Elicitor Chitosan Research Articles

The influence of chitosan on plant growth and -sitosterol content in adventitious roots of Talinum paniculatum in NFT hydroponic cultivation system

Beta-sitosterol is the most abundant type of phytosterol found in nature and it offers numerous health benefits for humans including anticancer, antidiabetic, and blood cholesterol-lowering properties. One biomass with a significant beta-sitosterol content is the Javanese ginseng root (Talinum paniculatum). However, Javanese ginseng has not been fully exploited and is often perceived as a mere wild plant. This research was conducted by cultivating Javanese ginseng using the Nutrient Film Technique (NFT) hydroponic method along with the addition of chitosan elicitors at various concentrations: 0, 12.5, 25, and 50 ppm. The purpose of this research was to determine the optimal chitosan concentration for the growth of Javanese ginseng, the beta-sitosterol content, and the productivity of -sitosterol in Javanese ginseng roots. The research revealed that a 12.5 ppm chitosan concentration could increase the root weight by 8.785 g and the shoot weight by 88 g. The growth rate increased to 3.457 g/day and the productivity of -sitosterol in the roots reached 25.084 mg/m2/month. On the other hand, the addition of chitosan led to a decrease in the root-to-shoot ratio, indicating an improved cultivation environment compared to cultivation without chitosan. Furthermore, the results of the research also indicated that the addition of chitosan did not affect the β-sitosterol content in the Javanese ginseng adventitious roots. Therefore, it can be concluded that the optimal chitosan concentration that positively impacts Javanese ginseng cultivated using the NFT hydroponic method is 12.5 ppm because chitosan generates Reactive Oxygen Species (ROS) which causing plant damage and cell death when threshold exceeded.

Additive and Specific Effects of Elicitor Treatments on the Metabolic Profile of Arabidopsis thaliana.

Several elicitors of plant defense have been identified and numerous efforts to use them in the field have been made. Exogenous elicitor treatments mimic the in planta activation of pattern-triggered immunity (PTI), which relies on the perception of pathogen-associated molecular patterns (PAMPs) such as bacterial flg22 or fungal chitins. Early transcriptional responses to distinct PAMPs are mostly overlapping, regardless of the elicitor being used. However, it remains poorly known if the same patterns are observed for metabolites and proteins produced later during PTI. In addition, little is known about the impact of a combination of elicitors on PTI and the level of induced resistance to pathogens. Here, we monitored Arabidopsis thaliana resistance to the bacterial pathogen Pseudomonas syringae pv. tomato DC3000 (Pto DC3000) following application of flg22 and chitosan elicitors, used individually or in combination. A slight, but not statistically significant increase in induced resistance was observed when the elicitors were applied together when compared with individual treatments. We investigated the effect of these treatments on the metabolome by using an untargeted analysis. We found that the combination of flg22 and chitosan impacted a higher number of metabolites and deregulated specific metabolic pathways compared with the elicitors individually. These results contribute to a better understanding of plant responses to elicitors, which might help better rationalize their use in the field. [Formula: see text] Copyright © 2024 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license.

Yeast extract and chitosan elicitation improves essential oil, regulates plant growth and antioxidative system in Lippia alba (Mill) N.E. Brown (Verbenaceae)

Lippia alba is one of the most used species in traditional medicine, having been the subject of intense exploration in search of the extraction of its essential oil, which contains several compounds of pharmacological importance. This study evaluated the effects of different concentrations of two biotic elicitors: yeast extract (YE) (0, 1, 2 and 4 g L−1) and chitosan (CH) (0, 1, 2 and 4 g L−1) in the accumulation of biomass, gas exchange, antioxidative system response, and production and profile of bioactive compounds (BCs). Foliar spraying with 4 g L−1 of CH favored the accumulation of shoot dry biomass and significantly increased the levels of chlorophyll a and carotenoids. Both elicitors were efficient to increase the essential oil content extracted from the leaves of L. alba and, in general, the elicitors tested at concentrations of 2 and 4 g L−1 showed the highest amounts of BCs and glandular trichome density. Chemical analysis of BCs revealed 46 different compounds, with Geranial and Geraniol being the main components. The application of YE induced the production of an exclusive compound (Trans-piperitol), while CH induced the formation of seven exclusive compounds (Santolina triene, Myrcenol, Neral, Cis-Pinocarvyl acetate, Dimethoxy-(Z)-citral, Geranyl acetate and Limonene aldehyde). Yeast extract and Chitosan proved to be efficient to increase the BCs content in Lippia alba, however, the application of 4 g L−1 of CH resulted in a higher production of shoot dry biomass, photosynthetic parameters, in the density of glandular trichomes and in the production of BCs.

Putative NAD(P)-Binding Rossmann Fold Protein Is Involved in Chitosan-Induced Peroxidase Activity and Lipoxygenase Expression in Physcomitrium patens.

Oxidative burst, the rapid production of high levels of reactive oxygen species in response to external stimuli, is an early defense reaction against pathogens. The fungal elicitor chitosan causes an oxidative burst in the moss Physcomitrium patens (formerly Physcomitrella patens), mainly due to the peroxidase enzyme Prx34. To better understand the chitosan responses in P. patens, we conducted a screen of part of a P. patens mutant collection to isolate plants with less peroxidase activity than wild-type (WT) plants after chitosan treatment. We isolated a P.patens mutant that affected the gene encoding NAD(P)-binding Rossmann fold protein (hereafter, Rossmann fold protein). Three Rossmann fold protein-knockout (KO) plants (named Rossmann fold KO lines) were generated and used to assess extracellular peroxidase activity and expression of defense-responsive genes, including alternative oxidase, lipoxygenase (LOX), NADPH oxidase, and peroxidase (Prx34) in response to chitosan treatment. Extracellular (apoplastic) peroxidase activity was significantly lower in Rossmann fold KO lines than in WT plants after chitosan treatments. Expression of the LOX gene in Rossmann fold KO plants was significantly lower before and after chitosan treatment when compared with WT. Peroxidase activity assays together with gene expression analyses suggest that the Rossmann fold protein might be an important component of the signaling pathway leading to oxidative burst and basal expression of the LOX gene in P. patens. [Formula: see text] Copyright © 2023 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license.

Conifer cell cultures as a tool for studying the induction of terpenoid defense compounds

ABSTRACT Conifer trees often increase their production of terpene resins after attack by herbivores or pathogens, a defense response that may be critical in their survival. Yet it has proved difficult to study such terpene induction under laboratory conditions because of the need for mature trees and specific organs and cells at the proper stage of development. Here we explore the potential of Norway spruce (Picea abies) cell cultures to be a convenient system for studying terpene induction in this species. We demonstrated that P. abies cell suspension cultures accumulated a mixture of monoterpenes (but not of sesquiterpenes or diterpenes), similar to that found in intact trees, but at level of only 0.5–2.5% those in intact trees. However, treatment with the hormone methyl jasmonate and the fungal elicitor chitosan increased monoterpene accumulation 2–4-fold. Based on in vitro assays of terpene synthase activity, this increase was driven by an increased rate of biosynthesis, and was likely not due to pH changes caused by hormone or fungal elicitor treatment. Since these defense responses of P. abies cell cultures are typical of the response of intact spruce needles and bark, such cultures may have promise as a laboratory system for studying the induction of terpene resin defenses.

Field Control Effect and Initial Mechanism: A Study of Isobavachalcone against Blister Blight Disease.

Blister blight (BB) disease is caused by the obligate biotrophic fungal pathogen Exobasidium vexans Massee and seriously affects the yield and quality of Camellia sinensis. The use of chemical pesticides on tea leaves substantially increases the toxic risks of tea consumption. Botanic fungicide isobavachalcone (IBC) has the potential to control fungal diseases on many crops but has not been used on tea plants. In this study, the field control effects of IBC were evaluated by comparison and in combination with natural elicitor chitosan oligosaccharides (COSs) and the chemical pesticide pyraclostrobin (Py), and the preliminary action mode of IBC was also investigated. The bioassay results for IBC or its combination with COSs showed a remarkable control effect against BB (61.72% and 70.46%). IBC, like COSs, could improve the disease resistance of tea plants by enhancing the activity of tea-plant-related defense enzymes, including polyphenol oxidase (PPO), catalase (CAT), phenylalanine aminolase (PAL), peroxidase (POD), superoxide dismutase (SOD), β-1,3-glucanase (Glu), and chitinase enzymes. The fungal community structure and diversity of the diseased tea leaves were examined using Illumina MiSeq sequencing of the internal transcribed spacer (ITS) region of the ribosomal rDNA genes. It was obvious that IBC could significantly alter the species' richness and the diversity of the fungal community in affected plant sites. This study broadens the application range of IBC and provides an important strategy for the control of BB disease.

Pharmacodynamic Acnalysis of Anti-chitosan in the Prevention and Treatment of Tomato Virus Diseases

Viral diseases are primary diseases of tomatoes with an occurrence rate generally reaching above 30% and up to 90% in severe cases. Control of viral diseases is an enormous challenge in crop protection. Application of insecticide for preventing virus transmission through reduction of insect vectors is considered an useful means. The crop breeding technology and tissue culture are also employed to generate viral resistant cultivar or virus-free seedlings. However, these methods are often less effective in practice because of viral mutations. It has been reported that chitosan, as an efficient plant resistance-inducing elicitor, can inhibit the infection of pathogenic bacteria, induce the production of phytochemicals and stimulate plant self-resistance, and has been widely used in the prevention and treatment of viral diseases. In this study, by investigating the field disease index and monitoring the form and content of the virus in the diseased leaves and new leaves before each application, it was clarified that continuous spraying of 0.5% chitosan water solution for 3 times at an interval of 7 days has a significant control effect of preventing tomato virus disease. Negative staining electron microscope observation method visually showed the existence and changes of virus in leaves; RT-PCR method analyzed the virus types as tomato spotted wilt virus (TSWV), tomato chlorosis virus (ToCV), tobacco mosaic virus (TMV); The qRT-PCR method further clarified that the inhibition rates of 0.5% chitosan solution on tomato spotted wilt and tomato chlorosis virus were 75.31% and 67.18%, respectively. It is concluded from our tests that the plant defence elicitor chitosan (a.i. 0.5%) is able to inhibit virus replication in crop cells and prevent the aggravation of tomato plant virus disease symptoms. Therefore, the strategy for the management of tomato virus disease is to apply the inducer chitosan regularly to maintain a low virus titer and prevent the occurrence and spread of virus disease.

Influence of drought stress and foliar application of chitosan on nutrient accumulation and phenolic composition of Thymus daenensis Celak

AbstractChanges in climate have intensified the drought in semi‐arid regions. A shift toward cultivation of low‐input crops, including high‐value medicinal and herbal plants seems a more sustainable alternative strategy. A 2‐year field study was conducted to investigate the influence of drought stress and chitosan on nutrient density and phenolic compounds of thyme. Treatments consisted of a factorial combination of three irrigation and three chitosan rates. Irrigation treatments consisted of keeping experimental plots at field capacity (no stress), irrigation when plots reached 50% of field capacity (mild stress), and irrigation when plots reached 25% of field capacity (severe stress). Chitosan rates were 0, 200, and 400 μL L−1, while K+, and to some degree Ca+2, accumulation increased by drought, N, P, and all micronutrients (Mn2+, Zn2+, Cu2+, and Fe2+) decreased steadily as drought stress intensified. Drought stress reduced N and P by 23%–19% and 35%–23%, respectively, over the 2 years. Application of chitosan enhanced the accumulation of macro and micronutrients. Drought stress resulted in alterations in phenolic composition. In mature plants, almost all phenolic compounds, except thymol, increased as drought stress intensified. Cinnamic acid and rosmarinic contents, as the two major identified compounds, increased by 31% and 45%, respectively, under severe drought. Similar to drought, chitosan elicitation was more effective in elevating phenolic compounds in mature plants. The response of thyme to chitosan was independent of soil moisture availability. The results indicated that application of 400 μL−1 chitosan improved nutrient density and dry matter while significantly saved irrigation water.

Chitosan Induces Sorghum Tolerance to Water Deficits by Positively Regulating Photosynthesis and the Production of Primary Metabolites, Osmoregulators, and Antioxidants

Current climate change scenarios require strategies that mitigate the effects of water deficits. Given that chitosan stimulates induced resistance responses, we tested the hypothesis that foliar application of this polysaccharide can have positive effects on the primary metabolite, antioxidant, and osmoregulatory metabolisms of sorghum, mitigating the effects of water deficit on grain yield. Sorghum plants were cultivated under either irrigated or water-deficit conditions and were either treated or untreated with chitosan, and we assessed the following responses: water potential, gas exchange, nutritional status, biosynthesis of primary and osmoregulatory metabolites, the activity of the antioxidant system constituents, and hydrogen peroxide and malondialdehyde contents. An active methodology was used to impose water stress on plants grown in pots with 20 kg of soil, 06 replications per treatment. Sorghum plants subjected to water deficit that were treated with chitosan exhibited higher stomatal conductance and transpiration than the untreated plants. Water restriction reduced the nutrient contents of leaves, but in the irrigated plants, chitosan treatment increased the tissue contents of certain nutrients and leaf concentrations of total proteins and total amino acids. In the plants under water-deficit conditions that were treated with chitosan, an elevated photosynthetic rate contributed to an increase in carbohydrate accumulation and a higher production of panicle and grain dry biomass compared with the untreated plants. The activity of catalase and ascorbate peroxidase also increased in response to chitosan. Overall, chitosan was effective in enhancing the water deficit tolerance of sorghum plants cultivated under water-deficit conditions by 57%. With this work, we generate perspectives for studies focusing on the development of water-deficit-resistant sorghum lineages, by means of chitosan elicitation.

Phenolics and terpenoids change in response to yeast extract and chitosan elicitation in Zataria multiflora cell suspension culture.

The online version contains supplementary material available at 10.1007/s13205-022-03235-x.

Preharvest Applications of Chitosan, Salicylic Acid, and Calcium Chloride Have a Synergistic Effect on Quality and Storability of Date Palm Fruit (Phoenix dactylifera L.)

The ‘Khenizi’ date palm is one of the most recognized date palm cultivars. It is commonly consumed at the Bisr, Rutab, and Tamr stages of ripening; however, the fruit has a short shelf/storage life at this stage of maturity even with refrigeration. Preharvest application of a natural elicitor chitosan (Ch) has been reported to have positive influences on quality and shelf life of many fruits; however, synergetic effects of Chand other natural elicitors have not been investigated. Therefore, this study aimed to investigate the synergistic effect of preharvest spray treatments with Ch 1% in combination with calcium chloride (Ca) 3% and salicylic acid (SA) 2 mm on ‘Khenizi’ date fruit quality and storage life. Fruit quality parameters, including physical and physiochemical characteristics, phytochemical content, and bioactive properties, were determined at harvest time and during cold storage at 2 °C for 60 days for 2 months. Our results revealed that a combination of these elicitors had significantly influenced the fruit quality during storage compared with control. For instance, Ch+SA and Ch+Ca+SA treatments improved total phenolic content (TPC), and the antioxidant activity at harvest and at specific times during the postharvest storage period. Furthermore, Ch+SA+Ca treatment significantly delayed senescence in treated fruits during cold storage for 45 days as compared with other treatments and the control. In addition, Ch+Ca-treated fruits had the lowest weight loss after 45 days of cold storage. Ch+SA treatment had the lowest microbial counts as compared with other treatments, including the control. The significance of this study is that it provides evidence that a combination of these elicitors has the potential to improve fruit quality at harvest, as well as during postharvest storage Future studies should be directed to fine tune the concentrations and combinations that may have commercial applications.

Synergistic Effect of Preharvest Spray Application of Natural Elicitors on Storage Life and Bioactive Compounds of Date Palm (Phoenix dactylifera L., cv. Khesab)

Despite the immense capabilities of the date palm, maintaining the fruit’s quality, marketability, and shelf life is still a challenge. This study aimed to assess the synergistic effect of a preharvest spray application of a natural elicitor chitosan, (Ch) 1% alone and in combination with salicylic acid (SA) 2 mM and calcium chloride (Ca) 3%; (Ch,SA, Ca,Ch+Ca, Ch+SA, Ch+SA+Ca), on the quality parameters, storage life, and bioactive compounds content of date fruit from ‘Khasab’ cultivar during cold storage for 60 days. The obtained results revealed that all treatments significantly retard senescence/decay of the fruit compared to the control. Ch+SA treated fruit followed by Ch, and Ch+SA+Ca had the lowest weight loss, color change, and the least decay after 60 days of storage. Ch+Ca, SA, Ca treated fruit had significantly lower levels of total soluble solids and highest total phenolic, tannins, and flavonoids contents compared to the control fruit. Antioxidant activities were found in all treatments, with significantly higher effect in Ch+SA+Ca and Ch+SA compared to the control. Our results provide an evidence for a synergistic effect of elicitors combination to extend the shelf life of date fruit during cold storage by preserving its quality and decreasing senescence/decay and recommend it as a promising strategy.

Chitosan elicitation of saponin accumulation in Psammosilene tunicoides hairy roots by modulating antioxidant activity, nitric oxide production and differential gene expression

Elicitation is one of the most effective strategies for enhancing plant bioactive compounds, such as triterpenoid saponins. Chitosan gained worldwide attention for biostimulant activity, but little is known about its roles in the elicitation of triterpenoid saponin in medicinal plants. Here, we explored the regulatory network of chitosan on saponin accumulation in hairy root cultures of Psammosilene tunicoides, a valuable medicinal herb known for its pain-relieving properties endemic to China. Compared with control, the highest total saponin accumulation exhibited a 4.55-fold enhancement in hairy roots elicited by 200 mg L−1 chitosan for nine days. High-performance liquid chromatography (HPLC) revealed the yields of quillaic acid, gypsogenin and gypsogenin-3-O-β-D-glucuronopyranoside were significantly increased after chitosan treatments. Moreover, exogenous chitosan application dramatically triggered the reactive oxygen species (ROS) scavenging enzyme activities and nitric oxide (NO) content in hairy roots. Comparative transcriptome analysis from chitosan-treated (1 and 9 d) or control groups revealed that differentially expressed genes (DEGs) were greatly enriched in plant-pathogen interaction and metabolic processes. The transcriptions of candidate DEGs involved in chitosan-elicited saponin metabolism were increased, especially genes encoding antioxidant enzymes (SOD, POD and GR), stress-responsive transcription factors (WRKYs and NACs) and terpenoid biosynthetic enzymes (DXS, GPPS and SE). Taken together, these results indicate that chitosan elicitor promotes triterpenoid saponin biosynthesis by enhancing antioxidant activities, NO production and differential gene expression in P. tunicoides hairy roots.

Ecofriendly management of stem rot of berseem caused by Sclerotinia trifoliorum

Stem rot, incited by Sclerotinia trifoliorum Eriksson is one of the most devastating soil borne fungal pathogens of berseem (Trifolium alexandrinum L.) inflicting significant fodder and seed yield losses. Eleven plant extracts, six organic inputs, one elicitor and five organic and inorganic salts were assayed for their effectiveness against S. trifoliorum under in vitro conditions. Extracts of Aegle marmelos and Cymbopogan citrates showed complete mycelial inhibition of S. trifoliorum at 5% concentration. Among organic inputs, panchgavya and fermented cow urine recorded 100% inhibition to mycelial growth of stem rot pathogen at 10% concentration. Elicitor (chitosan) and salts namely copper sulphate and potassium carbonate provided complete mycelial inhibition of test pathogen under in vitro conditions at 0.1, 2.0 and 5.0% concentrations, respectively. The plant extracts, organic inputs and salts that exhibited highest mycelial inhibition to S. trifoliorum under in vitro conditions were evaluated for their antifungal efficacy under greenhouse and field experiments during rabi 2017–18 and 2018–19. The extracts of chitosan (78.58; 77.15%), panchgavya (75.99; 67.14%), copper sulphate 71.38; 61.18%) and A. marmelos (71.75; 56.24%) have recorded highest percent disease control as compared to untreated control in greenhouse and field trials in rabi 2017–18 and 2018–19, respectively. Significant increase in green fodder yield of berseem from 9.87 to 33.38% was also recorded after treatment with plant extracts, organic inputs and some salts. The current study showed that plant extracts, organic inputs and salts have potential for the management of stem rot of berseem.

Field application of star polymer-delivered chitosan to amplify plant defense against potato late blight

• Complexation of star polymer (SPc) with chitosan leads to particle size reduction. • SPc can assemble with chitosan/eugenol through different binding forces. • Control effects of chitosan/eugenol delivered by SPc are improved. • SPc can be applied as a common adjuvant to improve control efficacy in the field. The application of environmentally-friendly fungicides, such as elicitors and botanical fungicides, to minimize the risk of exposure to the ecosystem has become a global trend. However, the bioactivity and absorbency of elicitors are critical factors that limit the large-scale field application. With the objective of exploring a sustainable method for controlling plant diseases, a star polymer (SPc) was constructed to deliver plant elicitors/botanical fungicides with a low production cost. The SPc could be complexed with chitosan through hydrogen bond and Van der Waals forces. The complexation of SPc with chitosan decreased chitosan particle size from 144.61 nm to 17.40 nm in an aqueous solution. The SPc could activate the endocytosis pathway of plants by a nano-delivery system to amplify the defense responses induced by the chitosan elicitor. The nano-sized chitosan/SPc complexes exhibited enhanced control effects against potato late blight, which is considered one of the most destructive crop pathogens threatening global food security. Similar to chitosan, the eugenol could assemble with SPc through electrostatic interactions, and the toxicity of eugenol delivered by SPc was also improved against potato late blight. As an adjuvant, SPc could be applied to increase chitosan and eugenol’s control efficacies in the field. Here we report the first application of a nano-delivery system to improve plant defenses to the best of our knowledge. The SPc adjuvant’s application appears to be suitable for delivering plant elicitors/botanical fungicides, which is beneficial for improving bioactivity and decreasing the application quantity and frequency of conventional fungicides.

Chitosan Elicitation Impacts Flavonolignan Biosynthesis in Silybum marianum (L.) Gaertn Cell Suspension and Enhances Antioxidant and Anti-Inflammatory Activities of Cell Extracts

Silybum marianum (L.) Gaertn is a rich source of antioxidants and anti-inflammatory flavonolignans with great potential for use in pharmaceutical and cosmetic products. Its biotechnological production using in vitro culture system has been proposed. Chitosan is a well-known elicitor that strongly affects both secondary metabolites and biomass production by plants. The effect of chitosan on S. marianum cell suspension is not known yet. In the present study, suspension cultures of S. marianum were exploited for their in vitro potential to produce bioactive flavonolignans in the presence of chitosan. Established cell suspension cultures were maintained on the same hormonal media supplemented with 0.5 mg/L BAP (6-benzylaminopurine) and 1.0 mg/L NAA (α-naphthalene acetic acid) under photoperiod 16/8 h (light/dark) and exposed to various treatments of chitosan (ranging from 0.5 to 50.0 mg/L). The highest biomass production was observed for cell suspension treated with 5.0 mg/L chitosan, resulting in 123.3 ± 1.7 g/L fresh weight (FW) and 17.7 ± 0.5 g/L dry weight (DW) productions. All chitosan treatments resulted in an overall increase in the accumulation of total flavonoids (5.0 ± 0.1 mg/g DW for 5.0 mg/L chitosan), total phenolic compounds (11.0 ± 0.2 mg/g DW for 0.5 mg/L chitosan) and silymarin (9.9 ± 0.5 mg/g DW for 0.5 mg/L chitosan). In particular, higher accumulation levels of silybin B (6.3 ± 0.2 mg/g DW), silybin A (1.2 ± 0.1 mg/g DW) and silydianin (1.0 ± 0.0 mg/g DW) were recorded for 0.5 mg/L chitosan. The corresponding extracts displayed enhanced antioxidant and anti-inflammatory capacities: in particular, high ABTS antioxidant activity (741.5 ± 4.4 μM Trolox C equivalent antioxidant capacity) was recorded in extracts obtained in presence of 0.5 mg/L of chitosan, whereas highest inhibitions of cyclooxygenase 2 (COX-2, 30.5 ± 1.3 %), secretory phospholipase A2 (sPLA2, 33.9 ± 1.3 %) and 15-lipoxygenase (15-LOX-2, 31.6 ± 1.2 %) enzymes involved in inflammation process were measured in extracts obtained in the presence of 5.0 mg/L of chitosan. Taken together, these results highlight the high potential of the chitosan elicitation in the S. marianum cell suspension for enhanced production of antioxidant and anti-inflammatory silymarin-rich extracts.

Chitosan elicitor stimulation of in vitro growth and ex vitro acclimatization of Lantana camara L.

Chitosan elicitor stimulation of in vitro growth and ex vitro acclimatization of Lantana camara L.

Chitosan primes plant defence mechanisms against Botrytis cinerea, including expression of Avr9/Cf-9 rapidly elicited genes.

Current crop protection strategies against the fungal pathogen Botrytis cinerea rely on a combination of conventional fungicides and host genetic resistance. However, due to pathogen evolution and legislation in the use of fungicides, these strategies are not sufficient to protect plants against this pathogen. Defence elicitors can stimulate plant defence mechanisms through a phenomenon known as defence priming. Priming results in a faster and/or stronger expression of resistance upon pathogen recognition by the host. This work aims to study defence priming by a commercial formulation of the elicitor chitosan. Treatments with chitosan result in induced resistance (IR) in solanaceous and brassicaceous plants. In tomato plants, enhanced resistance has been linked with priming of callose deposition and accumulation of the plant hormone jasmonic acid (JA). Large‐scale transcriptomic analysis revealed that chitosan primes gene expression at early time‐points after infection. In addition, two novel tomato genes with a characteristic priming profile were identified, Avr9/Cf‐9 rapidly elicited protein 75 (ACRE75) and 180 (ACRE180). Transient and stable over‐expression of ACRE75, ACRE180 and their Nicotiana benthamiana homologs, revealed that they are positive regulators of plant resistance against B. cinerea. This provides valuable information in the search for strategies to protect Solanaceae plants against B. cinerea.

Effects of some precursors and elicitors on the growth and α-glucosidase inhibitory activity of in vitro Urena lobata L. hairy roots

Recent studies have demonstrated the potential of in vitro Urena lobata L. hairy roots to inhibit α-glucosidase for supporting the treatment of type 2 diabetes. To increase the productivities of hairy roots with α-glucosidase inhibitory activity in in vitro culture conditions, this study focus on the effects of some metabolic factors such as precursors (L-phenylalanine, L-tyrosine) and elicitors (chitosan, methyl jasmonate, salicylic acid). They were added to the culture media to investigate the growth and α-glucosidase inhibitory activity of Urena lobata L. hairy roots. The results showed that for the effects of precursors, only phenylalanine (1 µM) increased root biomass with the highest of α-glucosidase inhibitory activity on the 25th day of culture. In contrast, tyrosine did not play any role in increasing the biomass and α-glucosidase inhibitory activity in Urena lobata L. hairy roots. For the effects of elicitors, only chitosan (50 mg/L) resulted in hairy roots with α-glucosidase inhibitory activity higher than the control after 3 days in culture medium. Other elicitors such as methyl jasmonate, salicylic acid had lower α-glucosidase inhibitory activity than the control. The results of this study demonstrated the potential of phenylalanine and chitosan in increasing the productivity of in vitro hairy roots with higher α-glucosidase inhibitory activity in Urena lobata L.

Stevia rebaudiana Bertoni responses to salt stress and chitosan elicitor

This study examined the effect of chitosan elicitor with four different concentrations (0, 0.2, 0.4 and 0.6 g/l) on physiological and biochemical properties of stevia under four levels of salinity stress (0, 50, 100, 150 mM level of NaCl). Salt stress caused reduction of chlorophyll a (Chl a), chlorophyll b (Chl b), total chlorophyll, carotenoid and total protein content. The increment of malondialdehyde (MDA) content was not significant in all NaCl levels, while the CAT and POX activities were increased as well as stevioside and rebaudioside A under salinity stress. On one side, chitosan treatments could compensate the reduction of physiological traits such as photosynthetic pigments and protein content. On the other side, chitosan caused multiple increases in malondialdehyde content, antioxidant enzymes activity (catalase and peroxidase), steviol glycosides (stevioside and rebaudioside A) under salt stress. We report for the first time, the potential of chitosan to enhance salinity-tolerant abilities in stevia through increment of the salt-adaptive factors and to diminish harmful damages caused by NaCl stress.