chitosan

Polymers with natural origin are known as biopolymers. Due to their biocompatibility and biodegradable properties, biopolymers have a wide range of applications in various fields such as agriculture, medicine, and industry. Biopolymers limit the activities of plant pathogens by increasing the immune system of plants by influencing resistance genes and also activating resistance mechanisms. Therefore, the use of these substances to combat plant pathogens has found a wide application in agriculture. The use of biopolymers to deal with plant pathogens such as fungi and bacteria is a suitable solution to reduce their damage. Also, treatment of the virus-infected plant with biopolymers reduces the symptoms and damage of the disease. The molecular antiviral mechanisms of some biopolymers such as chitosan, chitin, oligochitosan, β-glucans, lentine, alginate, hydrogel and their compounds in the management of plants viral diseases are described in this article.

The root–knot nematode (Meloidogyne incognita) on tomato (Solanum lycopersicum Linn.) is one of the most important plant pathogens, causing economic damage worldwide and in Iran. In order to biologically control this nematode, after nematode multiplication on the susceptible tomato variety (Early Orbana Y) and obtaining a pure and abundant nematode population, the plants were irrigated with a solution of 3 per thousand Probi 96 (containing Bacillus subtilis) and Chitoplus (containing chitosan). After 45 days of applying the treatments, the seedlings were transferred from the greenhouse to the laboratory, and growth indices such as fresh and dry shoot weight, shoot length, fresh and dry root weight, root length. Also, disease indices such as the average number of galls, the number of nematode egg masses in the root, the number of nematode eggs in the root, the number of second–stage juveniles in the soil, and the gall index were measured. The results showed that the use of B. subtilis and chitosan, either alone or in combination, led to an increase in plant growth indices and a reduction in nematode pathogenicity indices. Therefore, based on the results obtained in this study, it can be concluded that the use of these compounds is suggested as one of the effective strategies in an integrated management program for root–knot nematodes in tomatoes.

Chemical fungicides are widely used as effective control agents on a great diversity of fungal plant diseases. However, their excessive use, causes environmental pollution and health problems. Biological control as an environmentally friendly method can be a good alternative for chemical fungicides. Trichoderma is one of the antagonistic fungi with rapid adaptation to a wide variety of habitats. Trichoderma harzianum is a powerful agent for biocontrol of plant pathogens. It also can be used as a plant growth stimulant. However, its efficacy can be affected by biotic and abiotic factors, and encapsulation has been used to maximize its efficacy. Encapsulation process provides a protective barrier around the biocontrol agent, so the harmful external factors such as pH, humidity, and ultraviolet radiation do not damage its action. Encapsulation of the bioactive agents has been developed in recent years as a new potential tool for ecological and sustainable plant production. Encapsulation in biopolymer matrices has been recognized as an effective method for controlled release of a bioactive agent used for plant protection. Chitosan, the deacetylated derivative of chitin polysaccharide is one of the most important biopolymers that is widely used in biological and medical sciences especially for encapsulating essential oils and extracts due to its biocompatibility, low toxicity and biodegradability into safe byproducts. In this study, antifungal effects of nano capsulated Trichoderma extract (NCTE) and Trichoderma extract (TE) against Macrophomina phaseolina have been investigated.

 The nanocapsules were prepared by ionic gelation method. This is one of the most advantageous techniques for the production of nanocapsules. This technique is easy to perform and avoids the use of organic solvents. The biocompatible and biodegradable polymer, chitosan, was used as a capsule coating agent. After extraction of T. harzianum secondary metabolites, encapsulation process was carried out. Tripolyphosphate was used as cross-linking agent in the encapsulation process. The surface morphology of the nanoparticles was considered using Field Emission Scanning Electron Microscopy (FE-SEM). The mean particle sizes of the prepared nanoparticles were measured by Dynamic Light Scattering (DLS) technique. For consideration of the antifungal effects of nano encapsulated Trichoderma extract (NCTE) and Trichoderma extract (TE) against Macrophomina phaseolina, strile potato dextrose agar (PDA) containing different concentrations of NCTE and TE were prepared. After 5 days, colony diameter of the pathogen was measured in all treatments. The inhibitory effect was calculated compared with the control. Data were statistically analyzed by SAS software.

 The obtained results indicated that the prepared nanoparticles were spherical in shape and the average size was equal to 77.91 nm with poly dispersity index (PDI) 0.23554. PDI value indicated the physical stability of the nanoparticles and prevented aggregation of the particles. Antifungal effects of NCTE and TE were observed in all treatments, however nanocapsules contains Trichoderma extract were more effective than Trichoderma extract. In each treatment containing TE and NCTE, maximum inhibitory effect was related to concenteration of 30 percent. In consideration of ihibition percent of NCTE and TE on M. phaseolina within 5 days, it was found that on the first and second days, inhibitory effect of TE was more than NCTE. However, on the third, fourth and fifth days, there were no statistically significant difference between treatments in TE while in NCTE, a significant increasing was observed. The reason for the high inhibition percent in TE treatment in the first and second days was related to rapid release of active ingredients in the culture medium and the passage of time had no effect on improving its yield. According to the results in this research, it can be concluded that chitosan nanoparticles will be a good carrier for Trichoderma extract encapsulation. It also improves their antifungal activity against M. phaseolina.

Nano-encapsulation of the bioactive compounds enhances physical stability, protects them from oxidation process, controlling their release, improves water dispersion of hydrophobic compounds and enhances their bioactivity efficacy. In this study, nano encapsulation of Trichoderma extract, increased its antifungal effects over time. Nano encapsulated particles containing antagonistic fungi were able to control the pathogenic fungus more effectively and in a longer period of time due to the controlled release of the fungal extract. Results showed that antifungal efficiency of T. harzianum was increased by nano encapsulation procedure. Since chitosan is a biodegradable polymer without any harms for safety, this technique can be suggested as a good candidate for biological control. Our future investigations are directed to test nanocapsules simultaneously loaded with biological agents on M. phaseolina under greenhouse and field conditions.

Green mold (Penicillium digitatum) is one of the most important post-harvest pathogens of citrus fruits. Tens of thousands of citrus fruits are often destroyed by green mold in Iran every year. The use of chemical toxins to control the disease, in addition to negative environmental effects, leads to the selection of fungal-resistant populations and also endangers consumer health, so non-chemical control of the pathogen has become an important goal of researchers in recent years.

The essential oil components of myrtle (Myrtus communis L.) were extracted with a Clevenger apparatus and their compounds were identified with a gas chromatography apparatus with a mass spectrometer. The inhibitory effect of myrtle essential oil and the fungicides chitosan and thiabendazole on spore germination and colony growth was investigated by mixing with PDA and PDB under laboratory conditions and by impregnating the fruit surface during storage.

Thirteen compounds were identified in myrtle essential oil, which was quantitatively the highest compound 1-8 cineole. Myrtle essential oil at a concentration of 1700 ppm and chitosan at a concentration of 500 ppm inhibited 100% of fungal colony growth, as did the fungicide thiabendazole.

It is possible to use myrtle essential oil or chitosan as an alternative to the fungicide thiabendazole to control citrus green mold.

Today, Water base nanopesticides with small size can help to over comes the low solubility of pesticides to control pest in agriculture. In this paper, an oil-core silica/ polymer/ fipronil shell nanoparticles was prepared for insecticidal activity of fipronil in vitro was tested against termite (Microcerotermes gabrielis W. (Isoptera: Termitidae)), which, the result of the biological activity showed the effectiveness of fipronil nanparticles during 72 h at 15 ppm and make tunneable activity of fipronil insecticide.

Land use change, deforestation, grazing, intentional and unintentional fire and invasive pests and diseases are all the major cause of damage to the Zagros forest ecosystem. The green oak leaf roller (Tortrix viridana L.) is one of the important pests of Zagros forests. Larvae of the pest significantly damage the oak forests with feeding on leaves and buds of different species of oaks each year. Larvae enter 2'd instar after eating the internal contents of oak buds, then the third and 4th instars larvae consume whole buds and even oak leaves. After development to the 5th larval instar, they roll the leaves and enter the pupal stage. The attacked trees revitalize by creating new leaves from early May onwards. New leaves, pale green and are smaller than normal leaves. Continuation of the pest activity on Quercus species causes gradual weakness the trees and readiness to accept a variety of secondary pests and diseases in later years. Based on the status of Zagros forests and their importance in the conservation of soil and water sources, the nutritional indices of Tortrix viridana larvae of two species of Oak i.e. Quercus infectoria and Q. libani were determined to get a better understanding of this pest.
Since early April, with regular visits, last instar larvae (5th instar) of T. viridana in oak forests in Perdanan areas (around the village Ghabr Hossein) were collected and transferred to the laboratory chamber. The larvae were fed on the two oak species. The leaves of these species were collected and transported to the laboratory in a room at a temperature of 25°C and suitable photoperiod conditions. The larvae were fed individually or in a group. In a grouping method, 10 larvae in two replicates and in individually method 40 larvae (one larva per replicate) for each host were considered. Larval weight, amount of consumed food and weight of feces were estimated by using a sensitive digital Carriage scale (0.001 gr). Relative consumption rate (RCR), relative growth rate (RGR), the efficiency of conversion of ingested food (ECI), the efficiency of conversion of digested food (ECD) and approximate digestibility (AD) were also calculated. For statistical analysis t-test and SPSS17 software were used to compare the mean of the data.
Results of t-test (α=5%) indicated that the larval biomass, RGR, ECI, and AD were significantly different among the hosts in both methods of grouping and individually rearing of the larvae. In this study, Q. libani showed the lowest rate of digestibility. The larvae fed on Q. infectoria have the higher rate of AD than Q. libani because of high RCR, RGR, ECD and ECI. Also, the results related to the comparison of two methods (grouping and individually rearing of the larvae), on nutritional indices were significantly different and in both host trees, the rate of RGR, ECI and ECD in grouping method was more than individually rearing method. RCR is the indication of the insect's exploitation speed of food. In the other words, it shows feeding rate regarding insect's weight at the specific point of time depending on the amount of water and other nutrition physicochemical characteristics in insects. The result showed that this index rate in group rearing method on two host species is equal, but in individual rearing method on Q. infectoria, it is more than Q. libani. The possible reasons are more feeding of larvae in individual rearing method due to the lack of competition stress, the more likelihood of the desirability of Q. infectoria compared to Q. libani, the probability of the existence of antixenosis in Q. libani. The similar study investigating individual and group rearing methods in one insect species is not available. This result confirms that T. viridana larvae’s has a tendency toward social life and in the group situation, they eat effectively. In fact, although larvae in individual form feed more because of lack of competition stress, but in the group they make use of that little food in the best way.
In this study, Q. libani had low food quality. As a result, its relative consumption rate, relative growth rate, the efficiency of conversion of ingested food and efficiency of conversion of digested food was less than Q. infectoria. According to the results, Q. infectoria is an appropriate host for this pest. Also, it shows that the larvae were more considering the rate of larval biomass, RCR, RGR, ECI and ECD in grouping method than the single method.

Cucumber is one of the most important cucurbits in Iran. Cucumber mosaic virus (CMV) is one of the plant pathogen viruses with widest host range. Resistance induction in plants is one of the most effective methods in combating viral diseases. The effects of foliar spraying of chitosan (0, 500, 1000 and 1500 ppm(on molecular, biochemical, disease severity and virus concentration was investigated in greenhouse conditions through spraying of chitosan on cucurbit seedlings at two foliage stages, in a completely randomized design with three replicates. The results of enzyme linked immunosrobent assay (ELISA) and reverse transcription-polymerase chain reaction (PCR) proved systemic infection status of plants. The lowest amounts of virus concentration and disease severity were estimated as 0.46 and 40.7, respectively. Chitinase gene expression levels in chitosan foliar treatments with 500, 1000 and 1500 ppm, increased as 6.229, 11.703 and 14.19 times more than healthy control, respectively. The results of present study showed that chitosan treatment causes induced resistance, reduction of the concentration of virus and disease severity through increasing the expression of chitinase and peroxidase enzymes belonging to the families of pathogenesis-related protein, This study can be an introduction of chitosan usage for increasing expression (over expression) of these gens and providing induced resistance of cucumber to CMV.

In this research, the role of chitosan as a bio-inducer of defense mechanism in infected wheat by Fusarium graminearum, the causal agent of Fusarium head blight was investigated. To investigate the expression of genes associated with pathogenicity and enzymatic activity, a factorial experiment in a completely randomized design with four replications was done under greenhouse condition. The adjusted solution containing different concentrations of chitosan (0, 100, 200 and 500 mg l-1) were used via spray. Treated plants after 24 hours with a spore suspension (at a concentration of 106 Macro conidia ml-1) were inoculated by spikelet injection and were kept under greenhouse conditions. Sampling was performed at various time points after inoculation and then the expression level of some genes involved in resistance and activity of relative enzyme was studied. Data analysis showed that disease severity was reduced in treated plants compared with control plants. Enzyme measurement showed the greatest variation for peroxidase and polyphenol oxidase enzymes. The results of molecular analysis by qRT-PCR showed significantly increased mRNA expression levels of beta-1, 3-glucanase and oxalate oxidase genes. The results of this research indicate that chitosan could influence plant resistance against pathogenic fungi through induction of systemic acquire resistance.

The use of natural compounds for disease control and prevention has been considered because of the benefits. Using herbal essences has been developed due to having medicinal properties, antifungal, antibacterial and antioxidant secondary metabolites in the control of pathogens. In this study, the performance of three plant essential oils Cumin (Cuminum cyminum), cinnamon (Cinnamomum zeylanicum) and peppermint (Mentha sp.) and soluble chitosan in the prevention and treatment of rice sheath blight caused by the fungus Rhizoctionia solani in vitro and in Ziveh, were studied. This experiment was done in a completely randomized design with 500 treatments and 3 replications. Treatments consisted of three factors essential oils, each in five different concentrations (100, 200, 400, 600, 800, 1000 ppm) and the Factor chitosan in two concentrations 800 and 1000 milligram per liter and also two control included a positive control (culture medium along with tilt PDA) and negative control (dextrose agar medium potatoes without oil). Each treatment consists of three replicates each also includes three petri dish (for all treatments and positive and negative controls), respectively. Inhibition of different concentrations was determined using the Abbott formula. The full minimum inhibitory concentration of essential oils (MIC) and minimum fungicidal concentration of essential oils (MFC) was also calculated. The factorial experiment was considered in a completely randomized design with three replications in which every essence as a factor and different concentrations of essential oils, different levels of each factor. The results showed that essential oils of cinnamon and cumin inhibited 100% of the growth of R. solani were in effect concentrations ppm 200. The essential oil and chitosan 100% inhibition at concentrations of 600 and 1000 were one of their own. In addition to these three extracts of cinnamon, cumin and mint with a percentage of inhibition, respectively, 67/81, 50/82 and 33/83 showed similar results, with 50% inhibition chitosan least inhibition of pathogenic fungi on plant show.

Chitosan is a biodegradable natural compound derived from the bark of crabs and shrimp which have antimicrobial role against fungi and bacteria. Chitosan has directly effects on morphology of treated pathogens which reflect its fungistatical and fungicidal activity. It has been shown that chitosan increases production of glucanohydrolase، phenolic compounds and specific phytoalexin synthesis with antifungal activity and reduces enzymes such as polygalacturonase، pectin methyl-esterase that related to soft rot. In addition، chitosan can develop structural barriers via lignin synthesis. Therefore chitosan is considered as a new non-toxic biological material، inducer resistance of plants against diseases.

Blue mold caused by Peniciliium expansum Link. is a major postharvest decay agent in apple fruit.  In this research, the efficacy of two non-chemical compounds including chitosan and carnoba coating wax and Imazalil in inhibiting blue mold in apple cvs. Golden delicious and Red delicious and their association with polyphenol content was studied in laboratory condition. Additionally, the effect of two antagonistis (Trichoderma atroviride and T. haziamum) on a number of decaying fungi including Rhizopus stolonifer, Alternaria  alternata, P. expansum, Ulocladium sp., Aspergilus sp., Cladosporium fulvum and Monilia sp. was determined. Fungicide Imazalil and distilled water were used as controls. Based on the results, Golden delicious was more susceptible to P. expansum than Red delicious. In both cultivars, chitosan treatment reduced P. expansum decay in fruit and its growth in culture medium. The least to the most decay severities were observed in Imazalil, chitosan+Imizalil, chitosan, chitosan+wax and wax treatments and chitosan treatment reduced it up to 97% Polyphenol concentration was higher in Red delicious than Golden delicious and the most to the least polyphenol concentration were detected in chitosan, chitosan+Imizalil, chitosan+wax, Imizalil, wax and control (distilled water) treatments, respectively. Negative correlations were found between polyphenol concentration and P. expansum susceptibility and treatment (R=-0.989and -0.68, respectively). Accordingly, inducible and constitutive polyphenols might contribute in apple resistance to blue mold and in chitosan-induced protection. Both Trichoderma species in particulr T. atroviride inhibited all decaying agents. Based on these results, chitosan can be recommended as an effective nonchemical agent for apple protection against blue mold but carnoba wax has no protective effect.