Synergistic Effects of Oligochitosan and Pyraclostrobin in Controlling Leaf Spot Disease in Pseudostellaria heterophylla

Pseudostellaria heterophylla (or Taizishen in Chinese), a medicinal, edible, and ornamental Chinese herb, is seriously affected by leaf spot disease (LSD). Oligochitosan is a natural agricultural antibiotic that is produced via the degradation of chitosan, which is deacetylated from chitin; pyraclostrobin is a broad-spectrum and efficient strobilurin fungicide. In this work, the ability of pyraclostrobin, oligochitosan, and their formula to manage P. heterophylla leaf spot disease and their role in its resistance, leaf photosynthesis, agronomic plant traits, root growth, and root quality were studied. The results show that the joint application of oligochitosan and low-dosage pyraclostrobin could control LSD more efficiently, with control effects of 85.75-87.49% compared to high-dosage pyraclostrobin or oligochitosan alone. Concurrently, the application of this formula could more effectively improve the resistance, leaf photosynthesis, agronomic plant traits, root yield, and medicinal quality of P. heterophylla, as well as reduce the application of pyraclostrobin. This finding suggests that 30% pyraclostrobin suspension concentrate (SC) 1500-time + 5% oligosaccharin aqueous solutions (AS) 500-time diluent can be recommended for use as a feasible formula to manage LSD and reduce the application of chemical pesticides.

Formation Kinetics and Antimicrobial Activity of Silver Nanoparticle Dispersions Based on N-Reacetylated Oligochitosan Solutions for Biomedical Applications

The paper presents the results of the synthesis, a detailed kinetics study, and an investigation of the biological activity of silver nanoparticles (AgNPs) in aqueous solutions of N-reacetylated oligochitosan hydrochloride. UV-visible spectrophotometry and dynamic light scattering were employed to control silver ion reduction. The process was observed to follow a pseudo-first-order law. Transmission and scanning electron microscopy demonstrated that AgNPs ranging in size from 10 to 25 nm formed aggregates measuring 60 to 90 nm, with the aggregate surface coated by a 2-4 nm chitosan shell. X-ray microanalysis and powder X-ray diffractometry were used to study the phase composition, identifying two crystalline phases, nanocrystalline silver and AgCl, present in the dispersions. The antibacterial effect was assessed using the serial dilution method for dispersions with varying degrees of Ag+ conversion. Nanodispersions exhibited significant activity against Escherichia coli, Pseudomonas aeruginosa, Bacillus cereus, and Staphylococcus aureus. Interestingly, the activity did not appear to be heavily influenced by the presence of the AgCl phase or the concentration of Ag+ ions. These synthesized dispersions hold promise for the development of materials tailored for biomedical applications.

Nanogel Particles Based on Modified Nucleosides and Oligosaccharides as Advanced Delivery System

This work addresses the challenge of delivering bioactive molecules by designing biocompatible nanogel particles (NGPs) utilizing rationally modified nature-sourced building blocks: capryl-oligochitosan and oxidized inosine. Capryl substituents endowed the resultant NGPs with membrane-penetration capabilities, while purine-containing inosine allowed H-bond/π-π/π-cation interactions. The prepared NGPs were complexed with carboxyfluorescein-labeled single-stranded oligonucleotide (FAM-oligo) and DsRed-encoding plasmid DNA. The successful delivery of FAM-oligo to the cell cytoplasm of the Nicotiana benthamiana plant was observed. Alexa 555-labeled bovine serum albumin (Alexa 555-BSA) was also efficiently encapsulated and delivered to the plant. In addition to delivering FAM-oligo and Alexa 555-BSA separately, NGPs also successfully co-delivered both biomolecules to the plant. Finally, NGPs successfully encapsulated the drug amphotericin B and reduced its toxicity while maintaining its efficacy. The presented findings suggest that NGPs may become a promising platform for the advanced delivery of bioactive molecules in various applications.

Effect of Soft Preheating of Bovine Serum Albumin on the Complexation with Oligochitosan: Structure and Conformation of BSA in the Complex

Phase analysis, spectroscopic, and light scattering methods are applied to investigate the peculiarities of the interaction of oligochitosan (OCHI) with native and preheated bovine serum albumin (BSA) as well as the conformational and structural changes of BSA in BSA/OCHI complex. As shown, untreated BSA binds with OCHI mainly forming soluble electrostatic nanocomplexes, with the binding causing an increase in BSA helicity without a change in the local tertiary structure and thermal stability of BSA. In contrast, soft preheating at 56 °C enhances the complexation of BSA with OCHI and slightly destabilizes the secondary and local tertiary structures of BSA within the complex particles. Preheating at 64 °C (below the irreversible stage of BSA thermodenaturation) leads to further enhancement in the complexation and formation of insoluble complexes stabilized by both Coulomb forces and hydrophobic interactions. The finding can be promising for the preparation of biodegradable BSA/chitosan-based drug delivery systems.

Balance of Macrophage Activation by a Complex Coacervate-Based Adhesive Drug Carrier Facilitates Diabetic Wound Healing

Uncontrolled and sustained inflammation disrupts the wound-healing process and produces excessive reactive oxygen species, resulting in chronic or impaired wound closure. Natural antioxidants such as plant-based extracts and natural polysaccharides have a long history in wound care. However, they are hard to apply to wound beds due to high levels of exudate or anatomical sites to which securing a dressing is difficult. Therefore, we developed a complex coacervate-based drug carrier with underwater adhesive properties that circumvents these challenges by enabling wet adhesion and controlling inflammatory responses. This resulted in significantly accelerated wound healing through balancing the pro- and anti-inflammatory responses in macrophages. In brief, we designed a complex coacervate-based drug carrier (ADC) comprising oligochitosan and inositol hexaphosphate to entrap and release antioxidant proanthocyanins (PA) in a sustained way. The results from in vitro experiments demonstrated that ADC is able to reduce LPS-stimulated pro-inflammatory responses in macrophages. The ability of ADC to reduce LPS-stimulated pro-inflammatory responses in macrophages is even more promising when ADC is encapsulated with PA (ADC-PA). Our results indicate that ADC-PA is able to polarize macrophages into an M2 tissue-healing phenotype via up-regulation of anti-inflammatory and resolution of inflammatory responses. Treatment with ADC-PA around the wound beds fine-tunes the balance between the numbers of inducible nitric oxide synthase-positive (iNOS+) and mannose receptor-negative (CD206-) M1 and iNOS-CD206+ M2 macrophages in the wound microenvironment compared to controls. Achieving such a balance between the numbers of iNOS+CD206- M1 and iNOS-CD206+ M2 macrophages in the wound microenvironment has led to significantly improved wound closure in mouse models of diabetes, which exhibit severe impairments in wound healing. Together, our results demonstrate for the first time the use of a complex coacervate-based drug delivery system to promote timely resolution of the inflammatory responses for diabetic wound healing by fine-tuning the functions of macrophages.

Comparative Study of Chitosan and Oligochitosan Coatings on Mucoadhesion of Curcumin Nanosuspensions

Curcumin nanosuspensions (Cur-NSs), chitosan-coated Cur-NSs (CS-Cur-NSs), and oligochitosan-coated Cur-NSs (OCS-Cur-NSs) were prepared by using an ultrasonic homogenization technique. The mean particle size of Cur-NSs was 210.9 nm and significantly (p < 0.05) increased to 368.8 nm by CS coating and decreased to 172.8 nm by OCS coating. Encapsulation efficiencies of Cur-NSs, CS-Cur-NSs, and OCS-Cur-NSs were 80.6%, 91.4%, and 88.5%, respectively. The mucin adsorption of Cur-NSs was steeply increased about 3–4 times by CS and OCS coating. Morphological changes of these NSs were studied using circular dichroism spectroscopy, Fourier-transform infrared (FT-IR) spectroscopy, and transmission electron microscopy (TEM). Thus, CS-Cur-NSs and OCS-Cur-NSs showed great potential as mucoadhesive nano-carriers for the efficient delivery of water insoluble compounds like curcumin to the gastrointestinal system.

Self-Assembly of Phycoerythrin with Oligochitosan by Electrostatic Interaction for Stabilization of Phycoerythrin

Phycoerythrin (PE) is a natural water-soluble pigment protein with characteristic phycobilins and is sensitive to thermal and light environmental changes. In this study, PE was extracted from Porphyra haitanensis and PE-oligochitosan complexes (POC) were fabricated by a self-assembly approach. The effects of cationic oligochitosan on the binding interaction, structure, size distribution, and color stability of PE were evaluated. The stoichiometric number n was calculated to be 21.67 ± 2.65 (oligochitosan/PE) and the binding constant K was (6.47 ± 0.48) × 10⁵ M^-1. Cationic oligochitosan could electrostatically interact with PE and affect the PE structure by increasing the α-helix content. In addition, high concentrations of oligochitosan led to the formation of dense phycoerythrin protein granules. Moreover, at a reaction ratio of 20.0:1 (oligochitosan/PE), being approximately the predicted stoichiometric number n, the thermal stability (40-80 °C), natural light stability, and ultraviolet light irradiation (254 nm) stability of the POC were improved. This study provides an approach to reduce the susceptibility of PE upon environmental changes by forming a stable self-assembly complex, which will promote the application of PE as a natural pigment protein in food and chemical applications.

Sustainable Agriculture Systems in Vegetable Production Using Chitin and Chitosan as Plant Biostimulants

Chitin and chitosan are natural compounds that are biodegradable and nontoxic and have gained noticeable attention due to their effective contribution to increased yield and agro-environmental sustainability. Several effects have been reported for chitosan application in plants. Particularly, it can be used in plant defense systems against biological and environmental stress conditions and as a plant growth promoter—it can increase stomatal conductance and reduce transpiration or be applied as a coating material in seeds. Moreover, it can be effective in promoting chitinolytic microorganisms and prolonging storage life through post-harvest treatments, or benefit nutrient delivery to plants since it may prevent leaching and improve slow release of nutrients in fertilizers. Finally, it can remediate polluted soils through the removal of cationic and anionic heavy metals and the improvement of soil properties. On the other hand, chitin also has many beneficial effects such as plant growth promotion, improved plant nutrition and ability to modulate and improve plants’ resistance to abiotic and biotic stressors. The present review presents a literature overview regarding the effects of chitin, chitosan and derivatives on horticultural crops, highlighting their important role in modern sustainable crop production; the main limitations as well as the future prospects of applications of this particular biostimulant category are also presented.

The structure and stability analysis of the pea seed legumin glycosylated by oligochitosan

BACKGROUND

The functionality of pea proteins is relatively weak relative to that of soybean proteins, which limits the application of pea proteins in food and nutritional applications. Glycosylation is a promising approach to influence the protein structure and in turn change the functional properties of pea proteins.

RESULTS

In this study, the effect of transglutaminase-induced oligochitosan glycosylation on the structural and functional properties of pea seed legumin was studied. Different oligochitosan-modified legumin complexes (OLCs) were prepared by applying different molar ratios of legumin to oligochitosan (1:1 to 1:4) induced by transglutaminase (10 U g-1 protein). Results of sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), glucosamine, and free amino analysis showed that the legumin could be covalently bonded with the oligochitosan and were influenced by the applying dose of the oligochitosan. Infrared spectroscopy, fluorescence, and scanning electron microscopy analysis indicated that the structure of the different OLC samples could be changed to different extents. Moreover, although the emulsifying activity decreased, the emulsification stability, thermal stability, and in vitro digestive stability of the OLCs were remarkably improved relative to that of the untreated legumin.

CONCLUSION

Oligochitosan glycosylation could change the structure of the legumin and consequently improve its emulsification stability, thermal stability, and in vitro digestive stability. This study will facilitate the legumin functionalization by the glycosylation approach to fabricate protein-oligochitosan complex for potential food and nutritional applications. © 2020 Society of Chemical Industry.

Calcium-oligochitosan-pectin microcarrier for colonic drug delivery

Pectin-based hydrogel microcarriers have shown promise for drug delivery to the colonic region. Microcarriers must remain stable throughout the upper gastrointestinal tract for effective colonic delivery, an issue that traditional pectin-based microcarriers have faced. The positively-charged natural biopolymer oligochitosan and divalent cation Ca²⁺ were used to dually cross-link pectin-based hydrogel microcarriers to improve carrier stability through simulated gastric and intestinal environments. Microcarriers were characterized with Scanning Electron Microscope and Fourier-Transform Infrared analysis. An optical microscope was used to observe the change of microcarrier size and morphology over time in the simulated gastrointestinal environments. Fluorescently-labeled Dextran was used as a model drug for this system. Calcium-Oligochitosan-Pectin microcarriers exhibited relatively small drug release in the upper gastrointestinal regions and were responsive to the high pH and enzymatic activity of simulated colonic environment (over 94% release after 2 h), suggesting great potential for colonic drug delivery.

Design of a Novel Oxygen Therapeutic Using Polymeric Hydrogel Microcapsules Mimicking Red Blood Cells

The goal of this research was to develop a novel oxygen therapeutic made from a pectin-based hydrogel microcapsule carrier mimicking red blood cells. The study focused on three main criteria for developing the oxygen therapeutic to mimic red blood cells: size (5–10 μm), morphology (biconcave shape), and functionality (encapsulation of oxygen carriers; e.g., hemoglobin (Hb)). The hydrogel carriers were generated via the electrospraying of the pectin-based solution into an oligochitosan crosslinking solution using an electrospinning setup. The pectin-based solution was investigated first to develop the simplest possible formulation for electrospray. Then, Design-Expert^® software was used to optimize the production process of the hydrogel microcapsules. The optimal parameters were obtained through the analysis of a total of 17 trials and the microcapsule with the desired morphology and size was successfully prepared under the optimized condition. Fourier transform infrared spectroscopy (FTIR) was used to analyze the chemistry of the microcapsules. Moreover, the encapsulation of Hb into the microcapsule did not adversely affect the microcapsule preparation process, and the encapsulation efficiency was high (99.99%). The produced hydrogel microcapsule system shows great promise for creating a novel oxygen therapeutic.

In vivo comparison of wound healing and scar treatment effect between curcumin-oligochitosan nanoparticle complex and oligochitosan-coated curcumin-loaded-liposome

This study aimed to compare the in vivo effectiveness between curcumin-oligochitosan nanoplexes (CUR-OCH nanoplexes) and oligochitosan-coated curcumin-encapsulated liposomes (OCH-Lip-CUR) with respect to wound healing and scar treatment. Firstly, CUR-OCH nanoplexes was prepared by drug-polysaccharide complexation method and OCH-Lip-CUR was prepared by a combining method of lipid-film hydration and sonication. Their in vitro cytotoxicity and in vivo wound healing and scar treatment effectiveness were evaluated using 3T3 cells and mice Mus musculus var. Albino, respectively. The resutls indicated that both of them were in nanosize with a moderate PDI (less than 0.3), and exhibited negligible cytotoxicity at low CUR concentration (0.01 mg/mL). Moreover, their application onto wounds resulted in faster healing and higher scar treatment effectiveness than control samples. Interestingly, OCH-Lip-CUR exhibited higher in vivo effectiveness than CUR-OCH nanoplexes. However, based on their own advantages, both of them were good candidates for a commercial formulation for wound healing and scar treatment.

Effects of Different Oligochitosans on Isoflavone Metabolites, Antioxidant Activity, and Isoflavone Biosynthetic Genes in Soybean ( Glycine max) Seeds during Germination

Five oligochitosans with increasing degrees of polymerization (DPs), i.e., from chitotriose to chitoheptaose, were examined to clarify the structure-bioactivity relationship between the DPs of oligochitosans and their effects on the isoflavone metabolites, total phenolic and flavonoid contents (TPC and TFC, respectively), and antioxidant activity of soybean ( Glycine max) seeds during germination. Oligochitosans of different DPs exhibited varying influences on the TPC, TFC, and antioxidant activities of soybean seeds. Chitohexaose exerted a strong effect and significantly increased the aforementioned parameters in soybean seeds 72 h after germination. Genistin, malonylgenistin, and genistein were the main isoflavones found, and the genistin and genistein contents were significantly enhanced by 67.32% and 131.38%, respectively, after chitohexaose treatment. Several critical genes involved in the isoflavone biosynthesis (i.e., PAL, CHS, CHI, IFS) of soybeans treated with and without chitohexaose were analyzed, and results suggested that chitohexaose application could dramatically stimulate the transcription of these genes.

Functional Nanostructured Oligochitosan⁻Silica/ Carboxymethyl Cellulose Hybrid Materials: Synthesis and Investigation of Their Antifungal Abilities

Functional hybrid materials were successfully synthesized from low-cost waste products, such as oligochitosan (OCS) obtained from chitosan (one of the main components in crab shells) and nanosilica (nSiO₂) obtained from rice husk, in a 1:1 ratio (w/w), and their dispersion in the presence of carboxymethyl cellulose at pH 7 was stable for over one month without aggregation. The molecular weights, chemical structures, morphologies, and crystallinities of the obtained materials were characterized by GPC, FTIR, TEM, and XRD, respectively. The antifungal effects of OCS, nSiO₂, and the OCS/nSiO₂ hybrid materials were investigated via a disk-diffusion method. The results showed that the nanohybrid materials had better resistance to Phytophthora infestans fungus than the individual components, and a concentration of the OCS2/nSiO₂ hybrid material of 800 mg L⁻¹ was the lowest concentration where the material completely inhibited Phytophthora infestans growth, as measured via an agar dilution method. This study not only creates a novel environmentally friendly material with unique synergistic effects that can replace current toxic agrochemicals but also can be considered a new platform for further research in green agricultural applications.

Proteomic analysis of the inhibitory effect of oligochitosan on the fungal pathogen, Botrytis cinerea

BACKGROUND

The fungal pathogen Botrytis cinerea infects a broad range of horticultural plants worldwide, resulting in significant economic losses. A derivative of chitosan, oligochitosan, has been reported to be an eco-friendly alternative to synthetic fungicides.

RESULTS

Oligochitosan can greatly inhibit B. cinerea spore germination and induce protein carbonylation. To further investigate the molecular mechanism underlying the inhibitory effect, a comparative proteome analysis was conducted of oligochitosan-treated versus non-treated B. cinerea spores. The cellular proteins were obtained from B. cinerea spore samples and subjected to two-dimensional gel electrophoresis. In total, 21 differentially expressed proteins (DEPs) were identified. Three DEPs were up-regulated in the oligochitosan-treated versus the untreated spores, including scytalone dehydratase and a serine carboxypeptidase III precursor. By contrast, seven DEPs, including Hsp 88 and cell division cycle protein 48, were down-regulated by oligochitosan treatment. Notably, 10 DEPs, including phosphatidylserine decarboxylase proenzyme and ATP-dependent molecular chaperone HSC82, were only detected in the control spores, whereas one DEP, a non-annotated predicted protein, was only detected in the oligochitosan-treated spores.

CONCLUSION

Oligochitosan may affect the spore germination of B. cinerea by impairing protein function. These findings have practical implications with respect to the use of oligochitosan for controlling fungal pathogens. © 2018 Society of Chemical Industry.

Reversible Stability of Emulsion and Polymer Latex Controlled by Oligochitosan and CO₂

The addition of salt to a colloid solution ensures that emulsions can be easily separated into two phases and that polymer latexes can be coagulated. The switchable stability of emulsions and polymer latexes would improve the properties for their current applications. A switchable process of salt addition can be achieved using CO₂ and switchable water, and it is a novel, benign approach to achieving a switchable ionic strength in an aqueous solution. However, the problem associated with switchable water is that its additives are all synthetic tertiary amines, most of which are harmful to human beings and the environment. Oligochitosan, as a natural product, can also be used as a switchable water additive. In this paper, a new switchable water system using oligochitosan to change the ionic strength was explored for use in several potential industrial applications. The conductivity of the aqueous solution of oligochitosan (0.2 wt.%) was switched from 0.2 to 331 μS/cm through the addition and removal of CO₂. Oligochitosan and CO₂ were successfully utilized to reversibly break a crude oil emulsion. Polystyrene (PS) latexes could also be reversibly destabilized; the zeta potential of the PS latex changed between -5.8 and -45.2 mV in the absence and presence of CO₂ after oligochitosan was dissolved in the PS latex. The use of oligochitosan is a more environmentally friendly means for reversibly separating colloid solutions.

Response of Ustilago maydis against the Stress Caused by Three Polycationic Chitin Derivatives

Chitosan is a stressing molecule that affects the cells walls and plasma membrane of fungi. For chitosan derivatives, the action mode is not clear. In this work, we used the yeast Ustilago maydis to study the effects of these molecules on the plasma membrane, focusing on physiologic and stress responses to chitosan (CH), oligochitosan (OCH), and glycol-chitosan (GCH). Yeasts were cultured with each of these molecules at 1 mg·mL⁻¹ in minimal medium. To compare plasma membrane damage, cells were cultivated in isosmolar medium. Membrane potential (Δψ) as well as oxidative stress were measured. Changes in the total plasma membrane phospholipid and protein profiles were analyzed using standard methods, and fluorescence-stained mitochondria were observed. High osmolarity did not protect against CH inhibition and neither affected membrane potential. The OCH did produce higher oxidative stress. The effects of these molecules were evidenced by modifications in the plasma membrane protein profile. Also, mitochondrial damage was evident for CH and OCH, while GCH resulted in thicker cells with fewer mitochondria and higher glycogen accumulation.

Effects of Chitooligosaccharide Coating Combined with Selected Ionic Polymers on the Stimulation of Ornithogalum saundersiae Growth

Recently, agricultural and horticultural sectors have shown an increased interest in the use of biopolymers and their derivatives as growth biostimulators. So far, coating is a little known method of applying the biostimulators. Our three-year study investigated coating the bulbs of Ornithogalum saundersiae with chitooligosaccharide (COS), sodium alginate, carrageenan, gellan gum and xanthan gum. The coating method was based on the formation of polyelectrolyte complexes. The COS with 48,000 g mol⁻¹ molecular weight was contained by means of controlled free-radical degradation. Biopolymer coatings stimulated plant growth and flowering, total chlorophyll content, total polyphenol content and the levels of nitrogen, phosphorus, potassium and boron. The plants grown from the bulbs coated with COS + gellan gum exhibited the most vigorous growth, were first to flower, showed the highest antioxidant activity (DPPH), and the greatest content of pigments, polyphenols, l-ascorbic acid, potassium, phosphorus, zinc and manganese. These results suggest COS formulated with gellan gum shows promise as a potential biostimulator of plant growth.

Modified properties of a glycated and cross-linked soy protein isolate by transglutaminase and an oligochitosan of 5 kDa

BACKGROUND

Soy protein is an important protein ingredient for the food industry; however, its properties can be improved by enzymatic and chemical modifications. This study applied a new enzymatic glycation and cross-linking to modify soy protein isolate (SPI), using an oligochitosan of 5 kDa and transglutaminase. Properties of the obtained glycated and cross-linked SPI (GC-SPI) were unknown and thus assessed.

RESULTS

GC-SPI contained glucosamine of 13.6 g kg^-1 protein, but less reactable &bond;NH₂ than SPI (0.42 vs. 0.50 mol kg^-1 protein). Infrared spectra and circular dichroism results showed that GC-SPI other than SPI and cross-linked SPI had more &bond;OH in molecules, and was more disordered in secondary structure. In comparison with SPI, GC-SPI showed enhanced water-binding capacity, could form aggregates with enlarged hydrodynamic radius (180.2 vs. 82.9 nm) and negative zeta-potential (-31.2 vs. -27.7 mV) in dispersion, but exhibited lower thermal stability (e.g. greater mass loss) upon heating at a temperature above 288 °C. GC-SPI also had lower in vitro proteolytic digestibility than SPI due to the protein cross-linking.

CONCLUSION

Oligochitosan of 5 kDa and transglutaminase can be used to glycate and cross-link SPI. This approach is applicable to generate potential protein ingredient with good hydration and dispersive stabilisation. © 2016 Society of Chemical Industry.

Postharvest Application of Oligochitosan and Chitosan Reduces Calyx Alterations of Citrus Fruit Induced by Ethephon Degreening Treatment

In the present study, we investigated whether the postharvest application of oligochitosan and chitosan could be used as potential alternatives to 2,4-dichlorophenoxyacetic acid (2,4-D) treatment to prevent calyx senescence of mandarin fruits induced by degreening treatment. The results of scanning electron microscopy indicated that the ethephon degreening treatment could accelerate the formation of pedicel abscission layers. Treatments with 15 g kg^-1 oligochitosan, 5 g kg^-1 chitosan, and 50 mg kg^-1 2,4-D significantly suppressed the formation of pedicel abscission layers of ethephon degreening fruit and inhibited the browning of the calyx. These two treatments delayed the degradation of protopectin, cellulose, and lignin. Inhibition of the increase in the abscisic acid (ABA) content was also observed in these two treatments. In conclusion, these two treatments, particularly 15 g kg^-1 oligochitosan, could be potentially used as alternatives to 2,4-D to improve calyx alterations induced by the ethephon degreening treatment in mandarin fruits.

The Effect and Action Mechanisms of Oligochitosan on Control of Stem Dry Rot of Zanthoxylum bungeanum

In this report, the effects of two oligochitosans, i.e., oligochitosan A (OCHA) and oligochitosan B (OCHB), on control of dry rot of Zanthoxylumbungeanum (Z. bungeanum) caused by Fusariumsambucinum (F. sambucinum) were evaluated. First, both oligochitosans show desirable ability to decrease the infection of F. sambucinum. Second, the oligochitosans strongly inhibit the radial colony and submerged biomass growth of F. sambucinum. Lastly, these oligochitosans are capable of increasing the activities of phenylalanine ammonia lyase (PAL), polyphenoloxidase (PPO) and peroxidase (POD) significantly, as well as enhancing the content of total phenolics in Z. bungeanum stems. These findings indicate that the protective effects of OCHA and OCHB on Z. bungeanum stems against dry rot may be associated with the direct fungitoxic function against pathogen and the elicitation of biochemical defensive responses in Z. bungeanum stems. The outcome of this report suggests that oligochitosans may serve as a promising natural fungicide to substitute, at least partially, for synthetic fungicides in the disease management of Z. bungeanum.