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Selection of fluorescent pseudomonas strains with antagonistic activity against phytophthora palmivora (Butl.) in theobroma cacao L.Acebo Guerrero, Yanelis 26 January 2015 (has links)
Resumé<p>La pourriture brune de la cabosse de Theobroma cacao L. induite par Phytophthora palmivora est un maladie qui à l’échelle mondiale, cause de sérieuses pertes dans les plantations de cacao. L'utilisation de fongicides est coûteuse et est nuisible pour l'environnement. L'utilisation de micro-organismes est une alternative écologique<p>attractive pour les producteurs. L’objectif de ce travail est d’isoler et de caractériser des rhizobactéries de T. cacao avec une activité antagoniste contre Phytophthora palmivora, l'agent causal de la pourriture des cabosses. Parmi les 127 rhizobactéries isolés, trois isolats CP07, CP24 et CP30, identifiées comme Pseudomonas chlororaphis, ont montré une activité<p>antagoniste in vitro et in vivo contre P. palmivora. <p>La production d'enzymes lytiques, de sidérophores, de biosurfactants et d’HCN, ainsi que la détection de gènes codant pour des antibiotiques, la formation de biofilm et la mobilité des bactéries ont également été évalués pour les trois souches de rhizobactérie.<p>Le séquençage du génome de CP07 a confirmé la présence de gènes codant pour trois types de sidérophores, d’HCN, de phénazines et de biosurfactants de la famille de la viscosine, notamment. Un mutant de CP07 déficient dans la production viscosine a été généré et les études effectuées sur ce mutant indiquent que ce bio-tensioactif particulier est essentiel à la fois pour la mobilité bactérienne et pour la formation de biofilm, mais pas pour l'antagonisme in vitro contre Phytophthora, bien qu'il puisse contribuer à la bioprotection de T. cacao.<p>Cette étude fournit une base théorique pour l'utilisation potentielle de P. chlororaphis<p>CP07 comme un agent de lutte biologique pour la protection des plantes de cacao contre l'infection par P. palmivora.<p><p><p>Abstract<p>The black pod rot in Theobroma cacao L. is a major problem worldwide and in Cuba, is<p>one of the most important diseases. The use of chemical fungicides is expensive and<p>harmful to the environment. The use of microorganisms is an environmentally<p>attractive alternative for producers. In this work, fluorescent Pseudomonas strains were<p>isolated from cocoa rhizosphère. The in vitro antagonistic activity and bioprotection<p>against Phytophthora palmivora (Butler) was evaluated. Three strains with in vitro<p>antagonistic activity and bioprotection, CP07, CP24 and CP30, belonging to the species Pseudomonas chlororaphis, were obtained. P. chlororaphis CP07 was highlighted for the best behavior in vitro and in vivo. P. chlororaphis CP07 produces siderophores, HCN,<p>biosurfactants, exoproteases, lipases and motility (swarming and twitching). Genome<p>sequencing confirmed the presence of genes encoding three types of siderophores, HCN, phenazines, the biosurfactant viscosin, and exoproteases, among others. A mutant impaired in biosurfactant production was constructed. When the mutant was characterized, it was evident that the biosurfactant was not involved in the antagonistic effect in vitro against P. palmivora Mab1, although it is crucial to the motility and the ability to form biofilms. P. chlororaphis CP07 was selected as a potential biological control agent against Phytophthora. / Doctorat en Sciences / info:eu-repo/semantics/nonPublished
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Improving abiotic and biotic stress tolerance in floriculture cropsSouth, Kaylee 13 November 2020 (has links)
No description available.
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Biological control of clubroot (Plasmodiophora brassicae) by an endophytic fungus (Acremonium alternatum)Auer, Susann 18 August 2015 (has links)
The biological control of plant pests with beneficial microbes has become increasingly important over the last decades. Soil microbes such as fungi and bacteria colonise the roots of plants and promote their growth. Some beneficial microbes can trigger a weak plant defence response that enhances the immune response of the plant at subsequent pathogen attacks and therefore increase the resistance of the plant to other invaders. This mechanism is called “priming”.
While biocontrol agents are applied against a variety of plant pests fundamental knowledge of the molecular mechanisms of plant-microbe interactions is still lacking. Especially molecular studies on the role of resistance genes in the interaction of plants with beneficial endophytic fungi are rare.
In this study it was investigated how the fungal biocontrol agent Acremonium alternatum affects the development of the clubroot pathogen Plasmodiophora brassicae within the plant host Arabidopsis thaliana. Clubroot is a devastating disease in crop plants such as cabbage and rapeseed and causes abnormal root growth that leads to so called “club roots”. P. brassicae develops within the plant roots and forms resting spores that are very durable and stay infective in soils for up to 2 decades. The control of clubroot by chemical means is difficult and the disease continues to spread on all continents and was also found in Saxony, Germany in recent years.
In 2 preliminary studies the co-inoculation of clubroot plants with the fungus A. alternatum resulted in reduced clubroot symptoms in Chinese cabbage and Arabidopsis. It was therefore hypothesised that A. alternatum induces resistance mechanisms in the plant and thus enhances immunity.
The focus of this study was to test this hypothesis by carrying out expression analyses on root tissue of infected Arabidopsis plants. For this the plants were inoculated with spores of P. brassicae and A. alternatum before RNA was extracted from the roots, followed by cDNA synthesis and quantitative Reverse Transcriptase Polymerase Chain Reaction (RT-qPCR). A microarray of root tissue of infected Arabidopsis plants was carried out to depict the events at the stage of initial root hair infection with the clubroot pathogen. The findings from the gene expression analyses were verified for 2 genes with Arabidopsis mutants that are defective in the respective gene and with 2 overexpressor lines.
Clubroot symptoms were assessed by rating the root galls according to their stage of development. The overall plant health was further evaluated by recording the developmental stage of the plants (generative vs. vegetative), stem lengths and plant biomass. In addition, 2 local varieties of the economically important crop plant rapeseed (Brassica napus var. Ability and var. Visby) were investigated with qRT-PCR and by recording the disease parameters just described.
A second goal of this study was to assess the general biocontrol potential of the yet relatively unknown endophyte A. alternatum in terms of enzymatic activity and competitive behaviour against other phytopathogenic fungi. The potential of this fungus for the use in integrative pest management was investigated. The results presented here are novel findings for this fungus and have not been studied before.
The microarray from Arabidopsis roots revealed that the clubroot pathogen P. brassicae suppresses its recognition by pathogen receptors of the plant and thus prevents the host to induce resistance mechanisms. The fungus A. alternatum boosted the level of the pathogen recognition-related genes BAK1 and FLS2 and thus helped to establish early plant defence responses. PCR analyses confirmed that these early responses led to salicylic acid-dependent resistance in the plants which was maintained for several days as shown by elevated levels of the PATHOGENESIS-RELATED gene PR1. Marker genes for an alternative resistance pathway that is mediated over the plant signals jasmonate and ethylene were not activated in Arabidopsis.
The co-inoculation of Arabidopsis plants with the endophyte A. alternatum resulted in a significant reduction of clubroot symptoms by up to 24%. In rapeseed the reduction of disease symptoms was 19% and 28% when the plants were treated with a crude cell wall extract of A. alternatum before inoculation with the clubroot pathogen. PCR analyses from Arabidopsis showed a strong response of pathogen recognition genes to the cell wall extract and spores of the endophytic fungus. In rapeseed all of the investigated pathogen recognition genes were upregulated after the endophyte treatment but not with the clubroot pathogen. Together with the PCR results from the microarray these findings suggest that A. alternatum primes its host plant and enhances the resistance of the plant towards P. brassicae. In addition, the fungus increased biomass, stem lengths and survival rates of clubroot-infected plants.
In vitro tests revealed that the endophyte can solubilise phosphate and is not very competitive against other phytopathogenic fungi such as Aspergillus or Fusarium which is likely an effect of the relatively slow growth of the endophyte on agar plates.
From this study it can be concluded that i) the fungus Acremonium alternatum induces resistance mechanisms in Arabidopsis and 2 Brassica napus cultivars and facilitates the recognition of the clubroot pathogen Plasmodiophora brassicae; ii) that Arabidopsis and Brassica react differently to this beneficial microbe, a fact that has been observed for Plasmodiophora and other microorganisms as well; iii) living spores are not necessary for clubroot biocontrol in rapeseed as a crude cell wall extract reduces symptoms more efficiently.
Overall the endophyte A. alternatum is a very promising candidate for the use in integrative pest management in plant strengtheners or as biocontrol agent. / Die biologische Kontrolle von Pflanzenkrankheiten gewinnt zunehmend an Bedeutung. Bodenbewohnende Mikroben wie Pilze oder Bakterien kolonisieren die Wurzeln von Pflanzen und fördern deren Wachstum. Einige dieser förderlichen Mikroben aktivieren eine schwache Abwehrreaktion in der Pflanze die sich verstärkt bei einer weiteren Infektion mit einem Krankheitserreger. Dieser Mechanismus, den man “Priming” nennt, führt zu einer verbesserten Resistenz der Pflanze gegenüber Pflanzenpathogenen.
Obwohl natürliche Schädlingsbekämpfer bereits gegen eine Vielzahl an Krankheiten eingesetzt werden, weiss man über grundsätzliche molekulare Mechanismen dieser Pflanzen-Mikroben-Interaktionen nur wenig. Besonders die Rolle von Resistenzgenen ist bisher wenig erforscht, welche bei der Beziehung zwischen Pilzen und Pflanzen eine Rolle spielen.
In der hier vorliegenden Arbeit wurde untersucht, wie der endophytische Pilz Acremonium alternatum die Entwicklung des Krankheitserregers Plasmodiophora brassicae in der Pflanze Arabidopsis thaliana beeinflusst. Die Kohlhernie, ausgelöst von P. brassicae, ist eine verheerende Krankheit die u. a. bei Kohl und Raps auftritt und Wurzelgallen, so genannte “Hernien”, hervorruft. Der Krankheitserreger entwickelt sich im Wurzelsystem der Pflanze und bildet Dauersporen, die bis zu 20 Jahre lang im Boden infektiös überdauern können.
Ein Eindämmen der Krankheit mit Pflanzenschutzmitteln ist durch den komplexen Lebenslauf des Erregers sehr schwierig, das führte zu einer weltweiten Verbreitung der Kohlhernie. Auch in Sachsen wurden in den letzten Jahren Fälle von Kohlhernie gemeldet. Wie 2 Studien zeigen, führt die Ko-Inokulation von Kohlhernie-erkrankten Pflanzen mit A. alternatum zu einer Verringerung der Symptome in Chinakohl und Arabidopsis. Es wurde daher die Hypothese aufgestellt, dass der Pilz Resistenzmechanismen in der Pflanze anschaltet und damit ihre Immunität erhöht.
Um diese Hypothese zu testen, wurden in der hier vorliegenden Studie Genexpressionsanalysen an infizierten Arabidopsiswurzeln durchgeführt. Dafür wurden die Pflanzen zunächst mit Sporen des Kohlhernieerregers und des Pilzes inokuliert, es wurde RNA aus den Wurzeln extrahiert, in cDNA umgeschrieben und diese mittels quantitativer Reverse-Transkriptase-Polymerasenkettenreaktion (RT-qPCR) untersucht. Ein Microarray von Wurzeln infizierter Pflanzen wurde durchgeführt um die Ereignisse abzubilden, die sich zeitnah nach der Infektion in den Wurzeln abspielen. Die Ergebnisse der Genexpressionsanalysen wurden dann an Arabidopsismutanten, die einen Gendefekt im jeweiligen Gen haben, und an Überexprimierer-Pflanzen verifiziert.
Kohlherniesymptome an Pflanzen wurden durch eine Kategorisierung der Schadsymptome erfasst. Die allgemeine Pflanzengesundheit sowie der Entwicklungsstand der Pflanze, Stengellängen und das Frischgewicht wurden bestimmt. Zusätzlich wurden 2 Rapssorten, die in Sachsen angebaut werden, untersucht im Hinblick auf die Krankheitsenwicklung und die Reguation von Abwehrgenen.
Ein weiteres Ziel dieser Arbeit war es das Biokontrollpotential des bisher schlecht untersuchten Pilzes A. alternatum zu bestimmen. Dazu wurde in vitro die Enzymaktivität des Pilzes getestet sowie seine Konkurrenzfähigkeit gegenüber anderen pflanzenpathogenen Pilzen. Das Potential des Pilzes für die Anwendung im integrierten Pflanzenschutz wurde getestet. Die hier präsentieren Ergebnisse stellen neue Erkenntnisse dar, die für diesen Pilz noch nie untersucht wurden. Der Microarray von Arabidopsiswurzeln zeigte, dass der Kohlhernieerregers die Erkennung durch die Pflanze verhindert und damit Abwehrmechanismen verhindert. Der Pilz A. alternatum förderte die Aktivität der pflanzlichen Erkennungsrezeptoren FLS2 und BAK1 und setzte damit die Erkennung von P. brassicae in Gang. PCR-Analysen ergaben, dass diese früh induzierten Abwehrmechanismen zu einer systemischen Resistenz in der Pflanze führte durch die Aktivierung des Pathogenese-relevanten Gens PR1. Genmarker, die die Aktivität eines alternativen, von Jasmonat und Ethylen vermittelten Abwehrweges anzeigen, waren nicht ativiert.
Die Ko-Inokulation von Arabidopsis mit dem Endophyten führte zu einer signifikanten Reduktion der Krankheitssymptome um 24%. In Raps betrug die Reduktion 19% und 24% wenn die Pflanzen vor der Kohlhernie-Infektion mit einem Zellwandextrakt des Pilzes behandelt wurden. Mittels PCR konnte gezeigt werden, dass Gene für das Erkennen von Pathogenen in der Wurzel von Arabidopsis auf den Zellwandextrakt und Sporen des Pilzes reagieren. In Raps wurden alle der untersuchten Erkennungsgene aufreguliert nach der Infektion mit A. alternatum, nicht jedoch bei der Infektion mit P. brassicae.
Zusammenfassend lässt sich sagen, dass der endophytische Pilz A. alternatum die Wirtspflanze auf eine folgende Infektion vorbereitet (Priming) und systemische Abwehr-mechanismen in der Pflanze induziert, wenn diese mit Kohlhernie infiziert ist. Außerdem treibt der Pilz das Sprosswachstum voran, erhöht die Biomasse und fördert das Überleben von Kohlhernie-infizierten Pflanzen. In vitro-Tests ergaben, dass der Endophyt Kalziumphosphat löslich machen kann und wenig kompetitiv gegenüber Pflanzenpathogenen wie Aspergillus oder Fusarium ist. Dies ist vermutlich mit dem langsameren Wachstum des Endophyten im Gegensatz zu den anderen Pilzen zu erklären.
Aus den Ergebnissen dieser Arbeit lassen sich folgende Schlüsse ziehen: i) der endophytische Pilz Acremonium alternatum induziert Resistenzmechanismen in Arabidopsis und Raps und und fördert die Erkennung des Kohlhernieerregers Plasmodiophora brassicae; ii) Arabidopsis und Raps reagieren unterschiedlich auf diesen förderlichen Pilz, ein solcher Unterschied wurde bereits für Plasmodiophora und andere Mikroben beschrieben; iii) lebende Sporen des Pilzes sind nicht notwendig um Krankheitssymptome der Kohlhernie in Raps zu verringern, ein Zellwandextrakt von A. alternatum ist dafür besser geeignet.
Ganz allgemein lässt sich sagen, dass der endophytische Pilz Acremonium alternatum ein sehr vielversprechender Kandidat ist für den Einsatz im integrierten Pflanzenschutz in Pflanzenstärkungsmitteln oder als Biokontrollorganismus.
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Garlic dry rot: a comprehensive study from field to fork on casual agents and disease managementMONDANI, LETIZIA 31 March 2021 (has links)
L’aglio è coltivato a livello mondiale nelle regioni temperate, secondo la FAO nel 2016 1.5 milioni di ettari sono stati destinati a questa coltura. A partire dal 2002 Fusarium proliferatum è stato segnalato come principale agente causale del marciume secco dell’aglio in post raccolta. I sintomi sono identificabili come macchie necrotiche sui bulbilli e in presenza di forti infezioni è possibile osservare la presenza di micelio bianco. F. proliferatum è un patogeno in grado di produrre Fumonisina B1 e B2, micotossine che potrebbero accumularsi all’interno dei bulbi ed essere tossiche per il consumatore. In Italia nel 2012 il 30% del raccolto è stato perso a causa di questo patogeno. Essendo la Fusariosi una malattia emergente a livello mondiale in letteratura si trovano ancora scarse informazioni sul suo sviluppo a livello di campo e sulle strategie di contenimento.
1. Allo scopo di verificare la quantità di inoculo fungino presente nell’ambiente si è proceduto all’analisi dei suoli in presemina con specifica attenzione alla quantificazione e all’identificazione delle specie fungine presenti. A tale scopo è stata eseguita: la conta delle Unità Formanti Colonia per grammo di terreno (UFC/g) su terreni specifici per l’isolamento del genere Fusarium spp. per grammo di terreno. Le identificazioni sono state eseguite al microscopio ottico e confermate successivamente con metodi molecolari.
2. Per seguire l’avanzamento della malattia durante la stagione colturale, invece, si è proceduto al campionamento in tre fasi fenologiche (inizio formazione dei bulbilli BBCH 15, ingrossamento dei bulbilli BBCH 45, maturazione di raccolta BBCH 49) con caratterizzazione dei sintomi, isolamento e riconoscimento dei funghi associati al marciume.
3. Per verificare la correlazione tra andamento meteo e incidenza delle specie fungine associate al marciume secco, sono stati raccolti i dati di meteorologici relativi al totale delle piogge, ai gradi giorno, all’umidità relativa media e alla temperatura media nei quadrati corrispondenti alle aziende agricole oggetto di studio. I dati sono stati correlati attraverso il coefficiente di correlazione di Pearson con i valori di gravità e incidenza della malattia stimati a fine stagione colturale.
4. Per verificare l’insorgenza dalla malattia nella fase di post raccolta si è proceduto con campionamenti di bulbi in conservazione, posa in piastra di bulbilli sintomatici e asintomatici e calcolo dell’incidenza delle specie fungine associate ai sintomi del marciume.
5. Al fine di verificare la possibile presenza di fumonisine nei campioni analizzati durante la stagione colturale e nel post raccolta, si è proceduto all’analisi attraverso HPLC di estratti di aglio.
6. Per individuare possibili strategie di controllo della malattia durante la stagione colturale sono stati eseguiti test di efficacia di prodotti chimici e biologici in vitro e in campo. I prodotti chimici sono stati provati su PDA modificato inoculato centralmente con F. proliferatum, mentre per gli agenti di biocontrollo sono state allestite prove di coltura duale. La prova in campo, invece, è stata eseguita all’interno di un campo sperimentale a strip plot. L’aglio delle diverse tesi è stato conservato in cella frigorifera per 9 mesi, per valutare la persistenza dei prodotti utilizzati alla concia.
I risultati ottenuti hanno dimostrato che F. proliferatum e F. oxysporum sono le specie maggiormente associate al marciume dell’aglio durante la stagione colturale. L’andamento delle due specie è complementare e varia a seconda dell’andamento meteorologico della stagione colturale. F. proliferatum è correlato positivamente con l’aumento della temperatura e delle piogge, mentre F. oxysporum sembra prevalere nelle stagioni meno piovose ed ha mostrato correlazione positiva con la gravità dei sintomi rilevati in campo sulle corone.
La carica micotica di Fusarium nel terreno rimane costante negli anni di analisi, facendo presupporre un maggiore ruolo del seme nella trasmissione della malattia.
Per quanto riguarda il post raccolta, invece, F. proliferatum risulta la specie isolata con maggiore frequenza dai bulbilli e si correla positivamente ai sintomi rilevati sugli spicchi, confermando il suo ruolo come agente causale del marciume secco durante lo stoccaggio. F. oxysporum, invece, colonizza in prevalenza le radici e la parte basale della pianta dividendo il patosistema in due subsistemi: F. proliferatum-bulbi; F. oxysporum-radici. F. proliferatum è stato isolato anche dagli spicchi asintomatici con frequenza del 25%, ed è stato possibile rilevare la presenza di fumonisine con l’avanzare del tempo di stoccaggio in cella. Essendo il fungo presente anche sugli spicchi asintomatici maggiori studi saranno necessari per garantire la sicurezza dei consumatori. Infine, dalle prove di concia in campo è emerso che il principio attivo Tebuconazolo, riduce la comparsa dei sintomi da Fusarium, ma non in modo risolutivo. Ciononostante, una volta che il prodotto viene riportato a temperatura ambiente dopo lo stoccaggio in cella refrigerata, l’incidenza di F. proliferatum aumenta nuovamente con possibilità di sviluppo di danni al prodotto da commercializzare. / Since 2002, Fusarium proliferatum has been reported as the main causal agent of garlic dry rot during the postharvest stage, but information on the development of the disease throughout the production chain was nearly absent. Dry rot has caused huge economic losses in the past few years (up to 30 % of the yield), symptoms are visible on bulbs during storage as necrotic spots and in the most severe attacks, white mycelium may become visible on cloves. Few pest management strategies were tested in the recent past, but none were satisfactory. Due to the economic effect that this pathogen can have on local productions, the thesis aimed to deeply investigate the pathosystem with a field to fork approach and to test new strategies to control fungal infections.
First of all, the work focused on garlic (Allium sativum L.) cropping season, intending to clarify the role of F. proliferatum in bulb infection as well as the impact of crop growing conditions on the development of the pathogen. A 3-year study was conducted in Piacenza (northern Italy) by sampling six garlic farms with different dry rot history (three highly contaminated and three low contaminated). Soil samples were recovered at sowing time for the counting of fungal colony-forming units (CFU). Plant samples were collected at three relevant growth stages, from April to July, for which disease severity assessment and fungi isolations were performed. Fusarium was the most frequently isolated genus, and F. proliferatum and F. oxysporum the dominant species during the garlic cropping season. F. oxysporum was dominant in the first year of the study, but F. proliferatum registered the highest incidence in all the farms tested. F. oxysporum incidence was correlated with dry weather, whereas F. proliferatum was enhanced in rainy years. To conclude, F. proliferatum is confirmed to be associated with garlic bulbs, even at crop’s early growth stages and symptoms are visible mainly on roots and basal plates at the field stage, related to F. oxysporum.
Then, the focus was made in detecting the presence of F. proliferatum on garlic bulbs during prolonged storage, and to identify other fungal species associated with garlic dry rot. Moreover, fumonisin contamination in symptomatic and asymptomatic cloves were detected. Samples of 100 plants were collected over three production seasons in six farms located in Northern Italy at three-time points (at harvest, processing, and 6 months storage at –4° C). Results obtained lead to think that Fusarium–garlic pathosystem is split into two parts: basal plate/root and bulb. F. proliferatum had the highest incidence in infected bulbs and was confirmed as the causal agent of postharvest dry rot in garlic (mean incidence: 35.4%). F. oxysporum co-occurred with F. proliferatum but symptoms were visible only on basal plate/root. Dry rot incidence slightly increased during cold storage (from 14.6% at processing to 18.4% at 6-month storage); although, F. proliferatum incidence was stable during cold storage, fumonisin were produced from harvest through storage. Cloves showing symptoms were more contaminated compared to those asymptomatic, both by the fungus (mean incidence 39% vs 25.3%) and the toxin (287.0 vs 24.4 µg kg-1). Therefore, cold storage limits garlic dry rot, but health concerns related to fumonisin should be seriously considered.
Regarding disease management, garlic crop is commonly propagated by plant parts (cloves). To protect garlic crop from early growth stages it is important to find commercial products able to control the pathogen growth on seedlings. The experiment aimed to test in vitro and in vivo the efficacy of triazoles and biocontrol agents (BCAs) against F. proliferatum and F. oxysporum. In in vitro trials, the best performance was achieved by propiconazole+prochloraz (100%), followed by tebuconazole (88.9%). BCAs were less effective but still showed great capacity to control the pathogen with maximum growth inhibition of 80% (Trichoderma harzianum +T. gamsii). In both cases, temperature influenced the capacity to control the pathogen with minimum effect at 25°C compared to lower temperatures. In vivo bacterial BCAs showed a similar capacity to control Fusaria compared to chemical products (mean of severity index 18.6% and 11.7%, respectively) and did not show side effects on root length. In vitro and in vivo results are comparable, except for Trichoderma, with the worst performances in terms of disease severity on plants.
Finally, a field trial was designed to verify the efficacy of chemical and biological active ingredients as seed coating both at crop stage and postharvest, simulating the entire production chain, by taking into account visible symptoms and incidence of fungi. All products tested reduced the severity of symptoms on basal plates at the field stage, but none of them was able to reduce Fusarium incidence. A postharvest analysis conducted on bulbs demonstrated the efficacy of Tebuconazole, B. subtilis, and Trichoderma+B. subtilis in reducing the number of cloves showing symptoms per bulb (mean 34.3% vs control 45.8%). Moreover, Tebuconazole was able to reduce the incidence of F. proliferatum by 48% with respect to untreated control. The trial highlighted also that the incidence of F. proliferatum increased by 37% when garlic bulbs were kept for 15 days at room temperature simulating storage at consumers houses. Results obtained in the trial are promising and seed coating had a positive effect on garlic dry rot postharvest; although further studies are needed to test the persistence of seed coating treatments after prolonged storage period, especially when the product is kept outside cold chambers.
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Sustainable Coffee Farming in Hawai'i: Gathering GIS Data to Inform Development and Planning in the Rainforest and Protect Natural and Historic FeaturesO'Hearn, Connor E. 20 April 2021 (has links)
No description available.
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Microbial endophytes and their interactions with cranberry plantsBustamante Villalobos, Peniel 01 1900 (has links)
Virtuellement toutes les plantes hébergent des champignons et des bactéries endosymbiontes (endophytes). Ces microorganismes façonnent le développement de leur hôte et peuvent inhiber des phytopathogènes. Au niveau moléculaire, les interactions plante-endophyte sont médiées par des molécules secrétées y compris des protéines et métabolites secondaires. Au cours des dernières années, la recherche d’endophytes a augmenté chez nombreux plantes, cependant chez les Ericaceae les endophytes ne sont pas bien connus. Alors, on s’est mis à investiguer les endophytes racinaires de la canneberge, une plante membre d’Ericaceae native de l’Amérique du Nord. On a échantillonné quatre plants provenant d’une ferme commerciale organique. Au total, 30 souches fongiques et 25 bactériens ont été isolés. Les bactéries Pseudomonas sp. EB212, Bacillus sp. EB213 et EB214; et les champignons Hyaloscypha sp. EC200, Pezicula sp. EC205 et Phialocephala sp. EC208 ont supprimé la croissance de cinq pathogènes de la canneberge, incluant Godronia cassandrae, un champignon causant la pourriture des fruits de la canneberge au Québec. EB213 a été capable de promouvoir légèrement la croissance de plantules de la canneberge. En performant des techniques microscopiques, on a constaté l’habileté de EC200, EC205 et EC208 à coloniser internement les racines des plantules de la canneberge. De plus, les génomes de ces champignons ont été séquencés, assemblés et annotés. Les analyses génomiques se sont concentrées sur les protéines secrétées et les groupes des gènes impliqués dans la biosynthèse (GGB). On a trouvé un large répertoire de gènes codant pour des enzymes qui métabolisent les carbohydrates et d’autres codant pour des protéases. Les deux groupes d’enzymes seraient utiles à dégrader de la matière organique pour libérer des nutriments. Aussi bien, ces enzymes pourraient faciliter la colonisation des racines de la plante hôte. De plus, on a prédit des nombreuses protéines effectrices qui assisteraient les endophytes à éviter l’activation du système immunitaire des plants. A noter que parmi les GGB inférés dans les génomes de EC200, EC205 et EC208, environ 90% ne sont pas caractérisés. Finalement, on a performé des analyses transcriptomiques pour élucider la réponse de EC200, EC205 et EC208 envers la présence de leur hôte, simulée par l’addition d’un extrait de canneberge au milieu de culture. Les conclusions majeures sont que les racines des plantes de la canneberge qui ont été échantillonnées sont dominées par des microorganismes avec l’habileté d’inhiber des phytopathogènes ; et que les génomes de EC200, EC205 et EC208 codent pour un grand répertoire de protéines qui pourraient être liées aux interactions plante-endophyte. / Virtually all plants host fungal and bacterial endosymbionts (endophytes). These microbes shape plant development and may inhibit phytopathogens. At the molecular level, plant-endophyte interactions are mediated by secreted compounds, including proteins and secondary metabolites. While endophytes are increasingly studied in diverse plants, little is known about their presence in Ericaceae. Therefore, we set out to investigate the root endophytes of cranberry, an ericacean member native to North America. We sampled endophytes from four plants grown on an organic farm. In total, 30 fungal and 25 bacterial strains were isolated and identified. A subset of these, notably Pseudomonas sp. EB212, Bacillus sp. EB213 and EB214; and fungi Hyaloscypha sp. EC200, Pezicula sp. EC205, and Phialocephala sp. EC208, were tested for their ability to suppress phytopathogens. Altogether, they inhibited five cranberry pathogens, including Godronia cassandrae, an important cranberry fruit-rot agent in Quebec. EB213 was the only endophyte that increased the biomass of cranberry seedlings. Using microscopy techniques, we confirmed the ability of EC200, EC205, and EC208 to colonize cranberry roots internally. The genomes of these fungi were sequenced, assembled and annotated. Genomic analyses focused on secreted proteins and biosynthetic gene clusters (BGCs). We found an extensive repertoire of carbohydrate-active enzymes and proteases that could assist in recycling organic nutrients, rendering them accessible to plants; these enzymes may also facilitate root colonization. In addition, effector proteins were predicted; these molecules may assist endophytes to escape the plant immune system and favour colonization. We inferred 139 biosynthetic gene clusters (BGCs) across the three examined fungi. Remarkably, the product of around 90% of BGCs are unknown. Finally, transcriptomic analyses were performed to determine how EC200, EC205 and EC208 respond to the presence of cranberry, simulated by the addition of cranberry extract in the culture medium. The two major conclusions of this work are that the roots of the sampled cranberry plants are dominated by endophytes with biocontrol abilities, and that EC200, EC205 and EC208 encode a broad repertoire of proteins that could be involved in plant-endophyte interactions.
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An investigation into the use of biological control agents as a sustainable alternative to synthetic fungicides in treating powdery mildew in tunnel cucumbersHaupt, Michael Rory 31 January 2007 (has links)
The use of biological control agents (BCAs) in the past has shown limited success as its application has often been done incorrectly, and in addition, management practices are rarely altered to incorporate BCAs. Criteria for the correct application of BCAs have been devised as part of the research, and companies selling these products may use the said criteria. Such application will ensure the correct BCAs are used and, more specifically, used under the correct conditions. The powdery mildew (PM) fungus is often seen to develop resistance to synthetic fungicides and, therefore, alternative control measures are required. BCAs as an alternative pose less risk to the environment, workers and the consumer.
A pre-trial has been conducted with a range of BCAs to see if they can control powdery mildew (PM) in a greenhouse environment on hydroponically grown cucumber (Cucumis sativus L.) plants using the variety Baccara that has only a moderate tolerance to PM. The BCAs have been compared to the control (synthetic fungicide: Bravo). Comparative work includes Coyier's model, which has been modified and adapted for these trials to determine the percentage of leaf area covered by the PM infection. Furthermore, the number of fruit harvested per treatment, kilogram yield, total mass of yield and average fruit mass is also used to determine the efficacy of the BCAs as these factors have economic significance to commercial growers. The pre-trial showed promise until the fertigation computer failed, resulting in a nutrient shortage and imbalance, confirming that BCAs alone cannot control PM. Synthetic fungicides were applied until control of PM and plant nutrition was regained. BCAs were re-introduced and used until the end of crop production.
The confirmation from the pre-trial has led to the inclusion of silicon in conjunction with the BCAs in the two subsequent trials (Trials 1 & 2). Silicon was applied with the BCAs as a foliar spray on a weekly basis. In trials 1 and 2, the cucumber variety, Palladium, with a high genetic tolerance to PM is used, as this variety is suited to form part of the holistic approach used for trials 1 and 2.
Trial 1 showed that treatment A, containing Streptomyces griseovirdis and Streptomyces aureofaciens, had the highest yield. Both of these are bacterial BCAs and demonstrated their adaptability to varied climatic conditions, notably when low humidity was experienced. In treatment B, Trichoderma harzianum strains, Rifai and Uppington, show the slowest rate of PM development.
In trials 1 and 2, the best actual PM control was obtained by two fungal based BCAs (Trial 1, treatment C was Ampelomyces quisqualis) and (Trial 2, treatment B was Trichoderma harzianum strains, Rifai and Uppington), showing that fungal BCAs have a place for this application, but the growth-enhancing properties of bacterial based BCAs make economic sense and would make them attractive to growers. Treatment A (Streptomyces spp.) had the most number of fruit for the entire growing period and the best overall yield (kg yield) again. Two of the BCA / silicon treatments have marginally better PM control compared to that of the control (E) treatment, although not statistically significant. Treatment E (control) has the highest average fruit mass in this instance but does not have the highest yield (kg yield) when compared to treatments A and B, possibly due to the growth-enhancing properties of most of these BCAs.
Therefore, most of these BCA treatments give fairly inconsistent results that vary possibly according to season, humidity and temperature, making it difficult to predict their efficacy. Using combinations or weekly alternations of these BCAs with extremes of climatic adaptation will probably be the most reliable method of obtaining consistent results. Bacterial BCAs are shown to have lower humidity requirements and produce the most consistent results in terms of fruit number, yield and fruit mass and a combination of bacterial and fungal based BCAs would possibly be the best as this would control PM and yet still have the growth enhancing properties from the bacterial based BCAs. From the research, it can be said that some BCAs in trials 1 and 2 produce results similar to that of the control in terms of percentage leaf area covered by PM and some are shown to have improved yields. Results produced from certain BCA treatments are thus equal to the control; yet provide an environmentally friendly alternative to synthetic fungicides.
Silicon is listed as a beneficial element rather than an essential element; however, literature claims it to be highly effective in treating PM in cucurbits. Results from trials 1 and 2 show that control of PM is possible in most cases, when a holistic approach is used. This approach includes a cucumber variety with a high PM tolerance, optimum nutrition, cultural practices and silicon in combination with the BCAs. A complete change of management practices is necessary to implement such a BCA program. / Agriculture, Animal Health & Human Ecology / M. Tech. (Nature Conservation)
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FUNCTIONAL DIVERSITY OF FUNGI ASSOCIATED WITH DURUM WHEAT ROOTS IN DIFFERENT CROPPING SYSTEMS2013 June 1900 (has links)
Differences in pea (Pisum sativum L.) and chickpea (Cicer arietinum L.) microbial compatibility and/ or their associated farming practices may influence root fungi of the following crop and affect the yield. The main objective of this research was to explain the difference in durum wheat (Triticum turgidum L.) yield the year after pea and chickpea crops through changes in the functional diversity of wheat root fungi. The effect of fungicides used on chickpea on the root fungi of a following durum wheat crop was studied using plate culture and pyrosequencing. Pyrosequencing detected more Fusarium spp. in the roots of durum wheat after fungicide-treated chickpea than in non-fungicide treated chickpea. Plate culture revealed that the functional groups of fungi responded differently to fungicide use in the field but the effect on total community was non-significant. Highly virulent pathogens were not affected, but antagonists were suppressed. More fungal antagonists were detected after the chickpea CDC Luna than CDC Vanguard. Fungal species responded differently to the use of fungicides in vitro, but the aggregate inhibition effect on antagonists and highly virulent pathogens was similar.
The effect of chickpea vs. pea previous crop and different chickpea termination times on root fungi of a following durum wheat crop was studied. The abundance of Fusarium spp. increased after cultivation of both cultivars of chickpea as compared to pea according to pyrosequencing and was negatively correlated with durum yield. Plate culture analysis revealed that fungal antagonists were more prevalent after pea than both cultivars of chickpea and chickpea CDC Vanguard increased the abundance of highly virulent pathogens. The abundance of highly virulent pathogens in durum wheat roots was negatively correlated to durum yield. Early termination of chickpea did not change the community of culturable fungi in the roots of a following durum crop.
It is noteworthy that Fusarium redolens was identified for the first time in Saskatchewan and its pathogenicity was confirmed on durum wheat, pea and chickpea. The classical method of root disease diagnostics in cereals is based on the examination of the subcrown internode. I evaluated the method by comparing the fungal communities associated with different subterranean organs of durum wheat. The fungal community of the subcrown internode was different from that of roots and crown, suggesting cautious use of this method.
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An investigation into the use of biological control agents as a sustainable alternative to synthetic fungicides in treating powdery mildew in tunnel cucumbersHaupt, Michael Rory 31 January 2007 (has links)
The use of biological control agents (BCAs) in the past has shown limited success as its application has often been done incorrectly, and in addition, management practices are rarely altered to incorporate BCAs. Criteria for the correct application of BCAs have been devised as part of the research, and companies selling these products may use the said criteria. Such application will ensure the correct BCAs are used and, more specifically, used under the correct conditions. The powdery mildew (PM) fungus is often seen to develop resistance to synthetic fungicides and, therefore, alternative control measures are required. BCAs as an alternative pose less risk to the environment, workers and the consumer.
A pre-trial has been conducted with a range of BCAs to see if they can control powdery mildew (PM) in a greenhouse environment on hydroponically grown cucumber (Cucumis sativus L.) plants using the variety Baccara that has only a moderate tolerance to PM. The BCAs have been compared to the control (synthetic fungicide: Bravo). Comparative work includes Coyier's model, which has been modified and adapted for these trials to determine the percentage of leaf area covered by the PM infection. Furthermore, the number of fruit harvested per treatment, kilogram yield, total mass of yield and average fruit mass is also used to determine the efficacy of the BCAs as these factors have economic significance to commercial growers. The pre-trial showed promise until the fertigation computer failed, resulting in a nutrient shortage and imbalance, confirming that BCAs alone cannot control PM. Synthetic fungicides were applied until control of PM and plant nutrition was regained. BCAs were re-introduced and used until the end of crop production.
The confirmation from the pre-trial has led to the inclusion of silicon in conjunction with the BCAs in the two subsequent trials (Trials 1 & 2). Silicon was applied with the BCAs as a foliar spray on a weekly basis. In trials 1 and 2, the cucumber variety, Palladium, with a high genetic tolerance to PM is used, as this variety is suited to form part of the holistic approach used for trials 1 and 2.
Trial 1 showed that treatment A, containing Streptomyces griseovirdis and Streptomyces aureofaciens, had the highest yield. Both of these are bacterial BCAs and demonstrated their adaptability to varied climatic conditions, notably when low humidity was experienced. In treatment B, Trichoderma harzianum strains, Rifai and Uppington, show the slowest rate of PM development.
In trials 1 and 2, the best actual PM control was obtained by two fungal based BCAs (Trial 1, treatment C was Ampelomyces quisqualis) and (Trial 2, treatment B was Trichoderma harzianum strains, Rifai and Uppington), showing that fungal BCAs have a place for this application, but the growth-enhancing properties of bacterial based BCAs make economic sense and would make them attractive to growers. Treatment A (Streptomyces spp.) had the most number of fruit for the entire growing period and the best overall yield (kg yield) again. Two of the BCA / silicon treatments have marginally better PM control compared to that of the control (E) treatment, although not statistically significant. Treatment E (control) has the highest average fruit mass in this instance but does not have the highest yield (kg yield) when compared to treatments A and B, possibly due to the growth-enhancing properties of most of these BCAs.
Therefore, most of these BCA treatments give fairly inconsistent results that vary possibly according to season, humidity and temperature, making it difficult to predict their efficacy. Using combinations or weekly alternations of these BCAs with extremes of climatic adaptation will probably be the most reliable method of obtaining consistent results. Bacterial BCAs are shown to have lower humidity requirements and produce the most consistent results in terms of fruit number, yield and fruit mass and a combination of bacterial and fungal based BCAs would possibly be the best as this would control PM and yet still have the growth enhancing properties from the bacterial based BCAs. From the research, it can be said that some BCAs in trials 1 and 2 produce results similar to that of the control in terms of percentage leaf area covered by PM and some are shown to have improved yields. Results produced from certain BCA treatments are thus equal to the control; yet provide an environmentally friendly alternative to synthetic fungicides.
Silicon is listed as a beneficial element rather than an essential element; however, literature claims it to be highly effective in treating PM in cucurbits. Results from trials 1 and 2 show that control of PM is possible in most cases, when a holistic approach is used. This approach includes a cucumber variety with a high PM tolerance, optimum nutrition, cultural practices and silicon in combination with the BCAs. A complete change of management practices is necessary to implement such a BCA program. / Agriculture, Animal Health and Human Ecology / M. Tech. (Nature Conservation)
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Biološka aktivnost i hemijski sastav ekstrakata odabranih autohtonih makrogljiva / Biological activity and chemical caracteristics of selected extracts of autochtonous macrofungiJanjušević Ljiljana 18 September 2017 (has links)
<p>Prema postavljenim ciljevima u ovoj doktorskoj disertaciji sakupljeno je i <br />determinisano ukupno sedam vrsta autohtonih gljiva sa područja Fruške gore, Tare i Vršačkog brega, pet lignikolnih ‐ <em>Bjerkandera adusta</em>, <em>Pleurocybella porrigens</em>, St<em>ereum hirsutum, Stereum subtomentosum</em> i Trametes versicolor, i <br />dve terikolne ‐ <em>Amanita strobiliformis</em> i Hydnum repandum. Utvrđena je njihova biološka aktivnost (antiradikalska, antioksidativna, antimikrobna, anti‐acetilholinesterazna i citotokisčna) spram hemijskog sastava njihovih vodenih <br />(H<sub>2</sub>O), etanolnih (EtOH), metanolnih (MeOH) i polisaharidnih (PSH) ekstrakata. <br />Analiza hemijskog sastava odabranih vrsta uključila je određivanje hemijske <br />karakterizacije PSH ekstrakata ‐ FTIR analizom, određivanje fenolnog profila ‐ <br />HPMC/MS‐MS, sadržaja organskih kiselina ‐ HPLC, sadržaja masnih kiselina ‐ <br />GC‐FID i sadržaja biogenih elemenata ‐ AAS. Spektrofotometrijskim metodama<br />određen je ukupan sadržaj proteina i ukupan sadržaj fenola i flavonoida. <br />Prema antiradikalskoj aktivnosti OH<sup>• , </sup>O2<sup>•‐</sup>, OH<sup>•</sup>, Asc<sup>•</sup>, DPPH<sup>• </sup> i ABTS<sup>•+</sup> izdvojili <br />su se ekstrakti lignikolnih vrsta: MeOH ekstrakt vrste <em>P. porrigens</em>, H<sub>2</sub>O ekstrakt <em>P. porrigens</em>, MeOH ekstrakt <em>T. versicolor</em>, H<sub>2</sub>O ekstrakt <em>S. hirsutum, </em>MeOH ekstrakt <em>S. subtomentosum</em> i H<sub>2</sub>O ekstrakt <em>B. adusta</em>, navedenim redom. <br />Najjaču antioksidativnu aktivnost dobijenu FRAP i polarografskom HPMC <br />metodom ispoljili su PSH i H<sub>2</sub>O ekstrakti terikolne vrste <em>A. strobiliformis</em>. <br />Antimikrobna aktivnost analiziranih ekstrakata određena je ispitivanjem <br />antibakterijskog, antifungalnog i antiviralnog potencijala, pri čemu se izdvojila <br />vrsta <em> H. repandum</em> ispoljavajući najbolji efekat na Gram‐pozitivne i Gram‐<br />negativne bakterije i na sve analizirane fitopatogene izolate <em>(Fusarium </em>i <br />Alternaria) i<em> T. versicolor</em> na analizirani bakteriofag. Anti‐acetilholinesterazna <br />aktivnost određena je testovima in solid i in liquid, a najbolji procenat <br />inhibicije AChE ispoljili su EtOH ekstrakti vrsta <em>S. hirsutum</em>, <em>B. adusta</em>, <em>S</em>. <br /><em>subtomentosum</em> i <em>T. versicolor</em>. Citotoksična aktivnost ekstrakata određena je <br />MTT testom, a prema najboljoj ispoljenoj aktivnosti izdvojili su se MeOH <br />ekstrakt<em> P. porrigens </em>i ekstrakti<em> B. adusta</em>, H<sub>2</sub>O i EtOH. Citotoksična aktivnost <br />ovih lignikolnih vrsta naročito je izražena nakon 72 h. Na osnovu dobijenih <br />rezultata, gde su se istakle različite vrste i njihovi različiti ekstrakti u <br />primenjenim testovima, jasno je da biološka aktivnost i hemijski sastav zavise <br />od porekla, vrste i tipa ekstrakta analiziranih gljiva. Na osnovu tipa rastvarača <br />odnosno ekstrakata vrsta, koje su pokazale najbolju aktivnost spram pomenutih testova i na osnovu dobijenih korelacija kao i na osnovu detektovanih jedinjenja, pretpostavljamo da su za ispoljene aktivnosti u najvećoj meri odgovorna fenolna jedinjenja i polisaharidi. <br /> <br />Ispoljeni biopotencijal analiziranih vrsta gljiva upućuje na njihovu potencijalnu <br />upotrebu kao funkcionalne hrane i nutraceutika, kao i u biokontroli <br />fitopatogena.</p> / <p>According to the set aims of the presented PhD thesis, seven autochthonous fungal species from the region of Fruska Gora, Tara and Vršac Mountains were collected and determined: five lignicolous ‐ <em>Bjerkandera adusta, Pleurocybella porrigens, Stereum hirsutum, Stereum subtomentosum and Trametes versicolor</em>, and two terricolous ‐ <em>Amanita strobiliformis </em>and <em>Hydnum repandum</em>. Biological activity of these species (antiradical, antioxidant, antimicrobial, anti‐ acetylcholinesterase and cytotoxic) was determined in relation to the chemical composition of the extracts, aqueous (H<sub>2</sub>O), ethanolic (EtOH), methanolic (MeOH) and polysaccharide (PSH). Analysis of the chemical content of analyzed species included chemical characterization of PSH extracts – by FTIR analysis, determination of phenolic profile ‐ by HPMC/MS‐MS, content of organic acids ‐ by HPLC, fatty acid content ‐ by GC‐FID and content of biogenic elements ‐ by AAS. Spectrophotometric methods were applied for determination of the content of total proteins, polyphenols and flavonoids. According to the antiradical activity obtained towards OH<sup>•</sup>, О2<sup>•‐</sup>, OH<sup>•</sup>, Asc<sup>•</sup>, DPPH<sup>•</sup> and ABTS<sup>•+</sup> extracts of lignicolous species were singled out: <em>P. porrigens </em> (MeOH extract), <em> P. porrigens</em> (H<sub>2</sub>O extract), <em>T. versicolor</em> (MeOH extract),<em> S. hirsutum </em>(H<sub>2</sub>O extract), <em>S. subtomentosum</em> (MeOH extract) and <em>B. austa</em> (H<sub>2</sub>O extract), respectively. The highest antioxidant activity obtained by FRAP and the polarographic HPMC method was exhibited for PSH and H<sub>2</sub>O extracts of the terricolous species <em>A. strobiliformis</em>. The intimicrobial activity of analyzed extracts was determined by examination of antibacterial, antifungal and antiviral potentials, whereby the species <em>H. repandum </em>was separated by exhibiting the best effect on Gram‐positive and Gram‐negative bacteria, and all the analyzed hytopathogenic isolates (<em>Fusarium, Alternaria</em>) and <em>T. versicolor</em> against analyzed bacteriophage. Anti‐cetylcholinesterase activity was determined by tests in solid and in liquid, while the best percent of AChE inhibition was showed by EtOH extracts of the species <em>S. hirsutum, B. adusta, S. subtomentosum </em>and <em>T. versicolor</em>.bThe cytotoxic activity of extracts was determined by MTT assay, and according to the best activity, the MeOH extract of <em>P. porrigens</em>, and H<sub>2</sub>O and EtOH extracts of <em>B. adusta</em> were distinguished particularly after 72 h. Based on the results obtained, favoring different species and their different extracts in the applied tests, it is clear that the biological activity and chemical composition depend on the origin, species and type of extract of the analyzed fungi. Based on the type of solvent or extract of the species that showed the best activity in relation to the above tests and on the basis of the obtained correlations as well as on the basis of the detected compounds, we assume that the phenol compounds and polysaccharides are responsible for the activities performed.<br />Demonstrated bio‐potential of analyzed fungal species indicates their potential use as functional foods and nutraceutics, as well as in the biocontrol of phytopathogens.</p>
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