scholarly journals DMI-Fungicide Resistance in Venturia nashicola, the Causal Agent of Asian Pear Scab—How Reliable Are Mycelial Growth Tests in Culture?

2021 ◽  
Vol 9 (7) ◽  
pp. 1377
Author(s):  
Hideo Ishii ◽  
Hans Jorgen Cools ◽  
Kumiko Nishimura ◽  
Lorenzo Borghi ◽  
Kenji Kikuhara ◽  
...  
Keyword(s):  
Mycelial Growth ◽  
Field Performance ◽  
In Vitro Tests ◽  
Nucleotide Polymorphisms ◽  
In Planta ◽  
Venturia Nashicola ◽  
Dmi Fungicides ◽  
And Control ◽  
Dmi Resistance

Scab, caused by Venturia nashicola, is among the most serious diseases of Asian pears and control of this disease largely relies on sterol demethylation inhibitor (DMI) fungicides. However, pear growers have complained about field performance of DMIs since the mid-2000s. In this study, to evaluate pathogen sensitivity, mycelial growth tests and inoculation tests were conducted using DMI-amended culture medium and fungicide-sprayed potted pear trees, respectively. Results confirmed distribution of isolates resistant to fenarimol, hexaconazole, and difenoconazole in the field populations. Importantly, results from tests in culture did not fully correlate with those from tests in planta. Due to phenotypic instability of resistance and poor sporulation of this pathogen in culture, resistance is generally assessed by laborious and time-consuming inoculation with conidia collected from a field. To improve the result interpretation from in vitro tests, the isolates were genotyped: the CYP51 gene which encodes the target sterol 14α-demethylase was sequenced and various mutations have been detected in the coding sequence of DMI-resistant isolates. In addition to the detected single nucleotide polymorphisms, alternative mechanisms, not based on changes in the structure of the target protein, may also increase DMI resistance. Development of molecular methods for the diagnosis of DMI resistance seems to be challenging in V. nashicola.

scholarly journals Sensitivity of Mycosphaerella fijiensis from Banana to Trifloxystrobin

Plant Disease ◽  
2001 ◽  
Vol 85 (12) ◽  
pp. 1264-1270 ◽  
Author(s):  
K. M. Chin ◽  
M. Wirz ◽  
D. Laird
Keyword(s):  
Cross Resistance ◽  
In Vitro Tests ◽  
Mycosphaerella Fijiensis ◽  
In Planta ◽  
Baseline Sensitivity ◽  
Single Spore ◽  
Resistance Factors ◽  
Development Site ◽  
Disease Pressure

An ascospore germination method was developed and validated to assess the sensitivity of bulk samples of Mycosphaerella fijiensis to trifloxystrobin. Using this method, the sensitivity of 142 ascospore samples from banana plantations not treated with strobilurins was analyzed to establish a baseline of pathogen sensitivity. A bulk method was utilized for monitoring purposes because it avoids potential complications due to the isolation and propagation of single-spore isolates and enables the testing of larger samples. Following intensive use of strobilurins (6 to 11 applications per year) over 4 years, under conditions of high disease pressure and the absence of sanitary measures at a development site in Costa Rica, bulk samples with 50% effective concentration (EC50) resistance factors (RFs) in excess of 500 compared with the mean baseline sensitivity were detected. Single-ascospore isolates derived from spores germinating at the discriminatory dose of 3 μg/ml were also resistant, suggesting that the frequency of resistant individuals in bulk samples could be estimated from the relative numbers of ascospores growing at this dose. The resistance of selected isolates was confirmed in planta. In vitro tests with four resistant and two sensitive single-ascospore isolates collected from different locations and times indicated possible cross-resistance of trifloxystrobin to azoxystrobin, famoxadone, and fenamidone, but not to propiconazole.

scholarly journals Efficacy of Variable Tetraconazole Rates Against Cercospora beticola Isolates with Differing In Vitro Sensitivities to DMI Fungicides

Plant Disease ◽  
2012 ◽  
Vol 96 (12) ◽  
pp. 1749-1756 ◽  
Author(s):  
Melvin D. Bolton ◽  
Viviana Rivera-Varas ◽  
Luis E. del Río Mendoza ◽  
Mohamed F. R. Khan ◽  
Gary A. Secor
Keyword(s):  
Sugar Beet ◽  
Disease Severity ◽  
Cercospora Beticola ◽  
In Planta ◽  
Sensitivity Testing ◽  
In Vitro Sensitivity ◽  
Wide Range ◽  
Fungicide Efficacy ◽  
Dmi Fungicides

Cercospora leaf spot (CLS) of sugar beet is caused by the fungus Cercospora beticola. CLS management practices include the application of the sterol demethylation inhibitor (DMI) fungicides tetraconazole, difenoconazole, and prothioconazole. Evaluating resistance to DMIs is a major focus for CLS fungicide resistance management. Isolates were collected in 1997 and 1998 (baseline sensitivity to tetraconazole, prothioconazole, or difenoconazole) and 2007 through 2010 from the major sugar-beet-growing regions of Minnesota and North Dakota and assessed for in vitro sensitivity to two or three DMI fungicides. Most (47%) isolates collected in 1997–98 exhibited 50% effective concentration (EC50) values for tetraconazole of <0.01 μg ml–1, whereas no isolates could be found in this EC50 range in 2010. Since 2007, annual median and mean tetraconazole EC50 values have generally been increasing, and the frequency of isolates with EC50 values >0.11 μg ml–1 increased from 2008 to 2010. In contrast, the frequency of isolates with EC50 values for prothioconazole of >1.0 μg ml–1 has been decreasing since 2007. Annual median difenoconazole EC50 values appears to be stable, although annual mean EC50 values generally have been increasing for this fungicide. Although EC50 values are important for gauging fungicide sensitivity trends, a rigorous comparison of the relationship between in vitro EC50 values and loss of fungicide efficacy in planta has not been conducted for C. beticola. To explore this, 12 isolates exhibiting a wide range of tetraconazole EC50 values were inoculated to sugar beet but no tetraconazole was applied. No relationship was found between isolate EC50 value and disease severity. To assess whether EC50 values are related to fungicide efficacy in planta, sugar beet plants were sprayed with various dilutions of Eminent, the commercial formulation of tetraconazole, and subsequently inoculated with isolates that exhibited very low, medium, or high tetraconazole EC50 values. The high EC50 isolate caused significantly more disease than isolates with medium or very low EC50 values at the field application rate and most reduced rates. Because in vitro sensitivity testing is typically carried out with the active ingredient of the commercial fungicide, we investigated whether loss of disease control was the same for tetraconazole as for the commercial product Eminent. The high EC50 isolate caused more disease on plants treated with tetraconazole than Eminent but disease severity was not different between plants inoculated with the very low EC50 isolate.

scholarly journals Inhibition of Phytophthora parasitica and P. capsici by Silver Nanoparticles Synthesized Using Aqueous Extract of Artemisia absinthium

2015 ◽  
Vol 105 (9) ◽  
pp. 1183-1190 ◽  
Author(s):  
Mohammad Ali ◽  
Bosung Kim ◽  
Kevin D. Belfield ◽  
David Norman ◽  
Mary Brennan ◽  
...  
Keyword(s):  
Silver Nanoparticles ◽  
Aqueous Extract ◽  
Dose Response ◽  
Mycelial Growth ◽  
Plant Pathogens ◽  
Synthesis Methods ◽  
In Planta ◽  
Artemisia Absinthium ◽  
Plant Disease Management

Application of nanoparticles for controlling plant pathogens is a rapidly emerging area in plant disease management, and nanoparticles synthesis methods that are economical and ecofriendly are extensively investigated. In this project, we investigated the potential of silver nanoparticles (AgNPs) synthesized with aqueous extract of Artemisia absinthium against several Phytophthora spp., which cause many economically important crop diseases. In in vitro dose-response tests conducted in microtiter plates, 10 µg ml−1 of AgNPs inhibited mycelial growth of P. parasitica, P. infestans, P. palmivora, P. cinnamomi, P. tropicalis, P. capsici, and P. katsurae. Detailed in vitro dose-response analyses conducted with P. parasitica and P. capsici revealed that AgNPs synthesized with A. absinthium extract were highly potent (IC50: 2.1 to 8.3 µg ml−1) and efficacious (100%) in inhibiting mycelial growth, zoospore germination, germ tube elongation, and zoospore production. Interestingly, AgNP treatment accelerated encystment of zoospores. Consistent with in vitro results, in planta experiments conducted in a greenhouse revealed that AgNP treatments prevented Phytophthora infection and improved plant survival. Moreover, AgNP in in planta experiments did not produce any adverse effects on plant growth. These investigations provide a simple and economical method for controlling Phytophthora with AgNP without affecting normal plant physiology.

scholarly journals Salicylic acid in the induction of resistance to beet seedling damping-off and antifungal activity against Fusarium sp., in vitro

2016 ◽  
Vol 37 (1) ◽  
pp. 67 ◽  
Author(s):  
Douglas Junior Bertoncelli ◽  
Sérgio Miguel Mazaro ◽  
Rita De Cacia Dosciatti Serrão Rocha ◽  
Nean Locatelli Dalacosta ◽  
Adriano Lewandowski ◽  
...  
Keyword(s):  
Salicylic Acid ◽  
Antifungal Activity ◽  
Mycelial Growth ◽  
Experimental Unit ◽  
Damping Off ◽  
Potato Dextrose Agar Medium ◽  
Seedling Length ◽  
Fusarium Sp ◽  
And Control

The damping off is the main disease that affects the beet crop during the seedling production. The aim of this study was to evaluate different salicylic acid (SA) concentrations for resistance induction against damping-off in beet seedling and its antifungal activity against Fusarium sp., in vitro condition. Treatment of beet seed was with SA solution by immersion during 5 minutes in the 0.5, 1.0, 1.5 and 2.0 mM concentrations and control (distilled water). It was used four replications with 20 cells by experimental unit. The experiment was carried out for 14 days in cultivate chamber with temperature (23 oC ± 2°C), lighting (12 hours photoperiod) and humidity (70% ± 10%) controlled. After this time, the germination, damping off incidence, seedling length and fresh mass matter weight were evaluated. It was evaluated also in the seedling tissue the phenylalanine ammonia-lyase (PAL), ?-1.3 glucanase and chitinase level enzymes. In the in vitro the SA was putted in PDA (potato-dextrose-agar) medium, where the Fusarium sp. mycelial growth was evaluated. The SA applied for seeds treatment didn’t had effect significant on damping off of beet seedlings, but it induced the activity of ?-1.3 glucanase enzyme, it being this higher in nine times when compared the treatment control. The SA acted in the Fusarium sp. in vitro control with fungitoxic action, suppressed mycelial growth in 28% if compared to control.

scholarly journals The Effects of Selenium on Wheat Fusarium Head Blight and DON Accumulation Were Selenium Compound-Dependent

Toxins ◽  
2020 ◽  
Vol 12 (9) ◽  
pp. 573
Author(s):  
Xueyun Mao ◽  
Chen Hua ◽  
Liang Yang ◽  
Yuhui Zhang ◽  
Zhengxi Sun ◽  
...  
Keyword(s):  
Fusarium Head Blight ◽  
Essential Element ◽  
Fungal Growth ◽  
Sodium Selenate ◽  
In Planta ◽  
Head Blight ◽  
Resistant Varieties ◽  
And Control ◽  
Toxin Accumulation

Fusarium head blight (FHB) caused by Fusarium graminearum not only results in severe yield losses, but also contaminates wheat grains with deoxynivalenol (DON) toxins. Prevention and control of FHB and DON contamination rely mainly on resistant varieties and fungicides. Selenium (Se) is an essential element for humans and animals, and also a beneficial element for plants. In this work, four Se compounds, i.e., sodium selenite (Na2SeO3), sodium selenate (Na2SeO4), selenomethionine (SeMet) and selenocysteine (SeCys2), were supplemented in a trichothecene biosynthesis induction (TBI) solid medium at different dosages in in vitro experiments. The four Se compounds at the dosage of 20 mg∙L−1 were sprayed onto wheat spikes immediately after inoculation at anthesis. All four of the Se compounds significantly inhibited the mycelial growth and DON production in the in vitro experiment; however, in planta, their effects on FHB severity and toxin accumulation in grains were compound-dependent. SeMet consistently negatively regulated fungal growth and DON accumulation both in vitro and in planta, which could be a novel and proconsumer strategy for reducing the detriment of wheat FHB disease and DON accumulation.

scholarly journals Toxicity and Resistance Potential of Selected Fungicides to Galactomyces and Penicillium spp. Causing Postharvest Fruit Decays of Citrus and Other Crops

Plant Disease ◽  
2012 ◽  
Vol 96 (1) ◽  
pp. 87-96 ◽  
Author(s):  
A. H. McKay ◽  
H. Förster ◽  
J. E. Adaskaveg
Keyword(s):  
Mycelial Growth ◽  
Single Spore ◽  
Ph Values ◽  
Highly Active ◽  
Green Mold ◽  
Dmi Fungicides ◽  
Ph Range ◽  
Penicillium Spp ◽  
Twofold Decrease

A diverse collection of isolates of Galactomyces citri-aurantii and G. geotrichum, the causal pathogens of sour rots of citrus and other fruit crops, respectively, was evaluated for sensitivity to demethylation-inhibiting (DMI) fungicides of the triazole group. Propiconazole was found to be highly effective in reducing mycelial growth of both species in vitro. For 139 isolates of G. citri-aurantii, a mean effective concentration for 50% reduction of mycelial growth (EC50 value) of 0.34 μg/ml was determined; whereas, for 33 isolates of G. geotrichum, this value was 0.14 μg/ml. In a comparison of additional DMI fungicides, mean EC50 values for 60 isolates of G. citri-aurantii and 20 isolates of G. geotrichum, were 0.27 and 0.17 μg/ml for cyproconazole, 0.25 and 0.14 μg/ml for metconazole, and 1.16 and 0.73 μg/ml for tebuconazole, respectively. Propiconazole was also highly active against mycelial growth of imazalil-sensitive isolates of Penicillium digitatum, the pathogen that causes green mold of citrus, with a mean EC50 value of 0.008 μg/ml for 63 isolates. Imazalil-resistant isolates of this fungus were cross-resistant to propiconazole. When G. citri-aurantii and P. digitatum were grown at selected pH values between 3 and 9, inhibition by propiconazole occurred over the entire pH range. The fungicide was most effective at pH 5 when compared with the non-fungicide-amended control grown at the same pH. In laboratory mass platings of single-spore isolates sensitive to propiconazole onto selective media, isolates with an up to 81.6-fold decrease in sensitivity to the fungicide were recovered for P. digitatum. For G. geotrichum, isolates with an approximately twofold decrease in sensitivity were obtained. No isolates with reduced sensitivity were recovered for G. citri-aurantii. Propiconazole is currently being registered for postharvest use on citrus and other crops, and the information provided will be valuable in monitoring of fungicide resistance and in designing effective fungicide application strategies.

scholarly journals On the Applicability of Chitosan Oligomers-Amino Acid Conjugate Complexes as Eco-Friendly Fungicides against Grapevine Trunk Pathogens

Agronomy ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 324
Author(s):  
Laura Buzón-Durán ◽  
Natalia Langa-Lomba ◽  
Vicente González-García ◽  
José Casanova-Gascón ◽  
Jesús Martín-Gil ◽  
...  
Keyword(s):  
Amino Acid ◽  
Wood Decay ◽  
Field Trials ◽  
Fungal Species ◽  
In Vitro Tests ◽  
In Planta ◽  
Management Culture ◽  
Amino Acid Conjugate ◽  
Acid Conjugate

In a context in which the incidence and severity of grapevine fungal diseases is increasing as a result of both climate change and modern management culture practices, reducing the excessive use of phytosanitary products in viticulture represents a major challenge. Specifically, grapevine trunk diseases (GTDs), caused by several complexes of wood decay or xylem-inhabiting fungi, pose a major challenge to vineyard sustainability. In this study, the efficacy of chitosan oligomers (COS)–amino acid conjugate complexes against three fungal species belonging to the Botryosphaeriaceae family (Neofusicoccum parvum, Diplodia seriata, and Botryosphaeria dothidea) was investigated both in vitro and in planta. In vitro tests led to EC50 and EC90 effective concentrations in the 254.6−448.5 and 672.1−1498.5 µg·mL−1 range, respectively, depending on the amino acid involved in the conjugate complex (viz. cysteine, glycine, proline or tyrosine) and on the pathogen assayed. A synergistic effect between COS and the amino acids was observed against D. seriata and B. dothidea (synergy factors of up to 2.5 and 2.8, respectively, according to Wadley’s method). The formulations based on COS and on the conjugate complex that showed the best inhibition rates, COS−tyrosine, were further investigated in a greenhouse trial on grafted vines of two varieties (”Tempranillo” on 775P and “Garnacha” on 110R rootstock), artificially inoculated with the mentioned three Botryosphaeriaceae species. The in planta bioassay revealed that the chosen formulations induced a significant decrease in disease severity against N. parvum and B. dothidea. In summary, the reported conjugate complexes may be promising enough to be worthy of additional examination in larger field trials.

scholarly journals Synthesis and Characterization of Novel Copper Nanoparticles for the Control of Leaf Spot and Anthracnose Diseases of Olive

Nanomaterials ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 1667
Author(s):  
Panagiota Ntasiou ◽  
Alexandra Kaldeli Kerou ◽  
Theodora Karamanidou ◽  
Afrodite Vlachou ◽  
George T. Tziros ◽  
...  
Keyword(s):  
Leaf Spot ◽  
Mycelial Growth ◽  
Crop Protection ◽  
Attenuated Total Reflection ◽  
Colletotrichum Acutatum ◽  
In Planta ◽  
Colletotrichum Spp ◽  
Type 3

Olive crop is frequently treated with copper fungicides to combat foliar and fruit diseases such as olive leaf spot caused by Fusicladium oleagineum and anthracnose caused by Colletotrichum spp. The replacement of copper-based products with more eco-friendly alternatives is a priority. Metal nanoparticles synthesized in several ways have recently revolutionized crop protection with applications against important crop pathogens. In this study, we present the development of four copper-based nanoparticles (CuNP Type 1 to 4) synthesized with a wet chemistry approach. The CuNPs were characterized using Transmission Electron Microscopy, Dynamic Light Scattering, Laser Doppler Electrophoresis, and Attenuated Total Reflection measurements. In addition, the activity of the four CuNP types was tested in vitro and in planta against F. oleagineum and Colletotrichum spp. In vitro sensitivity measurements showed that for both pathogens, mycelial growth was the most susceptible developmental stage to the tested compounds. Against both pathogens, CuNP Type 1 and Type 2 were found to be more active in reducing mycelial growth compared to the reference commercial compounds of copper oxide and copper hydroxide. In planta experiments showed that CuNP Type 3 and CuNP Type 4 exhibited a strong protectant activity against both F. oleagineum and Colletotrichum acutatum with control efficacy values significantly higher than those achieved by the applications of either reference product.

scholarly journals Penapisan isolat rizobakteri indigenos untuk pengendalian (Ganoderma boninense) di pre nursery kelapa sawit (Elaeis guineensis Jacq.)

Jurnal Agro ◽  
10.15575/4665 ◽  
2019 ◽  
Vol 6 (2) ◽  
pp. 110-122
Author(s):  
Yulmira Yanti ◽  
Imam Rifai ◽  
Yogie Aditya Pratama ◽  
Muhammad Ihsan Harahap
Keyword(s):  
Plant Growth ◽  
Oil Palm ◽  
Control Plant ◽  
Stem Rot ◽  
In Planta ◽  
Basal Stem Rot ◽  
Plant Growth Promoting ◽  
Growth Promoting ◽  
And Control

Rizobakteri merupakan kelompok bakteri yang aktif mengkolonisasi akar tanaman, meningkatkan pertumbuhan dan mengendalikan patogen tanaman. Penelitian ini bertujuan untuk memperoleh isolat rizobakteri indigenous  terbaik dalam meningkatkan pertumbuhan kelapa sawit dan mengendalikan penyakit busuk pangkal batang di pre-nursery kelapa sawit secara in planta serta karakterisasi kemampuan antagonisnya secara in vitro. Penelitian bersifat eksperimental terdiri atas 3 tahap dengan menggunakan Rancangan Acak Lengkap (RAL): (1) Isolasi dan karakterisasi isolat rizobakteri indigenous  di Kabupaten Pasaman Barat, (2) Pengujian isolat rizobakteri indigenous  (RBI) sebagai plant growth promoting rihzobacteria (PGPR), dan untuk pengendalian G.boninense di pre-nursery kelapa sawit terdiri dari 29 perlakuan (27 isolat RBI, tanpa inokulasi G. boninense sebagai kontrol positif, dan inokulasi G. boninense sebagai kontrol negatif) dengan masing-masing 5 ulangan, serta (3) Pengujian aktivitas antagonisme isolat RBI terhadap G. boninense. Data dianalisis dengan sidik ragam, apabila berbeda nyata dilanjutkan dengan uji Least Significance Different (LSD) pada taraf 5%. Hasil penelitian menunjukkan diperoleh tiga isolat terbaik (R10 2.2, R9 2.1, dan R10 2.3) yang mampu meningkatkan pertumbuhan kelapa sawit dan menekan perkembangan penyakit busuk pangkal batang G.boninense secara in planta dan in vitro.ABSTRACTRhizobacteria is a group of bacteria that actively colonize plant roots, increase growth and control plant pathogen. The objective of the research was to obtain indigenous rhizobacteria isolate (RBI) to increase growth and control basal stem rot on oil palm seedlings in in planta and characterize of antagonistic ability in in vitro. Experimental research consisted of 3 stages by using Completely Randomized Design (CRD): (1) Isolation of indigenous rhizobacteria in West Pasaman region, (2) Indigenous rhizobacteria isolate testing as a plant growth promoting rhizobacteria (PGPR) and to control of G. boninense on pre nursery of oil palm consisted of 29 treatments (27 RBI isolates, without G. boninense inoculation as positive control, and G. boninense inoculation as negative control) with 5 replications each. (3) Testing of RBI isolate antagonism activity towards G. boninense. Data were analyzed by variance, if the result significantly different, it was continued by using Least Significance Different (LSD) at 5% level. The results showed that best three isolates (R10 2.2, R9 2.1 and R10 2.3) were able to increase growth of palm oil and to suppress the development of G.boninense basal stem rot in in planta and in in vitro.

scholarly journals In vitro evaluation of grapevine endophytes, epiphytes and sap micro-organisms for potential use to control grapevine trunk disease pathogens

2021 ◽  
Author(s):  
Robert Blundell ◽  
Molly Arreguin ◽  
Akif Eskalen
Keyword(s):  
Biological Control ◽  
Mycelial Growth ◽  
Fungal Pathogens ◽  
Dual Culture ◽  
Biological Control Agents ◽  
In Planta ◽  
Eutypa Dieback ◽  
Fungal Isolates ◽  
Wound Protection

SummaryGrapevine trunk diseases (GTDs) threaten the economic sustainability of viticulture worldwide causing a significant reduction of both yields and quality of grapes. Biological control presents a promising sustainable alternative to cultural and chemical methods to mitigate the effects of pathogens causing GTDs, including Botryosphaeria dieback, Eutypa dieback and Esca. This study aimed to identify naturally occurring potential biological control agents from a variety of grapevine tissues, including sap, cane and pith and evaluate their antagonistic activity against selected fungal pathogens responsible for GTDs in vitro. Bacterial and fungal isolates were preliminary screened in vitro to determine their antifungal activity via a dual culture assay against Neofusicoccum parvum and Eutypa lata. Among the fungal isolates, Trichoderma spp. inhibited E. lata mycelial growth up to 64% and N. parvum mycelial growth up to 73% with overgrowth and stopped growth being the likely antagonistic mechanisms. Among the bacterial isolates, Bacillus spp. inhibited E. lata mycelial growth up to 20% and N. parvum mycelial growth up to 40%. Select antagonistic isolates of Trichoderma, Bacillus and Aureobasidium spp. were subject to further dual culture antifungal analysis against Diplodia seriata and Diaporthe ampelina, with Trichoderma isolates consistently causing the greatest inhibition. Volatile organic compound antifungal analysis revealed that these Trichoderma isolates resulted significantly inhibited mycelial growth of N. parvum, E. lata and D. ampelina causing up to 20.11%, 60.55% and 70.9% inhibition respectively (P≤0.05). Multilocus sequence analysis revealed that the Trichoderma isolates are most closely related to Trichoderma asperellum and Trichoderma hamatum. This study identifies grapevine sap as a novel source of potential biological control agents for control of GTDs to support existing efforts to control GTDs. Further testing will be necessary to fully characterize these microbes mode of antagonism and assess their efficacy for pruning wound protection in planta.

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