Salinity Stress Tolerance in Potato Cultivars: Evidence from Physiological and Biochemical Traits

Physiological and Transcriptomic Analyses Demonstrate the Ca2+-Mediated Alleviation of Salt Stress in Magnolia wufengensis

Magnolia wufengensis, a newly discovered ornamental species in the Magnoliaceae family, is susceptible to salinity. Moreover, Ca2+ is an essential element for plant growth and is receiving increasing attention for its ability to mitigate the negative effects of environmental stress on plants. In the present study, we investigated the effect of Ca2+ on the growth and transcriptome of M. wufengensis under salt stress. The treatments used here were as follows: control, NaCl (150 mmol/L), CaCl2 (5 mmol/L), and NaCl (150 mmol/L) + CaCl2 (5 mmol/L). After a 60-day treatment period, plant growth indices were determined, and leaves were collected for physiological analysis and transcriptome investigation. The combined application of NaCl and CaCl2 alleviated phenotypic damage and restored seedling growth. Moreover, RNA sequencing data revealed that in the Na vs. control group and the NaCa vs. Na group, there were 968 and 2632 differentially expressed genes, respectively, which were both primarily enriched in secondary metabolism, glutathione metabolism, signaling hormone metabolism, glucose metabolism, and amino acid metabolism. These pathways were analyzed to screen key genes: the adenosine triphosphate (ATP)-binding cassette efflux transporter G1 (ABCG1) genes, which are related to transmembrane transport; the calmodulin genes, which are related to signal transmission; and the glutathione S-transferase (GST), glutathione peroxidase (GPX), and peroxidase (POD) genes related to antioxidant enzymes. Lastly, we constructed a hypothesis model of Ca2+-enhanced salt tolerance in M. wufengensis. This study reveals the potential mechanisms by which Ca2+ enhances the salt tolerance of M. wufengensis and provides a theoretical reference for its cultivation in saline areas.

The synergistic effects of organic composts and microelements co-application in enhancing potato productivity in saline soils

Soil salinity is a major threat hindering the optimum growth, yield, and nutritional value of potato. The application of organic composts and micronutrients can effectively ameliorate the salinity-deleterious effects on potato growth and productivity. Herein, the combined effect of banana and soybean composts (BCo and SCo) application alongside foliar supplementation of boron (B), selenium (Se), cobalt (Co), and titanium (Ti) were investigated for improving growth, physiology, and agronomical attributes of potato plants grown in saline alluvial soil. Salinity stress significantly reduced biomass accumulation, chlorophyll content, NPK concentrations, yield attributes, and tuber quality, while inducing malondialdehyde and antioxidant enzymes. Co-application of either BCo or SCo with trace elements markedly alleviated salinity-adverse effects on potato growth and productivity. These promotive effects were also associated with a significant reduction in malondialdehyde content and activities of peroxidase and superoxide dismutase enzymes. The co-application of BCo and B/Se was the most effective among other treatments. Principle component analysis and heatmap also highlighted the efficacy of the co-application of organic composts and micronutrients in improving the salinity tolerance of potato plants. In essence, the co-application of BCo with B and Se can be adopted as a promising strategy for enhancing the productivity of potato crops in salt-affected soils.

Exogenous ascorbic acid as a potent regulator of antioxidants, osmo-protectants, and lipid peroxidation in pea under salt stress

Pea (Pisum sativum L.), a globally cultivated leguminous crop valued for its nutritional and economic significance, faces a critical challenge of soil salinity, which significantly hampers crop growth and production worldwide. A pot experiment was carried out in the Botanical Garden, The Islamia University of Bahawalpur to alleviate the negative impacts of sodium chloride (NaCl) on pea through foliar application of ascorbic acid (AsA). Two pea varieties Meteor (V1) and Sarsabz (V2) were tested against salinity, i.e. 0 mM NaCl (Control) and 100 mM NaCl. Three levels of ascorbic acid 0 (Control), 5 and 10 mM were applied through foliar spray. The experimental design was completely randomized (CRD) with three replicates. Salt stress resulted in the suppression of growth, photosynthetic activity, and yield attributes in pea plants. However, the application of AsA treatments effectively alleviated these inhibitory effects. Under stress conditions, the application of AsA treatment led to a substantial increase in chlorophyll a (41.1%), chl. b (56.1%), total chl. contents (44.6%) and carotenoids (58.4%). Under salt stress, there was an increase in Na+ accumulation, lipid peroxidation, and the generation of reactive oxygen species (ROS). However, the application of AsA increased the contents of proline (26.9%), endogenous AsA (23.1%), total soluble sugars (17.1%), total phenolics (29.7%), and enzymatic antioxidants i.e. SOD (22.3%), POD (34.1%) and CAT (39%) in both varieties under stress. Salinity reduced the yield attributes while foliarly applied AsA increased the pod length (38.7%), number of pods per plant (40%) and 100 seed weight (45.2%). To sum up, the application of AsA alleviated salt-induced damage in pea plants by enhancing photosynthetic pigments, both enzymatic and non-enzymatic activities, maintaining ion homeostasis, and reducing excessive ROS accumulation through the limitation of lipid peroxidation. Overall, V2 (Sarsabz) performed better as compared to the V1 (Meteor).

Knowledge gaps on how to adapt crop production under changing saline circumstances in the Netherlands

Salinization, the increase and accumulation of salts in water and soil, impacts productivity of arable crops and is exacerbated by climate change. The Netherlands, like several other deltas and semi-arid regions, faces increasing salinization that negatively impacts agriculture and freshwater availability. Although a lot of salinity expertise exist in the Netherlands, several knowledge gaps on the impact of salinization in the Netherlands, as well as steps to facilitate closing this knowledge gaps to improve saline agriculture in the Netherlands, still exist. This review/opinion article moves beyond existing papers on salinization in bringing together various adaptation measures by thoroughly reviewing the measures through a triple P (People, Planet, Profit) lens. Five main salinity adaptation measures of the crop-soil-water continuum are 1) breeding and selection of salt tolerant varieties, 2) increased cultivation of halophytes, 3) soil management interventions, 4) use of biostimulants, and 5) irrigation techniques. These adaptation measures are described, discussed and analysed for their compliance to the sustainable development elements People, Planet and Profit. All five adaptation measures have potential positive impact on livelihood, contribute to food security and generate revenue but on the other hand, these measures may contribute to unwarranted changes of the ecosystem. The paper ends with a concluding chapter in which the bottlenecks and knowledge gaps that need resolving are identified based on the critical, including triple P, assessment of the discussed adaptation measures. Three key knowledge gaps on breeding, agronomy, environmental sciences and socioeconomics are identified with several approaches that lead to insights elucidated. Thereby informing on future research and action plans to optimize implementation of salinity adaptation measures in the Netherlands.

Salt stress influences the proliferation of Fusarium solani and enhances the severity of wilt disease in potato

Soil salinity has emerged as a critical abiotic stress in potato production, whereas wilt disease, caused by Fusarium solani, is the significant biotic stress. An experiment was performed to decipher the occurrence of wilt incidence by F. solani FJ1 under the influence of salinity in both in vitroand pot culture conditions. High salt concentration negatively influenced root and shoot development in the variety "Kufri Jyoti" but positively affected the mycelial growth and sporulation behaviours of F. solani FJ1. There was abundant whitish mycelial growth with enhanced biomass and high sporulation (microconidia production) in F. solani FJ1 cultured on salt-supplemented media. Moreover, under high salinity conditions (EC 2-8 dS m-1), severe wilting and rotting of vascular bundles were observed in plants artificially inoculated with F. solani FJ1. The mortality rate of potato plants was significantly higher under individual and combined stresses as compared to control. The wilt index of individual and combined stressed plants was also substantially higher compared to the control. Additionally, compared to the control, there was a significant decrease in total chlorophyll content and membrane stability index of the leaves under combined stress. However, the total phenols were increased under stress conditions. The total sugar content of potato plants decreased in infected plants, but increased when exposed to salt stress or a combination of salt stress and pathogen infection. F. solani infection also increased the activity of peroxidase (POX) and decreased the activity of phenylalanine ammonia-lyase (PAL) and catalase (CAT). These results suggest that Fusarium wilt and dry rot will be a more severe disease for potato cultivation in saline soils.

Salt-Induced Early Changes in Photosynthesis Activity Caused by Root-to-Shoot Signaling in Potato

Salinity is one of the most dangerous types of stress in agriculture. Acting on the root, salinity causes changes in physiological processes in the shoot, especially photosynthesis, which is crucial for plant productivity. In our study, we used potato plants, the most important crop, to investigate the role of salt-induced signals in changes in photosynthesis activity. We found a salt-induced polyphasic decrease in photosynthesis activity, and the earliest phase started several minutes after salt addition. We found that salt addition triggered rapid hydraulic and calcium waves from root to shoot, which occurred earlier than the first phase of the photosynthesis response. The inhibition of calcium signals by lanthanum decreased with the formation of rapid changes in photosynthesis. In addition to this, a comparison of the characteristic times of signal propagation and the formation of a response revealed the role of calcium waves in the modulation of rapid changes in photosynthesis. Calcium waves are activated by the ionic component of salinity. The salt-induced decrease in transpiration corresponds in time to the second phase of the photosynthetic response, and it can be the cause of this change. The accumulation of sodium in the leaves occurs a few hours after salt addition, and it can be the cause of the long-term suppression of photosynthesis. Thus, salinity modulates photosynthetic activity in plants in different ways: both through the activation of rapid distant signals and by reducing the water input and sodium accumulation.

High throughput phenotyping of functional traits and key indices for selection of salt tolerant Mustard [Brassica juncea (L.) Czern & Coss] genotypes

The current scanty knowledge about the salt tolerance mechanism underlying the ability of plants to tolerate salt stress hinders the potential production of numerous crops, including Indian mustard. To explore the traits and mechanism for salt tolerance, high throughput phenotyping of 250 stabilized F7:8 recombinant inbred lines (RILs) mapping population of Indian mustard were conducted under control and salinity (ECiw 12 dS m-1 ) for 54 morpho-physio-seed-quality traits. Most of the traits were reduced with variable percentages under salt stress. The stress tolerance index (STI) of YPP showed a significant negative association with Na+ concentration of root (RNa), indicating that RILs with low Na+ concentration have high seed yield and a positive significant association with STI of yield-related traits, photosynthesis rate (Pn), intrinsic water use efficiency (inWUE), fresh weight of upper leaf (USFW), fresh weight of branches (BrFW), fresh weight of basal leaf (BLFW), and fresh weight of middle leaf (MLFW) revealed that by improving these traits seed yield per plant (YPP) was improved. Based on principal component analysis (PCA) of 54 STI and new index composite selection index (CSI), RILs viz., R114, R150, R164, R170, and R206 were identified as stable performers which can be exploited for quantitative trait loci (QTLs)/gene discovery and serve as potential donors to combat salt stress. Our research will serve to determine the relative importance of different functional traits of salt tolerance mechanisms that can be used to screen colossal germplasm.

Plant salinity stress, sensing, and its mitigation through WRKY

Salinity or salt stress has deleterious effects on plant growth and development. It imposes osmotic, ionic, and secondary stresses, including oxidative stress on the plants and is responsible for the reduction of overall crop productivity and therefore challenges global food security. Plants respond to salinity, by triggering homoeostatic mechanisms that counter salt-triggered disturbances in the physiology and biochemistry of plants. This involves the activation of many signaling components such as SOS pathway, ABA pathway, and ROS and osmotic stress signaling. These biochemical responses are accompanied by transcriptional modulation of stress-responsive genes, which is mostly mediated by salt-induced transcription factor (TF) activity. Among the TFs, the multifaceted significance of WRKY proteins has been realized in many diverse avenues of plants' life including regulation of plant stress response. Therefore, in this review, we aimed to highlight the significance of salinity in a global perspective, the mechanism of salt sensing in plants, and the contribution of WRKYs in the modulation of plants' response to salinity stress. This review will be a substantial tool to investigate this problem in different perspectives, targeting WRKY and offering directions to better manage salinity stress in the field to ensure food security.

Variability in morpho-biochemical, photosynthetic pigmentation, enzymatic and quality attributes of potato for salinity stress tolerance

Salt stress has emerged as a growing global concern, exerting a significant impact on agricultural productivity. The challenges of salt stress on potatoes are crucial for ensuring food security and sustainable agriculture. To address this issue a pot trial was executed to evaluate the impacts of NaCl in the soil on the growth, photosynthetic pigments, and quality attributes of potato, plants were grown in soil spiked with various concentrations of NaCl (0, 1, 3, 5, 7 g kg-1 of soil). Results revealed that salt stress have negative impacts on the growth, biomass, photosynthesis and quality attributes of potato. Lower level of salt stress 1 g kg-1 of soil improved the fresh and dry biomass of leaves (78.70 and 47.74%) and tubers (86.04 and 88.92%) as compared to control, respectively. Higher levels of salt stress (7 g kg-1) increased lipid peroxidation in leaves and improved the enzymatic antioxidants. It was observed that enzyme activities i.e., SOD (134.97%), POD (101.02%), and CAT (28.87%) increased in leaves and are inversely related to the NaCl concentration. The combination of reduction in chlorophyll contents and soluble sugars resulted in lower levels of quality attributes i.e., amylose (68.90%) and amylopectin (16.70%) of potato. Linear relationship in growth, biomass and physiological attributes showed the strong association with increased salt stress. Furthermore, the PCA-heatmap synergy offers identifying clusters of co-regulated attributes, which pinpoint the physiological responses that exhibit the strongest correlation with increasing salt stress levels. Findings indicate that potato can be grown successfully with (1 g kg-1 of NaCl in soil) without negative impacts on plant quality. Furthermore, this study contributes valuable insights into the complexities of salt stress on potato plants and provides a foundation for developing strategies to enhance their resilience in salt-affected environments.

A Review of Potato Salt Tolerance

Potato is the world's fourth largest food crop. Due to limited arable land and an ever-increasing demand for food from a growing population, it is critical to increase crop yields on existing acreage. Soil salinization is an increasing problem that dramatically impacts crop yields and restricts the growing area of potato. One possible solution to this problem is the development of salt-tolerant transgenic potato cultivars. In this work, we review the current potato planting distribution and the ways in which it overlaps with salinized land, in addition to covering the development and utilization of potato salt-tolerant cultivars. We also provide an overview of the current progress toward identifying potato salt tolerance genes and how they may be deployed to overcome the current challenges facing potato growers.

In vitro and in vivo screening for the identification of salt-tolerant sugarcane (Saccharum officinarum L.) clones: molecular, biochemical, and physiological responses to salt stress

Sugarcane is a glycophyte whose growth and yield can be negatively affected by salt stress. As the arable lands with potential saline soils expand annually, the increase of salt-tolerance in sugarcane cultivars is highly desired. We, herein, employed in vitro and in vivo conditions in order to screen sugarcane plants for salt tolerance at the cellular and at the whole plant levels. Calli of sugarcane cv. Khon Kaen 3 (KK3) were selected after culturing in selective media containing various NaCl concentrations, and regenerated plants were then reselected after culturing in selective media containing higher NaCl concentrations. The surviving plants were finally selected after an exposure to 254 mM NaCl under greenhouse conditions. A total of 11 sugarcane plants survived the selection process. Four plants that exhibited tolerance to the four different salt concentrations applied during the aforementioned screening process were then selected for the undertaking of further molecular, biochemical, and physiological studies. The construction of a dendrogram has revealed that the most salt-tolerant plant was characterized by the lowest genetic similarity to the original cultivar. The relative expression levels of six genes (i.e., SoDREB, SoNHX1, SoSOS1, SoHKT, SoBADH, and SoMIPS) were found to be significantly higher in the salt-tolerance clones than those measured in the original plant. The measured proline levels, the glycine betaine content, the relative water content, the SPAD unit, the contents of chlorophyll a and b, as well as the K⁺/Na⁺ ratios of the salt-tolerant clones were also found to be significantly higher than those of the original plant.When the salt-tolerant clones were grown in a low saline soil, they exhibited a higher Brix percentage than that of the original cultivar.

Salt Tolerance Potential in Onion: Confirmation through Physiological and Biochemical Traits

Production of many crops, including onion, under salinity is lagging due to limited information on the physiological, biochemical and molecular mechanisms of salt stress tolerance in plants. Hence, the present study was conducted to identify salt-tolerant onion genotypes based on physiological and biochemical mechanisms associated with their differential responses. Thirty-six accessions were evaluated under control and salt stress conditions, and based on growth and bulb yield. Results revealed that plant height (6.07%), number of leaves per plant (3.07%), bulb diameter (11.38%), bulb yield per plant (31.24%), and total soluble solids (8.34%) were reduced significantly compared to control. Based on percent bulb yield reduction, seven varieties were classified as salt tolerant (with <20% yield reduction), seven as salt-sensitive (with >40% yield reduction) and the remaining as moderately tolerant (with 20 to 40% yield reduction). Finally, seven salt-tolerant and seven salt-sensitive accessions were selected for detailed study of their physiological and biochemical traits and their differential responses under salinity. High relative water content (RWC), membrane stability index (MSI), proline content (PRO), and better antioxidants such as super oxide dismutase (SOD), peroxidase (POX), catalase (CAT), and ascorbate peroxidase (APX) were observed in tolerant accessions, viz. POS35, NHRDF Red (L-28), GWO 1, POS36, NHRDF Red-4 (L-744), POS37, and POS38. Conversely, increased malondialdehyde (MDA) and hydrogen peroxide (H2O2) content, reduced activity of antioxidants, more membrane injury, and high Na+/K+ ratio were observed in sensitive accessions, viz. ALR, GJWO 3, Kalyanpur Red Round, NHRDF Red-3 (L-652), Agrifound White, and NHRDF (L-920). Stepwise regression analysis identified bulb diameter), plant height, APX, stomatal conductance (gS), POX, CAT, MDA, MSI, and bulb Na+/K+ ratio as predictor traits accounting for maximum variation in bulb yield under salinity. The identified seven salt-tolerant varieties can be used in future onion breeding programs for developing tolerant genotypes for salt-prone areas.