Carbohydrate polymers exhibit great potential as effective elicitors in organic agriculture: A review

Effects of Exogenous Application of Methyl Jasmonate and Salicylic Acid on the Physiological and Molecular Response of 'Dusa' Avocado to Rosellinia necatrix

Methyl jasmonate (MeJA) and salicylic acid (SA) are important in mediating plant responses to abiotic and biotic stresses. MeJA and SA can act as elicitors by triggering plant defense responses similar to those induced by pathogens and may even provide long-term protection against them. Thus, exogenous application of MeJA and SA could protect susceptible avocado plants against white root rot (WRR) disease caused by the necrotrophic fungus Rosellinia necatrix, one of the main diseases affecting avocado orchards. This work evaluates the effects of MeJA or SA on the physiological and molecular response of susceptible 'Dusa' avocado rootstock and their ability to provide some protection against WRR. The application of MeJA and SA in avocado increased photoprotective mechanisms (nonphotochemical chlorophyll fluorescence quenching) and upregulated the glutathione S-transferase, suggesting the triggering of mechanisms closely related to oxidative stress relief and reactive oxygen species scavenging. In contrast to SA, MeJA's effects were more pronounced at the morphoanatomical level, including functional traits such as high leaf mass area, high stomatal density, and high root/shoot ratio, closely related to strategies to cope with water scarcity and WRR disease. Moreover, MeJA upregulated a greater number of defense-related genes than SA, including a glu protease inhibitor, a key gene in avocado defense against R. necatrix. The overall effects of MeJA increased 'Dusa' avocado tolerance to R. necatrix by inducing a primed state that delayed WRR disease symptoms. These findings point toward the use of MeJA application as an environmentally friendly strategy to mitigate the impact of this disease on susceptible avocado orchards.

Characterization of carboxylated cellulose nanofibrils and oligosaccharides from Kraft pulp fibers and their potential elicitor effect on the gene expression of Capsicum annuum

Biomass-derived oligo- and polysaccharides may act as elicitors, i.e., bioactive molecules that trigger plant immune responses. This is particularly important to increase the resistance of plants to abiotic and biotic stresses. In this study, cellulose nanofibrils (CNF) gels were obtained by TEMPO-mediated oxidation of unbleached and bleached kraft pulps. The molecular structures were characterized with ESI and MALDI MS. Analysis of the fine sequences was achieved by MS and MS/MS of the water-soluble oligosaccharides obtained by acid hydrolysis of the CNF gels. The analysis revealed the presence of two families: one corresponding to homoglucuronic acid sequences and the other composed by alternating glucose and glucuronic acid units. The CNF gels, alone or with the addition of the water-soluble oligosaccharides, were tested on Chili pepper (Capsicum annuum). Based on the characterization of the gene expression with Next Generation Sequencing (NGS) of the C. annuum's total messenger RNA, the differences in growth of the C. annuum seeds correlated well with the downregulation of the pathways regulating photosynthesis. A downregulation of the response to abiotic factors was detected, suggesting that these gels would improve the resistance of the C. annuum plants to abiotic stress due to, e.g., water deprivation and cold temperatures.

Molecular Mechanism Underlying Pathogenicity Inhibition by Chitosan in Cochliobolus heterostrophus

Chitosan, as a natural nontoxic biomaterial, has been demonstrated to inhibit fungal growth and enhance plant defense against pathogen infection. However, the antifungal pattern and mechanism of how chitosan application evokes plant defense are poorly elucidated. Herein, we provide evidence that chitosan exposure is fungicidal to C. heterostrophus. Chitosan application impairs conidia germination and appressorium formation of C. heterostrophus and has a pronounced effect on reactive oxygen species production, thereby preventing infection in maize. In addition, the toxicity of chitosan to C. heterostrophus requires Mkk1 and Mps1, two key components in the cell wall integrity pathway. The Δmkk1 and Δmps1 mutants were more tolerant to chitosan than the wild-type. To dissect chitosan-mediated plant defense response to C. heterostrophus, we conducted a metabolomic analysis, and several antifungal compounds were upregulated in maize upon chitosan treatment. Taken together, our findings provide a comprehensive understanding of the mechanism of chitosan-alleviated infection of C. heterostrophus, which would promote the application of chitosan in plant protection in agriculture.

Biopolymers as Seed-Coating Agent to Enhance Microbially Induced Tolerance of Barley to Phytopathogens

Infections of agricultural crops caused by pathogen ic fungi are among the most widespread and harmful, as they not only reduce the quantity of the harvest but also significantly deteriorate its quality. This study aims to develop unique seed-coating formulations incorporating biopolymers (polyhydroxyalkanoate and pullulan) and beneficial microorganisms for plant protection against phytopathogens. A microbial association of biocompatible endophytic bacteria has been created, including Pseudomonas flavescens D5, Bacillus aerophilus A2, Serratia proteamaculans B5, and Pseudomonas putida D7. These strains exhibited agronomically valuable properties: synthesis of the phytohormone IAA (from 45.2 to 69.2 µg mL-1), antagonistic activity against Fusarium oxysporum and Fusarium solani (growth inhibition zones from 1.8 to 3.0 cm), halotolerance (5-15% NaCl), and PHA production (2.77-4.54 g L-1). A pullulan synthesized by Aureobasidium pullulans C7 showed a low viscosity rate (from 395 Pa·s to 598 Pa·s) depending on the concentration of polysaccharide solutions. Therefore, at 8.0%, w/v concentration, viscosity virtually remained unchanged with increasing shear rate, indicating that it exhibits Newtonian flow behavior. The effectiveness of various antifungal seed coating formulations has been demonstrated to enhance the tolerance of barley plants to phytopathogens.

In vitro and in silico analyses reveal the interaction between LysM receptor-like kinase3 of Solanum tuberosum and the carbohydrate elicitor Riclin octaose

As a carbohydrate elicitor, Riclin octaose (Rioc) activates the pattern-triggered immunity of Solanum tuberosum L., while how the plant perceives Rioc is unknown. Here, a pattern recognition receptor StLYK3 (LysM receptor-like kinase3) whose transcription level was significantly up-regulated after Rioc elicitation was investigated in vitro and in silico. The nucleotide that encoded the ectodomain of StLYK3 (StLYK3-ECD) was heterologously expressed in the Pichia pastoris strain GS115. The purified StLYK3-ECD had the molecular weight of 25.08 kDa and pI of 5.69. Afterwards interaction between StLYK3-ECD and Rioc was analyzed by isothermal titration calorimetry. The molar ratio of ligand to receptor, dissociation constant, and enthalpy were 1.28 ± 0.04, 26.7 ± 3.1 μM, and -45.0 ± 1.8 kJ mol-1 , respectively. Besides, molecular dynamics results indicated that StLYK3-ECD contained three carbohydrate-binding motifs and the first two motifs probably contributed to the interaction with Rioc via hydrogen bond and van de Waals' forces. Amino acids containing hydroxyl, amidic, and sulfhydryl groups took the main portion in the docking site. Moreover, replacing the 92nd threonyl (T) of StLYK3-ECD with valyl (V) resulted in the alteration of the preferred docking site. The dissociation constant drastically increased to 841.6 ± 232.4 μM. In conclusion, StLYK3 was a potential receptor of Rioc.

The M/G ratio of alginate oligosaccharides: The key to enhance the coloration of strawberries

Alginate oligosaccharides (AOS) have various biological activities in the regulation of plant growth and development. However, little is known about the effect on fruit coloration. We assessed the impacts of varying Mannuronate/Guluronate ratio (M/G ratios) of AOS, namely oligoguluronate (GAOS), oligomannuronate (MAOS), and heterogeneous AOS (HAOS), and delved into the structure-function relationship, as well as the mechanisms of regulation. The promotion of strawberry coloration was observed in HAOS (M/G ratio ≈ 1.58; Mw = 2800 Da) and MAOS (M/G ratio ≈ 6.77; Mw = 6000 Da), whereas GAOS (M/G ratio ≈ 0.2; Mw = 5500 Da) did not exhibit any significant effect. The metabolomics analysis revealed that the impact of AOS was predominantly observed on the biosynthesis of flavonoids. The predominant flavonoids present in strawberries were anthocyanins. The application of HAOS and MAOS on strawberries increased anthocyanin content. This was accompanied by an up-regulation of genes related to the JA synthesis pathway. Additionally, transcription factors and structural genes related to anthocyanin synthesis and transport were up-regulated. The findings suggest that HAOS and MAOS may trigger the JA pathway, leading to an elevation in anthocyanin metabolism and consequent enhancement of strawberry coloration.

PCAP-1a, an exopolysaccharide from Pectobacterium actinidiae, exerts the dual role of immunogenicity and virulence in plants

Plant defense mechanisms begin with the recognition of microbe-associated molecular patterns or pathogen-associated molecular patterns (MAMPs/PAMPs). Several carbohydrates, such as chitin, were reported to induce plant defenses, acting as elicitors. Regrettably, the structures of polysaccharide elicitors have rarely been characterized, and their recognition receptors in plants remain unknown. In the present study, PCAP-1a, an exopolysaccharide (PCAP-1a) purified from Pectobacterium actinidiae, was characterized and found to induce rapid cell death of dicotyledons, acting as a polysaccharide elicitor to induce plant immunity. A series of pattern-triggered immunity (PTI) responses were triggered, including reactive oxygen species production, phosphorylation of mitogen-activated protein kinases and gene transcriptional reprogramming. Moreover, we confirmed that CERK1 is probably one of the immune coreceptors for plants to recognize PCAP-1a. Notably, PCAP-1a also promotes the infection caused by P. actinidiae. In conclusion, our study supports the potential of PCAP-1a as a toxin that plays a dual role of virulence and immune induction in pathogen-plant interactions.

Polymer Gel Substrate: Synthesis and Application in the Intensive Light Artificial Culture of Agricultural Plants

This work is devoted to the description of the synthesis of hydrogels in the process of cryotropic gel formation based on copolymerization of synthesized potassium 3-sulfopropyl methacrylate and 2-hydroxyethyl methacrylate (SPMA-co-HEMA) and assessing the potential possibility of their use as substrates for growing plants in intensive light culture in a greenhouse. Gel substrates based on the SPMA-co-HEMA were created in two compositions, differing from each other in the presence of macro- and microelements, and their effects were studied on the plants' physiological state (content of chlorophylls a and b, activity of catalase and peroxidase enzymes, intensity of lipid peroxidation, elemental compositions) at the vegetative period of their development and on the plants' growth, productivity and quality of plant production at the final stages of development. Experiments were carried out under controlled microclimate conditions. Modern and standard generally accepted methods of gels were employed (ATR-FTIR and 13C NMR spectral studies, scanning electron microscopy, measurement of specific surface area and pore volume), as well as the methods of the physiological and chemical analysis of plants. The study demonstrated the swelling ability of the created gel substrates. Hydrogels' structure, their specific surface area, porosity, and pore volume were investigated. Using the example of representatives of leaf, fruit and root vegetable crops, the high biological activity of gel substrates was revealed throughout the vegetation period. Species specificity in the reaction of plants to the presence of gel substrates in the root-inhabited environment was revealed. Lettuce, tomato and cucumber plants were more responsive to the effect of the gel substrate, and radish plants were less responsive. At the same time, more pronounced positive changes in plant growth, quality and productivity were observed in cucumber and lettuce in the variant of gel substrates with macro- and microelements and in tomato plants in both variants of gel substrates. Further research into the mechanisms of the influence of gel substrates on plants, as well as the synthesis of new gel substrates with more pronounced properties to sorb and retain moisture is promising.

High-Density Chitosan Induces a Biochemical and Molecular Response in Coffea arabica during Infection with Hemileia vastatrix

The coffee industry faces coffee leaf rust caused by Hemileia vastratix, which is considered the most devastating disease of the crop, as it reduces the photosynthetic rate and limits productivity. The use of plant resistance inducers, such as chitosan, is an alternative for the control of the disease by inducing the synthesis of phytoalexins, as well as the activation of resistance genes. Previously, the effect of chitosan from different sources and physicochemical properties was studied; however, its mechanisms of action have not been fully elucidated. In this work, the ability of food-grade high-density chitosan (0.01% and 0.05%) to control the infection caused by the pathogen was evaluated. Subsequently, the effect of high-density chitosan (0.05%) on the induction of pathogenesis-related gene expression (GLUC, POX, PAL, NPR1, and CAT), the enzymatic activity of pathogenesis-related proteins (GLUC, POX, SOD, PPO, and APX), and phytoalexin production were evaluated. The results showed that 0.05% chitosan increased the activity and gene expression of ß-1,3 glucanases and induced a differentiated response in enzymes related to the antioxidant system of plants. In addition, a correlation was observed between the activities of polyphenol oxidase and the production of phytoalexin, which allowed an effective defense response in coffee plants.

Transcriptomic data exploring the effect of agave fructans on the induction of the defense system in avocado fruit

The effect of 20% high degree polymerized agave fructans (HDPAF) on the induction of the defense system in avocado fruits was investigated by transcriptomic analysis at 1, 24 and 72 h after treatment, and the effect of HDPAF on respiration rate and ethylene production was also analyzed. Transcriptomic profiling revealed 5425 differentially expressed genes (DEGs), 55 of which were involved in the pathways related to plant defense response to pathogens. Key genes were associated with phenylpropanoid biosynthesis, mitogen-activated protein signaling, plant hormone signaling, calcium ion signal decoding, and pathogenesis-related proteins. Dysregulated genes involved in ethylene biosynthesis were also identified, and the reduction in ethylene production by HDPAF was corroborated by gas chromatography, where three days of delayed peak production was observed compared to that in water-treated fruits. These results help to understand the mechanism of induction of the avocado defense system by applying HDPAF and support the application of HDPAF as an efficient postharvest treatment to extend the shelf life of the fruit.

Oligosaccharides increased both leaf biomass and steviol glycosides content of Stevia rebaudiana

Steviol glycosides (SGs) are a variety of important natural sweeteners. They are 200-350 times sweeter than sucrose without calories. Currently, their production is still mainly dependent on extraction from Stevia rebaudiana Bertoni (stevia). Oligosaccharides are environmentally friendly elicitors that promote plant growth and accumulation of secondary metabolites. In the present study, different concentrations of chitosan oligosaccharides (COS) and alginate oligosaccharides (AOS) were applied to stevia to explore their effect on growth and SGs biosynthesis. It was found that both COS and AOS promoted biomass production by increasing the leaf number and photosynthetic efficiency, which may be related to the decreased content of abscisic acid. The content of SGs was significantly increased after 50 mg/L AOS treatment, which not only increased the contents of stevioside (STV) and rebaudioside A (Reb A) significantly, but some important minority glucosides, like Reb E, Reb D, and Reb M. The increased SGs contents were the combined effect of the higher expression of SGs biosynthesis related genes, including KAH, UGT74G1, UGT85C2, and UGT91D2. The geometry changes of stem induced by COS and AOS may help to increase the lodging resistance of stevia. Thus, COS and AOS can be used in the field planting of stevia to increase the yield of SGs for industrial purposes.

A Novel Composite Hydrogel Material for Sodium Removal and Potassium Provision

Sodium ions are commonly found in natural water sources, and their high concentrations can potentially lead to adverse effects on both the water sources and soil quality. In this study, we successfully synthesized potassium polyacrylate (KMAA) hydrogel through free radical polymerization and evaluated its capability to remove sodium ions from and supply potassium ions to aqueous solutions. To assess its performance, inductively coupled plasma emission spectroscopy (ICP) was employed to analyze the sodium ion removal capacity and potassium ion exchange capability of the KMAA hydrogel at various initial sodium ion concentrations and pH values. The results demonstrated that the KMAA hydrogel exhibited remarkable efficiency in removing sodium ions and providing potassium ions. At pH 7, the maximum adsorption capacity for sodium ions was measured at 70.7 mg·g-1. The Langmuir model, with a correlation coefficient of 0.98, was found to be more suitable for describing the adsorption process of sodium ions. Moreover, at pH 4, the maximum exchange capacity for potassium ions reached 243.7 mg·g-1. The Freundlich model, with a correlation coefficient of 0.99, was deemed more appropriate for characterizing the ion exchange behavior of potassium ions. In conclusion, the successfully synthesized KMAA hydrogel demonstrates superior performance in removing sodium ions and supplying potassium ions, providing valuable insights for addressing high sodium ion concentrations in water sources and facilitating potassium fertilizer supply.

Insights into the Antifungal Properties of Myxobacteria Outer Membrane β-1,6-Glucanase

Fungal cell wall decomposition enzymes exhibit great potential for the development of efficient antifungal agents. However, their practical application is restricted due to incomplete understanding of the action mode. In our previous study, we identified that a novel outer membrane (OM) β-1,6-glucanase GluM is deployed by predatory myxobacteria to feed on fungi. In this work, we provide deep insights into the antifungal mechanism of β-1,6-glucanase and its potential in improving plant disease resistance. The fungal cell wall decomposition ability of GluM resulted in irregular hyphae morphology, changed chitin distribution, increased membrane permeability, and leakage of cell constituents in Magnaporthe oryzae Guy11. Under the attack pattern, the cell wall integrity pathway was activated by strain Guy11 for self-protection. GluM exhibited a distinct endo-model toward fungal cell wall; the favorite substrate of GluM toward fungal β-1,6-glucan may give reason for its efficient antifungal activity compared with Trichoderma β-1,6-glucanase. Moreover, released glucans from GluM hydrolysis of fungal cell wall functioned as an elicitor and induced rice immunity by means of jasmonic acid pathway. Based on the dual roles of antifungal properties, gluM transgenic plants conferred enhanced resistance against fungal infection.

Elicitor Activity of Low-Molecular-Weight Alginates Obtained by Oxidative Degradation of Alginates Extracted from Sargassum muticum and Cystoseira myriophylloides

Alginates extracted from two Moroccan brown seaweeds and their derivatives were investigated for their ability to induce phenolic metabolism in the roots and leaves of tomato seedlings. Sodium alginates (ALSM and ALCM) were extracted from the brown seaweeds Sargassum muticum and Cystoseira myriophylloides, respectively. Low-molecular-weight alginates (OASM and OACM) were obtained after radical hydrolysis of the native alginates. Elicitation was carried out by foliar spraying 20 mL of aqueous solutions (1 g/L) on 45-day-old tomato seedlings. Elicitor capacities were evaluated by monitoring phenylalanine ammonia-lyase (PAL) activity, polyphenols, and lignin production in the roots and leaves after 0, 12, 24, 48, and 72 h of treatment. The molecular weights (Mw) of the different fractions were 202 kDa for ALSM, 76 kDa for ALCM, 19 kDa for OACM, and 3 kDa for OASM. FTIR analysis revealed that the structures of OACM and OASM did not change after oxidative degradation of the native alginates. These molecules showed their differential capacity to induce natural defenses in tomato seedlings by increasing PAL activity and through the accumulation of polyphenol and lignin content in the leaves and roots. The oxidative alginates (OASM and OACM) exhibited an effective induction of the key enzyme of phenolic metabolism (PAL) compared to the alginate polymers (ALSM and ALCM). These results suggest that low-molecular-weight alginates may be good candidates for stimulating the natural defenses of plants.

Effect of Biotic Elicitors on the Growth, Antioxidant Activity and Metabolites Accumulation in In Vitro Propagated Shoots of Pueraria tuberosa

Pueraria tuberosa contains a wide range of bioactive compounds, including polyphenols, alkaloids, and phytosterols, which make it valuable to the pharmaceutical and food industries. Elicitor compounds trigger the defense mechanisms in plants and are widely used to increase the yield of bioactive molecules in in vitro cultures. The present study was conducted to evaluate the effects of different concentrations of biotic elicitors such as yeast extract (YE), pectin (PEC), and alginate (ALG) on growth, antioxidant activity, and metabolite accumulation in in vitro propagated shoots of P. tuberosa. The elicitors applied to shoot cultures of P. tuberosa significantly increased biomass (shoot number, fresh weight, and dry weight), and metabolites such as protein, carbohydrates, chlorophyll, total phenol (TP), and total flavonoid (TF) contents, as well as antioxidant activity compared to untreated control. Biomass, TP, and TF contents, as well as antioxidant activity, were most significant in cultures treated with 100 mg/L PEC. In contrast, chlorophyll, protein, and carbohydrate increased most in cultures treated with 200 mg/L ALG. Application of 100 mg/L of PEC led to the accumulation of high amounts of isoflavonoids including puerarin (220.69 μg/g), daidzin (2935.55 μg/g), genistin (5612 μg/g), daidzein (479.81 μg/g), and biochanin-A (111.511 μg/g) as analyzed by high-performance liquid chromatography (HPLC). Total isoflavonoids content of 100 mg/L PEC treated shoots was obtained as 9359.56 μg/g, 1.68-fold higher than in vitro propagated shoots without elicitors (5573.13 μg/g) and 2.77-fold higher than shoots of the mother plant (3380.17 μg/g). The elicitor concentrations were optimized as 200 mg/L YE, 100 mg/L PEC, and 200 mg/L ALG. Overall, this study showed that the application of different biotic elicitors resulted in better growth, antioxidant activity, and accumulation of metabolites in P. tuberosa, which could lead to obtaining phytopharmaceutical advantages in the future.

Enhancement of bioactive compounds and biological activities of Centella asiatica through ultrasound treatment

Centella asiatica possess various health-promoting activities owing to its bioactive compounds such as triterpenes, flavonoids, and vitamins. Ultrasound treatment during the post-harvest process is a good strategy for eliciting secondary metabolite in plants. The present study investigated the effect of ultrasound treatment for different time durations on the bioactive compounds and biological activities of C. asiatica leaves. The leaves were treated with ultrasound for 5, 10, and 20 min. Ultrasound elicitation (especially for 10 min) markedly elevated the accumulation of stress markers, leading to enhanced phenolic-triggering enzyme activities. The accumulation of secondary metabolites and antioxidant activities were also significantly improved compared with that in untreated leaves. In addition, ultrasound-treated C. asiatica leaves protected myoblasts against H₂O₂-induced oxidative stress by regulating reactive oxygen species production, glutathione depletion, and lipid peroxidation. These findings indicate that elicitation using ultrasound can be a simple method for increasing functional compound production and enhancing biological activities in C. asiatica leaves.

Ulva prolifera polysaccharide enhances the root colonisation by Bacillus amyloliquefaciens strain Cas02

The application of biocontrol agent is important for the sustainable development of agriculture. Unsuccessful or limited colonisation by plant growth-promoting rhizobacteria (PGPR) has become an important constraint factor for their commercial application. Here, we report that Ulva prolifera polysaccharide (UPP) promotes root colonisation by Bacillus amyloliquefaciens strain Cas02. UPP serves as an environmental signal for bacterial biofilm formation and its glucose residue is used as a carbon source for the synthesis of the exopolysaccharides and poly-gamma-glutamate present in biofilm matrix. Greenhouse experiments demonstrated that UPP could effectively enhance the root colonisation by Cas02 in both the bacterial population and survival time under natural semiarid soil conditions. Furthermore, the microbiome analysis also indicated the promoted colonisation by Cas02, as well as the improved bacterial rhizosphere community structure, after combined treatment of UPP and Cas02. This study provides a practical approach to improve the biocontrol agent with seaweed polysaccharides.

Chitosan application towards the improvement of grapevine performance and wine quality

Intensification of agrochemicals application in vineyards has raised several concerns in Viticulture and Oenology value chain. Efforts have been developed to optimize grapevine health and productivity, assuring that viticulture is sustainable and competitive in today’s wine market. Viticulture practices have constantly been improved for a more sustainable and environment-friendly production, reducing the application of agrochemicals, replacing them by natural compounds that can have a double effect: protect grapevine against pathogens and improve compounds related to grape organoleptic quality. In this context, the development and optimization of alternative strategies to improve and enhance plant defences and grape/wine quality is becoming a necessity. Since the 1980s, chitosan has become a compound of special interest due to its double effect as elicitor and grapevine biostimulant, representing a complement to soil fertilisation, and reducing the negative effects nutrients leaching into the groundwater. The present review aims to present the wide possibilities of chitosan applications on grapevines to prevent and combat the main diseases and to improve wine quality. In this way, relevant studies about chitosan application will be presented as well as some concerns and limitations in order to cover the knowledge gaps inherent to its application in vineyard and wine as well.

Meta-analysis of chitosan-mediated effects on plant defense against oxidative stress

Chitosan, as a natural non-toxic biomaterial, has been demonstrated to enhance plant defense against oxidative stress. However, the general pattern and mechanism of how chitosan application modifies the amelioration of oxidative stress in plants have not been elucidated yet. Herein, we performed a meta-analysis of 58 published articles up to January 2022 to fill this knowledge gap, and found that chitosan application significantly increased the antioxidant enzyme activity (by 40.6 %), antioxidant metabolites content (by 24.6 %), defense enzyme activity (by 77.9 %), defense-related genes expression (by 103.2 %), phytohormones (by 26.9 %), and osmotic regulators (by 23.2 %) under stress conditions, which in turn notably reduced oxidative stress (by 32.2 %), and increased plant biomass (by 28.1 %) and yield (by 15.7 %). Moreover, chitosan-mediated effects on the amelioration of oxidative stress depended on the properties and application methods of chitosan. Our findings provide a comprehensive understanding of the mechanism of chitosan-alleviated oxidative stress, which would promote the application of chitosan in plant protection in agriculture.

Sugarcane multitrophic interactions: Integrating belowground and aboveground organisms

Sugarcane is a crop of major importance used mainly for sugar and biofuel production, and many additional applications of its byproducts are being developed. Sugarcane cultivation is plagued by many insect pests and pathogens that reduce sugarcane yields overall. Recently emerging studies have shown complex multitrophic interactions in cultivated areas, such as the induction of sugarcane defense-related proteins by insect herbivory that function against fungal pathogens that commonly appear after mechanical damage. Fungi and viruses infecting sugarcane also modulate insect behavior, for example, by causing changes in volatile compounds responsible for insect attraction or repelling natural vector enemies via a mechanism that increases pathogen dissemination from infected plants to healthy ones. Interestingly, the fungus Fusarium verticillioides is capable of being vertically transmitted to insect offspring, ensuring its persistence in the field. Understanding multitrophic complexes is important to develop better strategies for controlling pathosystems affecting sugarcane and other important crops and highlights the importance of not only studying binary interactions but also adding as many variables as possible to effectively translate laboratory research to real-life conditions.

Agricultural Applications of Superabsorbent Polymer Hydrogels

This review presents data from the past five years on the use of polymeric superabsorbent hydrogels in agriculture as water and nutrient storage and retention materials, as well as additives that improve soil properties. The use of synthetic and natural polymeric hydrogels for these purposes is considered. Although natural polymers, such as various polysaccharides, have undoubted advantages related to their biocompatibility, biodegradability, and low cost, they are inferior to synthetic polymers in terms of water absorption and water retention properties. In this regard, the most promising are semi-synthetic polymeric superabsorbents based on natural polymers modified with additives or grafted chains of synthetic polymers, which can combine the advantages of natural and synthetic polymeric hydrogels without their disadvantages. Such semi-synthetic polymers are of great interest for agricultural applications, especially in dry regions, also because they can be used to create systems for the slow release of nutrients into the soil, which are necessary to increase crop yields using environmentally friendly technologies.

Domestic Cooking Affects the Prebiotic Performances of Chinese Yam

The appropriate domestic cooking methods can retain and protect the biological properties of foods well. Thus, the objective of this study was to unravel the effect of different cooking methods on the microbiota modulatory properties of yam and their non-starch polysaccharides by an in vitro simulated digestion and fermentation model. The results showed that different cooking processes led to different changes in polysaccharide content. The polysaccharide content of yam increased by 21.3~108.2% or decreased by 12.0% compared with that of raw yam. Additionally, the soluble polysaccharides contents in all cooked yam samples significantly increased by 16.85~119.97% after in vitro digestion. The regulation of whole-yam digesta on gut microbiota was partly related with yam polysaccharides. Both yam and yam polysaccharide fermentation appeared to promote beneficial bacteria, such as Bifidobacteria, Bacteroides spp. and Megasphaera and suppressed bacterial pathogens such as Ruminococcusforques and Escherichia-Shigella. Household cooking significantly influenced the prebiotic performances of yam and yam polysaccharides by changing the heat-sensitive microbial substrates and their physiology properties. According to our results, normal-pressure steaming and normal-pressure boiling processes can retain the microbiota modulatory effects of Chinese yam.

The carbohydrate elicitor Riclinoctaose facilitates defense and growth of potato roots by inducing changes in transcriptional and metabolic profiles

Promoting both root growth and defense is conducive to the production of potatoes (Solanum tuberosum L.), while the role of elicitors in this topic hasn't been fully understood. To investigate the effect of Riclinoctaose (RiOc) on root growth and defense, potato tissue cuttings were cultivated with different concentration of RiOc (0, 50, 200 mg/L) for 5 weeks and changes in root morphology, transcription, enzymatic and metabolomic profiles were monitored over time. The results indicated that RiOc triggered the salicylic acid (SA)-mediated defense response and facilitated the growth of adventitious and lateral roots in a dose- and time-dependent manner. MPK3/MPK6, SA- and auxin-signaling pathways and transcription factors such as WUS, SCR and GRAS4/GRAS9 participated in this process. Moreover, the ¹H NMR based metabolome profiling demonstrated that potato roots altered the primary metabolism to respond to the RiOc elicitation and efficiency in production and allocation of defense and growth-related metabolites was improved. After 5-week treatment, the level of glucose, N-acetylglucosamine, glutamine, asparagine, isoleucine, valine, 3-hydroxyisovalerate and ferulate increased, while acetate, acetoacetate, fucose, and 2-hydroxyphenylacetate declined. In conclusion, RiOc played dual roles in activating the SA-mediated defense response and in promoting growth of potato roots by inducing changes in root transcription and metabolism.

Influence of the sulfate content of the exopolysaccharides from Porphyridium sordidum on their elicitor activities on date palm vitroplants

Given the increasing interest that is being paid to polysaccharides derived from algae as plant natural defense stimulators, the degree of sulfation of exopolysaccharides produced by P. sordidum for inducing defense responses in date palm vitroplants was investigated. Firstly, the culture parameters of P. sordidum were optimized to maximize the amount of sulfate in EPS using a Box-Behnken experimental design and the elicitor effects of two EPS which differ in the sulfation degrees were compared. Results demonstrated that the concentrations of NaCl, NaNO3 and MgSO4 set at 28, 0.54 and 16.31 g/L, respectively yielded the best sulfate contents. To elucidate defense-inducing activities in date palm vitroplants, EPS with the highest sulfate content (EPS1) were prepared for comparison with those obtained under standard conditions (EPS0). A fucoidan extracted from Cystoseira compressa was used as positive control and MgSO4 as negative control. Both EPS and the fucoidan displayed H2O2 accumulation and expression of PR1, SOD, PAL and WRKY genes. Interestingly, EPS1 was significantly more bioactive than EPS0 and the fucoidan suggesting that the elicitor activity is positively correlated with the sulfate groups content of this polysaccharide.

The Use of Carbohydrate Biopolymers in Plant Protection against Pathogenic Fungi

Fungal pathogens cause significant yield losses of many important crops worldwide. They are commonly controlled with fungicides which may have negative impact on human health and the environment. A more sustainable plant protection can be based on carbohydrate biopolymers because they are biodegradable and may act as antifungal compounds, effective elicitors or carriers of active ingredients. We reviewed recent applications of three common polysaccharides (chitosan, alginate and cellulose) to crop protection against pathogenic fungi. We distinguished treatments dedicated for seed sowing material, field applications and coating of harvested fruits and vegetables. All reviewed biopolymers were used in the three types of treatments, therefore they proved to be versatile resources for development of plant protection products. Antifungal activity of the obtained polymer formulations and coatings is often enhanced by addition of biocontrol microorganisms, preservatives, plant extracts and essential oils. Carbohydrate polymers can also be used for controlled-release of pesticides. Rapid development of nanotechnology resulted in creating new promising methods of crop protection using nanoparticles, nano-/micro-carriers and electrospun nanofibers. To summarize this review we outline advantages and disadvantages of using carbohydrate biopolymers in plant protection.

Application of Elicitors in Grapevine Defense: Impact on Volatile Compounds

Elicitors as alternatives to agrochemicals are widely used as a sustainable farming practice. The use of elicitors in viticulture to control disease and improve phenolic compounds is widely recognized in this field. Concurrently, they also affect other secondary metabolites, such as aroma compounds. Grape and wine aroma compounds are an important quality factor that reflects nutritional information and influences consumer preference. However, the effects of elicitors on aroma compounds are diverse, as different grape varieties respond differently to treatments. Among the numerous commercialized elicitors, some have proven very effective in improving the quality of grapes and the resulting wines. This review summarizes some of the elicitors commonly used in grapevines for protection against biotic and abiotic stresses and their impact on the quality of volatile compounds. The work is intended to serve as a reference for growers for the sustainable development of high-quality grapes.

Oligomers of Carboxymethyl Cellulose for Postharvest Treatment of Fresh Produce: The Effect on Fresh-Cut Strawberry in Combination with Natural Active Agents

In this study, oligomers of carboxymethyl cellulose (O-CMC) were used as a new postharvest treatment for fresh produce. The oligomers were prepared by green and cost-effective enzymatic hydrolysis and applied to prevent spoilage and improve storability of fresh-cut strawberries. The produce quality was improved by all formulations containing O-CMC in comparison to the control, as indicated by the decrease in decay incidence, weight loss (min ~2–5 times less), higher firmness, microbial load decrease, better appearance, and sensorial quality of the fruits. Natural resources: ascorbic acid, gallic acid, and vanillin were further added to enhance the beneficial effect. O-CMC with vanillin was most efficient in all of the tested parameters, exhibiting the full prevention of fruit decay during all 7 days of refrigerated storage. In addition, fruits coated with O-CMC vanillin have the smallest weight loss (%), minimum browning, and highest antimicrobial effect preventing bacterial (~3 log, 2 log) and yeast/mold contaminations. Based on the obtained positive results, O-CMC may provide a new, safe, and effective tool for the postharvest treatment of fresh produce that can be used alone or in combination with other active agents.

Induction of Defense Gene Expression and the Resistance of Date Palm to Fusarium oxysporum f. sp. Albedinis in Response to Alginate Extracted from Bifurcaria bifurcata

In many African countries, the Bayoud is a common disease spread involving the fungus Fusarium oxusporum f. sp. albedinis (Foa). The induction of plant natural defenses through the use of seaweed polysaccharides to help plants against pathogens is currently a biological and ecological approach that is gaining more and more importance. In the present study, we used alginate, a natural polysaccharide extracted from a brown algae Bifurcaria bifurcata, to activate date palm defenses, which involve phenylalanine ammonia-lyase (PAL), a key enzyme of phenylpropanoid metabolism. The results obtained showed that at low concentration (1 g·L-1), alginate stimulated PAL activity in date palm roots 5 times more compared to the negative control (water-treated) after 24 h following treatment and 2.5 times more compared to the laminarin used as a positive stimulator of plant natural defenses (positive control of induction). Using qRT-PCR, the expression of a selection of genes involved in three different levels of defense mechanisms known to be involved in response to biotic stresses were investigated. The results showed that, generally, the PAL gene tested and the genes encoding enzymes involved in early oxidative events (SOD and LOX) were overexpressed in the alginate-treated plants compared to their levels in the positive and negative controls. POD and PR protein genes selected encoding β-(1,3)-glucanases and chitinases in this study did not show any significant difference between treatments; suggesting that other genes encoding POD and PR proteins that were not selected may be involved. After 17 weeks following the inoculation of the plants with the pathogen Foa, treatment with alginate reduced the mortality rate by up to 80% compared to the rate in control plants (non-elicited) and plants pretreated with laminarin, which agrees with the induction of defense gene expression and the stimulation of natural defenses in date palm with alginate after 24 h. These results open promising prospects for the use of alginate in agriculture as an inducer that triggers immunity of plants against telluric pathogens in general and of date palm against Fusarium oxysporum f. sp. albedinis in particular.

Mechanisms of plant cell wall surveillance in response to pathogens, cell wall-derived ligands and the effect of expansins to infection resistance or susceptibility

Cell wall integrity is tightly regulated and maintained given that non-physiological modification of cell walls could render plants vulnerable to biotic and/or abiotic stresses. Expansins are plant cell wall-modifying proteins active during many developmental and physiological processes, but they can also be produced by bacteria and fungi during interaction with plant hosts. Cell wall alteration brought about by ectopic expression, overexpression, or exogenous addition of expansins from either eukaryote or prokaryote origin can in some instances provide resistance to pathogens, while in other cases plants become more susceptible to infection. In these circumstances altered cell wall mechanical properties might be directly responsible for pathogen resistance or susceptibility outcomes. Simultaneously, through membrane receptors for enzymatically released cell wall fragments or by sensing modified cell wall barrier properties, plants trigger intracellular signaling cascades inducing defense responses and reinforcement of the cell wall, contributing to various infection phenotypes, in which expansins might also be involved. Here, we review the plant immune response activated by cell wall surveillance mechanisms, cell wall fragments identified as responsible for immune responses, and expansin's roles in resistance and susceptibility of plants to pathogen attack.

Bioactive Carbohydrate Polymers-Between Myth and Reality

Polysaccharides are complex macromolecules long regarded as energetic storage resources or as components of plant and fungal cell walls. They have also been described as plant mucilages or microbial exopolysaccharides. The development of glycosciences has led to a partial and difficult deciphering of their other biological functions in living organisms. The objectives of glycobiochemistry and glycobiology are currently to correlate some structural features of polysaccharides with some biological responses in the producing organisms or in another one. In this context, the literature focusing on bioactive polysaccharides has increased exponentially during the last two decades, being sometimes very optimistic for some new applications of bioactive polysaccharides, notably in the medical field. Therefore, this review aims to examine bioactive polysaccharide, taking a critical look of the different biological activities reported by authors and the reality of the market. It focuses also on the chemical, biochemical, enzymatic, and physical modifications of these biopolymers to optimize their potential as bioactive agents.

Polysaccharides from Chrysanthemun indicum L. enhance the accumulation of polysaccharide and atractylenolide in Atractylodes macrocephala Koidz

Atractylodes macrocephala Koidz. (AM), an herb of traditional Chinese medicine, is well-known for anti-oxidant, anti-tumor and immune regulation potential. However, it is low bioactive compound content that restricts the application of this species. Elicitation is considered as an effective method to enhance biomass and bioactive compound in plants. Our precious study found that polysaccharide of Chrysanthemun indicum L. could promote plant growth by triggering plant defense. In the present study, polysaccharide of Chrysanthemun indicum L. is used to stimulate the accumulation of biomass and bioactive compound with different concentration in Atractylodes macrocephala Koidz. during pot, plot and field experiments. The results suggested that polysaccharide of Chrysanthemun indicum L. could significantly enhance the accumulation of biomass, atractylenolides and polysacchrides. Moreover, 2 mg/mL is determined and verified to be the appropriate concentration during field experiments. In addition, RT-qPCR revealed that CIP-induced terpenoid synthesis in AM mainly depended on mevalonate (MVA) pathway. This is the first report on the discovery of polysaccharide of Chrysanthemun indicum L. for the enhanced accumulation of biaomass and bioactive compound and the use of its for agricultural production.

Differential induction of antioxidant and anti-inflammatory phytochemicals in agitated micro-shoot cultures of Ajuga integrifolia Buch. Ham. ex D.Don with biotic elicitors

Ajuga integrifolia Buch. Ham. ex D.Don, a member of Lamiaceae family is pharmaceutically an active perennial herb widely spread in China, Afghanistan and Pakistan Himalayan region. The application of biotic elicitors is a promising approach to cover limitations of in vitro cell technology and challenges faced by pharmaceuticals industry for bulk up production. The current study involved the induction of agitated micro-shoot cultures with the aim to investigate the growth-promoting as well as phytochemicals enhancement role of yeast extract (YE) and pectin (PE). The results showed that both elicitors induced a considerable physiological response. Biomass accumulation was observed maximum (DW: 18.3 g/L) against PE (10 mg/L) compared to YE and control. Eleven secondary phytocompounds were quantified using high-performance liquid chromatography. PE (50 mg/L) was found to be effective in elicitation of rosmarinic acid (680.20 µg/g), chlorogenic acid (294.12 µg/g), apigenin (579.61 µg/g) and quercetin (596.89 µg/g). However, maximum caffeic acid (359.52 µg/g) and luteolin (546.12 µg/g accumulation was noted in PE (1 mg/L) treatment. Harpagide, aucubin, harpagoside and 8-O-acetyl-harpagoside production was suppressed by both elicitors except for YE (100 mg/L). Catalpol accumulation in micro-shoot cultures was also downregulated except in response to YE (50 and 100 mg/L). Antioxidant activity and anti-inflammatory activity remained higher under PE (50 mg/L) and YE (100 mg/L) respectively. Therefore, results suggested that Ajuga integrifolia micro-shoot cultures treated with yeast extract and pectin might be an efficient bio-factory to produce commercially potent specific secondary metabolites.

Transcriptomic and metabolomic profiling revealed the role of succinoglycan Riclin octaose in eliciting the defense response of Solanum tuberosum

Activating the defense response of plants by elicitors provides a promising method for biocontrol of pathogens. The homogeneous octaose (RiOc) which was depolymerized from the succinoglycan Riclin was investigated as a novel elicitor to activate the immune system of potato (Solanum tuberosum L.). After foliar spray, RiOc quickly induced accumulation of reactive oxygen species in potato leaves in a dose-dependent manner. Transcriptomic analysis revealed that 2712 out of 30,863 genes were differentially expressed at the early stage (24 h), while 367 of them were changed later (72 h). Results from the transcriptome and quantitative RT-PCR suggested that RiOc was probably perceived by the receptor LYK3 and it activated the MKK2/3/9/-MPK6/7 signaling cascade and promoted the salicylic acid-mediated defense response. Meanwhile, RiOc changed the metabolome profile of potato leaves over time as demonstrated by the ¹H NMR-based metabolomic analysis. Homeostasis of amino acids was affected at the early stage while the secondary metabolism was strengthened later. More importantly, RiOc significantly reduced the severity of potato leaf lesions caused by the late blight pathogen Phytophthora infestans. In conclusion, RiOc effectively improved the resistance of potato to P. infestans by eliciting the salicylic acid-mediated defense response. RiOc becomes a promising carbohydrate-based elicitor for biocontrol of plant pathogens. KEY POINTS: • Homogeneous Riclin octaose was a novel elicitor for biocontrol of plant pathogens. • Riclin octaose primed the salicylic acid-mediated defense response of potato plants. • Riclin octaose changed the metabolome profile of potato leaves over time.

Structural characterization and evaluation the elicitors activity of polysaccharides from Chrysanthemum indicum

This research evaluates the elicitors activity and structure characterization of four Chrysanthemum indicum polysaccharides (CIPs) which were isolated from C. indicum, obtained CIP1, CIP2, CIP3, CIP4. Results demonstrated that there was a distinct difference in inducibility and CIP3 was significantly stronger than other CIPs through bioactivity-tests. Taking CIP3 with total carbohydrate content 91.93 % as a representative, its structure was elucidated as a relative molecular weight of 8. 741 × 10³ g/mol and mainly composed of xylose, galacturonic acid, galactose and glucuronic acid. Through GC, IR and NMR, CIP3 was determined to possess a backbone comprised of T-α-d-GalpA, 1,4-α-d-GlcpA, 1,2-α-d-Xylp, 1,3-α-l-Rhap, 1,2,4-α-l-Rhap and sidechains comprised of 1,3-β-d-Galp, 1,6-α-d-Galp, T-α-Glcp, 1,3-β-d-Glcp, 1,4-α-d-Glcp, 1,3,4-α-d-Manp, T-α-l-Fucp. Further results indicated that CIP3 with active sidechains could significantly increase the expression of defense genes in Atractylodes macrocephala Koidz (AM). It is believed that the sidechains of CIP3 were necessary to its elicitor activity via bioactivity tests.

Influence of a Natural Plant Antioxidant on the Ageing Process of Ethylene-norbornene Copolymer (Topas)

In the field of polymer technology, a variety of mainly synthetic additives are used to stabilize the materials during processing. However, natural compounds of plant origin can be a green alternative to chemicals such as synthetic polyphenols. An analysis of the effect of hesperidin on the aging behavior of ethylene-norbornene copolymer was performed. The evaluation of changes in the tested samples was possible by applying the following tests: determination of the surface energy and OIT values, mechanical properties analysis, colour change measurements, FT-IR and TGA analyses. The obtained results proved that hesperidin can be effectively used as natural stabilizer for polymers. Furthermore, as a result of this compound addition to Topas-silica composites, their surface and physico-mechanical properties have been improved and the resistance to aging significantly increased. Additionally, hesperidin can act as a dye or colour indicator and only few scientific reports describe a possibility of using flavonoids to detect changes in products during their service life, e.g., in food packaging. In the available literature, there is no information about the potential use of hesperidin as a stabilizer for cycloolefin copolymers. Therefore, this approach may contribute not only to the current state of knowledge, but also presents an eco-friendly solution that can be a good alternative to synthetic stabilizers.

Optimization of Exopolysaccharides Production by Porphyridium sordidum and Their Potential to Induce Defense Responses in Arabidopsis thaliana against Fusarium oxysporum

Polysaccharides from marine algae are one novel source of plant defense elicitors for alternative and eco-friendly plant protection against phytopathogens. The effect of exopolysaccharides (EPS) produced by Porphyridium sordidum on elicitation of Arabidopsis thaliana defense responses against Fusarium oxysporum was evaluated. Firstly, in order to enhance EPS production, a Box-Behnken experimental design was carried out to optimize NaCl, NaNO₃ and MgSO₄ concentrations in the culture medium of microalgae. A maximum EPS production (2.45 g/L) higher than that of the control (0.7 g/L) was observed for 41.62 g/L NaCl, 0.63 g/L NaNO₃ and 7.2 g/L MgSO₄ concentrations. Structurally, the EPS contained mainly galactose, xylose and glucose. Secondly, the elicitor effect of EPS was evaluated by investigating the plant defense-related signaling pathways that include activation of Salicylic or Jasmonic Acid-dependent pathway genes. A solution of 2 mg/mL of EPS has led to the control of fungal growth by the plant. Results showed that EPS foliar application induced phenylalaline ammonia lyase and H₂O₂ accumulation. Expression profile analysis of the defense-related genes using qRT-PCR revealed the up-regulation of Superoxide dismutases (SOD), Peroxidase (POD), Pathogenesis-related protein 1 (PR-1) and Cytochrome P450 monooxyge-nase (CYP), while Catalase (CAT) and Plant defensin 1.2 (PDF1.2) were not induced. Results suggest that EPS may induce the elicitation of A. thaliana's defense response against F. oxysporum, activating the Salicylic Acid pathway.

Ecofriendly conversion of algal waste into valuable plant growth-promoting rhizobacteria (PGPR) biomass

With the development of marine biorefinery concept, utilisation of algal waste during industrial processing as well as some "green tide" waste biomass has become an important research topic. In this work, a single-step microwave process was used to hydrolyse Laminaria japonica processing waste (LJW) and Enteromorpha prolifera (EP), producing a growth medium suitable for microbial cultivation. The medium contained a range of mono- and polysaccharides as well as macro- and micronutrients that could be used by the microbes. The cultivation behavior of three plant growth-promoting rhizobacteria (PGPR) strains (Bacillus subtilis strain Tpb55, Bacillus amyloliquefaciens strain Cas02, and Burkholderia pyrrocinia strain Lyc2) in the two media were investigated. LJW hydrolysate from 180 °C and EP hydrolysate from 150 °C performed better cultivation efficiency than those hydrolysates from other microwave conditions. Saccharide analysis showed that microbes metabolized some monosaccharide such as glucose, mannose during cultivation, leaving polysaccharide unused in the medium. Furthermore, hydrolysate-strain cultivation mixtures were applied to pepper growth. The EP hydrolysate-Cas02 broth showed better plant growth-promoting effect compared to other treatments, which might be attributed to the higher indole-3-acetic acid (IAA) production of Cas02 in the EP hydrolysate. This work shed lights on the conversion of algal waste to PGPR biomass as well as the co-application of algal hydrolysates- strains cultivation broth for a better plant growth promotion.

Recent advances in the knowledge of wine oligosaccharides

Oligosaccharides are carbohydrates with a low polymerization degree containing between three and fifteen monosaccharide residues covalently linked through glycosidic bonds. Oligosaccharides are related to plant defense responses and possess beneficial attributes for human health. Research has focused in wine oligosaccharides only in the last decade. In this paper, a summary of these works is provided. They include: (i) wine oligosaccharides origins, (ii) techniques for isolating oligosaccharide fraction and determining their content, composition and structure, (iii) their dependence on the grape origin and cultivar and winemaking process, and (iv) the connection between oligosaccharides and wine sensorial attributes. Further research is required regarding the impact of agricultural aspects and winemaking techniques on wine oligosaccharides. The knowledge concerning their influence on sensorial and physicochemical properties of wines and on human health should also be improved. The implementation of laboratory methods will provide better understanding of these compounds and their performance within wine's matrix.

Recognition Pattern, Functional Mechanism and Application of Chitin and Chitosan Oligosaccharides in Sustainable Agriculture

Background:

Application of chitin attracts much attention in the past decades as the second abundant polysaccharides in the world after cellulose. Chitin oligosaccharides (CTOS) and its deacetylated derivative chitosan oligosaccharides (COS) were shown great potentiality in agriculture by enhancing plant resistance to abiotic or biotic stresses, promoting plant growth and yield, improving fruits quality and storage, etc. Those applications have already served huge economic and social benefits for many years. However, the recognition mode and functional mechanism of CTOS and COS on plants have gradually revealed just in recent years.

Objective:

Recognition pattern and functional mechanism of CTOS and COS in plant together with application status of COS in agricultural production will be well described in this review. By which we wish to promote further development and application of CTOS and COS–related products in the field.