جستجوی مقالات مرتبط با کلیدواژه « fire blight » در نشریات گروه « گیاهپزشکی »

There are many epiphytic bacteria live on surface of pome fruit tree foliage, and have been proven to show antagonistic activity against Erwinia amylovora, the causal agent of fire blight disease. In order to characterize and assess antagonistic potential and genetic diversity of epiphytic bacteria associated with pome fruit trees in orchards of West Azarbaijan province samplings were carried out from foliage of apple, pear, and quince trees during spring, summer and autumn in 2014. Epiphytic bacteria were isolated and their antagonistic potential against E. amylovora were evaluated and then bacterial isolates were identified. The isolated bacteria were categorized into three group including Pantoea agglomerans, Pseudomonas fluorescens and other unknown Gram-positive bacteria. Genetic diversity among the Pseudomonas and Pantoea isolates were studied using Rep-PCR technique. Resulted data were analyzed in NTSYSpc v2.02e software and compared using UPGMA and Jaccard similarity coefficient methods. Also, the analyses of the BoxA1R primer’s band patterns separated ten groups with at least 75% similarity among the pseudomonad isolates. Similarly, nine groups with 70% similarity within the Pantoea isolates were discovered. These results showed a high genetic diversity among the epiphytic strains of Pseudomonas and Pantoea in west Azarbaijan pome fruit orchards.

One of the most destructive diseases of pome fruit species which causes irreparable damage to gardening products worldwide is fire blight disease caused by Erwinia amylovora. In Iran, it was first observed in pear trees in Alborz province and then spread across fruit orchards in the country. One of the main problems in fire blight management is evaluating causal agent genotypic characteristics. Thus, the present research was conducted to characterize genotypic features of E. amylovora as the cause of fire blight disease in pome fruit species in Hamadan province, Iran.

In this study, the samples with symptoms of canker on shoots and blight blossoms were observed and collected from the orchards in Hamadan province located in the west of Iran. After isolation, the isolates were purified for further studies. Phenotypic, biochemical, and pathogenicity tests were performed due to standard bacterial criteria. Phenotypic and biochemical tests of strains were examined by Ntsys-pc 2.02 software. A total of 15 representative isolates were selected and analyzed due to the size of amplified DNA using primers Ea71 and genetic features of the rep-PCR test using primers ERIC and BOX. For more accuracy and higher reliability of the specific primers results, the 16S rDNA_ gene of two representative isolates was amplified and subjected to sequencing.

Based on the biochemical, pathogenicity and molecular tests, a total of 34 isolates were identified as E. amylovora. Due to the numerical analysis, the data obtained by phenotypic and biochemical tests were similar at 89% level. Therefore, the isolates obtained from a specific host or region was grouped very close to each other. In the PCR tests survey, the isolates amplified 187 base pair expected fragments. The results of determining sequences indicated that both isolates were similar to E. amylovora showing 97% identity to the type of strains in the NCBI database. Due to data from the rep-PCR analysis, the isolates were divided into three groups at the similarity level of 77%.

The results of genetic diversity using rep-PCR showed that there is no significant difference among E. amylovora bacterial isolates from different regions of Hamadan Province. Moreover, they showed high similarity to each other and placed close to each other. Our results confirm other studies regarding phenotypic characteristics of E. amylovora. Our results confirm that the isolates are homogenous in Hamadan province of Iran. To summary, these findings can be applied to breeding programs to better management of the bacterial disease.

Erwinia amylovora is a gram-negative bacterium that causes fire blight, an important disease in pome fruit trees. The aim of this study was to generate a transposon mutant library using mini-Tn5 lacZ1, in an Erwinia amylovora native isolate for identification of some virulence associated genes in this strain. Among 1500 mutated colonies, two colonies which indicated less virulence on immature pear fruits were selected for further analysis. The DNA sequencing results of the two selected mutants showed a transposon insertion in an araC family transcriptional regulator gene and an insertion in nonribosomal peptide synthetase (NRPS). This study demonstrated that the araC transcriptional regulator and the NRPS genes are required for full virulence of E. amylovora. More studies are necessary to identify the role of these genes in physiology and virulence of E. amylovora.

In the present study, antimicrobial effects of the ethanolic herbal extracts of seven medicinal plants including Absinthe, Chamomile, Cumin, Asafoetida, Gum tree, Balm and Tree of heaven against Erwinia amylovora bacterium were investigated. Virulence assay of the bacterial isolates on the immature pear fruit of the Spadona pear cultivar was performed, and the most pathogenic bacterium isolate was selected for further evaluation. Sensitivity of the selected isolate to two copper compounds and five antibiotics was examined. Antibacterial properties were assessed at three concentrations using the disk-diffusion method. To investigate the synergistic effect of the plant extract with copper compounds, the extract of Balm, which have been indicated maximum antibactericidal effect was used. The Balm plant extract was also tested on the seedling of Spadona pear. The ethanolic extract of Balm had the most significant antibacterial effects with the mean inhibition zone diameter of 15.66 mm against the GA3 isolate. The bactericidal effects were not exerted by Chamomile and Heaven tree. Moreover, the results indicated no synergistic effects in the plant extracts of Balm and the tested copper compounds. Our results demonstrated the positive stimulating effects of the plant resistance system by the Balm extract. Evaluation of guaiacol peroxidase at seven different intervals indicated the elevated level of GPX within the first 24 hours compared to the control and bacterial treatment. The results of this research can introduce novel suggestions for future researches in order to control fire blight disease of pome fruit trees via using active components of medicinal plants.

Fire blight, caused by the bacterium, Erwinia amylovora, is a serious disease of pome fruits in many regions of the world and Iran. Several models based on climatic and phonological data were developed to prevent fire blight during bloom, thus improving our ability to control this phase of the disease by the timely application of antibiotics sprays in orchard. In this study (i) the causal agent of fire blight were detriminated in infected orchards (ii) removal infected plant tissues (iii) air temperature, and relative humidity were recorded (iiii) spraying and application of treatments were performed to prevent the blossom blight and based on claimatic condition, phonological trees and Thomson model. Experiment was performed as Random Complete Blocks Design (RCBD) with three replications. Results showed minimum effects in streptomycin 100ppm treatment (6.22%- 8.5%) on preventing of infection, especially when applied three bloom sprays during sensitive stages of flowering at 150C-18.10C. Then oxytetracycline 200ppm and starner 300ppm were ranked next respectively (8.533%-16.33%). The effective hess of copper oxycloride 1/1000 is depending on relative humidity and rain. Results that indicated interaction among bloom period, time of flowering and temperature could reduce number of spraying compared to Thomson model. Therefore we can use this technique in orchards of Golmakan, Chenaran, Nyshabour, Mashhad and other geographic areas where pome fruits are grown and have similar climatic condition.

During 2011 to 2012, different Pome orchards in Isfahan province were surveyed and the samples with fire blight symptoms such as water soaking of infected tissues, necrosis, wilt and tissue necrosis, scorched and in some cases death of the entire tree, were collected. Forty nine bacterial strains were isolated using NA, SNA and EMB media. Based on standard physiological and biochemical tests, the isolates were identified as Erwinia amylovora. In the PCR assayisolates were identified as E. amylovora, based on 1000 bp DNA fragments using A/B specific primers. In rep-PCR assay representative strains produced different fingerprints patterns using REP, ERIC, BOX primers. The results of this study demonstrated that fire blight disease is distributed in Isfahan province and collected E. amylovora strains from various regions of Isfahan province are genotypically homogenous with more than 71% similarity.

In order to evaluate the role of infected host parts, cankers, etc. in dispersion and survival of fire blight of pome fruits, thirteen fruit gardens throughout Semnan province were inspected during 2007-2008. Infected plant parts were collected from different localities and the causal agent was isolated from different samples using SNA (sucrose nutrient agar) medium following standard methods. Results indicated that epiphytic population of bacteria at a range of 3×103–10 cfu/flower in pear and 3×106 – 1.7 ×107 cfu/flower in quince caused blossom blight during rainy days with moderate temperature. It was found that except apple trees of Tash region, pome fruits of remaining regions were infected with the disease. Higher disease incidence occurred in quince 88%), pear (55%) and apple (24%) respectively. It was also found that the role of different plant parts in maintenance of fire blight was directed by weather in such a way that total plant parts of quince and specially their cankers caused highest disease incidence. It was found that the disease can be transmitted to the next year by different infected plant parts of pome fruit trees while one year old cankers of trunks and main branches had the most important role in this connection.

Nowadays، biocontrol of plant pathogens is a priority to reduce environmental effects of chemical pesticide applications. In this regard، antimicrobial plant products are in the center of attention. In this study، the inhibitive potential of methanol، ethanol، acetone، and chloroform extracts of rind، gel، latex and whole leaf of Aloe vera was evaluated using agar diffusion disc method against Erwinia amylovora and Xanthomonas arboricola pv. juglandis. Also، bacteriostatic and bactericidal activities were tested by minimal inhibitive and bactericidal concentration methods. All leaf parts of A. vera had antibacterial potential against these bacteria except for latex. However، X. arboricola pv. juglandis was more sensitive to Aloe products than E. amylovora. Chloroform was not suitable solvent for releasing antibacterial substances from Aloe. Rind extracts had no bactericidal or bacteriostatic effects on E. amylovora but they were the most effective ones on X. arboricola pv. juglandis. Gel extracts had much more bactericidal potential on both bacteria. On the whole، 31 chemicals were identified using gas chromatography which 25 of them were found in latex. Some antibacterial substances such as cinnamic acid، tetradecanoid acid، 2-hydroxy propionate، sitosterol، carvone، lupeol، 1-heptanol، 2-propyle، 1،2- benzene di-carboxylic acid were found in different parts of A. vera leaf. The antibacterial activity of A. vera against the causal agents of apple and pear fire blight and walnut bacterial blight can be considered as a biocontrol potential in the future.

Fire blight is important disease of pome fruit trees. The role of mitochondrial electron transport chain in interaction of host-pathogen has been verified. The purpose of this research was to study the role of chloroplast electron transport chain in this interaction and to determine the eventual site of pathogen effecter protein (s) influence. For this، effects of several chloroplasts electron transport chain inhibitors including Methylviologen، Glutaraldehyde and Diuron، with various sites of inhibition was evaluated on symptoms progress. All tests were performed and compared on in vitro shootlets of apples، MM-111 (tolerant) and MM-106 (susceptible) and pears، Harrow Sweet (tolerant) and Spadona (susceptible). For distinctness of necrosis causes by inhibitory effects inhibitors from those from pathogen، in a series of primary experiments، the effects of inhibitors concentrations were evaluated on shootlets in absence of pathogen and provided at least 168 h without necrosis of inhibitors. Subsequently، effects of inhibitors were evaluated on necrosis of pathogen after shootlets inoculation. The results showed that chloroplasts electron transport chain inhibitors retarded symptom progress in all tested cultivars. The results confirm previous results observed by uracil inhibition of chloroplasts and represent more evidence for role of this chain in host/E. amylovora interaction. In addition، according to impeding site of inhibitors، NADP reduction complex is the most probable site of effecter proteins interaction in host chloroplasts.

Fire blight disease caused by Erwinia amylovora is a destructive disease of pome fruits including apple worldwide. Use of resistant cultivars is the most efficient method of disease control. In the present research، we investigated genetic resistance of 89 local and imported commercial apple cultivars in natural contaminated conditions to the bacterial disease using Beltsville scoring system (USDA) in horticulture Research station of Kamalshahr، Karaj (Iran)، during triennial observations، 2007-2009. Apple cultivars differed significantly (P)

Fire blight caused by Erwinia amylovora (Burrill) Winslow et al. is one of the most catastrophic bacterial diseases of pome fruits. Among the various host plants, the quince (Cydonia oblonga) tree is one of the most susceptible hosts to the disease. Using the tolerant cultivars is the most economic method for disease control. This research was carried out in order to study the rootstock role on susceptibility of budded quince genotypes to the disease. 13 quince genotypes from central region of Iran, as well as cultivar "Isfahan" as control, were budded on quince and crataegus rootstocks and were evaluated for fire blight resistance in the greenhouse condition by using Ea273, S1 and Z1 isolates of bacteria in spring, 2007. Resistances were evaluated by necrosis progress rate and index of varietal susceptibility (I.V.S) in the shoots. On quince rootstock, the cultivar "Isfahan" and genotype SHA1 with 57.9 and 90.4% final disease progress, showed the lowest and highest symptoms respectively, while on crataegus rootstock, PH2 and NB3 genotypes with 71.5 and 100% final disease progress showed the lowest and highest symptoms, respectively. Results showed crataegus rootstock increased damage severity in 11 genotypes and decreased in other 3, compared with quince rootstock. Effect of rootstock type on the susceptibility changes in KVD3 and NB3 were the highest and in NB4 and PH2 were the lowest. According to the results in most quince genotypes, the crataegus rootstock can not be effective to increase resistance to disease.