Development Of Salt-tolerant Crops Research Articles

Haplotype analysis and marker development of five salt-tolerant-related genes in rice (Oryza sativa L.).

Salinity stress is a great threat to the growth and productivity of crops, and development of salt-tolerant crops is of great necessity to ensure food security. Although a few genes with natural variations that confer salt tolerance at germination and seedling stage in rice have been cloned, effective intragenic markers for these genes are awaited to be developed, which hinder the use of these genes in genetic improvement of salt tolerance in rice. In this study, we first performed haplotype analysis of five rice salt-tolerant-related genes using 38 rice accessions with reference genome and 4,726 rice germplasm accessions with imputed genotypes and classified main haplotype groups and haplotypes. Subsequently, we identified unique variations for elite haplotypes reported in previous studies and developed 11 effective intragenic makers. Finally, we conducted genotyping of 533 of the 4,726 rice accessions from worldwide and 70 approved temperate geng/japonica cultivars in China using the developed markers. These results could provide effective donors and markers of salt-tolerant-related genes and thus could be of great use in genetic improvement of salt tolerance in rice.

Morpho-physiological and genetic characteristics of a salt-tolerant mutant line in soybean (Glycine max L.)

Morpho-physiological and genetic characteristics of a salt-tolerant mutant line in soybean (Glycine max L.)

Gene regulation at transcriptional and post-transcriptional levels to combat salt stress in plants.

Soil salinity is a major challenge that will be faced more and more by human population in the near future. Higher salt concentrations in the soil limit the growth and production of crops, which poses serious threats to global food production. Various plant breeding approaches have been followed in the past which are reported to reduce the effect of salt stress by inducing the level of protective metabolites like osmolytes and antioxidants. Conventional breeding approaches are time-consuming and not cost-effective. In recent times, genetic engineering has been largely followed to confer salt tolerance through introgressions of single transgenes or stacking multiple transgenes. However, most of such works are limited only at the laboratory level and field trials are still awaited to prove the long-term efficacy of such transgenics. In this review, we attempt to present a broad overview of the current strategies undertaken to develop halophytic and salt-tolerant crops. The salt-induced damages in the plants are highlighted, followed by representing the novel traits, associated with salt stress, which can be used for engineering salt tolerance in glycophytic crops. Additionally, the role of transcriptional and epigenetic regulation in plants for amelioration of salt-induced damages has been reviewed. The role of post-transcriptional mechanisms such as microRNA regulation, genome editing and alternative splicing, during salt stress, and their implications in the development of salt-tolerant crops are also discussed. Finally, we present a short overview about the role of ion transporters and rhizobacteria in the engineering of salt tolerance in crop species.

OXS2 is Required for Salt Tolerance Mainly through Associating with Salt Inducible Genes, CA1 and Araport11, in Arabidopsis

Salt stress is one of the abiotic stresses affecting crop growth and yield. The functional screening and mechanism investigation of the genes in response to salt stress are essential for the development of salt-tolerant crops. Here, we found that OXIDATIVE STRESS 2 (OXS2) was a salinity-induced gene, and the mutant oxs2-1 was hypersensitive to salt stress during seed germination and root elongation processes. In the absence of stress, OXS2 was predominantly localized in the cytoplasm; when the plants were treated with salt, OXS2 entered the nuclear. Further RNA-seq analysis and qPCR identification showed that, in the presence of salt stress, a large number of differentially expressed genes (DEGs) were activated, which contain BOXS2 motifs previously identified as the binding element for AtOXS2. Further ChIP analysis revealed that, under salt stress, OXS2 associated with CA1 and Araport11 directly through binding the BOXS2 containing fragments in the promoter regions. In conclusion, our results indicate that OXS2 is required for salt tolerance in Arabidopsis mainly through associating with the downstream CA1 and Araport11 directly.

Identification of salt-tolerant cowpea genotypes using ISSR markers and proteome analysis.

Soil salinity globally affects the productivity of staple food crops. Therefore, an understanding of the molecular mechanisms that lead to salt tolerance induced by antioxidant mechanisms can assist in the development of salt-tolerant crops. To decipher the molecular fingerprint of salt resistance, in this study, six salt-tolerant cowpea genotypes at the seedling stage were assessed for their antioxidant responses, yield, genetic polymorphism and proteomics under salt stress. Leaves and roots showed distinct tissue-specific responses to salinity, and leaves showed a better protection against salt stress-induced oxidative stress than roots. Inter simple sequence repeat (ISSR) fingerprinting allowed molecular discrimination between salt-tolerant cowpea genotypes. Proteome analysis of cowpea leaves under salt stress revealed up-regulation of ATP synthase, vacuolar ATPase, pentatricopeptide repeat protein, flavanone 3-hydroxylase and outer envelope pore protein. Thus, ISSR and proteome analysis allow the identification of salt-tolerant cowpea cultivars.

Salt-Induced Tissue-Specific Cytosine Methylation Downregulates Expression of HKT Genes in Contrasting Wheat (Triticum aestivum L.) Genotypes.

Plants have evolved several strategies, including regulation of genes through epigenetic modifications, to cope with environmental stresses. DNA methylation is dynamically regulated through the methylation and demethylation of cytosine in response to environmental perturbations. High-affinity potassium transporters (HKTs) have accounted for the homeostasis of sodium and potassium ions in plants under salt stress. Wheat (Triticum aestivum L.) is sensitive to soil salinity, which impedes its growth and development, resulting in decreased productivity. The differential expression of HKTs has been reported to confer tolerance to salt stress in plants. In this study, we investigated variations in cytosine methylation and their effects on the expression of HKT genes in contrasting wheat genotypes under salt stress. We observed a genotype- and tissue-specific increase in cytosine methylation induced by NaCl stress that downregulated the expression of TaHKT2;1 and TaHKT2;3 in the shoot and root tissues of Kharchia-65, thereby contributing to its improved salt-tolerance ability. Although TaHKT1;4 was expressed only in roots and was downregulated under the stress in salt-tolerant genotypes, it was not regulated through variations in cytosine methylation. Thus, understanding epigenetic regulation and the function of HKTs would enable an improvement in salt tolerance and the development of salt-tolerant crops.

The evolution of halophytes, glycophytes and crops, and its implications for food security under saline conditions.

The effective development of salt tolerant crops requires an understanding that the evolution of halophytes, glycophytes and our major grain crops has involved significantly different processes. Halophytes (and other edaphic endemics) generally arose through colonization of habitats in severe disequilibrium by pre-adapted individuals, rather than by gradual adaptation from populations of 'glycophytes'. Glycophytes, by contrast, occur in low sodium ecosystems, where sodium was and is the major limiting nutrient in herbivore diets, suggesting that their evolution reflects the fact that low sodium individuals experienced lower herbivory and had higher fitness. For domestication/evolution of crop plants, the selective pressure was human imposed and involved humans co-opting functions of defense and reproductive security. Unintended consequences of this included loss of tolerance to various stresses and loss of the genetic variability needed to correct that. Understanding, combining and manipulating all three modes of evolution are now critical to the development of salt tolerant crops, particularly those that will offer food security in countries with few economic resources and limited infrastructure. Such efforts will require exploiting the genetic structures of recently evolved halophytes, the genetic variability of model plants, and endemic halophytes and 'minor' crops that already exist.

Advances in salt tolerance

Advances in and prospects for the development of salt tolerant crops are discussed. The genetic approach to the salinity problem is fairly new, but research has become quite active in a short span of time. Difficulties and opportunities are outlined. Salinity varies spatially, temporally, qualitatively, and quantitatively. In addition, the responses of plants to salt stress vary during their life cycle. Selection and breeding, including the use of wide crosses, are considered the best short-term approaches to the development of salt tolerant crops, but the new biotechnological and molecular biological techniques will make increasingly important contributions. Cooperation is called for among soil and water scientists, agronomists, plant physiologists and biochemists, cytologists, and plant geneticists, breeders, and biotechnologists. Given such cooperation and adequate support for these endeavors, the potential for increasing productivity in salt-affected areas can be realized.