جستجوی مقالات مرتبط با کلیدواژه « xanthomonas » در نشریات گروه « گیاهپزشکی »

In order to isolate pathogenic bacteria from the hosts of bean and alfalfa, 140 bacterial isolates were cultured and purified on NA medium in East and West Azerbaijan provinces. Based on the color and appearance of the colonies, the isolates that were close to the desired Xanthomonas bacteria were selected. After re-cultivation and purification, a total of 62 isolates were obtained. To perform the pathogenicity test of the isolates, each of them was inoculated individually to its host and kept in greenhouse conditions for two weeks. 33 strains were able to cause pathogenicity on the host. The strains were able to amplify the 239 bp fragment of Xanthomonas specific gene, which is part of the ITS gene. Therefore, these strains were considered as Xanthomonas bacteria. Based on genetic fingerprinting by rep-PCR method, the strains isolated from bean and alfalfa was divided into four and three groups, respectively, which results indicated genetic diversity between the strains. Based on the sequencing of 16S rRNA, gyrB and rpoD genes, the strains isolated from alfalfa were identified as X. alfalfae subsp. alfalfae and bean strains were identified as X. phaseoli pv. pahseoli. By reviewing the available sources, the present research is the first report of the isolation, identification and genetic diversity of these strains from bean and alfalfa hosts in East and West Azerbaijan provinces.

Pathogenic bacteria are one of the most important factors in reducing the yield of plant products. In the past, the management of these pathogens was limited to the use of antibacterial compounds or resistance inducers, but with the discovery of bacteriophages in recent decades, attention to their use has increased. Bacteriophages or phages are viruses that specifically affect bacterial cells. Currently, hundreds of bacteriophages have been isolated and tested against plant pathogenic bacteria, and there are still many more that need to be investigated. This approach requires special protocols to identify new phages, understand the emergence of phage-resistant clones and the infectivity of other bacterial species. Phage therapy or the use of phages to biological control plant pathogenic bacteria due to its cheapness, very high specificity of phages against bacteria, no negative effect on humans or animals, and no environmental pollution, as a suitable method to control these pathogens can be considered.

Autophagy plays an important role in the process of plant development and interaction with pathogens such as fungi, bacteria, and plant viruses. Autophagy is linked to immunity and disease resistance through inhibition of programmed cell death (PCD) and is recognized as an important defense component in plants. Autophagy also helps selectively eliminate pathogens through specific interactions. A number of pathogens have acquired the ability to cope with or evade autophagy and use it to develop the disease. Some other pathogens also use the autophagy system as pathogenic factors. Therefore, understanding cellular processes such as responses related to autophagy genes are very important for studying pathological physiology and plant immunity. The role of autophagy in the immune system and the plant's defense response to pathogens is described in this article.

Walnut is one of the most important fruit trees in Iran, which is always exposed to pathogens, especially bacteria. The three most important bacterial diseases of walnut in Iran are bacterial blight (Xanthomonas arboricola pv. juglandis), skin cankers (Brenneria nigrifluens, Brenneria rubrifacians) and crown gall (Agrobacterium tumefaciens). Bacteriological characteristics and pathogenicity of pathogenic bacteria, methods of managing these diseases, along with suggestions for identifying resistant genotypes of walnut trees by molecular methods are described in this article.

Antibacterial, antifungal and antioxidant activity of methanolic extracts of Colocynth (Citrullus colocynthis) seeds, Camelthorn  (Alhagi maurorum) fruit and Chinaberry (Melia azedarach) leaves on eight bacteria and three fungi, which usually cause damage to agricultural products examined in this research.

Antimicrobial activity of selected plants in six concentrations on 11 microorganisms including, three gram-positive bacteria vs. Bacillus subtilis, Staphylococcus aureus, and Rathayibacter toxicus, and five gram-negative bacteria vs. Escherichia coli, Pseudomonas aeruginosa, Pseudomonas syringae subsp. syringae, Pseudomonas viridiflava, and Xanthomonas campestris pv. campestris, as well as three fungi vs. Pyricularia oryzae, Fusarium oxysporum and Botrytis cinerea was measured using the disk diffusion method. Also, the antioxidant activity of the extracts of these  plants was evaluated by measuring the enzymes of catalase and guaiacol peroxidase and evaluating the ability to trap DPPH radicals. In addition, the amount of total phenols and flavonoids in these plants extracts were measured.

Methanolic extract of Colocynth seeds had the highest antibacterial activity, the highest activity of catalase and guaiacol peroxidase enzymes and the highest percentage of DPPH radical inhibition. Methanolic extracts of these plants had no effect on fungal colony growth.

Methanolic extract of Colocynth seeds can be considered as potential sources of bactericides in agriculture.

Algae are the most important plant growth stimulants due to their high content of minerals, amino acids, vitamins and growth regulators such as auxin, cytokinin and gibberellin. Use of these stimuli in crops can improve rooting, yield, photosynthetic capacity and their resistance to pathogens. Application of algae (mainly seaweeds) against various plant diseases including bacterial, fungal, viral and nematode diseases as well as pests has been proven. Seaweeds are used as a powder or extract mixed with soil, or foliar spray to control of plant diseases. They are usually involved in controlling plant pathogens by inducing plant resistance, antagonistic activity by induced activity of other microorganisms, and enhancing plant growth. In general, seaweeds can be applied as biofertilizers, biostimulators and soil amendments in integrated plant diseases management programs.

 Citrus bacterial canker caused by Xanthomonas citri subsp. citri is an economically important disease in many tropical and subtropical countries. Several pathotypes of this pathogen have been described which, in addition to certain genotypic features, are distinguished above all by their geographical origin and their host range. Citrus bacterial canker disease is wide spread in Iran and a major threat to the production of Mexican lime (Citrus aurantifolia). Therefore, management of citrus canker is inevitable in citrus growing areas where citrus canker has been established. Application of copper-based bactericides is a standard control measure for management of citrus canker worldwide. Therefore, their long-term use leads to the development of resistant isolates. Plant extracts and essential oils with an antimicrobial effect have become particularly important as an environmentally friendly method for the treatment of plant diseases. Many researchers have recently focused on studying plant extracts and essential oils that contain antimicrobial compounds. 

 The present study was carried out on the antibacterial effect of ‌Common yarrow (Achillea millefolium), Ginger (Zingiber offcinale), Golden marguerite (Anthemis tinctoria), Fennel (Foeniculum vulgare), Common sage (Salvia officinalis), Gum tragacanth (Astaragalus gossypinus), Summer savory (Satureja hortensis) and True cardamom (Elettaria cardamomum) against two pathotype of Xanthomonas citri subsp. citri under laboratory and greenhouse conditions. 

 All essential oils have an inhibitory effect on multiplication of Xanthomonas citri subsp. citri. The antibacterial test results showed that the essential oils of Ginger and True cardamom strongly inhibited the growth of Xanthomonas citri subsp. citri pathotype, especially the pathotype A*, whereas other essential oils showed moderate to weak activities. 

 The essential oils of these eight plants, especially ginger and cardamom, have good potential for the management of citrus bacterial canker.

In this study effect of systemic resistance inducing fluorescent pseudomonads on wheat bacterial leaf streak was investigated. According to the importance of produced siderophore by this kind of bacteria in the induction of systemic resistance, CAS agar medium was used for screening of the isolates with the highest potential for siderophore production. From the 200 isolates that isolated from North West part of Iran, 37 could produce a large amount of siderophore and the diameter of hallo zones produced by these isolates on CAS medium agar was more than 15 mm. Ethylene production bioassay was used for screening the isolates with the potential for induction of systemic resistance in wheat. Among these isolates, only four increased the plant reaction potential against XTC and concentration of ethylene produced by leaf pieces of plants treated by these isolates was more than 2 pmol/ml air. The effect of selected isolates on bacterial leaf streak of wheat in growth chamber was investigated and it was found that only 58A can significantly decrease this disease. Investigation of the enzymatic changes of plant treated by this isolate during pathogenicity process showed that the presence of this bacterium on the wheat roots doesn’t have any effect on peroxidase (PO) and phenylalanine ammonia lyase (PAL) activity in foliage, but after inoculation of the pathogen, the activity of both of them increased.

Plant pathogenic bacteria have evolved specialized strategies to infect their hosts. In this regard، the key virulence factors are effector proteins، cell wall degrading enzymes، toxins، extracellular polysaccharides and phytohormones. The interactions between plant pathogenic bacteria and their hosts have resulted in an evolutionary system between host defense responses and pathogen virulence factors. Pathogenic bacteria are continually under pressure to diversify their mechanisms to prevent host defenses and optimize nutrient availability. In turn، these virulence mechanisms have shaped the evolution of plant innate immunity. In this paper، the pathogenicity and virulence factors of plant pathogenic bacteria are discussed.

Some samples of leaves and twinges of ‘Mexican‘lime, with bacterial canker symptoms were collected in spring and summer of 2012, from Ilam province. Some bacterial isolates were isolated from infected tissues using classic methods. Primary identification of bacterial isolates was performed based on phenotypic characterization and spectral absorption properties of yellow pigment. Pathogenicity of isolates was approved on detached leaves and seedlings of Mexican lime and grapefruit in the greenhouse condition. The results of Phenotypic and genotypic identification, using four pair specific primers indicated that all isolates belong to Xanthomonas citri subsp. citri. The first identification results were approved using gyrB sequence analysis in candidate isolates. Comparing genetic fingerprint profiles with 3 type strains and other strains obtained from Kerman, Sistan and Balochestan, Hormozgan and Fars provinces showed that all Iranian isolates are similar in case of genetic fingerprint profile.

Banana is one of the important fruit in tropical humid areas. In Iran it grows under plastic cover in the Mazandaran and Golestan provinces. Bacterial leaf spot and necrosis disease of banana have been reported from these provinces. Symptoms of this disease are seen as necrotic spots on central young leaves. Spreading these spots, the diseased leaves become completely rotten and the plant growth will stop. Causal pathogen is the bacterium, Xanthomonas campestris pv. musacearum, which produces yellow mucoid colony. This is agram-negative, non-fluorescent, oxidase negative and catalase positive bacterium. Pathogenicity test of bacterium can be proven by its inoculation to banana leaves. Disease symptoms, sampling, isolation and methods of pathogenicity test of the bacterium, and disease management have been described in detail.