Development Of Salt-tolerant Varieties Research Articles

Evaluation of Germplasm for Seedling Stage Salinity Tolerance in Rice (Oryza Sativa L.)

Salinity affects rice growth and development. Mostly all growth stages from germination to maturity are affected by the salinity. Among all the stages, seedling and reproductive stages are the most sensitive stages to salinity, which results in considerable yield losses. Development of salt tolerant varieties is most feasible approach for improving the production of rice in salt affected soils as seedling stage is necessary for better crop improvement. Overall 76 rice germplasm lines were evaluated at RARS, Maruteru, West Godavari, A.P during Kharif 2020 for salinity tolerance at seedling stage. The different parameters like root length, shoot length, shoot Na+ content, shoot K+ content, Na+/K+ content and SIS (salt injury score) at 10th and 16th day were studied under hydroponics subjecting to electrical conductivity of 6 and 12 dSm-1, at a pH of 5.0. Salinity scoring during seedling stage was noted as per the modified standard evaluation score (SES) of IRRI, revealed that four genotypes FL478, MTU1290, MTU1061 and MCM109 as tolerant, 23 genotypes as moderately tolerant, 42 were susceptible and remaining seven genotypes namely BPT2848, BPT3140, Hallabhatta, MTU1271, MTU1121, BPT2846 and Krishnahamsa are highly susceptible. The phenotypic study signified that Na+/K+ ratio is the key note for salinity tolerance.

Genome-Wide Analysis of MYB Transcription Factors in the Wheat Genome and Their Roles in Salt Stress Response.

Large and rapidly increasing areas of salt-affected soils are posing major challenges for the agricultural sector. Most fields used for the important food crop Triticum aestivum (wheat) are expected to be salt-affected within 50 years. To counter the associated problems, it is essential to understand the molecular mechanisms involved in salt stress responses and tolerance, thereby enabling their exploitation in the development of salt-tolerant varieties. The myeloblastosis (MYB) family of transcription factors are key regulators of responses to both biotic and abiotic stress, including salt stress. Thus, we used the Chinese spring wheat genome assembled by the International Wheat Genome Sequencing Consortium to identify putative MYB proteins (719 in total). Protein families (PFAM) analysis of the MYB sequences identified 28 combinations of 16 domains in the encoded proteins. The most common consisted of MYB_DNA-binding and MYB-DNA-bind_6 domains, and five highly conserved tryptophans were located in the aligned MYB protein sequence. Interestingly, we found and characterized a novel 5R-MYB group in the wheat genome. In silico studies showed that MYB transcription factors MYB3, MYB4, MYB13 and MYB59 are involved in salt stress responses. qPCR analysis confirmed upregulation of the expression of all these MYBs in both roots and shoots of the wheat variety BARI Gom-25 (except MYB4, which was downregulated in roots) under salt stress. Moreover, we identified nine target genes involved in salt stress that are regulated by the four MYB proteins, most of which have cellular locations and are involved in catalytic and binding activities associated with various cellular and metabolic processes.

A REVIEW ON RESPONSE OF RICE (ORYZA SATIVA L.) UNDER SALINITY STRESS IN TERMS OF ITS GROWTH, DEVELOPMENT, CHARACTERISTICS, AND BIOCHEMICAL LEVEL

Salinity is an important environmental factor that limits growth and yield of rice. It currently affects millions of hectares of soils otherwise suitable for rice cultivation in South and Southeast Asia. Attempts to understand the mechanisms of salt tolerance have revealed several key enzymes and altered biochemical pathways to infer crop resistance to salt stress. Over the past few decades, we have witnessed extensive research into the development of salt-tolerant varieties through traditional methods, improvisation with modern molecular tools and techniques. Rice (Oryza sativa L.) is the staple food crop in many countries around the world. Being a glycophyte by nature, its growth can be severely affected in the presence of excessive salt. Rice is particularly susceptible to salinity in the early vegetative and late reproductive stages, and the response of crops to excess salt toxicity at the biochemical and molecular levels as well as at the physiological level has been well studied and documented. This review aims to summarizes the different responses of rice, especially to salt toxicity, exhibited the detailed physiological, morphological, molecular and biochemical changes that occur in the rice plants.

Optimizing Seedling Number and Hill Spacing: A Way Forward to Harness Productivity Potential of Salt-Tolerant Rice Cultivars in Salt-Affected Soils

Harnessing the potential of sodic soils in the Indo-Gangetic plains necessitates the development of salt-tolerant varieties and matching management practices as the management practices required for rice production in salt-affected soils are entirely different from those in normal soils. Field experiments with the main plots comprising two treatments T1:2 seedlings and T2:4 seedlings hill−1, subplot three hill spacing treatments S1: 15 × 15 cm, S2: 15 × 20 cm, S3: 20 cm × 20 cm and sub–subplot with two salt-tolerant varieties V1: CSR 36, V2: CSR 43 were conducted at the Indian Council of Agricultural Research-Central Soil Salinity Research Institute (ICAR-CSSRI), Regional Research Station, Lucknow, Uttar Pradesh, India, during 2011, 2012 and 2013 kharif seasons to develop matching management practices for salt-tolerant varieties through optimizing the number of seedlings hill−1 and hill density to enhance productivity and profitability in salt-affected soils. The experiment was set up in split plot design replicated thrice. The results revealed that transplanting of 4 seedlings hill−1 at a hill spacing of 15 cm × 20 cm proved better crop establishment and produced significantly higher grain yield over rest of the treatments. Planting of 4 seedlings hill−1 resulted in higher gross and net returns than planting of 2 seedlings hill−1. Transplanting of CSR 36 with 4 seedlings hill−1 at a hill spacing of 15 × 20 cm found superior in terms of grain yield, gross and net returns over CSR 43 with rest of the spacing treatments.

An In Vitro System for Studying the Effect of Salt Stress in Groundnut (Arachis hypogaea L.)

Background: Groundnut (Arachis hypogaea L.) is an important cash crop in the tropical and subtropical regions of the world. Salinity is a major threat to agriculture globally and is one of the greatest inhibitions with regard to the expansion of cultivated land. The development of salt-tolerant varieties will be of great help in increasing crop yield by bringing newer areas of land under cultivation which are otherwise considered unfit owing to high salinity. Objective: The present work was undertaken to assess the suitability of tissue culture systems, which provide better control over conditions of growth, for identifying salt tolerant varieties. Methods: Groundnut plants were grown under both in vitro and in vivo conditions under salt stress. Few biochemical parameters were analyzed under both conditions. Results: It was found that there was an increase in the biochemical parameters like phenolic compounds, hydrogen peroxide, peroxidase enzyme and proteins in the salt-treated plants. The trends were similar in both cases except for a set of marginally higher values in the in vitro cultures. Conclusion: The results point towards the potential of plant tissue culture system as effective and reliable for carrying out salt tolerance studies in groundnut. The system is easy to control so that tolerance potential of the plants can be well assessed. Keywords: Antioxidant, reactive oxygen species, stress, tolerance, variety, tissue culture.

Identification, analysis and development of salt responsive candidate gene based SSR markers in wheat

BackgroundSalinity severely limits wheat production in many parts of the world. Development of salt tolerant varieties represents the most practical option for enhancing wheat production from these areas. Application of marker assisted selection may assist in fast tracking development of salt tolerant wheat varieties. However, SSR markers available in the public domain are not specifically targeted to functional regions of wheat genome, therefore large numbers of these need to be analysed for identification of markers associated with traits of interest. With the availability of a fully annotated wheat genome assembly, it is possible to develop SSR markers specifically targeted to genic regions. We performed extensive analysis to identify candidate gene based SSRs and assessed their utility in characterizing molecular diversity in a panel of wheat genotypes.ResultsOur analysis revealed, 161 SSR motifs in 94 salt tolerance candidate genes of wheat. These SSR motifs were nearly equally distributed on the three wheat sub-genomes; 29.8% in A, 35.7% in B and 34.4% in D sub-genome. The maximum number of SSR motifs was present in exons (31.1%) followed by promoters (29.8%), 5’UTRs (21.1%), introns (14.3%) and 3’UTRs (3.7%). Out of the 65 candidate gene based SSR markers selected for validation, 30 were found polymorphic based on initial screening and employed for characterizing genetic diversity in a panel of wheat genotypes including salt tolerant and susceptible lines. These markers generated an average of 2.83 alleles/locus. Phylogenetic analysis revealed four clusters. Salt susceptible genotypes were mainly represented in clusters I and III, whereas high and moderate salt tolerant genotypes were distributed in the remaining two clusters. Population structure analysis revealed two sub-populations, sub-population 1 contained the majority of salt tolerant whereas sub-population 2 contained majority of susceptible genotypes. Moreover, we observed reasonably higher transferability of SSR markers to related wheat species.ConclusionWe have developed salt responsive gene based SSRs in wheat for the first time. These were highly useful in unravelling functional diversity among wheat genotypes with varying responses to salt stress. The identified gene based SSR markers will be valuable genomic resources for genetic/association mapping of salinity tolerance in wheat.

The response of transgenic Brassica species to salt stress: a review.

Salt stress is considered one of the main abiotic factors to limit crop growth and productivity by affecting morpho-physiological and biochemical processes. Genetically, a number of salt tolerant Brassica varieties have been developed and introduced, but breeding of such varieties is time consuming. Therefore, current focus is on transgenic technology, which plays an important role in the development of salt tolerant varieties. Various salt tolerant genes have been characterized and incorporated into Brassica. Therefore, such genetic transformation of Brassica species is a significant step for improvement of crops, as well as conferring salt stress resistance qualities to Brassica species. Complete genome sequencing has made the task of genetically transforming Brassica species easier, by identifying desired candidate genes. The present review discusses relevant information about the principles which should be employed to develop transgenic Brassica species, and also will recommend tools for improved tolerance to salinity.

Genetic Dissection of Seedling Stage Salinity Tolerance in Rice Using Introgression Lines of a Salt Tolerant Landrace Nona Bokra.

Salinity is an important abiotic stress affecting rice production worldwide. Development of salt tolerant varieties is the most feasible approach for improving rice productivity in salt affected soils. In rice, seedling stage salinity tolerance is crucial for better crop establishment. Quantitative trait loci (QTL) mapping using introgression lines (ILs) is useful for identification and simultaneous transfer of desirable alleles into elite genetic background. In the present study, 138 ILs derived from the cross between a high yielding elite salt susceptible japonica rice cultivar Jupiter and a salt tolerant indica landrace Nona Bokra were evaluated for salt tolerance at seedling stage in a hydroponics experiment and were genotyped using 126 simple sequence repeat markers. A total of 33 additive QTLs were detected by composite interval mapping for 8 morphophysiological traits. The phenotypic responses, genomic composition, and QTLs identified from the study indicated that Na/K ratio is the key factor for salinity tolerance. The mechanisms of tolerance might be due to homeostasis between Na+ and K+ or Na+ compartmentation. Gene ontology (GO) analysis revealed that significant GO terms in the selected QTL regions were associated with the genes/pathways involved in signaling, enzyme inhibition, and ion transport. Because majority of QTLs are with small effects, marker-assisted recurrent selection is proposed to accumulate favorable alleles for improving salt tolerance using the tolerant ILs identified in this study. The tolerant ILs also provide an opportunity for functional genomics studies to provide molecular insights into salt tolerance mechanisms in Nona Bokra.

Effects of salt stress on plant growth characteristics and mineral content in diverse rice genotypes

ABSTRACTWhen rice is grown under moderate salinity (6 dS m−1), yields are reduced by up to 50%. The development of salt-tolerant varieties is a key strategy for increasing yields. We conducted an experiment using a hydroponic system with ion components similar to seawater to determine useful parameters for assessing salt tolerance. Two-week-old seedlings were grown for 7 days on Yoshida hydroponic solution. The treatment group then additionally received an artificial seawater solution (electrical conductivity, 12 dS m−1). After a 2-week period of salt stress, standard evaluation scores (SES) of visual salt injuries were assessed. The K, Na, Mg, and Ca contents were then determined in the roots, sheaths, and leaves of each plant. Following the SES results, we divided the 37 genotypes into four groups: salt-tolerant groups (STGs), moderately salt-tolerant groups, salt-sensitive groups (HSSGs), and highly salt-sensitive groups (HSSGs). In the control, STGs had the highest sheath K content (30.1 mg g−1 dried weight [DW]), whereas HSSGs had the lowest (21.4 mg g−1 DW). Sheath K was also highly and negatively correlated with SES. This suggests that sheath K may be useful for identifying salt-tolerant varieties under non-saline conditions. Plant growth was significantly affected under salt stress, but STGs had the smallest decrease in sheath DW. SES was significantly correlated with sheath and leaf Na, sheath K and Mg, and sheath and leaf Na/K and Na/Mg ratios. The results suggested that sheath K, Na/K, and Na/Mg may be useful indicators for genetic analyses of salt-tolerant varieties under salt-stress conditions. The salt-tolerant cultivars, KCR20, KCR124, and KCR136, are possible candidates for such studies because they had high sheath K content (31.19, 31.21, 29.44 mg g−1 DW, respectively) under non-saline conditions and low SES (3.3, 3.6, 3.9, respectively), and low sheath Na/K (0.64, 0.52, 0.92, respectively) and Na/Mg ratios (2.96, 2.27, 3.03, respectively) under salt-stress conditions.