all chromosomes except chromosome 9. All detected QTLs had significant threshold (LOD>4) and also approved by both IM and CIM methods.