Salt-tolerant Varieties Research Articles

GENETIC DIVERSITY AND ASSOCIATION ANALYSIS OF SALT TOLERANCE IN ASIATIC COTTON (GOSSYPIUM ARBOREUM) WITH MOLECULAR MARKERS

Gossypium arboreum possesses favorable characteristics that are valuable for developing superior cotton cultivars. This study was carried out to analyze genetic diversity and identify marker-trait association analysis related to salt tolerance using SSR markers for 215 accessions of G. arboreum. The salt tolerance-related traits like germination rate, fresh weight, stem length, water content, chlorophyll content, electric conductivity, and MDA of the accessions were identified using 150 mM salt for 7 days of seedling growth.
 According to the comprehensive index of salt tolerance, 215 accessions were categorized mainly into four groups. Twenty four accessions were classified as highly tolerant to salt treatment (>2.5). The natural population was classified into 3 main groups by phylogenetic analysis. The classifications of phylogenetic analysis were largely congruent with the breeding history and ecological region.
 Twenty-two strong marker-trait associations were obtained with strict significant P value i.e. P< 0.01 and four makers including NAU1023, NAU1099, JESPR222, and NAU2783 were significantly related to salt tolerance. The marker NAU2783 was highest associated (P= 1.98E-12) with relative electric conductivity, and with the highest phenotype variation of 20.87%. Some markers are significantly associated with more than two traits. MUSS020 was significantly (P<0.01) associated with relative fresh weight, and relative MDA, NAU1375 was associated with relative fresh weight and relative stem length, while NAU3468 was significantly associated with relative fresh weight, relative germination rate, and relative water content. The strong marker-trait association results might provide insights for marker-assistant selecting salt-tolerant varieties and will be useful for future cotton breeding programs.

Low apoplastic Na+ and intracellular ionic homeostasis confer salinity tolerance upon Ca2SiO4 chemigation in Zea mays L. under salt stress.

Salinity is known to have a greater impact on shoot growth than root growth. Na+ buildup in plant tissue under salt stress has been proposed as one of the main issues that causes growth inhibition in crops via ionic imbalances, osmotic stress and pH disturbances. However, the evidence for apoplastic Na+ buildup and the role of silicon in Na+ accumulation at the subcellular level is still enigmatic. The current study focuses on the accumulation of Na+ in the apoplast and symplast of younger and older leaves of two maize varieties (Iqbal as salt-tolerant and Jalal as salt-sensitive) using hydroponic culture along with silicon supplementation under short-term salinity stress. Subcellular ion analysis indicated that silicon nutrition decreased Na+ concentration in both apoplastic washing fluid and symplastic fluid of maize under salt stress. The addition of silicon under NaCl treatment resulted in considerable improvement in fresh biomass, relative water content, chlorophyll content, and concentration of important subcellular ions (i.e., Ca2+, Mg2+, and K+). Knowledge of subcellular ion analysis is essential for solving the mechanisms underlying vital cellular functions e.g. in the current study, the soluble Na+ concentration in the apoplast of older leaves was found to be significantly greater (36.1 mM) in the salt-sensitive variety under NaCl treatment, which was 42.4% higher when compared to the Na+ concentration in the salt-tolerant variety under the same treatment which can influence permeability of cell membrane, signal transduction pathways and provides insights into how ion compartmentalization can contributes to salt tolerance. Calcium silicate enrichment can contribute to increased growth and improved ionic homeostasis by minimizing leaf electrolyte leakage, improving mechanical functions of cell wall and reducing water loss, and improved photosynthetic function. In current investigation, increased water content and intracellular ionic homeostasis along with reduced concentration of Na+ in the maize leaf apoplast suggest that calcium silicate can be used to ameliorate the adverse effects of salt stress and obtain yield using marginal saline lands.

Metods for creating salt – tolerant long – grin varieties in Karakalpakstan

The article presents the results of breeding methods for creating salt-tolerant long – grain rice varieties. For this purpose, collection samples and the best varieties of rice from different ecological and geographical zones were studied according to agrobiological characteristics in comparison with the zoned ultra-early ripening long – grain varieties “Sanam”. After a comprehensive study and comprehensive assessment in the field conditions, ultra-early ripening long-grain forms with positive traits and properties were identified. These selected varieties were assessed far salt tolerance in laboratory conditions during the seed germination phase in an artificially created 1.5% solution (NaCl) of sodium chloride. A high concentration of sodium chloride has an adverse effect on germination rates and seedling size. At high concentrations of saline solution, these indicators sharply decrease in all studied varieties. However, such a decrease, depending on the genotypic characteristics of the variety samples, does not occur to the same extent. Under saline conditions, the characteristic differences between the characteristic of the seedling and the root system changes greatly. The growth and formation of roots was particularly inhibited compared aboveground part of the seedlings. Changes in the performance of the root system in a saline environment for the better can be considered adaptive properties to stressful salinity conditions. Based on the study of germination and seedling parameters, the most salt-tolerant varieties were identified, including Almaz; D-42 (D-11) 35-05-2); D-134 (D-34) (D-143); D-61 (K-316) Viktoriya). These varieties successfully overcome the adverse effects of high concentrations, of sodium chloride solution.

Ascophyllum nodosum SWE enhances root anatomy, but not POD activity in both a salt-tolerant and salt-sensitive soybean ( Glycine max) variety exposed to salt stress.

There is growing evidence that seaweed extracts (SWE) may be a solution for mitigating the negative effects of salt stress on crop yield and quality, as they introduce bioactive ingredients able to regulate the expression of growth-inducing and stress-responsive genes. We demonstrate that SWE slightly ameliorated the negative physical growth effects of salt stress, especially in the root anatomy of the salt-sensitive (Clark) variety. The SWE did not stimulate or enhance peroxidase (POD) activity in either the salt-sensitive (Clark) or salt-tolerant variety (Manokin). However, a complete assessment of other antioxidant enzymes (SOD, CAT, APX) involved in the ROS detoxification process is further required.

Genetic transformation of GmFBX322 gene and salt tolerance physiology in soybean.

Soybean is one of the most important food crops, breeding salt-tolerant soybean varieties is of great significance to alleviate soybean shortage. In this study, the F-box protein family homologous gene GmFBX322 was cloned from the soybean variety Williams 82 and overexpressed in the Shennong 9 soybean variety to further study and explore the physiological mechanism of soybean salt tolerance. GmFBX322 was constructed on the vector pTF101:35S, and integrated into the genome of Shennong 9 soybean variety by Agrobacterium EHA101-mediated cotyledonary node transformation technology, and 4 overexpressed transgenic lines were obtained, molecular assays were performed on the transformed plants. The expression of GmFBX322 was detected by qRT-PCR and it was found that the leaves of the 4 transgenic lines increased by 2.49, 2.46, 2.77, 2.95 times compared with the wild type; after salt treatment for 12 hours, it was found that the expression of wild type Shennong 9 Inducible expression of GmFBX322. After 72 hours of salt treatment, the leaves of wild-type Shennong 9 soybean plants showed obvious wilting and chlorosis, while the leaves of GmFBX322 plants overexpressing GmFBX322 showed no obvious changes. The leaves were taken at 0, 6, 12, 24, and 48 hours of salt stress to determine the antioxidant activity. Ability and osmotic adjustment level, etc. The results showed that the catalase activity in the leaves of the transgenic lines 2265, 2267, 2269, and 2271 was 2.47, 2.53, 3.59, 2.96 times that of the wild-type plant after 48 hours of salt treatment; the soluble sugar content was 1.22, 1.14, and 1.22 of the wild-type plant. 1.14, 1.57 times; the proline content is 2.20, 1.83, 1.65, 1.84 times of the wild type. After comparing the physiological indicators determined by the experiment, the transgenic lines performed better than the control group, indicating that overexpression of GmFBX322 can enhance the salt tolerance of soybean plants. To verify the function of GmFBX322 gene related to stress resistance, add it to the candidate gene of stress resistance, and provide scientific basis for the selection and breeding of salt-tolerant varieties.

SOYBEAN GERMPLASM SHOWS VARIATION IN FARMERS PARTICIPATORY TRIAL IN THE COASTAL REGION OF BANGLADESH

The cultivation of soybean is still concentrated in the coastal region of greater Noakhali District of Bangladesh, where salinity hinders crop production. There is no suitable salt tolerant variety so far. At Bangabandhu Sheikh Mujibur Rahman Agricultural University, 170 soybean genotypes were screened and finally three,namely AGS313 (BU soybean-3), G00028 (BU soybean-4), and BD2330 were found fairly salt tolerant at 5 and 10 dSm-1 salinity. In Rabi 2022-23 season the selected three genotypes, G00056 as a high yielding promising genotype, and three varieties namely BU soybean-2, BARI soybean-6 and Binasoybean-2, i.e. altogether seven genotypes were grown in 700 decimals land, both saline and non-saline soils, of 12 farmers in different upazillasof Noakhali, Laksmipur and Bhola districts. The seeds were sown by the last week of January’ 23. Salinity of the fields at harvestwas found 5- 13 dSm-1, thoughinitially varied from 0 – 4 dSm-1. Yield contributing characters were measured appropriately. Standard error was used for showing the mean differences. Farmers’ discussion on the performance of the genotypes were held from time to time. Salinity decreasedplant height, maturityduration, number of pods plant-1, 1000-seed weight and grain yield ha-1. However, AGS313 and G00028 were affected less than other genotypes. Under non-saline and low saline conditions relatively higher yield was found in BU soybean2 (2657 kg ha-1 in Bhola, 3397 kgha-1 in Subornachar), G00056 (2341 in Laksmipur sadar, 3390 kg ha-1 in Subornachar), AGS313 (2612 in Ramgoti, 3266 kg ha-1 in Subornachar) and G00028 (2464 in Bhola sadar, 3374 kg ha-1 in Subornachar) compared to other genotypes. The lowest yield was found in BARI soybean6 (1715 kg ha-1 in Ramgoti) followed by Binaoybean-2 (1868 kg ha-1 in Laksmipur sadar). However, under saline field conditions (5- 8 dSm-1) G00028 (866 kg ha-1 in Komolnagar, 1374 kg/ha in Subornachar) and AGS313 (860 kg ha-1in Ramgoti, 1333 kg ha-1 in Subornachar) produced substantially higher yield than other genotypes/ varieties. The lowest yield was obtained from G00056 (170 kg ha-1) from Komolnagar. Based on the results of multi-location trials, and discussions with the farmers the genotypes AGS313 and G00028 were registered as BU soybean-3and BU soybean-4, respectively as relatively salt tolerant varieties from the National Seed Board.

Advanced Mutant Line Developed from Fatemadhan Shows Salinity Tolerance at both Seedling and Reproductive Stages

The generation of high-yielding rice mutants and their assessment under salt stress offers a great possibility to isolate salt tolerant line(s) with desired trait of interest. Two separate experiments were conducted at the seedling and reproductive stages of rice to assess the level of salinity tolerance of few advanced high-yielding rice mutants. In the first experiment, rice seedlings were grown under hydroponic conditions and 14-day-old seedlings were subjected to salt stress (EC=10 dS/m; 7 days). Salt stress caused significant reduction in root and shoot length and biomass and leaf chlorophyll content; however, a little reduction was found in the mutant Line-1. In contrast, a sharp increase in shoot Na+/K+ ratio was found in all the genotypes except, Binadhan-10, FL-478 and the mutant Line-1, which exhibited little increased ratio. The second experiment involved exposure of plant to salt stress (EC=10 dS/m) for three weeks at the late booting stage in a sizable plastic tub filled with field soil. Salt stress resulted in a significant decrease in yield and yield attributing traits in all the genotypes except Binadhan-10. Grain yield per panicle was found significantly positive correlation with panicle length, the number of filled grains per panicle, and 100-seed weight under both control and salt stress conditions. Based on the studied traits and stress tolerance indices, Binadhan-10 and mutant Line-1 categorized as salt tolerant and rest of the genotypes were categorized as susceptible, which is also evident from the biplot of principal component analysis. Considering the results from both of the experiments, mutant Line-1 was found tolerant genotype at both seedling and reproductive stage. However, further studies are required to determine the genetic issues controlling the salinity tolerance in mutant Line-1 and the high-yield potential of mutant Line-65 under control condition in a way to develop salt tolerant and high-yielding rice varieties, respectively.

Genome-wide identification of the C2H2 zinc finger gene family and expression analysis under salt stress in sweetpotato.

The higher plant transcription factor C2H2 zinc finger protein (C2H2-ZFP) is essential for plant growth, development, and stress response. There are limited studies on C2H2-ZFP genes in sweetpotato, despite a substantial number of C2H2-ZFP genes having been systematically found in plants. In this work, 178 C2H2-ZFP genes were found in sweetpotato, distributed randomly on 15 chromosomes, and given new names according to where they were located. These members of the zinc finger gene family are separated into six branches, as shown by the phylogenetic tree. 24 tandem repeats of IbZFP genes and 46 fragment repeats were identified, and a homology study revealed that IbZFP genes linked more regions with wild relative species of sweetpotato as well as rhizome plants like potato and cassava. And we analyzed the expression patterns of IbZFP genes during the early development of sweetpotato storage roots (SRs) and salt stress using transcriptome data, and identified 44 IbZFP genes that exhibited differences in expression levels during the early expansion of sweetpotato SRs in different varieties, and 92 IbZFP genes that exhibited differences in expression levels under salt stress in salt tolerant and salt sensitive sweetpotato varieties. Additionally, we cloned six IbZFP genes in sweetpotato and analyzed their expression patterns in different tissues, their expression patterns under abiotic stress and hormone treatment, and subcellular localization. The results showed that the IbZFP genes had tissue specificity in sweetpotato and were induced to varying degrees by drought and salt stress. ABA and GA3 treatments also affected the expression of the IbZFP genes. We selected IbZFP105, which showed significant differences in expression levels under salt stress and ABA treatment, to be heterologously expressed in Arabidopsis thaliana. We found that IbZFP105 OE lines exhibited higher tolerance to salt stress and ABA stress. This indicates that IbZFP105 can enhance the salt tolerance of plants. These results systematically identified the evolution and expression patterns of members of the C2H2-ZFP gene family in sweetpotato, providing a theoretical basis for studying the role of IbZFP genes in the development of sweetpotato SRs and in resistance to stress.

Variety-driven rhizosphere microbiome bestows differential salt tolerance to alfalfa for coping with salinity stress.

Soil salinization is a global environmental issue and a significant abiotic stress that threatens crop production. Root-associated rhizosphere microbiota play a pivotal role in enhancing plant tolerance to abiotic stresses. However, limited information is available concerning the specific variations in rhizosphere microbiota driven by different plant genotypes (varieties) in response to varying levels of salinity stress. In this study, we compared the growth performance of three alfalfa varieties with varying salt tolerance levels in soils with different degrees of salinization. High-throughput 16S rRNA and ITS sequencing were employed to analyze the rhizosphere microbial communities. Undoubtedly, the increasing salinity significantly inhibited alfalfa growth and reduced rhizosphere microbial diversity. However, intriguingly, salt-tolerant varieties exhibited relatively lower susceptibility to salinity, maintaining more stable rhizosphere bacterial community structure, whereas the reverse was observed for salt-sensitive varieties. Bacillus emerged as the dominant species in alfalfa's adaptation to salinity stress, constituting 21.20% of the shared bacterial genera among the three varieties. The higher abundance of Bacillus, Ensifer, and Pseudomonas in the rhizosphere of salt-tolerant alfalfa varieties is crucial in determining their elevated salt tolerance. As salinity levels increased, salt-sensitive varieties gradually accumulated a substantial population of pathogenic fungi, such as Fusarium and Rhizoctonia. Furthermore, rhizosphere bacteria of salt-tolerant varieties exhibited increased activity in various metabolic pathways, including biosynthesis of secondary metabolites, carbon metabolism, and biosynthesis of amino acids. It is suggested that salt-tolerant alfalfa varieties can provide more carbon sources to the rhizosphere, enriching more effective plant growth-promoting bacteria (PGPB) such as Pseudomonas to mitigate salinity stress. In conclusion, our results highlight the variety-mediated enrichment of rhizosphere microbiota in response to salinity stress, confirming that the high-abundance enrichment of specific dominant rhizosphere microbes and their vital roles play a significant role in conferring high salt adaptability to these varieties.

Genome-wide analysis of the SCAMPs gene family of soybean and functional identification of GmSCAMP5 in salt tolerance

The effect of salt damage on plants is mainly caused by the toxic effect of Na+. Studies showed that the secretory carrier membrane proteins were associated with the Na+ transport. However, the salt tolerance mechanism of secretory carrier protein (SCAMP) in soybean was yet to be defined. In this study, ten potential SCAMP genes distributed in seven soybean chromosomes were identified in the soybean genome. The phylogenetic tree of SCAMP domain sequences of several plants can divide SCAMPs into two groups. Most GmSCAMPs genes contained multiple Box4, MYB and MYC cis-elements indicated they may respond to abiotic stresses. We found that GmSCAMP1, GmSCAMP2 and GmSCAMP4 expressed in several tissues and GmSCAMP5 was significantly induced by salt stress. GmSCAMP5 showed the same expression patterns under NaCl treatment in salt-tolerant and salt-sensitive soybean varieties, but the induced time of GmSCAMP5 in salt-tolerant variety was earlier than that of salt-sensitive variety. To further study the effect of GmSCAMP5 on the salt tolerance of soybean plants, compared to GmSCAMP5-RNAi and EV-Control plants, GmSCAMP5-OE had less wilted leave and higher SPAD value. Compared to empty vector control, less trypan blue staining was observed in GmSCAMP5-OE leaves while more staining in GmSCAMP5-RNAi leaves. The Na+ of GmSCAMP5-RNAi plants leaves under NaCl stress were significantly higher than that in EV-Control plants, while significantly lower Na+ in GmSCAMP5-OE plants than in that EV-Control plants. The contents of leaves K+ of GmSCAMP5-RNAi, EV-Control, and GmSCAMP5-OE plants under NaCl stress were opposite to that of leaves Na+ content. Finally, salt stress-related genes NHX1, CLC1, TIP1, SOD1, and SOS1 in transformed hairy root changed significantly compared with the empty control. The research will provide novel information for study the molecular regulation mechanism of soybean salt tolerance.

Corrigendum to: Salt tolerance in Brassicaceae crops: physiological responses and molecular mechanisms.

Soil salinisation is a growing threat to global agriculture, reducing crop yields. Brassicaceae crops are vital vegetables and cash crops. Salt stress significantly affects the growth and development of Brassicaceae crops. A better understanding of the molecular and physiological mechanisms of salt tolerance is of theoretical and practical importance to improve Brassicaceae crop's salt tolerance and crop quality. Combined with previous research results, we discuss recent advances in research on salt stress response and salt tolerance in Brassicaceae crops. We summarised recent research progress on the physiological and molecular mechanisms of ionic homeostasis, antioxidant regulation, hormonal regulation and accumulation of osmotic-adjustment substances. We also discussed the molecular mechanism of Brassicaceae crop salt tolerant varieties from the perspective of differentially expressed genes, differentially expressed proteins and metabolites through transcriptome, proteome and metabonomic analysis methods. This paper summarises the molecular mechanisms in the perspective of differentially expressed genes, differentially expressed proteins, and metabolites through transcriptomic, proteome and metabolomics analysis. The review provides abundant data for accelerating the breeding of salt-tolerant Brassicaceae and laid a foundation for understanding the mechanism of salt tolerance of Brassicaceae crops and breeding salt-tolerance varieties.

Morphological and biochemical variations caused by salinity stress in some varieties of Pennisetum glaucum L.

The salinity of the soil is a severe challenge to the sustainability of agricultural production. It causes significant loss in the productivity of crop plants. To overcome this problem, one of the possible solutions could be the identification and cultivation of salinity tolerant crop plants in salt affected land. Therefore, this study was designed to screen some varieties of Pearl Millet (Pennisetum glaucum L. Family Poaceae), an equally important cereal crop for food and forage, for salinity tolerance in a pot experiment. Some eighteen varieties of Pearl Millet were utilized to investigate the morphometric and biochemical variations induced by saline stress. The plants were grown for three weeks under normal conditions in sand culture in disposable PVP cups with three inches diameter. Afterwards, the plants were challenged with salinity stress (aqueous solution of NaCl applied in successive steps of 50, 100, 150 and 200 mM with Hoagland’s nutrients). The plants adopted salinity stress after one week and harvested for various physio-biochemical attributes. The results showed that the varieties YBS-93, YBS-94, YBS-95 and YDR-8-1 exhibited tolerance toward salinity stress as their shoot length, root length, biomass production and K+ was maintained under salt stress. The levels of proline contents and free amino acids in their leaves were relatively higher under salt stress as compared with other varieties. The accumulation of Na+ in theses varieties was lower as compared to other varieties under saline stress. These findings indicated their potential strategy to cope with salinity stress. While theYBS-83, YBS-98, YCMP-19 and YCMP-34 varieties among the subjected eighteen varieties of Pearl Millet were screened as most sensitive varieties to salinity stress in these experimental conditions. Because these varieties had reduction in shoot length, root length biomass production and K+. Other varieties did not show any significant success in salinity stress management. This study has provided significant preliminary screening data of morphological and biochemical aspects of eighteen varieties of Pearl Millet for their capability of salinity tolerance. Further molecular investigations are underway which will be helpful in revealing insights of the salt tolerance mechanism and signaling pathways in the screened salt tolerant varieties.

Evaluation Of Salt-Tolerant Traditional Rice Varieties in Mekong Delta, Vietnam

This study was carried out from 9/2022 to 2/2023, at Can Tho University, Vietnam. This study evaluated seedling stages’ salt tolerance in nutrient solution using three electrical conductivity (EC) salt concentrations of 9.38, 12.50, and 15.63 dS/m with fifteen traditional rice varieties. Five traditional salt-tolerant rice varieties at the seedling stage (level 5) at 15.63 dS/m were selected. Furthermore, we evaluated salt tolerance at EC 9.38, 12.50, and 15.63 dS/m in the vegetative and reproductive stages of seven rice varieties (a tolerant variety, Doc Phung, a sensitive variety, IR28, and five rice salt-tolerant varieties were selected at seedling stage). This study showed that an increase in EC concentrations in the soil significantly reduced plant height, panicle/plant, panicle length, a 1000 grain weight, and yield. The addition of 9.38 dS/m EC can distinguish tolerance and sensitive genotypes. The grain yield of sensitive genotypes decreased by 90%–100% at 9.38 dS/m EC, whereas the tolerant genotypes showed <60% in grain yield reduction. Selected traditional rice varieties of Nang Cha Ran, Nep Than, Trang Lun, Gie Hanh, and Nang Tich were salt tolerant at their seedling stage and vegetative and reproductive stages were at EC 9.38 dS/m.

OsSTS, a Novel Allele of Mitogen-Activated Protein Kinase Kinase 4 (OsMKK4), Controls Grain Size and Salt Tolerance in Rice

Soil salinization is one of the most common abiotic stresses of rice, which seriously affects the normal growth of rice. Breeding salt-tolerant varieties have become one of the important ways to ensure food security and sustainable agricultural development. However, the mechanisms underlying salt tolerance control still need to be clarified. In this study, we identified a mutant, termed salt-tolerant and small grains(sts), with salt tolerance and small grains. Gene cloning and physiological and biochemical experiments reveal that sts is a novel mutant allele of Mitogen-activated protein Kinase Kinase 4 (OsMKK4), which controls the grain size, and has recently been found to be related to salt tolerance in rice. Functional analysis showed that OsSTS is constitutively expressed throughout the tissue, and its proteins are localized to the nucleus, cell membrane, and cytoplasm. It was found that the loss of OsSTS function enhanced the salt tolerance of rice seedlings, and further studies showed that the loss of OsSTS function increased the ROS clearance rate of rice seedlings, independent of ionic toxicity. In order to explore the salt tolerance mechanism of sts, we found that the salt tolerance of sts is also regulated by ABA through high-throughput mRNA sequencing. Salt and ABA treatment showed that ABA might alleviate the inhibitory effect of salt stress on root length in sts. These results revealed new functions of grain size gene OsMKK4, expanded new research ideas related to salt tolerance mechanism and hormone regulation network, and provided a theoretical basis for salt-tolerant rice breeding.

Differential biochemical and metabolic responses of contrast rice cultivars (<i>Oryza sativa</i> L.) under salt stress

More than half of the global population uses rice as the fundamental staple food; therefore, it is one of the most popular crops in the world. However, it is susceptible to salt stress, particularly among monocot crops, which reduces rice cultivation yield and threatens global food security. This research investigates the role of some factors, including amino acids, antioxidant enzymes, and sugars, in the response to the salinity stress of three contrasting rice cultivars, Dai Thom 8 (salt-sensitive), OC 10 (moderately salt-tolerant), and OM 9577 (salt-tolerant) in the seedling stage. The salt-tolerant varieties exhibited remarkable differences in physiological and biochemical traits, including enhancement of growth capacity, reduction of cell membrane damage via lowering lipid peroxidation, minimization of ROS generation, enhancement of free radical scavenging activity, and SOD, POD, and CAT enzyme activities. Additionally, the study analyzed the presence of 13 sugars using GC-MS and found that all three rice cultivars shared seven common sugars in similar quantities. However, OM 9577 had a higher content of the other six sugars compared to OC 10 and Dai Thom 8. It is one of the important biochemical factors responsible for the difference in the response mechanism to NaCl stress among rice varieties, specifically lyxofuranose (3.268%), a-D-xylopyranose (5.727%), mannopyranose (12.86%), α-D-glucopyranose (6.399%), ß-D-glucopyranose (5.509%), and D-arabinose (1.512%). Furthermore, the quantification of 20 amino acids through HPLC-DAD revealed that the salt-tolerant rice cultivars had higher concentrations of 11 amino acids than the salt-sensitive ones, including proline, isoleucine, serine, ornithine, histidine, glutamic acid, asparagine, alpha-alanine, aspartic acid, glutamine, and valine. These findings provide promising biochemical indicators for selecting salt-tolerant rice cultivars or improving existing varieties through traditional hybridization or gene transfer methods. Understanding these responses can significantly contribute to enhancing rice cultivation and ensuring food security in regions facing salinity challenges.

Salt tolerant fungal endophytes alleviate the growth and yield of saline-affected wheat genotype PBW-343

The purpose of this work was to assess how salt-tolerant wheat endophytic fungi promoted the growth of salt-sensitive wheat after inoculation. The endophytic fungal assemblages from salt-tolerant wheat genotypes (KRL-213, KRL-210 and KRL-19) and from salt-sensitive wheat genotype (PBW-343) were characterized, identified and determined for the current study. Of the fifty fungal isolates collected from both the salt-tolerant and the salt-sensitive wheat genotypes, 8 isolates recovered from salt-tolerant varieties were found to be resistant at high salt concentrations. These 8 isolates were characterized through several biochemical tests, such as plant growth promoting assay, extracellular enzymatic assay, carbohydrate utilization assay, antagonism versus plants pathogens and capacity to promote wheat seedlings (pot experiments). All tests revealed the positive results for 4 fungal strains (K13TR/150, K19TR/200, K-19TL/150 and K-19TL/200). These 4 fungi were identified as Aspergillus medius (K19TR/200), Cladosporium parahalotolerant (K13TR/150), Aspergillus versicolor (K19TL/150) and Aspergillus nishimurae (K19TL/200) through 18 S rDNA sequencing. Out of these, C. parahalotolerant and A. medius showed the synergistic effect with each other, so these 2 isolates were used in further experiments. These 2 isolates were involved in increasing the root-shoot length, proline and MDA contents. SEM and fluorescence microscopy were used to detect endophytic fungal colonization in the root of seedlings. C. parahalotolerant and A. medius heavily colonized the roots and it was noticed on the 21st day of the growth phase. These findings imply that fungal isolates have the potential to confer stress tolerance to their respective hosts and may enhance the agricultural production in the future, especially considering the changes in climate.

Analysis of Morphological, Physiological, and Biochemical Traits of Salt Stress Tolerance in Asian Rice Cultivars at Seedling and Early Vegetative Stages

Rice (Oryza sativa L.) is a primary energy food for the Asian population. One of the greatest constraints in rice production is soil salinity because rice is very susceptible to salt. Meanwhile, many agricultural lands in Asia are in saline areas. It is important to identify and develop salt-tolerant rice varieties that highly adapt to Asian climates. By combining morphological, physiological, and biochemical assessments for screening the salt tolerance of 116 Asian rice cultivars, we were able to classify them into tolerant, moderate, and sensitive rice cultivars under salinity stress conditions and also understand salt tolerance mechanisms. The rice cultivars that are salt-tolerant include Pokkali from India, TCCP 266 and IR 45427 from the Philippines, and Namyang 7 from Republic of Korea. However, salt-sensitive rice varieties like IR29 and IR58 are from the Philippines, and Daegudo and Guweoldo are from Korea. The salt-tolerant varieties showed signs of tolerance, including a lower percent reduction in germination percentage, root length, root fresh weight, shoot length, plant biomass, and chlorophyll content. In order to maintain the cellular osmotic balance under saline conditions, the salt-tolerant varieties exhibited less membrane damage, a lower Na/K ratio, high proline and sugar accumulation, and lower levels of malondialdehyde (MDA) and hydrogen peroxide (H2O2). Pokkali from India, TCCP 266 and IR 45427 from the Philippines, and Namyang 7 from Republic of Korea are recommended as valuable germplasm resources for Asian rice breeding programs in saline agricultural areas.

Influence of Incremental Short Term Salt Stress at the Seedling Stage on Root Plasticity, Shoot Thermal Profile and Ion Homeostasis in Contrasting Wheat Genotypes

Understanding the component traits determining salt stress tolerance is a major breeding target in wheat. The lack of genetic resources suited to salt-affected regions and the complexity of the traits involved impede progress in breeding salt-tolerant wheat varieties. This study was conducted with four bread wheats, namely (Triticum aestivum) Kharchia-65 (K-65), BT-Schomburgk (BTS), HD-2687, and HD-3298. Treatments were imposed on plants with varying electrical conductivity (control, 5 dS m−1, 10 dS m−1, and 15 dS m−1) with a combination of three different salts NaCl, CaCl2·2H2O, and Na2SO4. We evaluated variations in root system architecture, canopy temperature (depicted as a thermal image), reactive oxygen species (ROS) homeostasis, and leaf stomatal density in response to incremental doses of salt stress in a hydroponic experiment. As the plants were sampled after short-term exposure to stress (within 3 weeks of stress imposition), the plants were expected to be in a quiescent state. Due to the osmotic effect, the growth of the plants was compromised, and the associated decrease in stomatal conductance increased the canopy temperature. ROS accumulation and antioxidant enzyme activity did not follow a definite pattern. The antioxidant system’s tolerance to ROS comes into action much later in the tolerance mechanism. That could probably be the reason behind the varied response in ROS accumulation and antioxidant enzymes after short-term exposure to salt stress. Thermal images could effectively differentiate between salt-tolerant (K65) and sensitive (HD2687) genotypes. The variation in Na+/K+ ratio also suggested a genotypic variation in salt tolerance. The genotypes of K-65 maintained a better root system, while HD2687 showed severe reduction in root biomass and other root traits under salt stress. The PCA data also point out genotypic variation in lateral and main root traits in response to different salt stress levels. For salt tolerance in wheat, the main contributing root traits were total root length, total surface area, total root volume, tips, and other main, lateral root traits. The idea of differential control of RSA dynamics is novel and can be further explored to understand natural variation in salt stress tolerance.

Na+-preferential ion transporter HKT1;1 mediates salt tolerance in blueberry.

Soil salinity is a major environmental factor constraining growth and productivity of highbush blueberry (Vaccinium corymbosum). Leaf Na+ content is associated with variation in salt tolerance among blueberry cultivars; however, the determinants and mechanisms conferring leaf Na+ exclusion are unknown. Here, we observed that the blueberry cultivar 'Duke' was more tolerant than 'Sweetheart' and accumulated less Na+ in leaves under salt stress conditions. Through transcript profiling, we identified a member of the high-affinity K+ transporter (HKT) family in blueberry, VcHKT1;1, as a candidate gene involved in leaf Na+ exclusion and salt tolerance. VcHKT1;1 encodes a Na+-preferential transporter localized to the plasma membrane and is preferentially expressed in the root stele. Heterologous expression of VcHKT1;1 in Arabidopsis (Arabidopsis thaliana) rescued the salt hypersensitivity phenotype of the athkt1 mutant. Decreased VcHKT1;1 transcript levels in blueberry plants expressing antisense-VcHKT1;1 led to increased Na+ concentrations in xylem sap and higher leaf Na+ contents compared with wild-type plants, indicating that VcHKT1;1 promotes leaf Na+ exclusion by retrieving Na+ from xylem sap. A naturally occurring 8-bp insertion in the promoter increased the transcription level of VcHKT1;1, thus promoting leaf Na+ exclusion and blueberry salt tolerance. Collectively, we provide evidence that VcHKT1;1 promotes leaf Na+ exclusion and propose natural variation in VcHKT1;1 will be valuable for breeding Na+-tolerant blueberry cultivars in the future.

Marker-assisted enhancement of bacterial blight (Xanthomonas oryzae pv. oryzae) resistance in a salt-tolerant rice variety for sustaining rice production of tropical islands.

Bacterial blight (BB) caused by Xanthomonas oryzae pv. oryzae is a major disease of rice, specially in the tropical regions of the world. Developing rice varieties with host resistance against the disease is the most effective and economical solution for managing the disease. Pyramiding resistance genes (Xa4, xa5, xa13,and Xa21) in popular rice varieties using marker-assisted backcross breeding (MABB) has been demonstrated as a cost-effective and sustainable approach for establishing durable BB resistance. Here, we report our successful efforts in introgressing four resistance genes (Xa4, xa5, xa13, and Xa21) from IRBB60 to CARI Dhan 5, a popular salt-tolerant variety developed from a somaclonal variant of Pokkali rice, through functional MABB. Both BB and coastal salinity are among the major challenges for rice production in tropical island and coastal ecosystems. Plants with four, three, and two gene pyramids were generated, which displayed high levels of resistance to the BB pathogen at the BC3F2 stage. Under controlled salinity microplot environments, the line 131-2-175-1223 identified with the presence of three gene pyramid (Xa21+xa13+xa5) displayed notable resistance across locations and years as well as exhibited a salinity tolerance comparable to the recurrent parent, CARI Dhan 5. Among two BB gene combinations (Xa21+xa13), two lines, 17-1-69-334 and 46-3-95-659, demonstrated resistance across locations and years, as well as salt tolerance and grain production comparable to CARI Dhan 5. Besides salinity tolerance, five lines, 17-1-69-179, 46-3-95-655, 131-2-190-1197, 131-2-175-1209, and 131-2-175-1239, exhibited complete resistance to BB disease. Following multilocation testing, potential lines have been identified that can serve as a prospective candidate for producing varieties for the tropical Andaman and Nicobar Islands and other coastal locations, which are prone to BB and coastal salinity stresses.