Non-saline Conditions Research Articles

Salt tolerance of Cressa cretica and its rhizosphere microbiota

The dwarf shrub Cressa cretica is a thermocosmopolitan halophilic species. Different mechanisms confer salt stress tolerance such as tissue and osmotic tolerance and ion exclusion, as well as the associated microbiota. The aims were (i) to investigate the best conditions for C. cretica seed germination and to examine the tolerance of germinated seeds and seedlings to different salt concentrations and (ii) to characterize the rhizosphere and bulk soil microbiota. Germination and growth experiments were conducted to address plant salt tolerance, and with Illumina sequencing the microbiota of rhizosphere and bulk soil was investigated. While high salt concentrations (600, 800, and 1000 mM NaCl) inhibited C.cretica seed germination, recovery of ungerminated seeds under non-saline conditions was high, indicating osmotic rather than toxic effects of high salt concentrations. The microbiota found in rhizosphere and bulk soil showed high similarity with that found in previous studies on halophyte-associated microbiota, among the Planctomyces, Halomonas and Jeotgalibacillus. Concluding, salt stress responses on the plant level were shown, as has the involvement of associated halotolerant bacteria. Still, the potential role for mitigating saline stress by the bacterial associates of C. cretica, most of them microbial dark matter, will have to be investigated, as will the contributions of archaea and fungi.

Zinc and potassium fertilizer recommendation for cotton seedlings under salinity stress based on gas exchange and chlorophyll fluorescence responses

Cotton is typically grown in warm regions in which salinity and nutrient deficiency stresses are ubiquitous and often simultaneously influence plant growth. Under saline conditions, fertilizer recommendation is highly challenging, since nutrient application may increase or decrease plant salt tolerance, which may complicate prediction of crop yield. So far, no investigations have been conducted in salt-affected soils to determine optimum concentrations of potassium (K) and zinc (Zn) fertilizers based on chlorophyll fluorescence (ChlF) and gas exchange (GEx) responses in upland cotton (Gossypium hirsutum L.). Accordingly, in this study, a factorial experiment was conducted in a complete block design with six replicates under controlled conditions. Treatments included various K2SO4 (0, 50, 100, and 150 kg ha−1), and ZnSO4 (0, 50, and 100 kg ha−1) concentrations applied to soil before planting. Cottonseeds were sown in non-saline soils and soils formerly salinized with natural saline water diluted to 15 dS m−1. One month after sowing, results showed that salinity significantly decreased dry weight, chlorophyll content index, photosynthesis rate (A), leaf to air vapor pressure, transpiration rate (E), stomatal conductance, and minimum fluorescence of dark-adapted leaf, but increased root to shoot ratio (R/Sh). Under salinity, combined application of K and Zn boosted physiological properties including yield of photosystem II photochemistry (ФPSII), A, and E without improving biomass. Combined application of K and Zn at highest concentrations decreased R/Sh by 93% compared to the control. Rate of increase was higher in E than that of A leading to reduction in water use efficiency. High Zn concentration in saline soils increased non-photochemical quenching and energy loss in form of heat. Under non-saline condition, Zn application significantly decreased A probably due to inhibitory effect on electron transfer within photosystem II. K significantly increased stomatal conductance and accordingly E. GEx parameters were more sensitive to used treatments than ChlF parameters. Based on GEx and ChlF responses, the most salt-tolerant cotton seedlings were obtained under combined application of 50 kg K2SO4 ha−1 and 50 kg ZnSO4 ha−1, thus these concentrations are recommended for optimal establishment of cotton seedlings under salinity stress.

Salt tolerance enhancement Of wheat (Triticum Asativium L) genotypes by selected plant growth promoting bacteria.

The study was conducted at green house and laboratories of Agriculture Botany Department, Faculty of Agriculture, Suez Canal University, Ismailia governorate, Egypt during 2018/2019 to test rhizosphere growth promoting bacteria as known strategy to increase salinity tolerance of six genotypes of wheat namely; Line 404, Line 356, Line 420, Line432, Sakha 93 and Line 380 were grown under 3000 ppm and 5000 ppm of salinity. Four bacterial strains were used namely; Pseudomonas fluorescens NBRC 14160, Serratia liquefaciens ATCC 27592, Bacillus subtilis SBMP4 and Bacillus megaterium NBRC 15308. All the strains could be able to tolerate salinity levels up to 3% NaCl and produced indole acetic acid (IAA). The both strains Pseudomonas fluorescens NBRC 14160 and Bacillus megaterium NBRC 15308 were grow on NA media supplemented with 6% NaCl, and showed 1-aminocyclopropane-1-carboxylate (ACC) deaminase activity and Pseudomonas fluorescens NBRC 14160 strain also fixed nitrogen. PCR results confirmed the previous results for both strains. Pseudomonas fluorescens NBRC 14160 and Bacillus megaterium NBRC 15308 were selected to study their reflection in vivo on wheat plants growth at different levels of salinity. The selected strains were able to improve plants growth under salinity stress conditions when compared with non-inoculated plants for all wheat genotypes especially sakha93 showed the highest mean values over rest genotypes under saline and non-saline conditions. Results of genetic parameters for studied traits showed that values of PCV were higher than GCV values for most studied traits. Germination percentage, shoot length and potassium content had high values of heritability and genetic advance, so these traits might use in selection of plant breeding programs for salinity tolerance.

Jasmonic and Abscisic Acid Contribute to Metabolism Re-adjustment in Strawberry Leaves under NaCl Stress

ABSTRACT The aim of this research was to evaluate the effect of exogenous jasmonic acid and abscisic acid, at different salinity regimes, on primary and secondary metabolic changes in ʻKurdistanʼ and ʻQueen Elisaʼ strawberry leaves. To this end, strawberry plants were induced by gradual NaCl salinity (10 mmol•L−1) and shock salinity. The plants were sprayed with ABA (40 mmol•L−1) and JA treatments up to 40 mmol•L−1. In both cultivars, salt shock stress significantly enhanced the total antioxidant capacity, though the JA treatment outperformed the ABA treatment. Increasing JA level in the presence of ABA resulted in downswing in total phenolic content (6.42% in ʻKurdistanʼ and 23.13% in ʻQueen Elisaʼ) and antioxidant capacity (12.9% in ʻKurdistanʼ and 17.7% in ʻQueen Elisaʼ) at non-saline conditions. Adding both hormonesresulted in a 20.82% increase in total phenolic content and a 17.86% increase in total antioxidant capacity in ‘Kurdistan’ at gradual salt stress; however, in ʻQueen Elisaʼ, the same treatment resulted in 21.98% increase in total phenol and 11.92% increase in total antioxidant capacity at salt shock. Salt shock induced tyrosine increase and both hormones enhanced asparagine, alanine, histidine, and GABA contents in ʻQueen Elisaʼ. The study reveals that the applation of abscisic acid along with different jasmonic acid concentrations activates the protective mechanism of the strawberry plant against NaCl stress. Further studies are needed to compare the exact salt stress tolerance mechanisms for these cultivars. Abbreviations: JA: Jasmonic acid; ABA: Abscisic Acid; GABA: γ-Aminobutyric acid

Combined effects of brassinosteroid and kinetin mitigates salinity stress in tomato through the modulation of antioxidant and osmolyte metabolism

Salinity stress reduces growth and yield productivity of most crop plants. Potentiality of kinetin (Kn) and epi-brassinolide (EBL), either individually or combinedly in preventing the salinity (100 mM NaCl) stress mediated oxidative damage and photosynthetic inhibition was studied in Solanum lycopersicum. Combined application of Kn and EBL imparted much prominent impact on the growth, photosynthesis and metabolism of antioxidants, osmolytes and secondary metabolites. Synthesis of chlorophylls and carotenoids increased and the photosynthetic parameters like stomatal conductance, intercellular CO2 concentration and net photosynthesis were significantly improved due to application of Kn and EBL. Photosystem II functioning (Fv/Fm), photochemical quenching and electron transport rate (ETR) improved significantly in Kn and EBL treated plants imparting significant decline in salinity induced non-photochemical quenching. Exogenous Kn and EBL effectively prevented the oxidative damage by significantly declining the generation of hydrogen peroxide and superoxide under saline and non-saline conditions as reflected in lowered lipid peroxidation and electrolyte leakage. Reduced oxidative damage in Kn and EBL treated plants was accompanied down-regulation of protease and lipoxygenase concomitant with up-regulation of the antioxidant system and the accumulation of compatible osmolytes. Treatment of Kn and EBL proved effective in enhancing the contents of redox homeostasis, ascorbic acid and reduced glutathione, and the secondary metabolites assisting the enzymatic antioxidant system in combating the salinity stress efficiently. Results suggest that combined application of Kn and EBL regulate growth and photosynthesis in tomato more effectively than their individual application through a probable regulatory crosstalk mechanism.

Identification and denitrification characteristics of a salt-tolerant denitrifying bacterium Pannonibacter phragmitetus F1

A salt-tolerant denitrifying bacterium F1 was isolated in this study, which has high nitrite (NO2−–N) and nitrate (NO3−–N) removal abilities. The salt tolerance capacity of strain F1 was further verified and the effects of initial pH, initial NaNO2 concentration and inoculation size on the denitrification capacity of strain F1 under saline conditions were evaluated. Strain F1 was identified as Pannonibacter phragmitetus and named Pannonibacter phragmitetus F1. This strain can tolerate NaCl concentrations up to 70 g/L, and its most efficient denitrification capacity was observed at NaCl concentrations of 0–10 g/L. Under non-saline condition, the removal percentages of NO2−–N and NO3−–N by strain Pannonibacter phragmitetus F1 at pH of 10 and inoculation size of 5% were 100% and 83%, respectively, after cultivation for 5 days. Gas generation was observed during the cultivation, indicating that an efficient denitrification performance was achieved. When pH was 10 and the inoculation size was 5%, both the highest removal percentages of NO2−–N (99%) and NO3−–N (95%) by strain Pannonibacter phragmitetus F1 were observed at NaCl concentration of 10 g/L. When the NaCl concentration was 10 g/L, strain Pannonibacter phragmitetus F1 can adapt to a wide range of neutral and alkaline environments (pH of 7–10) and is highly tolerant of NaNO2 concentration (0.4–1.6 g/L). In conclusion, strain Pannonibacter phragmitetus F1 has a great potential to be applied in the treatment of saline wastewater containing high nitrogen concentrations, e.g. coastal aquaculture wastewater.

Modulation in growth, gas exchange, and antioxidant activities of salt-stressed rice (Oryza sativa L.) genotypes by zinc fertilization

Salt stress poses a major threat against rice that is reinforced by Zn deficiency especially in calcareous and alkaline soils due to high pH, calcareousness, and climate of arid to semi-arid. The current study was conducted with the objective to ameliorate the salt stress impact through exogenous Zn application. There were four rice genotypes (BAS-2000, KSK-133, IR-6, and BAS-198) that were subjected to two salinity levels (control and 70 mM) in the presence of two levels of zinc (control and 15.00 mg kg−1). Results revealed that salinity stress adversely affected the biochemical, morphological, and physiological activities of all rice genotypes. The application of Zn significantly improved the crop performance both under saline and non-saline conditions. Studies further exhibited that KSK-133 is found as a leading genotype at salt-stressed conditions by showing less reduction in plant growth attributes, i.e., plant biomass, SPAD value, stomatal conductance, photosynthetic rate, transpiration rate, antioxidant enzymes such as superoxide dismutase (SOD) and catalase (CAT) activities, Zn concentration, and K: Na relative to percent of control treatment. The results of our experiment clearly indicated that under salt-stressed conditions, KSK-133 performed well than BAS-2000 and IR-6 while genotype BAS-198 was observed to be sensitive against salinity stress. In case of non-saline conditions by Zn application, BAS-2000 performed well compared with others.

Nitrogen availability prevents oxidative effects of salinity on wheat growth and photosynthesis by up-regulating the antioxidants and osmolytes metabolism, and secondary metabolite accumulation

BackgroundSalinity is one of the damaging abiotic stress factor. Proper management techniques have been proposed to considerably lower the intensity of salinity on crop growth and productivity. Therefore experiments were conducted to assess the role of improved nitrogen (N) supplementation on the growth and salinity stress tolerance in wheat by analyzing the antioxidants, osmolytes and secondary metabolites.ResultsSalinity (100 mM NaCl) stress imparted deleterious effects on the chlorophyll and carotenoid synthesis as well as the photosynthetic efficiency. N supplementation resulted in increased photosynthetic rate, stomatal conductance and internal CO2 concentration with effects being much obvious in seedlings treated with higher N dose. Under non-saline conditions at both N levels, protease and lipoxygenase activity reduced significantly reflecting in reduced oxidative damage. Such effects were accompanied by reduced generation of toxic radicals like hydrogen peroxide and superoxide, and lipid peroxidation in N supplemented seedlings. Antioxidant defence system was up-regulated under saline and non-saline growth conditions due to N supplementation leading to protection of major cellular processes like photosynthesis, membrane structure and function, and mineral assimilation. Increased osmolyte and secondary metabolite accumulation, and redox components in N supplemented plants regulated the ROS metabolism and NaCl tolerance by further strengthening the antioxidant mechanisms.ConclusionsFindings of present study suggest that N availability regulated the salinity tolerance by reducing Na uptake and strengthening the key tolerance mechanisms.

Arbuscular mycorrhizal colonization increases yield of mungbean (Vigna radiata L.) at moderate level of salinity

ABSTRACT Mungbean is an important crop species cultivated in Southeast Asia and middle east regions where expanded salinity is a central point restricting plant development and yield profitability. In the present study, the impact of arbuscular mycorrhizal (AM) inoculation on improving biomass, plant resilience, nodulation, AM colonization, sporulation, yield, yield traits, nutrient concentration and uptake of mungbean under five salinity levels was investigated. The trial was laid in a factorial randomized completely block design with four replications. Five salinity treatments (0, 2, 4, 6 and 8 dS m−1) considered as the first factor and mycorrhizal inoculation as the second factor. The soil-based AM fungal inoculum containing 275 ± 20 spores along with colonized Sorghum bicolor root sections was applied to each mycorrhizal pot. The results demonstrated that mycorrhizal inoculation increased yield and other yield contributing traits of mungbean relative to non-mycorrhizal plants under saline conditions. The increased yield and yield traits might be associated with increased dry biomass, plant resilience, nodulation, colonization, nutrient concentration and uptake of mungbean under AM inoculation. Plant resilience was noteworthy in mycorrhizal plants (96.6%, 87.6%, 81.3%, and 74.7% treated with 2, 4, 6, and 8 dS m−1, respectively) than in non-mycorrhizal plants (92.4%, 76.9%, 68.2%, and 63.0%, respectively). The effect of AM inoculation was more conspicuous in soil with more salinity. Nutrient concentration increased in mungbean due to AM inoculation. At different salinity, the root biomass was also higher in AM inoculated mungbean, relative to non-inoculated plant. Eventually, nutrients uptake per plant increased by 21.4%, 26.0%, 20.1%, 20.2%, 23.7%, 22.9%, 32.4%, and 26.9% of N, P, K, S, Ca, Mg, B, and Zn, respectively, in mungbean due to AM inoculation relative to non-mycorrhizal plants. The plant dry biomass, nodulation, colonization, nutrient concentration, and uptake were increased by AM inoculation under saline and non-saline conditions leading to an improved yield of mungbean.

Effects of Gellan Oligosaccharide and NaCl Stress on Growth, Photosynthetic Pigments, Mineral Composition, Antioxidant Capacity and Antimicrobial Activity in Red Perilla.

The growing market demand for plant raw materials with improved biological value promotes the extensive search for new elicitors and biostimulants. Gellan gum derivatives may enhance plant growth and development, but have never been used under stress conditions. Perilla (Perilla frutescens, Lamiaceae) is a source of valuable bioproducts for the pharmaceutical, cosmetic, and food industries. However, there is not much information on the use of biostimulators in perilla cultivation. In this work we investigated the effects of oligo-gellan and salt (100 mM NaCl) on the yield and quality of red perilla (P. frutescens var. crispa f. purpurea) leaves. Plants grown under stress showed inhibited growth, smaller biomass, their leaves contained less nitrogen, phosphorus, potassium, total polyphenol and total anthocyanins, and accumulated considerably more sodium than control plants. Treatment with oligo-gellan under non-saline conditions stimulated plant growth and the fresh weight content of the above-ground parts, enhanced the accumulation of nitrogen, potassium, magnesium and total polyphenols, and increased antioxidant activity as assessed by DPPH and ABTS assays. Oligo-gellan applied under saline conditions clearly alleviated the stress effects by limiting the loss of biomass, macronutrients, and total polyphenols. Additionally, plants pretreated with oligo-gellan and then exposed to 100 mM NaCl accumulated less sodium, produced greater amounts of photosynthetic pigments, and had greater antioxidant activity than NaCl-stressed plants. Irrespective of the experimental treatment, 50% extract effectively inhibited growth of Escherichia coli and Staphylococcus aureus. Both microorganisms were the least affected by 25% extract obtained from plants untreated with either NaCl or oligo-gellan. In conclusion, oligo-gellan promoted plant growth and enhanced the quality of red perilla leaves and efficiently alleviated the negative effects of salt stress.

Effects of Rhizobium Strain on the Growth, Nodulation, N2 Fixation and Ions Accumulation in Vicia Faba Plant Under Salt Stress

Vicia faba L.-rhizobia symbiosis is utilized in different biological ways to improve the productivity of faba beans. This research aims to analyze the effects of the Rhizobium strain on nodulation, N2 fixation, growth, and ion accumulation under salt stress in Viciafaba. The commercial cultivar of faba beans (Viciafaba L. var. minor) was inoculated with the Rhizobium leguminosarumbiovar, by considering viciae strains S10 and S16, after 15 days of growth. This inoculation was carried out in the solution culture consisting of two salt concentrations; 0 mmole l-1NaCl and 50 mmole l-1NaCl. The results revealed that under saline and non-saline conditions, S10 and S16 strains of Rhizobium leguminosarum resulted in the formation of ineffective and effective symbiosis with faba beans. However, the presence of salt stress resulted in increasing the biomass of nodule and nitrogen content. The concentrations of sodium and chloride, in shoot and root, were increased in the presence of salinity. However, potassium concentration was only increased in the shoot. With and without salinity, phosphorus concentration in the shoots was not modified. The results revealed that the salt tolerance of faba beans, inoculated with two strains of Rhizobium were found to possess association with their stable growth. Moreover, the salt tolerance of faba beans inoculated with two salts tolerant rhizobia was also associated with an increment in the capacity of faba beans to increase nodulation and the concentration of shoot N2, Na and Cl-content. In addition, salt tolerance of this variety, inoculated with Rhizobium strains was associated with a decrement in the concentration of K+ in shoot under the salt constraints.

Heteromorphic seeds of coastal halophytes Arthrocnemum macrostachyum and A. indicum display differential patterns of hydrogen peroxide accumulation, lipid peroxidation and antioxidant activities under increasing salinity

Reactive oxygen species homeostasis during germination of heteromorphic seeds is not fully understood. This study elucidates changes in levels of hydrogen peroxide (H2O2), malondialdehyde (MDA) and enzymatic antioxidants in heteromorphic seeds of contrasting congeneric halophytes Arthrocnemum macrostachyum (C3 perennial) and A. indicum (C4 perennial) during germination under increasing salinity. There was no dormancy in A. macrostachyum (black and brown) and A. indicum (large and small) seeds. Seeds of A. macrostachyum displayed greater salinity tolerance compared to A. indicum seeds. Under non-saline conditions, large A. indicum seeds and brown A. macrostachyum seeds showed slightly higher germination than their respective counterparts. H2O2 content of black compared to brown A. macrostachyum seeds increased with salinity and that of small compared to large A. indicum seeds increased only in 400 mM NaCl. High catalase and ascorbate peroxidase with constitutive superoxide dismutase levels coincided with unaltered MDA in black A. macrostachyum seeds under salinity. Whereas, there was a decline in most antioxidant enzyme activities alongside low/unchanged H2O2 in the brown A. macrostachyum seeds under salinity. Unaltered H2O2 and MDA with low/unchanged antioxidant enzyme activities in large A. indicum seeds under salinity occurred. Unchanged enzyme activities alongside a rise in H2O2 and MDA levels were observed in the small A. indicum seeds under salinity. These data hence highlight differential H2O2 homeostasis strategies in the heteromorphic seeds of the test species.

A large-scale screening of quinoa accessions reveals an important role of epidermal bladder cells and stomatal patterning in salinity tolerance

The presence of epidermal bladder cells (EBCs) in halophytes allows considerable amount of Na+ being accumulated in these external structures, away from the metabolically active mesophile cells. Also, stomatal patterning may represent a primary mechanism by which plants can optimise its water-use efficiency under saline condition. This investigation was aimed to explore the varietal differences in a salinity tolerance of quinoa (Chenopodium quinoa) by evaluating a broad range of accessions and linking the overall salinity tolerance with changes in stomatal characteristics and EBC parameters. One hundred and fourteen accessions were grown under temperature-controlled glasshouse under non-saline and 400 mM NaCl conditions, and different physiological and anatomical characteristics were measured. Accessions were classified into three classes (sensitive, intermediate and tolerant) based on a relative dry weight defined as salinity tolerance index (STI). Results showed a large variability in STI indicating a strong genetic variation in salinity tolerance in quinoa. Bladders density was increased in a majority of accessions under saline condition while the bladder’s diameter remained unchanged; this resulted in a large variability in a bladder’s volume as a dependant variable. Stomata density remained unchanged between saline and non-saline conditions while the stomata length declined between 3% to 43% amongst accessions. Leaf Na+ concentration varied from 669 μmol/gDW to 3155 μmol/gDW under saline condition and, with an exception of a few accessions, leaf K+ concentration increased under saline conditions. Correlation analysis indicated a significant positive association between EBC diameter and STI on one hand and EBC volume and STI on the other hand, in a salt-tolerant group. These observations are consistent with the role of EBCs in sequestration of toxic Na+ in the external structures, away from the cytosol. A negative association was found between EBC density and diameter in salt-sensitive plants. A negative association between STI and stomata length was also found in a salt-tolerant group, suggesting that these plants were able to efficiently regulate stomatal patterning to balance water loss and CO2 assimilation under saline conditions. Both salt-sensitive and salt-tolerant groups had the same Na+ concentration in the shoot under saline conditions; however, a negative association between leaf Na+ concentration and STI in salt-sensitive plants indicated a more efficient Na+ sequestration process into the EBCs in salt-tolerant plants.

Ecological role of bracteoles in seed dispersal and germination of the North African halophyte Atriplex mollis under contrasting environments

ABSTRACTThe patterns of germination responses of Atriplex mollis seeds reveal species-specific tolerances and represents the adaptive strategies of species to stressful environments. To the best of our knowledge, this is the first report about germination patterns of A. mollis providing basic information for its conservation and reintroduction into degraded lands. Herein, two seed lots, with and without bracteoles, were tested for germination (i.e. salinity and drought). The highest germination percentage was under non-saline conditions, and with increasing NaCl-salinity, seed germination is inhibited. Bracteoles did not affect germination at low salinity levels, but significant inhibition becomes evident at −0.75 MPa. Moreover, PEG-induced osmotic stress had an adverse effect on germination of seeds with or without bracteoles at −0.75 MPa (ca. 20% and 10%, respectively). Bracteoles have a significant decreased effect on germination during recovery; they showed more detrimental effects following NaCl than PEG incubation. Importantly, the flotation of dispersal units with bracteoles was less than 60% under in freshwater and reached 100% at 27 g NaCl L−1. It is concluded that bracteoles play a dual role by inhibiting germination under high salinity levels and enhancing it under less negative osmotic potential.

Unveiling Purple Bacteria Salt Tolerance Mechanisms for Environmental Monitoring in Photo-Bioelectrochemical Systems

Photo-bioelectrochemical systems allow for the integration of photosynthetic bacteria at an electrode surface for the conversion of solar energy into electrical current.1 Among various applications, these systems open for the continuous monitoring of toxic compounds in the environment based on their cytotoxic effects on bacteria activity. However, a challenge for the on-field application is the exposure of bacterial cells to a diverse range of condition, requiring robust, versatile microorganisms capable of tolerating dynamic environments. Rhodobacter capsulatus (R. capsulatus) is a purple, photosynthetic bacterium with an outstanding versatile metabolism. Specifically, its versatility is thought to be due to a bacteria phage-like element, the R. capsulatus gene transfer agent (rcGTA), enabling horizontal gene transfer across microorganisms, which results in an expedited evolution to new environmental stresses. The rcGTA has been seen to facilitate resistance to antibiotics2 and provides a mechanism for adaptation to various environmental conditions. Integrating this bacterium with an electrode for photo-bioelectrochemical system development proves to be challenging due to the active redox center’s location inside of the thick cellular membrane. Previous work in our group has succeeded in mediating this redox active center employing monomeric quinones for mediating the extracellular electron transfer to the electrode.3 Current research is focused on engineering redox hydrogels to enhance the extracellular electron transfer in high saline, resulting in equal or higher currents compared to non-saline. To further improve photo-bioelectrocatalysis performance through adaptation of the cells to high saline conditions, we investigated the adaptation mechanism using techniques to study the rcGTA, and bioinformatics to evaluate differential expression of genes in both saline and non-saline conditions. Further research will be focused on harnessing these findings to decrease adaptation time to high salinities and evaluating the bioelectrochemical performance of these adapted strains through chronoamperometry and cyclic voltammetry experiments. The successful completion of this study will contribute towards the design of a photo-bioelectrochemical system for toxic compound detection in high saline conditions, and further increase our knowledge of salt adaptation mechanisms and the gene transfer agent of Rhodobacter capsulatus.

Genetic-environment interaction and genetic advance of superior wheat mutants by Francis and Kannenberg’s method

Increasing salinity, in the coastal area, is one of the major reasons of reducing wheat production. It is necessary to develop high yielding salt tolerant genotypes for sustainable yield of wheat in these areas. In our previous study, 37 lines were selected based on Francis and Kannenberg (1978) method following mean and standard deviation (SD) constructed in scattered plot diagram. In the present study, these selected lines along with ‘Prodip’ were grown in two different conditions: one is non-saline condition (BINA, Mymensingh) and another is saline condition (BINA, Satkhira). These wheat genotypes were evaluated to select the best performing lines which are stable in both the environment for their yield attributes. In RCBD trail with 3 replications, it was revealed that there were variations for plant height, flag leaf duration, spike length, spikelets per spike, 100-grain weight, number of tiller and yield per plant. Plant height, spikelets per spike and yield per plant showed higher heritability, higher phenotypic coefficient of variation and genetic advance. However, spike length, number of tiller and flag leaf duration showed medium heritability. Genotype-environment interaction and stability analysis showed variation for plant height, flag leaf duration, 100 grain weight and yield per plant and the line L-61-18, L-879-2, L-879-22, L-880-7, L-880-18 and L-880-43 were the most potential and stable genotypes in both saline and non-saline environments for yield. Higher selection score was obtained from L-880-38 followed by L-879-34 and L-880-36 and lower selection score was obtained from L-880-34 respectively. Importance should be given on plant height, spike length, spikelet per spike and yield per plant for selection of salt tolerant wheat line in future wheat research programme.
 Progressive Agriculture 30 (1): 20-31, 2019

Modulation of C:N:P stoichiometry is involved in the effectiveness of a PGPR and AM fungus in increasing salt stress tolerance of Sulla carnosa Tunisian provenances

Sulla carnosa (Hedysarum carnosum Desf.) is an important legume grown as animal feed on salt-affected areas. Here, we assess the influence of plant-growth-promoting bacteria (PGPR) (Bacillus subtilis) with or without the mycorrhizal fungus (AMF) Rhizophagus intraradices on four S. carnosa Tunisian provenances (Sidi khlif, Thelja, Kalbia and Kerker) grown in the greenhouse under saline and non-saline conditions. Plant growth, mineral nutrition, C:N:P stoichiometry in plant shoots, and soil enzymatic activities were considered. Microbial effectiveness on plant (roots and shoots) growth ranged from insignificant in Kerker to highly positive in the provenances Sidi khlif and Kalbia. In the latter provenance, the positive effect on growth was more pronounced under dual than single inoculation. Plant growth declined significantly under salt stress compared to the control, but Sidi khlif provenance was the most severely impacted. Especially in Kalbia, shoot mineral (N, P, K, Mg, Cu, and Fe) concentrations increased significantly in salt-stressed plants inoculated with R. intraradices as compared to the salt-stressed and non-inoculated plants. This suggests that inoculation with R. intraradices during nursery establishment contributes to salt stress alleviation by maintaining a favourable nutrient profile in Kalbia provenance. Shoots of Sidi khlif plants inoculated with B. subtilis demonstrated distinct C:N:P stoichiometry as compared to salt-treated and non-inoculated plants, indicating that B. subtilis could increase plant tolerance to salt stress through nutrient allocation patterns. The efficiency of B. subtilis in Kalbia and Thelja was due to the high IAA production by this strain under stress conditions. Application of PGPR and AMF improved soil quality by increasing the activities of soil enzyme such as urease, alkaline phosphatase, β-glucosidase and dehydrogenase compared to their respective non-inoculated controls. From this study, we conclude that microbial inoculation was necessary for S. carnosa provenances to reach their optimal nutrition under saline and non-saline conditions. Thus, the use of adequate microbial inocula and provenance could be a critical issue for the successful ecological stability of this Mediterranean legume, thereby improving its suitability for the remediation of saline lands.

A quantitative approach for fertilizer recommendation under saline conditions

ABSTRACTAll existing fertility models are originally derived for non-saline conditions. Under salinity, fertilization is challenging and may lead to amelioration or deterioration of plant salt tolerance. This investigation aimed to develop new deterministic models for fertilizer recommendation in salt-affected soils integrating salinity and fertility models. Based on statistical parameters, the nutritional-salinity nonlinear-nonlinear model was the most efficient followed by the linear-nonlinear model. The latter is preferred due to its simplicity. Model parameters were expressed as functions of nutrient rates and demonstrated drastic variations under fertilization. Zinc deficiency was more limiting than salinity while salinity was more detrimental than potassium deficiency. The EC causing 50% yield reduction () varied from 15 dS m−1 in control treatment to, respectively, 17 and 8 dS m−1 at highest zinc and potassium rates. Similarly, salinity threshold () value was altered from 5 dS m−1 to 6.4 and 3 dS m−1. Accordingly, application of 100 and 50 kg ha−1 zinc and potassium appeared to be promising to improve cotton seedling vigor under severe salinity (15 dS m−1). Although and inconsistently change under fertilization, our proposed models can reasonably well estimate the required fertilizer quantity to achieve the yield goal under certain soil salinity.

Potassium Silicate Improves Salinity Resistant and Affects Fruit Quality in Two Strawberry Cultivars Grown Under Salt Stress

ABSTRACTThe response of ‘Kurdistan’ and ‘Paros’ strawberry cultivars to potassium silicate (K2O3Si) under sodium chloride (NaCl) salinity stress was studied in terms of vegetative parameters, sodium (Na) and potassium (K) content and fruit quality. K2O3Si could recover dry mass distribution of NaCl-stressed strawberry organs. Kurdistan cultivar tended to keep higher dry weight of leaves to maintain its photosynthetic apparatus activity. Inhibitory impact of K2O3Si on Na uptake of leaf was more obvious than root. Implementation of K2O3Si in some cases increased Total Soluble Solid (TSS) and Titratable Acidity (TA), which are the main factors determining taste of strawberry fruit. Furthermore, phenols and flavonoids were increased in Paros cultivar by effect K2O3Si under saline and non-saline conditions, respectively. Overall, our data suggest that silicon supply in strawberry plants not only could be used as a routine strategy to maintain growth and yield under salinity but also it could be beneficial for improvement of fruit quality attributes and health-related constituents.Abbreviations: ANOVA: Analysis of Variance; CRD: Completely Randomized Design; DPPH: 1,1-Diphenyl-2-picryl-hydrazyl; FF: Fruit Firmness; LSD: Least Significant Difference; PAL: Phenyl Alanine Ammonia Lyase; ROS: Reactive Oxygen Species; TSS: Total Soluble Solid; TAA: Total Antioxidant Activity; TA: Titratable Acidity; TAC: Total Anthocyanin; TF: Total Flavonoids; TP: Total Phenolics;

Effect of exogenous application of salicylic acid on salt-stressed sorghum growth and nutrient contents

This study was conducted to investigate the effect of salinity and foliar application of salicylic acid (SA) on sorghum biomass and nutrient contents. Treatments were comprised of salinity levels (0 and 100 mM NaCl) and SA concentrations (0.3, 0.7, 1.1 and 1.5 mM). Salinity increased sodium (Na), chlorine (Cl) and copper (Cu) but decreased nitrogen (N), phosphorus (P), potassium (K), magnesium (Mg), sulfur (S), iron (Fe), zinc (Zn) and manganese (Mn) contents and the root and shoot dry matter. Fe and Zn were the most affected nutrients by salinity. However, SA reduced Na and Cl but increased plant dry matter and nutrient content. SA had greater positive effects on root than on shoot dry matter. Maximum increases through SA were achieved in N, K, Fe, Mn, Cu, and shoot weight under salt stress but in Zn and root weight under non-saline condition. In most cases 1.1 mM was the most effective SA concentration in reducing the negative effects of salinity.