Salicylic Acid Content Research Articles

Effect of lipid-polysaccharide edible coatings on enhancing shelf life and quality of guava (Arka Kiran)

The physicochemical properties of guava (Arka Kiran) fruits were examined in relation to pre- and post-harvest treatments, both individually and in combination, using various edible compounds, including hexanal, chitosan, and salicylic acid. The fruits were treated with different concentrations of hexanal (2%), chitosan (1%), and salicylic acid (500 ppm) and assessed for various physico–chemical parameters. In the storage study, guava fruits treated with these edible compounds were stored under both ambient conditions (30°C ± 1°C) and cold storage conditions (10 ± 2°C). The fruits treated with 2% hexanal demonstrated the most significant improvements in quality-related parameters under cold storage and ambient conditions. The combination of pre-harvest spray and post-harvest treatments using 2% hexanal in cold storage significantly delayed physiological weight loss (24.55%), preserved total soluble solids (10.25 ºBrix), and maintained ascorbic acid content (135.05µg) by the 18th day of the storage period. Furthermore, pre-and post-harvest treatment with chitosan under cold storage conditions significantly enhanced the retention of antioxidant activity and phenolic content in guava fruit. Overall, the treatment with 2% hexanal proved to be the most effective in regulating physicochemical changes and improving the storage quality of guava fruits.

Characterization of the chitinase gene family in Saccharum reveals the disease resistance mechanism of ScChiVII1.

A chitinase gene ScChiVII1 which is involved in defense against pathogen stress was characterized in sugarcane. Chitinases, a subclass of pathogenesis-related proteins, catalyze chitin hydrolysis and play a key role in plant defense against chitin-containing pathogens. However, there is little research on disease resistance analysis of chitinase genes in sugarcane, and the systematic identification of their gene families has not been reported. In this study, 85 SsChi and 23 ShChi genes, which were divided into 6 groups, were identified from the wild sugarcane species Saccharum spontaneum and Saccharum hybrid cultivar R570, respectively. Transcriptome analysis and real-time quantitative PCR revealed that SsChi genes responded to smut pathogen stress. The chitinase crude extracted from the leaves of transgenic Nicotiana benthamiana plants overexpressing ScChiVII1 (a homologous gene of SsChi22a) inhibited the hyphal growth of Fusarium solani var. coeruleum and Sporisorium scitamineum. Notably, the chitinase and catalase activities and the jasmonic acid content in the leaves of ScChiVII1 transgenic N. benthamiana increased after inoculation with F solani var. coeruleum, but the salicylic acid, hydrogen peroxide, and malondialdehyde contents decreased. Comprehensive RNA sequencing of leaves before (0day) and after inoculation (2days) revealed that ScChiVII1 transgenic tobacco enhanced plant disease resistance by activating transcription factors and disease resistance-related signaling pathways, and modulating the expression of genes involved in the hypersensitive response and ethylene synthesis pathways. Taken together, this study provides comprehensive information on the chitinase gene family and offers potential genetic resources for disease resistance breeding in sugarcane.

Study on the Relationship between Secondary Metabolites and Resistance to Anthracnose in Stylosanthes

Stylosanthes is an excellent tropical leguminous forage. Anthracnose caused by Colletotrichum gloeosporioides is a major limiting factor in Stylosanthes production, which can lead to reduced forage and seed production and decreased quality. How to quickly screen resistant parents and varieties of Stylosanthes that are resistant to anthracnose has become an urgent problem to be solved in production. In this study, the high-performance liquid chromatography detection technology was established for simultaneous analysis of the content of salicylic acid, triethyl orthobenzoate, indazole, and soyasapogenol B in Stylosanthes leaves. The technology was further applied in the analysis of the relationship between secondary metabolites and resistance to anthracnose in 105 accessions of Stylosanthes. The result shows that salicylic acid is the most important factor for resistance to anthracnose. By detecting the content of salicylic acid in Stylosanthes leaves, a rapid screening technology for anthracnose-resistant parents and varieties of Stylosanthes was established, and 5 accessions of Stylosanthes with high resistance to anthracnose were screened. This study is of great significance to the Stylosanthes germplasm preservation and identification and its breeding.

Degradation of salicylic acid coordinated to Fe3O4 nanoparticles by H2O2

Salicylic acid (SA) has strong tendency to form complexes with iron (III). Depending upon the concentrations of SA, the complexes formed are FeR+, FeR2+, FeR32+where R represents salicylate ion (-OC₆H₄COO-). Fe3O4 nanoparticles binds with the salicylate ions through the sites having Fe3+ and at the site containing Fe2+ reacts with H2O2 to produces OH* radicals. The OH* radicals oxidise the salicylic acid attached to Fe3O4 nanoparticles. Thus, the degradation occurs through the formation of SA-Fe3O4 nanoparticles complexes and then followed by the reaction with H2O2 at the nanoparticle site. FT-IR, TGA were used to confirm the synthesis of Fe3O4 nanoparticles as well as to investigate SA-Fe3O4 nanoparticles complex formation and the degradation of the complex by H2O2. Spectrophotometric studies were employed for the monitoring of the degradation of SA at the surface. Here, the nanoparticles act as platform to which both the reactants SA and H2O2 get activated and the degradation reaction occurs. The concentrations of SA, H2O2, nanoparticle dosage, surfactants and polymers were changed and the % degradation were noted. It has been observed that the degradation percentage decreased with the increase in nanoparticle dosage, [surfactant] and [polymers]. The [H2O2] and [HClO4] gave peaked-like curve for the degradation of SA for the plot of % degradation versus concentrations of H2O2 and HClO4. Degradation of SA was observed maximum at [H2O2](= 8.0 × 10−4 mol dm−3) and at [HClO4] (= 1.0 × 10−2 mol dm−3).

Physiological characteristics during the formation of aromatic components in xylem of Aquilaria sinensis induced by exogenous substances.

An inductive combination of plant growth regulators, inorganic salts, and fungi is essential for the formation of aromatic components in the xylem of Aquilaria sinensis. However, the dynamics of xylem physiology and the relationships between physiological properties and aromatic components after artificial induction remain unclear. In this study, the changes in physiological properties of A. sinensis xylem during induction were determined and analyzed under four induction treatments and a control group. The defense hormone contents of jasmonic acid, salicylic acid, aminocyclopropane-1-carboxylic acid, and abscisic acid obtained from the four induction treatments increased significantly. However, the concentrations of gibberellin and indoleacetic acid were decreased compared to the control group. An initially upward and then downward trend was observed in the main antioxidant enzyme activities. Additionally, malonaldehyde content decreased obviously, while proline content tended to increase and then decrease as induction continued. The total and soluble sugar content was evidently reduced after treatment, and the soluble sugar content recovered more rapidly with time. Thirty-three aromatic components were identified in all treatments, and the primary aromatic components were terpenes, aromatics and chromones, the relative contents of which varied among treatments. These results provide new insights for optimization and innovation of agarwood induction techniques by exploring the formation of aromatics in the xylem of A. sinensis and its physiological responses following induction with exogenous substances (ethephon, NaCl, CaCl2 and fungal mixed solution).

Effect of elevated ammonium on biotic and abiotic stress defense responses and expression of related genes in cucumber (Cucumis sativus L.) plants

Ammonium (NH4+) enhances plant defense mechanisms but can be phytotoxic as the sole nitrogen source. To investigate the impact of a balanced NH4+ and NO3− ratio on plant defense parameters without adverse effects, cucumber plants (Cucumis sativus L.) were grown under control (14 mM NO3− + 2 mM NH4+) and elevated level of NH4+ (eNH4+, 8 mM NO3−+ 8 mM NH4+). Plants subjected to eNH4+ showed significantly increased shoot and root biomass by about 41% and 47%, respectively. Among the antioxidant enzymes studied, ascorbate peroxidase (EC 1.11.1.11) activity was increased up to 3.3 fold in eNH4+ compared with control plants, which was associated with enhanced resistance to paraquat. Upregulation of PATHOGENESIS RELATED PROTEIN 4 (PR4) and LIPOXYGENASE 1 (LOX1), accompanied by increased concentrations of salicylic acid and nitric oxide, conferred more excellent resistance of eNH4+ plants to powdery mildew infection. However, the expression levels of ACC OXIDASE 1 (ACO1) and RESPIRATORY BURST OXIDASE HOMOLOGS B (RBOHB) were lower in eNH4+ plants, which was consistent with decreased NADPH oxidase activity and lower leaf H2O2 levels. The biosynthesis of phenolics was enhanced, whereas the activities of polymerizing enzymes and lignin deposition were reduced by half in eNH4+ plants. Besides, a significant effect on plant biomass under salt or drought stress has not been observed between control and eNH4+ plants. These results showed that different defense pathways are distinctively affected by eNH4+ treatment, and the NH4+ to NO3− ratio may play a role in fine-tuning the plant defense response.

Atomistic insights into salicylic acid treatment on human keratinized skin by XPS combined with argon gas cluster sputtering: A pilot study

Stratum corneum is the skin's outermost layer, whose main constituent is keratin. The treatment of dermatological diseases showing hyperkeratosis is a serious problem in dermatology and cosmetics seriously affecting the population showing increasing prevalence. One of the treatment is a peeling agent like salicylic acid (SA), categorized as a keratolytic agent, however its mode of action is not fully understood. X-ray photoelectron spectroscopy (XPS) is a method for monitoring the changes of surface composition at atomistic level in 5–10 nm depth. The development of argon cluster sputtering enabled the investigation of deeper regions (nanometric level) even for biomaterials. In this pilot study, the mode of action of SA has been studied at atomistic level for the first time. Different concentrations of SA (3, 5, 10 wt%) in different time frames (1 day, 1 week, 1 month) was applied on human keratinized skin. The carbon, nitrogen and oxygen peak have not shown changes during the treatment, not showing the suggested desmolytic mechanism of SA. However, significant changes were observed in the sulfur peak, with increasing time and concentration the rate of sulfonate and sulfate was increased compared to thiol group indicating the break of sulfide bonds between the polypeptide chains in keratin, indicating that keratolysis happens at nanometric level. Already a 1 week-10 wt% SA treatment resulted in higher rate of sulfate compared to sulfonate indicating further oxidation of the keratolytic product. However, 1 month-10 wt% treatment resulted in the same surface composition as 3 wt%-1-month treatment indicating that enough time with low concentration can exert the same effect as higher concentrations. These findings have relevance in the design of future SA-based dermatologic therapies.

Salicylic acid altered the fatty acids compositions and nutrient status of shallot (Allium hirtifolium) grown under drought stress

In arid and semi-arid regions, water shortage is a persistent challenge, significantly affecting plant growth and productivity. To mitigate the detrimental effects of drought, the use of plant growth regulators, such as salicylic acid (SA), has proven to be an effective strategy for enhancing plant resilience, as well as improving yield and quality. This study aimed to investigate the impact of SA on the nutrient composition, yield, and overall quality of shallot plants over three cropping seasons (2020, 2021, and 2022) under drought stress conditions. A split-plot design with four replicates was employed, where irrigation levels (0 %, 50 %, 75 %, and 100 % of the plant's water requirements) were the main factor, and varying concentrations of SA (0, 0.5, 0.75, and 1 mM) were the secondary factor. The results revealed that drought stress increased the concentrations of key micronutrients—iron, copper, sodium, potassium, manganese, and zinc—while reducing magnesium content, ash content, and overall yield. However, the application of SA counteracted these effects by significantly enhancing magnesium content, ash content, and yield in shallot plants. In addition, drought stress increased the levels of palmitic, palmitoleic, and oleic acids while reducing the levels of stearic, linoleic, and linolenic acids. The highest concentrations of linoleic acid (ω6, 110.1 mg) and linolenic acid (ω3, 24.242 mg) were recorded under full irrigation and 75 % water requirement treatments, respectively. SA application further enhanced the levels of stearic, oleic, and linoleic acids, improving the overall nutritional quality of shallot plants. In conclusion, the application of optimal concentrations of SA significantly improves the yield, quality, and nutritional value of shallot plants under drought stress, making it a valuable approach for managing water stress in agriculture.

Integrative multi-omics analysis of chilling stress in pumpkin (Cucurbita moschata).

Pumpkin (Cucurbita moschata) is an important vegetable crop that often suffers from low-temperature stress during growth. However, the molecular mechanism involved in its response to chilling stress remains unknown. In this study, we comprehensively investigated the effect of chilling stress in pumpkin seedlings by conducting physiological, transcriptomic, and metabolomic analyses. Under chilling stress, there was an overall increase in relative electrical conductivity, along with malondialdehyde, soluble sugar, and soluble protein contents, but decreased superoxide dismutase and peroxidase activities and chlorophyll contents in seedling leaves compared with controls. Overall, 5,780 differentially expressed genes (DEGs) and 178 differentially expressed metabolites (DEMs) were identified under chilling stress. Most DEGs were involved in plant hormone signal transduction and the phenylpropanoid biosynthesis pathway, and ERF, bHLH, WRKY, MYB, and HSF transcription factors were induced. Metabolomic analysis revealed that the contents of salicylic acid (SA), phenylalanine, and tyrosine increased in response to chilling stress. The findings indicated that the SA signaling and phenylpropanoid biosynthesis pathways are key to regulating the responses to chilling stress in pumpkins. Overall, our study provides valuable insights into the comprehensive response of C. moschata to chilling stress, enriching the theoretical basis of this mechanism and facilitating the development of molecular breeding strategies for pumpkin tolerance to chilling stress.

Exogenous Salicylic Acid Regulates Fruiting Body Development, Secondary Metabolite Accumulation, Cell Wall Integrity, and Endogenous Salicylic Acid Content under Heat Stress in Pleurotus ostreatus.

High-temperature or heat stress (HS) represents a significant environmental challenge that adversely affects crop growth and poses a substantial threat to agricultural production. Pleurotus ostreatus, recognized as the second most widely cultivated edible fungus worldwide, is particularly susceptible to the detrimental effects of HS. Enhancing the HS resistance of P. ostreatus is crucial for increasing its yield. In a prior investigation, we discovered that salicylic acid (SA) enhanced the resistance of P. ostreatus mycelia to HS through a metabolic rearrangement. The present study further investigated the effects of SA on P. ostreatus under HS. Cultivation experiments revealed that exogenous SA improved the mycelium recovery growth rate, yield, and fruiting body quality after HS. Further experiments revealed that exogenous SA mitigated the damage to the MAPK-Slt2 signal produced by HS while maintaining cell wall integrity. Furthermore, we hypothesized that the phenylalanine ammonia-lyase pathway might serve as a source for SA. In this context, we identified two salicylic hydroxylases, Po1102164 and Po1104438. Both HS and exogenous SA were found to elevate intracellular SA levels, thereby enhancing the resistance of P. ostreatus to HS.

The Role of Salicylic Acid in Salinity Stress Mitigation in Dizygostemon riparius: A Medicinal Species Native to South America.

Salicylic acid (SA) is a bioregulator well-known for mitigating salinity damage in plants. However, no studies have examined the interaction between SA and salinity in Dizygostemon riparius, a species rich in bioactive molecules. Therefore, we aimed to evaluate the effect of SA application on Dizygostemon riparius under different salinity levels. A completely randomized experiment was conducted in a 2 × 3 factorial design (two SA concentrations of 0 and 100 µM and three salinity concentrations of 0, 200, and 400 mM NaCl) with five replicates. At 400 mM NaCl, leaf temperature increased by 11%, while relative water content and total soluble carbohydrates decreased by 30% and 35%, respectively, leading to reduced biomass accumulation. Notably, the SA application mitigated these effects by restoring relative water content under 400 mM NaCl and improving carboxylation efficiency and intrinsic water-use efficiency under 200 mM NaCl. Additionally, dry biomass was maintained under both 200 and 400 mM NaCl with SA treatment. These findings suggest that SA has a promising potential to alleviate salt stress in Dizygostemon riparius. Our results could inform cultivation practices, opening new perspectives on the use of SA as an attenuator of salinity stress.

Seasonal Changes in Salicylic and Jasmonic Acid Levels in Poplar with Differing Stress Responses

Poplars are essential tree species with critical roles in wood production, ecological conservation, environmental protection, and climate change mitigation. Plants of different poplar populations exhibit varying responses to biotic and abiotic stresses, largely driven by phytohormones—key regulators of plant growth and stress responses. Phytohormones control fundamental processes such as cell division, growth, tissue differentiation, organ development, and resistance to environmental challenges such as temperature extremes and drought. In this study, we conducted a quantitative analysis of phytohormone levels in the leaves of two populations of poplar species from the same geographical region over a one-year period, covering the early, mid, and late growth stages. Our results revealed that salicylic acid (SA) and jasmonic acid (JA) concentrations in the stress-resistant poplar (RP) increased significantly during the late growth stage (September), particularly in response to elevated pathogen pressure and fluctuating climatic conditions. In contrast, the susceptible poplar (SP) consistently exhibited lower levels of SA and JA across all growth stages, particularly during the mid-growth stage (characterized by high temperatures and low precipitation) and the late growth stage, when pathogen stress typically intensifies. The limited increase in phytohormone levels in the SP suggests a weaker defense response compared with the RP. These findings demonstrate that climatic factors significantly influence the phytohormonal dynamics in poplars, with the RP exhibiting more robust regulation of SA and JA to mitigate both biotic and abiotic stresses. This study provides a theoretical framework for better understanding the resistance mechanisms in Populus and offers insights for improving stress tolerance in future breeding programs.

Establishment of numerical model for precooling broccoli with ice water integrated with salicylic acid and its effect on broccoli apparent quality

Postharvest precooling is crucial for delaying yellowing of broccoli efficiently removing field heat. In this experiment, a numerical model for ice water precooling broccoli was established, and based on this, the main precooling parameters were optimized. Furthermore, the appropriate concentration of salicylic acid (SA) in the process of ice water integrated with SA precooling was determined. Through numerical simulation and experimental validation, the ice water precooling treatment with a 30 % ice volume fraction and a 1:1 mass ratio of ice water to broccoli was identified as optimal for achieving the best precooling uniformity and meeting the specified temperature requirements. Application of 2 mmol L-1 SA integrated with ice water precooling treatment effectively delayed yellowing, and maintained the apparent quality of broccoli, manifested as a higher h° value (chromaticity value) and chlorophyll content, a lower yellowing index. The shelf life of the treated broccoli was extended by 3 d

Isolation and Identification of Multi-Traits PGPR for Sustainable Crop Productivity Under Salinity Stress

High salinity poses a significant threat to arable land globally and contributes to desertification. Growth-promoting rhizobacteria assist plants in mitigating abiotic stresses and enhancing crop productivity through the production of siderophores, exopolysaccharides (EPS), solubilisation of phosphate, indole-3-acetic acid (IAA), and other secondary metabolites. This study aimed to isolate, identify, and characterise bacteria that exhibit robust growth-promoting properties. A total of 64 bacterial isolates from the rhizosphere of Miscanthus sinensis were evaluated for plant growth-promoting (PGP) traits, including IAA, EPS, siderophores, and solubilisation of phosphate. Among them, five isolates were selected as plant growth-promoting rhizobacteria (PGPR) based on their PGP features and identified via 16S rRNA sequencing: Enterococcus mundtii strain INJ1 (OR122486), Lysinibacillus fusiformis strain INJ2 (OR122488), Lysinibacillus sphaericus strain MIIA20 (OR122490), Pseudomonas qingdaonensis strain BD1 (OR122487), and Pseudomonas qingdaonensis strain MIA20 (OR122489), all documented in NCBI GenBank. BD1 demonstrated a higher production of superoxide dismutase (SOD) (17.93 U/mg mL), catalase (CAT) (91.17 U/mg mL), and glutathione (GSH) (0.18 U/mg mL), along with higher concentrations of IAA (31.69 µg/mL) and salicylic acid (SA) (14.08 ng/mL). These isolates also produced significant quantities of amino and organic acids. BD1 exhibited superior PGP traits compared to other isolates. Furthermore, the NaCl tolerance of these bacterial isolates was assessed by measuring their growth at concentrations ranging from 0 to 200 mM at 8-h intervals. Optical density (OD) measurements indicated that BD1 and INJ2 displayed significant tolerance to salt stress. The utilisation of these isolates, which enhances plant growth and PGP traits under salt stress, may improve plant development under saline conditions.

Spectrometric method for simultaneous quantification of nadifloxacin and salicylic acid in a novel topical dosage form

Acne vulgaris is a prevalent skin disorder that affects many individuals. In the search for effective acne therapy, researchers have found that a combination of Nadifloxacin and Salicylic Acid may produce a synergistic effect. To further investigate this, a study was conducted to devise a spectrophotometric method for simultaneously measuring the concentrations of Nadifloxacin and Salicylic Acid in a novel topical formulation. Simultaneous Estimation Method was employed using methanol as the solvent. Nadifloxacin exhibited an absorbance maximum of 291 nm, while Salicylic Acid showed an absorbance maximum of 297 nm in methanol. Linearity experiments were conducted to determine the concentration ranges for both drugs, which were found to be 2–12 ppm for Nadifloxacin and 5–30 ppm for Salicylic Acid. The recovery results of Nadifloxacin ranged from 82 % to 95 %, while those of Salicylic Acid ranged from 97 % to 110 %. These results indicate the accuracy and reliability of the method. This method was further validated in accordance with the guidelines provided by the International Council for Harmonization (ICH) of Technical Requirements for Human Use. The proposed method has demonstrated its applicability for the simultaneous and quantitative assessment of Nadifloxacin and Salicylic Acid in various dosage forms. This development is significant as it provides a reliable and efficient means of measuring the concentrations of these two drugs in acne therapy formulations.

Phytohormones and Mineral Nutrient Changes in Young Plants of Grapevine Genotypes at Different Growth Stages

Climate change is considered a threat for viticulture by altering phenology, yield, and key physiological processes. The plant responses depend on the genotype characteristics and the microclimate of crop area. In this research, “Castellana Negra”, “Negramoll”, and “Tintilla” were cultivated for 102 days, and physiological variables were assessed under natural conditions. Results indicated similar trends in growth between “Negramoll” and “Tintilla”, while ”Castellana Negra” grew slowly and possessed fewer leaves compared to the other genotypes. Stomatal conductance was constant among the genotypes, excepting “Negramoll”, which demonstrated lower values at d 76 compared to “Castellana Negra” and “Tintilla”, coinciding with the elevated leaf temperature. Regarding the hormonal changes, “Castellana Negra” accumulated the highest concentration of salicylic acid (SA) compared to “Negramoll” and “Tintilla”, which showed similar content. Furthermore, an antagonistic change between SA and jasmonic acid (JA) was observed in all genotypes, as well as between abscisic acid (ABA) and JA at the beginning and end of the trial. The variations in micronutrients did not show a clear tendency between cultivars. Therefore, to thoroughly elucidate the role of phytohormones and other physiological factors in the growth and development of these genotypes under varying environmental conditions, long-term experiments could be conducted.

Regulation of Physiological and Biochemical Mechanisms Related to Water Stress Tolerance in Barley and Improvement of Growth and Productivity Using Salicylic Acid and Chitosan

The present investigation aimed to assess the impacts of three Salicylic Acid (SA) concentrations (T2=100, T3=200, T4=300ppm), three Chitosan concentrations (T5=150, T6=225, T7=300ppm) and T8= Salicylic Acid (100 ppm) with Chitosan (150 ppm) mixture in comparison to control treatment (T1) on two barley cultivars Giza126 and Giza 134 under rainfed conditions. Some vegetative and yield traits were recorded, plant height, spike length, number of gains spike-1, number of spikes/m2, 1000 grain weight, biological and grain yield. A split plot design was performed with three replications. The field experiment was conducted in the northern west coast region of Egypt (Marsa Matruh government) under the rainfed condi­tions during 2019/2020 and 2020/2021 growing seasons. The results showed a direct relationship between increased foliar application and increased yield attributes. Results indicated that Giza 126 cultivar as affected by T4 showed the most desirable values for grains spikes-1 in first season, spikes/m2, biological yield and grain yield during the first and second seasons respectively. In addition, barley cultivar Giza 126 as affected by T3 showed the highest values for grains spikes-1 in second season. On the other hand, barley cultivar Giza 134 as affected by T4 showed the highest values for plant height, spike length and 1000-grain weight in first and second seasons respectively. From results, it can be concluded that the Salicylic Acid (SA) concentration 300 ppm is recommendable for improving the productivity of barley under rainfed conditions of Egypt. To study the potential role of SA and Chitosan on water stress tolerance mechanisms some biochemical and physiological parameters were recorded. Application of SA and Chitosan decreased significantly Reactive Oxygen Species (ROS) measuring by determined the concentrations of MDA and H2O2 especially SA with concentrations 300 ppm (T4). For osmolytes (proline, SSC and SPC), all treatments using SA and Chitosan induced significant increase in osmolytes content compared with control under water stress only in the two studied barley genotypes, except for treatment with Chitosan 225 and 300 ppm in Giza 126 for proline content. Similar results were recorded for antioxidant enzymes activity (CAT, POX and PPO) which showed up-regulation for all treatments compared with control under water stress for the two studied genotypes. On contrast, APX antioxidant enzyme recorded the highest activity in control treatment under water stress only. In general, for all studied treatments comparing with control, application of SA300 ppm and the mixture between SA100 and Chitosan150 ppm were the best treatment for induction of up and down regulation of biochemical and physiological component in the barley cells which is known as defense system against water stress damage.

Overexpressing CsSABP2 enhances tolerance to Huanglongbing and citrus canker in C. sinensis.

Huanglongbing (HLB) and citrus canker, arising from Candidatus Liberibacter asiaticus (CaLas) and Xanthomonas citri pv. Citri (Xcc), respectively, have been imposing tremendous losses to the global citrus industry. Systemic acquired resistance (SAR) has been shown to be crucial for priming defense against pathogen in citrus. Salicylic acid (SA) binding protein 2 (SABP2), which is responsible for converting methyl salicylate (MeSA) to SA, is essential for full SAR establishment. Here, we characterized the functions of four citrus SABP2 genes (CsSABP2-1, CsSABP2-1V18A , CsSABP2-2 and CsSABP2-3) against HLB and citrus canker. In vitro enzymatic assay revealed that all four proteins had MeSA esterase activities, and CsSABP2-1 and CsSABP2-1V18A has the strongest activity. Their activities were inhibited by SA except for CsSABP2-1V18A. Four genes controlled by a strong promoter 35S were induced into Wanjincheng orange (Citrus sinensis Osbeck) to generate transgenic plants overexpressing CsSABP2. Overexpressing CsSABP2 increased SA and MeSA content and CsSABP2-1V18A had the strongest action on SA. Resistance evaluation demonstrated that only CsSABP2-1V18A had significantly enhanced tolerance to HLB, although all four CsSABP2s had increased tolerance to citrus canker. The data suggested the amino acid Val-18 in the active site of CsSABP2 plays a key role in protein function. Our study emphasized that balancing the levels of SA and MeSA is crucial for regulating SAR and conferring broad-spectrum resistance to HLB and citrus canker. This finding offers valuable insights for enhancing resistance through SAR engineering.

Effects of Salicylic Acid on Physiological Responses of Pepper Plants Pre-Subjected to Drought under Rehydration Conditions.

Capsicum annuum L. has worldwide distribution, but drought has limited its production. There is a lack of research to better understand how this species copes with drought stress, whether it is reversible, and the effects of mitigating agents such as salicylic acid (SA). Therefore, this study aimed to understand the mechanisms of action of SA and rehydration on the physiology of pepper plants grown under drought conditions. The factorial scheme adopted was 3 × 4, with three water regimes (irrigation, drought, and rehydration) and four SA concentrations, namely: 0 (control), 0.5, 1, and 1.5 mM. This study evaluated leaf water percentage, water potential of shoots, chlorophylls (a and b), carotenoids, stomatal conductance, chlorophyll a fluorescence, and hydrogen peroxide (H2O2) concentration at different times of day, water conditions (irrigation, drought, and rehydration), and SA applications (without the addition of a regulator (0) and with the addition of SA at concentrations equal to 0.5, 1, and 1.5 mM). In general, exogenous SA application increased stomatal conductance (gs) responses and modified the fluorescence parameters (ΦPSII, qP, ETR, NPQ, D, and E) of sweet pepper plants subjected to drought followed by rehydration. It was found that the use of SA, especially at concentrations of 1 mM in combination with rehydration, modulates gs, which is reflected in a higher electron transport rate. This, along with the production of photosynthetic pigments, suggests that H2O2 did not cause membrane damage, thereby mitigating the water deficit in pepper plants. Plants under drought conditions and rehydration with foliar SA application at concentrations of 1 mM demonstrated protection against damage resulting from water stress. Focusing on sustainable productivity, foliar SA application of 1 mM could be recommended as a technique to overcome the adverse effects of water stress on pepper plants cultivated in arid and semi-arid regions.

Callose and Salicylic Acid Are Key Determinants of Strigolactone-Mediated Disease Resistance in Arabidopsis

Research has demonstrated that strigolactones (SLs) mediate plant disease resistance; however, the basal mechanism is unclear. Here, we provide key genetic evidence supporting how SLs mediate plant disease resistance. Exogenous application of the SL analog, rac-GR24, increased Arabidopsis thaliana resistance to virulent Pseudomonas syringae. SL-biosynthetic mutants and overexpression lines of more axillary growth 1 (MAX1, an SL-biosynthetic gene) enhanced and reduced bacterial susceptibility, respectively. In addition, rac-GR24 promoted bacterial pattern flg22-induced callose deposition and hydrogen peroxide production. SL-biosynthetic mutants displayed reduced callose deposition but not hydrogen peroxide production under flg22 treatment. Moreover, rac-GR24 did not affect avirulent effector-induced cell death between Col-0 and SL-biosynthetic mutants. Furthermore, rac-GR24 increased the free salicylic acid (SA) content and significantly promoted the expression of pathogenesis-related gene 1 related to SA signaling. Importantly, rac-GR24- and MAX1-induced bacterial resistance disappeared completely in Arabidopsis plants lacking both callose synthase and SA. Taken together, our data revealed that callose and SA are two important determinants in SL-mediated plant disease resistance, at least in Arabidopsis.