salt tolerance

Genetic engineering becomes a hopeful tool to develop stress tolerance transgenic plants including salt tolerance transgenic plants. The subject of this study was the transformation of tomato with a vascular antiporter gene using Agrobacterium. The pBZP plasmid harboring AVP1 gene was transferred to E.coli for amplification and then transferred to Agrobacterium for tomato transformation. Cotyledon and hypocotyl explants inoculated with recombinant Agrobacterium transferred to MS medium supplemented with three concentrations of BAP for plant regeneration. Analysis of variance showed there was no interaction between BAP and explant type in regeneration capacity but both explant and BAP concentration in medium had significant effect on transformation efficiency. Mean compression using Duncan multiple rang test at 5 percent level showed that highest regeneration of transgenic plants achieved in MS medium supplemented with 2 mg/L BAP. Regeneration efficiency from Cotyledon explant was more than cotyledonary explants. Genomic DNA of putative transgenic plants extracted and analyzed by PCR for presence of transgene using AVP1 gene specific primers. The results showed 440 bp of AVP1 amplicon in transgenic plants. The transgenic plants transferred to greenhouse for next investigations.

Salinity is a major abiotic stress that limits the growth and productivity of plants in many parts of the world due to increased use of poor-quality water for irrigation and soil salinity. Plant adaptation or tolerance to salinity stress involves alteration in physiological processes and metabolic pathways and activating molecular or gene networks. In this study, 2DE technique was used to identify proteins responsive to salinity stress in maize. Two maize lines with different responses to salinity stress; R10 (tolerant) and S46 (sensitive) were selected. In the eight-leaf stage, salinity stress treatment of 8 dS/m was applied to plants for 20 days and then leaf proteins were extracted. Spots with more than a 1.5-fold increase or decrease in their expression were isolated and sequenced by mass spectrometry. Functional classification of protein spots per line after MS/MS revealed that the differentlly expressed proteins have different metabolic activities. In the tolerant line (R10), 5 spots including Pyruvate orthophosphate dikinase proteins, ATP synthase subunit beta, Germin-like protein, Chlorophyll a-b binding protein, Triosephosphate isomerase, and 40S ribosomal protein, respectively showed an increased expression level. Moreover, in the sensitive line (S46), one spot showed an increased expression level that related to Proteasome subunit beta proteins, and two spots including Chlorophyll a-b binding protein and Ribulose bisphosphate carboxylase small chain protein showed a decreased expression level. The proteins identified in this study and the possible related biochemical pathways provide new information on the response of maize lines (R10 and S46) to salinity stress.

In order to study the effect of salinity on yield and physiological traits of sunflower and genetic analysis of these traits under salinity conditions, a factorial experiment based on completely randomized design with three replications were performed outside the greenhouse in an open air area under natural environmental conditions. The studied factors were included 2 salinity stress levels (normal and 6 dS/m) and sunflower recombinant inbred lines (102 lines derived from the cross PAC2 ×RHA266 together with parental lines). Traits such as grain yield per plant, chlorophyll content, net photosynthetic rate, leaf relative water content, Na+ and K+ concentrations were measured after flowering. The effect of salinity was significant on grain yield, leaf relative water content, Na+ and K+ concentrations as well as on Na+/K+ and K+/ Na+ ratios. For all traits, significant differences were observed between the genotypes studied. Genetic analysis of studied traits was done using a linkage map comprising 221 molecular markers (210 SSR/11 SNP) with an average distance of 7.44 cM between markers via composite interval mapping (CIM) procedure. Totally, 10 and 8 QTLs were detected for studied traits under normal and salt stress conditions, respectively. The phenotypic variance explained by QTLs (R2) ranged from 10.4%- 34.4%. The results showed the existence of co-localized QTLs for some of the studied traits under normal and salt stress conditions including Na+.S.4.1 with Na+/K+.S.4.1, Chl.NS.6.1 with K+.S.6.1. Using co-localized QTLs in different environmental conditions and different years could enhance the efficiency of marker-assisted selection in plant breeding programs.

Peroxidase and Catalyse are two important enzymes involved in reaction of many crop species to salt tolerance. Assessment of activity of these enzymes in the seedlings of barley during salt stress and using quantitative data for mapping of QTLs involved in salt tolerance has been addressed in this study. Parents of four barley mapping populations were exposed to the different concentrations (0 mM، 100mM and 200 mM) of salt (NaCl) and the level of activity of Catalase and Proxidase were quantified in the seedlings stage. There was a high variation in enzymatic activities of parents of OWB population (Dom and Rec) in 200mM of NaCl. In order to map QTLs involved in salt tolerance in OWB، 94 doubled haploid lines were exposed to 0 mM and 200mM of NaCl and the activity of Catalase and Peroxidase were quantified. Mapping of QTLs was performed using MAPQTL5 software. The results showed that the position of QTLs depends on both concentration of salt and on the type of enzyme. For Peroxidase activity there was no QTL mapped despite a high variation between individuals of mapping population while for Catalase in the concentration of 200 mM of NaCl، two QTLS in Chromomes 3 (3H) and 4 (4H) were mapped. Two other minor QTLs with LOD values slightly lower than the threshold were mapped in chromosomes 5 (1H) and 7 (5H). The results showed that quantification of the level of activity of Catalase can be used as quantitative data for mapping of QTLs involved in salt tolerance in barley

Sainfoin (Onobrychis viciifolia Scop.) is widely grown as forage and pasture legume in Iran and is tolerant to environmental stresses. Developing cultivars with higher salt tolerance at germination stage will increase seedling establishment and yield. This experiment was conducted to determine the effects of different concentrations of sodium chloride (0، 0. 1، 0. 2، 0. 3 M) on the germination، seedling growth، Na and K uptake of ten Iranian sainfoin genotypes. Results indicated that salt has significant effects on all parameters and the threshold for germination was determined as 0. 2 Molar. Increasing the salt concentration decreased germination percentage، rate of germination، seedling viability percentage، root length، shoot length، root and shoot dry weight، percentage of Na uptake and K/Na ratio. In contrast shoot length/root length ratio and percentage of K uptake was significantly increased. The sainfoin genotypes showed considerable variation for salt tolerance based on the measured characters at germination stage and a variety selected from Khonsar population (KH304A) was found the most tolerant one. Cluster analysis based on all of the recorded characters, classified the genotypes in three clusters that mainly supported germination parameters of entries. Results indicated that there is sufficient genetic variation for salt tolerance among the studied genotypes and they can be used to improve salt tolerance of sainfoin in breeding programs.