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Relevant bibliographies by topics / Phytopathogen

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Academic literature on the topic 'Phytopathogen'

Author: Grafiati

Published: 4 June 2021

Last updated: 15 June 2024

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Journal articles on the topic "Phytopathogen"

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Malta, Camilla Martins, Eskálath Morganna Silva Ferreira, Thamar Holanda Da Silva, Divina Anne Batista Oliveira, Filipe Miguel Pereira Da Silva, Juliana Fonseca Moreira Da Silva, and Raphael Sanzio Pimenta. "Isolation of epiphytic yeasts from Eugenia dysenterica DC. fruits and evaluation of their antimicrobial activity against phytopathogenic fungi." Boletim do Museu Paraense Emílio Goeldi - Ciências Naturais 14, no. 2 (August 27, 2019): 223–31. http://dx.doi.org/10.46357/bcnaturais.v14i2.176.

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Plants commonly interact with microorganisms that may influence their physiology and performance. Epiphytic yeasts are microorganisms that can be found in the phylosphere, in significantly larger numbers in fruits than in other plant tissues due to their higher nutritional content. The present study aimed to contribute to knowledge of epiphytic yeasts associated with Eugenia dysenterica DC. fruits and to evaluate their antimicrobial activity against phytopathogens. E. dysenterica fruits were collected, washed in saline solution, and sonicated. Each fruit solution was plated in three Petri dishes with NYDA medium. Yeast identification was performed through morphological and physiological criteria, and richness evaluation was performed using the Jackknife 1 estimator. All isolated yeasts were tested for diffusible substances against three phytopathogenic fungi. Only four of 42 isolates were inhibited sporulation of Aspergillus parasiticus, but none was able to inhibit or diminish mycelium growth of any tested phytopathogen. The present study contributes to the characterization of the E. dysenterica microbiome, presenting the first report of in vitro A. parasiticus sporulation inhibition by epiphytic yeasts and suggesting their promising use in biological control of this phytopathogen.

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Foronda, Cervando Gutierrez, Marybel Lozano, and Lily Salcedo Ortiz. "Quinoa saponins, biological controller against Cercospora coffeicola and Moniliophthora roreri." Horticulture International Journal 5, no. 2 (March 12, 2021): 61–62. http://dx.doi.org/10.15406/hij.2021.05.00204.

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An extract rich in saponins obtained from quinoa residues showed in vitro anti-fungal activity against the coffee phytopathogen Cercospora coffeicola, with an antifungal index of inhibition (AI) of 22.39 ± 4.5% at 120 mg/mL, and against the cocoa phytopathogen Moniliophthora roreri, with an AI of 55.8 ± 1.6% at 60 mg/mL. The results showed a potential of this saponin-extract for the biological control of these phytopathogens.

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Bulmakova, D. S., G. I. Shagieva, D. L. Itkinaa, O. A. Leninа, M. R. Sharipova, and A. D. Suleimanova. "Antagonistic Strains of <i>Pantoea brenneri</i> as Plant Protectors." Микология и фитопатология 57, no. 5 (September 1, 2023): 352–61. http://dx.doi.org/10.31857/s0026364823050033.

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The antagonistic activity of Pantoea brenneri strains against a wide range of phytopathogenic threats was studied. It has been established that the strains are characterized by fungicidal activity against the micromycetes Fusarium sambucinum, F. oxysporum, F. solani, Rhizoctonia solani, Alternaria sp., Ascochyta kamchatica, Colletotrichum coccodes as well as antibacterial activity against the phytopathogen Erwinia amylovora, which causes bacterial burn of fruit trees. It has been shown that the cell suspension and supernatant of the culture liquid of Pantoea brenneri strains suppress Fusarium on potato tubers during storage. Pantoea brenneri strains have been found to be safe for model animals. A conclusion was made about the prospects of using P. brenneri strains as objects for the creation of environmentally friendly plant protection products against phytopathogens.

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Oppong-Danquah, Ernest, Martina Blümel, Silvia Scarpato, Alfonso Mangoni, and Deniz Tasdemir. "Induction of Isochromanones by Co-Cultivation of the Marine Fungus Cosmospora sp. and the Phytopathogen Magnaporthe oryzae." International Journal of Molecular Sciences 23, no. 2 (January 11, 2022): 782. http://dx.doi.org/10.3390/ijms23020782.

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Microbial co-cultivation is a promising approach for the activation of biosynthetic gene clusters (BGCs) that remain transcriptionally silent under artificial culture conditions. As part of our project aiming at the discovery of marine-derived fungal agrochemicals, we previously used four phytopathogens as model competitors in the co-cultivation of 21 marine fungal strains. Based on comparative untargeted metabolomics analyses and anti-phytopathogenic activities of the co-cultures, we selected the co-culture of marine Cosmospora sp. with the phytopathogen Magnaporthe oryzae for in-depth chemical studies. UPLC-MS/MS-based molecular networking (MN) of the co-culture extract revealed an enhanced diversity of compounds in several molecular families, including isochromanones, specifically induced in the co-culture. Large scale co-cultivation of Cosmospora sp. and M. oryzae resulted in the isolation of five isochromanones from the whole co-culture extract, namely the known soudanones A, E, D (1-3) and their two new derivatives, soudanones H-I (4-5), the known isochromans, pseudoanguillosporins A and B (6, 7), naphtho-γ-pyrones, cephalochromin and ustilaginoidin G (8, 9), and ergosterol (10). Their structures were established by NMR, HR-ESIMS, FT-IR, electronic circular dichroism (ECD) spectroscopy, polarimetry ([α]D), and Mosher’s ester reaction. Bioactivity assays revealed antimicrobial activity of compounds 2 and 3 against the phytopathogens M. oryzae and Phytophthora infestans, while pseudoanguillosporin A (6) showed the broadest and strongest anti-phytopathogenic activity against Pseudomonas syringae, Xanthomonas campestris, M. oryzae and P. infestans. This is the first study assessing the anti-phytopathogenic activities of soudanones.

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Shestibratov, Konstantin, Oleg Baranov, Natalya Subbotina, Vadim Lebedev, Stanislav Panteleev, Konstantin Krutovsky, and Vladimir Padutov. "Early Detection and Identification of the Main Fungal Pathogens for Resistance Evaluation of New Genotypes of Forest Trees." Forests 9, no. 12 (November 23, 2018): 732. http://dx.doi.org/10.3390/f9120732.

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The growing importance of forest plantations increases the demand for phytopathogen resistant forest trees. This study describes an effective method for early detection and identification of the main fungal phytopathogens in planting material of silver birch (Betula pendula) and downy birch (B. pubescens), based on the estimation of the size of the internal transcribed spacers (ITS1 and ITS2) in the 18S-5.8S-28S rDNA gene cluster, which are species-specific for most micromycetes. The electrophoretic assay of the ITS1 and ITS2 loci has allowed us to identify predominant phytopathogenic fungal species in downy and silver birch in planta. This new molecular genetic method can be used to screen birch and other forest trees for different fungal pathogens to evaluate disease resistance. This information can be useful in breeding new genotypes of forest trees, including transgenic clones with modified wood composition.

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Tsers, Ivan, Azat Meshcherov, Olga Gogoleva, Olga Petrova, Natalia Gogoleva, Mira Ponomareva, Yuri Gogolev, Viktor Korzun, and Vladimir Gorshkov. "Alterations in the Transcriptome of Rye Plants following the Microdochium nivale Infection: Identification of Resistance/Susceptibility-Related Reactions Based on RNA-Seq Analysis." Plants 10, no. 12 (December 10, 2021): 2723. http://dx.doi.org/10.3390/plants10122723.

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Microdochium nivale is a progressive and devastating phytopathogen that causes different types of cereal crop and grass diseases that are poorly characterized at the molecular level. Although rye (Secale cereale L.) is one of the most resistant crops to most of the phytopathogens, it is severely damaged by M. nivale. The recent high-quality chromosome-scale assembly of rye genome has improved whole-genome studies of this crop. In the present work, the first transcriptome study of the M. nivale-infected crop plant (rye) with the detailed functional gene classification was carried out, along with the physiological verification of the RNA-Seq data. The results revealed plant reactions that contributed to their resistance or susceptibility to M. nivale. Phytohormone abscisic acid was shown to promote plant tolerance to M. nivale. Flavonoids were proposed to contribute to plant resistance to this pathogen. The upregulation of plant lipase encoding genes and the induction of lipase activity in M. nivale-infected plants revealed in our study were presumed to play an important role in plant susceptibility to the studied phytopathogen. Our work disclosed important aspects of plant-M. nivale interactions, outlined the directions for future studies on poorly characterized plant diseases caused by this phytopathogen, and provided new opportunities to improve cereals breeding and food security strategies.

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Гнатюк, Т. Т., Н. В. Житкевич, and В. П. Патика. "Xanthomonas fuscans subsp. fuscans — a Pathogen of Small Brown Spot of Legumes." Mikrobiolohichnyi Zhurnal 86, no. 1 (February 23, 2024): 57–65. http://dx.doi.org/10.15407/microbiolj86.01.057.

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Xanthomonas fuscans subsp. fuscans is known as an obligate phytopathogen — the pathogen of small brown spot of beans that gradually expands the range of host plants and spreads worldwide on legumes. The review provides data on the problems of the pathogen’s systematics and its change depending on the new research and improvement of methods for studying biological properties. Historical data on the first stages of isolation of X. fuscans subsp. fuscans from bean and new stages of its spread and isolation from soybean in Ukraine, after which the pathogen moved from the monophage to polyphage status within the same plant family. The importance of X. fuscans subsp. fuscans as a potentially dangerous phytopathogen, as evidenced by the presence of its samples in many collections of living microorganisms in the world and the quarantine status of the pathogen in a number of European countries are underlined. It has been shown that the phytopathogen X. fuscans subsp. fuscans does not differ significantly from other xanthomonads in terms of its cultural, morphological, physiological, and biochemical properties, especially those that cause diseases of leguminous plants. At the same time, the only but the main feature of this bacterial culture is emphasized — the increased amount and activity of the intracellular enzyme tyrosinase, which distinguishes X. fuscans from all other bacterial phytopathogens and not only among xanthomonads. The variants of the stage of synthesis of tyrosinase and melanin in bacteria, due to which the black-brown pigment is formed, and the lack of research on the pathway of tyrosinase synthesis in phytopathogenic bacteria, in particular X. fuscans subsp. fuscans, are analized. The data on genotypic properties of X. fuscans subsp. fuscans, its affinity with other pathogens of the genus Xanthomonas that cause diseases of leguminous plants, and the possible role of the phenomenon of «horizontal gene transfer» in their affinity along with differences in biological properties are considered. The analyzed literature indicates the potential danger of the causative agent of small brown spot of legumes and the need for constant monitoring of the spread and study of its biological properties to develop methods for controling the spread of X. fuscans subsp. fuscans.

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Vega, Clara, Miguel Rodríguez, Inmaculada Llamas, Victoria Béjar, and Inmaculada Sampedro. "Silencing of Phytopathogen Communication by the Halotolerant PGPR Staphylococcus Equorum Strain EN21." Microorganisms 8, no. 1 (December 24, 2019): 42. http://dx.doi.org/10.3390/microorganisms8010042.

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Increasing world food demand together with soil erosion and indiscriminate use of chemical fertilization highlight the need to adopt sustainable crop production strategies. In this context, a combination of plant growth-promoting rhizobacteria (PGPR) and pathogen management represents a sustainable and efficient alternative. Though little studied, halophilic and halotolerant PGPR could be a beneficial plant growth promotion strategy for saline and non-saline soils. The virulence of many bacterial phytopathogens is regulated by quorum sensing (QS) systems. Quorum quenching (QQ) involves the enzymatic degradation of phytopathogen-generated signal molecules, mainly N-acyl homoserine lactones (AHLs). In this study, we investigate plant growth-promoting (PGP) activity and the capacity of the halotolerant bacterium Staphylococcus equorum strain EN21 to attenuate phytopathogens virulence through QQ. We used biopriming and in vivo tomato plant experiments to analyse the PGP activity of strain EN21. AHL inactivation was observed to reduce Pseudomonas syringae pv. tomato infections in tomato and Arabidopsis plants. Our study of Dickeya solani, Pectobacterium carotovorum subsp. carotovorum and Erwinia amylovora bacteria in potato tubers, carrots and pears, respectively, also demonstrated the effectiveness of QS interruption by EN21. Overall, this study highlights the potential of strain S. equorum EN21 in plant growth promotion and QQ-driven bacterial phytopathogen biocontrol.

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Mironov, Vladimir, Anna Shchelushkina, Olga Selitskaya, Yury Nikolaev, Alexander Merkel, and Shenghua Zhang. "Introducing Autochthonous Bacterium and Fungus Composition to Enhance the Phytopathogen-Suppressive Capacity of Composts against Clonostachys rosea, Penicillium solitum and Alternaria alternata In Vitro." Agronomy 13, no. 11 (November 18, 2023): 2841. http://dx.doi.org/10.3390/agronomy13112841.

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Given their numerous positive characteristics, composts are widely used agriculturally in sustainable development and resource-saving technologies. The management of phytopathogen-suppressive potential and the fertilizing capacity of composts are of great interest. This study examines the impact of introducing the autochthonous compost species Bacillus subtilis, B. amyloliquefaciens, Pseudomonas aeruginosa, and Aspergillus corrugatus, both individually and in combination, to composts containing dry matter comprising 36% solid compost and 7% compost suspensions to study their phytopathogen-suppressive and phytostimulation activity. The test phytopathogens were Clonostachys rosea, Penicillium solitum, and Alternaria alternata. This is the first report on compost’s potential to biologically control C. rosea and P. solitum. Classical microbiological and molecular biological methods were used to evaluate the survival rate of microorganisms in compost and validate these results. Test plant (Raphanus sativus) germination indexes were determined to evaluate the phytotoxic/phytostimulation effects of the substrates. To assess the effectiveness of biocontrol, mycelial growth inhibition was measured using in vitro tests. The introduction of composition increased the composts’ fertilizing properties by up to 35% and improved antagonistic activity by up to 91.7%. Autochthonous bacterial–fungal composition can promote resistance to fungal root and foliar phytopathogens and raise the fertilizing quality of compost.

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Valiullin, Lenar, Rishat Mukhammadiev, Rinat Mukhammadiev, Nikolay Budenkov, Alina Mukhammadieva, Marat Mukhamedyarov, and Tatiana Bagaeva. "Comparative characterization of lectins of pathogenic and saprophytic filamentous fungi Fusarium solani." E3S Web of Conferences 462 (2023): 02022. http://dx.doi.org/10.1051/e3sconf/202346202022.

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In the present study, we isolated, purified and characterized the lectin of the phytopathogenic fungus Fusarium solani 6 and compared it with the properties of the lectin of the saprophytic strain Fusarium solani 4. Electrophoretically homogeneous lectin was obtained from the mycelium of the fungus F. solani 6 by hydrophobic chromatography and gel filtration. The molecular weight of the native lectin molecule was established to be 30.0 kDa, and it was found that it consists of two identical subunits. Comparison of the physicochemical properties of the lectin of the phytopathogenic strain with the lectin of the saprophytic strain showed that the F. solani 6 lectin was a more thermostable and alkali-resistant protein. F. solani 6 lectin showed affinity for simple sugars, and F. solani 4 lectin - for glycoproteins. In contrast to the lectin of a saprophytic fungus, the treatment of pea seedling roots with F. solani lectin 6 before they were infected with the phytopathogen led to a decrease in the degree of damage to the plant root system and the prevalence of Fusarium. These results open up prospects for further study of the phytopathogen lectin and its potential application as a means of eliciting action.

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Dissertations / Theses on the topic "Phytopathogen"

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Peng, Xiaowen. "Total synthesis of the phytopathogen (+)-fomannosin." The Ohio State University, 2006. http://rave.ohiolink.edu/etdc/view?acc_num=osu1155158634.

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Forizs, Laetitia. "Metabolism and pathogenicity in the phytopathogen Rhodococcus fascians." Doctoral thesis, Universite Libre de Bruxelles, 2012. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/209742.

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Rhodococcus fascians is a Gram-positive phytopathogenic bacterium which induces the development of leafy galls, local amplifications of multiple buds, on most infected plants. This process is linked to the production of phytohormones along with the presence of essential virulence-associated genes like the plasmid loci att and fas and the chromosomal gene vicA. However, the presence of these genes is not sufficient to ensure the infection phenotype development, indicating that other genes play a role in R. fascians pathogenicity. In this work, we studied the metabolic modifications occurring when the bacterium interacts with its host using a proteomic approach. A comparison between virulent and avirulent strains showed variations in the expression of catalases. In the virulent strain, besides the transitory induction of the att locus expression, the bacterium changes its metabolism from the Krebs cycle to the glyoxylate shunt, a process which is frequently observed in bacteria confronted to a hostile environment. The expression of the shunt-specific enzyme isocitrate lyase increased, while expression of fumarate hydratase and pyruvate dehydrogenase decreased. Hence, we focused on the link between the glyoxylate shunt and virulence. A screening of a R. fascians mutant library based on the capacity of bacteria to use acetate as the sole carbon source, a metabolic pathway depending on the glyoxylate shunt, resulted in the identification of a new gene essential for R. fascians pathogenicity. This gene encodes a glycosyl transferase, an enzyme known to be involved in the bacterial cell wall biosynthesis but possibly also implicated in cytokinin secretion. A mutant in this gene harboured an altered colony phenotype and could not induce malformations on infected plants. Accordingly, our results were integrated in the leafy gall pathology model recently presented by Stes et al. (2011). Finally, the several questions that are raised by this work, allowed us to suggest further research perspectives in order to unveil a little more of the R. fascians mysterious ways to interact with the plant./Rhodococcus fascians est une bactérie Gram-positive phytopathogène qui induit le développement de galles feuillées, des amplifications locales de multiples bourgeons, sur la plupart des plantes infectées. Ce processus est lié à la production de phytohormones ainsi qu’à la présence de gènes essentiels associés à la virulence tels que les loci plasmidiques att et fas et le gène chromosomique vicA. Cependant, la présence de ces gènes ne suffit pas à garantir le développement du phénotype d’infection, indiquant que d’autres gènes jouent un rôle dans la pathogénicité de R. fascians. Dans ce travail, nous avons étudié les modifications métaboliques qui se produisent lorsque la bactérie interagit avec son hôte par une approche protéomique. Une comparaison entre les souches virulente et avirulente a mis en évidence des variations d’expression au niveau des catalases. Dans la souche virulente, outre l’induction transitoire de l’expression du locus att, la bactérie change son métabolisme pour passer du cycle de Krebs au shunt du glyoxylate, un processus fréquemment observé chez les bactéries confrontées à un environnement hostile. L’expression de l’isocitrate lyase, enzyme spécifique au shunt, augmente, tandis que celle de la fumarate hydratase et de la pyruvate déhydrogénase diminue. Nous nous sommes donc intéressés au lien entre le shunt du glyoxylate et la virulence. Le screening d’une banque de mutants de R. fascians basé sur la capacité de la bactérie à utiliser l’acétate comme seule source de carbone, une voie métabolique dépendant du shunt du glyoxylate, a permis d’identifier un nouveau gène essentiel pour la pathogénicité de R. fascians. Ce gène code pour une glycosyl transferase, une enzyme impliquée dans la biosynthèse de la paroi bactérienne mais également dans la sécrétion des cytokinines. Un mutant dans ce gène présente un phénotype de colonie altéré et ne peut induire de malformations chez les plantes infectées. Finalement, nos résultats et les pistes d’interprétations que nous avons émisent nous permettent de compléter le modèle de l’interaction R. fascians-plante proposé récemment par Stes et al. (2011). Des perspectives de recherches visant une meilleure compréhension de ce pathosystème sont proposées.
Doctorat en Sciences
info:eu-repo/semantics/nonPublished

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Calassanzio, Matteo <1989&gt. "Studies of sustainable strategies to control phytopathogen agents." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2020. http://amsdottorato.unibo.it/9411/1/PhD%20Thesis%20Calassanzio%20Matteo.pdf.

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Choosing natural enemies to suppress pest population has been for a long the key of biological control. Overtime the term biological control has also been applied to the use of suppressive soils, bio-disinfection and biopesticides. Biological control agents (BCA) and natural compounds, extracted or fermented from various sources, are the resources for containing phytopathogens. BCA can act through direct antagonism mechanisms or inducing hypovirulence of the pathogen. The first part of the thesis focused on mycoviruses infecting phytopathogenic fungi belonging to the genus Fusarium. The development of new approaches capable of faster dissecting the virome of filamentous fungi samples was performed. The semiconductor-based sequencer Ion Torrent™ and the nanopore-based sequencer MinION have been exploited to analyze DNA and RNA referable to viral genomes. Comparison with GeneBank accessions and sequence analysis allowed to identify more than 40 putative viral species, some of these mycovirus genera have been studied as inducers of hypovirulence in several phytopathogenic fungi, therefore future works will focus on the comparison of the morphology and physiology of the fungal strain infected and cured by the viruses identified and their possible use as a biocontrol agent. In a second part of the thesis the potential of botanical pesticides has been evaluated for the biocontrol of phloem limited phytopathogens such as phytoplasmas. The only active compounds able to control phytoplasmas are the antibiotic oxytetracyclines and in vitro direct and fast screening of new antimicrobials compounds on media is almost impossible due to the difficulty to culture phytoplasmas. For this reason, a simple and reliable screening method was developed to evaluate the effects of antimicrobials directly on phytoplasmas by an “ex-vivo” approach. Using scanning electron microscopy (SEM) in parallel with molecular tools (ddRT-PCR), the direct activity of tetracyclines on phytoplasma cells was verified, identifying also a promising compound showing similar activity.

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Mobbs, Daniel James. "Studies towards the control of the phytopathogen Botrytis cinerea." Thesis, University of Sussex, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.297945.

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Chibi, Nancy. "Molecular and phenotypic characterisation of the phytopathogen 'Pseudomonas syringae' pv. 'tabaci'." Thesis, Royal Holloway, University of London, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.409299.

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Monson, Rita Elaine. "Regulation of quorum sensing in the phytopathogen Erwinia carotovora subsp. atroseptica." Thesis, University of Cambridge, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.611200.

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Barenstrauch, Margot. "Characterization of oxylipin signaling in the chemical interaction between the endophyte Paraconiothyrium variabile and the phytopathogen Fusarium oxysporum." Thesis, Paris, Muséum national d'histoire naturelle, 2018. http://www.theses.fr/2018MNHN0010/document.

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Les champignons endophytes sont des microorganismes non-pathogènes impliqués dans des associations mutualistes avec les plantes. Les endophytes foliaires, en particulier, représentent un groupe très divers, mais leurs interactions avec la plante hôte et ses micro-organismes associés sont peu connues. Des travaux préliminaires initiés par notre équipe, explorant la diversité microbienne foliaire du conifère Cephalotaxus harringtonia, ont permis d’isoler la souche fongique Paraconiothyrium variabile (Ascomycota), un antagoniste du phytopathogène Fusarium oxysporum. Au cours de leur interaction, on détecte des quantités moindres de beauvéricine, une mycotoxine synthétisée par F. oxysporum. En parallèle, on observe une augmentation de la synthèse de deux oxylipines, l’acide 13-hydroperoxyoctadécadiénoïque (13-HPODE) et l’acide 13-oxo-octadécadiénoïque (13-oxo-ODE), dans la zone de confrontation. L'objectif de ce travail était de comprendre les mécanismes conduisant à la diminution de la beauvéricine au cours de l'interaction et d'explorer le rôle des oxylipines dans la régulation de cette dernière. Dans mon travail de thèse, je montre la présence de deux gènes lox chez P. variabile (pvlox1 et pvlox2) codant tous deux pour des manganèse lipoxygénases, potentiellement à l'origine des acides 13-HPODE et 13-oxo-ODE. Pvlox2 est spécifiquement induit pendant l'interaction, et ces résultats sont corroborés par une synthèse accrue de 13-HPODE chez P. variabile. Par ailleurs, l'interaction avec l’endophyte, ainsi que l'ajout de l’oxylipine 13-HPODE, régulent positivement la voie de biosynthèse de la beauvéricine, comme l’indiquent les teneurs plus élevées en mycotoxines observées chez F. oxysporum. Enfin, nous avons montré que la beauvéricine inhibait la croissance de l’endophyte, mais que ce dernier était capable de dégrader la mycotoxine, expliquant ainsi les faibles quantités de beauvericine observées initialement dans la zone de compétition. Ce travail contribue à la compréhension du rôle des oxylipines dans la communication inter-microbienne
Endophytic fungi are non-pathogenic microorganisms involved in mutualistic associations with their host. Foliar endophytes, in particular, represent a very diverse group but little is known about their interactions with the host and its associated micro-organisms. In preliminary work, exploring the leaf microbial diversity of the conifer Cephalotaxus harringtonia, our team isolated the fungal strain Paraconiothyrium variabile (Ascomycota), an antagonist of the phytopathogen Fusarium oxysporum. During their interaction, decreased amounts of the F. oxysporum mycotoxin beauvericin, and higher amounts of the two oxylipins, 13-hydroperoxyoctadecadienoic acid (13-HPODE) and 13-oxo-octadecadienoic acid (13-oxo-ODE), were observed in the confrontation zone. The objective of the present work was to understand the mechanisms leading to beauvericin decrease during the interaction and to explore the role of oxylipins in beauvericin regulation. In my thesis work I show the presence of two lox genes in P. variabile (pvlox1 and pvlox2) coding both for manganese lipoxygenases, potentially at the origin of 13-HPODE and 13-oxo-ODE. Pvlox2 is specifically induced during the interaction, which lead to an increased synthesis of 13-HPODE in P. variabile. The endophyte itself, as well as the oxylipin 13-HPODE, up-regulated the beauvericin biosynthesis gene beas, which was paralleled by higher mycotoxin content in the mycelium of F. oxysporum. Finally, we showed that beauvericin inhibited the endophyte’s growth, but the latter was capable to degrade the mycotoxin, which explains the lower amounts of beauvericin found in the competition zone. This work presents pioneer undertaking to elucidate the role of oxylipins in inter-microbial crosstalk

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Fisher, Emily Jane Dangl J. L. "Identification of virulence factors in the phytopathogen P. syringae by molecular evolution." Chapel Hill, N.C. : University of North Carolina at Chapel Hill, 2008. http://dc.lib.unc.edu/u?/etd,1812.

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Thesis (Ph. D.)--University of North Carolina at Chapel Hill, 2008.
Title from electronic title page (viewed Dec. 11, 2008). "... in partial fulfillment of the requirements for the degree of Doctor of Philosophy in the Department of Biology." Discipline: Biology; Department/School: Biology.

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Massa, Claudia. "Structural and Functional Studies of a Polygalacturonase from the Phytopathogen Burkholderia cepacia." Doctoral thesis, SISSA, 2006. http://hdl.handle.net/20.500.11767/4012.

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Brual, Typhaine. "Unraveling virulence regulation in pectinolytic bacteria : Insights from ArcZ and RsmC." Electronic Thesis or Diss., Lyon, INSA, 2023. http://www.theses.fr/2023ISAL0100.

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Les bactéries pectinolytiques du genre Dickeya prospèrent dans diverses niches écologiques, y compris l'eau, le sol et les plantes, s'adaptant à des environnements complexes et en constante évolution, façonnés par diverses interactions biotiques et abiotiques.Dans cette thèse, nous avons étudié les mécanismes qui régulent la virulence du genre Dickeya, en particulier D. dadantii et D. solani.Nos principaux résultats concernent la régulation post-transcriptionnelle exercée par le sRNA ArcZ et la régulation post-traductionnelle modulée par la protéine RsmC. ArcZ est un acteur clé de l'adaptation de D. solani, régulant la motilité en fonction des conditions environnementales et favorisant la virulence lors de l'infection des plantes. En outre, ArcZ joue un rôle essentiel dans la résistance à l’acidité.RsmC, quant à lui, est impliqué dans la régulation de la motilité et joue un rôle complexe dans la virulence. Nos résultats suggèrent de nouvelles interactions pour RsmC et ouvrent des perspectives pour l'étude d'autres fonctions non documentées.En un mot, notre étude révèle comment des régulateurs tels que ArcZ et RsmC orchestrent les réponses bactériennes à un environnement dynamique. Ces résultats mettent en évidence l'adaptabilité des espèces du genre Dickeya et soulignent l'importance du contexte écologique dans l'étude du comportement bactérien
Pectinolytic bacteria of the genus Dickeya thrive in diverse ecological niches including water, soil and plants, adapting to complex and ever-changing environments shaped by various biotic and abiotic interactions. In this thesis, we investigated the mechanisms that regulate the virulence of the genus Dickeya, in particular D. dadantii and D. solani. Our main findings concern post-transcriptional regulation exerted by the sRNA ArcZ and post-translational regulation modulated by the protein RsmC. ArcZ is a key player in D. solani adaptation, regulating motility according to environmental conditions and enhancing virulence during plant infection. In addition, ArcZ plays a critical role in acid resistance. RsmC, in turn, is involved in the regulation of motility and has a complex role in virulence. Our results suggest novel interactions for RsmC and open perspectives for studying other undocumented functions. In a word, our study reveals how regulators such as ArcZ and RsmC orchestrate bacterial responses to a dynamic environment. These findings highlight the adaptability of Dickeya species and underscore the importance of ecological context in the study of bacterial behavior

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Books on the topic "Phytopathogen"

1

Kumar, Ajay, ed. Microbial Biocontrol: Sustainable Agriculture and Phytopathogen Management. Cham: Springer International Publishing, 2022. http://dx.doi.org/10.1007/978-3-030-87512-1.

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Briggs, Georgett C. The identification and characterization of putative quorum sensing system in the phytopathogen pseudomonas syringae pathovar tomato DC3000. Ottawa: National Library of Canada, 2002.

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Crous, Pedro W. Phytopathogenic fungi from South Africa. Stellenbosch, South Africa: University of Stellenbosch, Dept. of Plant Pathology Press, 2000.

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Singh, Baleshwar, and National Bureau of Plant Genetic Resources (India), eds. World distribution of phytopathogenic bacteria. New Delhi: Division of Plant Quarantine, National Bureau of Plant Genetic Resources, 1995.

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Thind, B. S. Phytopathogenic procaryotes and plant diseases. Jodhpur: Scientific Publishers (India), 2012.

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Singh, Udai B., Ravindra Kumar, and Harikesh Bahadur Singh, eds. Detection, Diagnosis and Management of Soil-borne Phytopathogens. Singapore: Springer Nature Singapore, 2023. http://dx.doi.org/10.1007/978-981-19-8307-8.

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L, Singleton Larry, Mihail Jeanne D, and Rush Charles M. 1951-, eds. Methods for research on soilborne phytopathogenic fungi. St. Paul, Minn: APS Press, 1992.

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Katsy, Elena I., ed. Plasticity in Plant-Growth-Promoting and Phytopathogenic Bacteria. New York, NY: Springer New York, 2014. http://dx.doi.org/10.1007/978-1-4614-9203-0.

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K, Chatterjee Arun, and Vidaver Anne K, eds. Advances in plant pathology.: Application to phytopathogenic bacteria. London: Academic Press, 1986.

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Rawson, Jennifer Margaret. Transposable elements in the phytopathogenic fungus Stagonospora nodorum. Birmingham: University of Birmingham, 2000.

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Book chapters on the topic "Phytopathogen"

1

Ghatak, Abhijeet. "Evolution and Adaptation in Phytopathosystems." In The Phytopathogen, 3–20. Waretown, NJ : Apple Academic Press, 2017.: Apple Academic Press, 2017. http://dx.doi.org/10.1201/9781315366135-1.

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Holkar, Somnath K., Pratibha Kaushal, and Sanjeev Kumar. "Host Preference by Evolving Insect Vectors in Relation to Infection of Plant Viruses." In The Phytopathogen, 259–304. Waretown, NJ : Apple Academic Press, 2017.: Apple Academic Press, 2017. http://dx.doi.org/10.1201/9781315366135-10.

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Prasad, Pramod, Subhash C. Bhardwaj, Hanif Khan, Om P. Gangwar, and Subodh Kumar. "Changes in Wheat Physiology and Biochemistry in Context to Pathogen Infection." In The Phytopathogen, 307–29. Waretown, NJ : Apple Academic Press, 2017.: Apple Academic Press, 2017. http://dx.doi.org/10.1201/9781315366135-11.

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Meena, Ashok K., Shankar L. Godara, and Anand K. Meena. "Dispersal and Adaptation of Phytopathogens on the Global and Continental Scales and its Impact on Plant Diseases." In The Phytopathogen, 331–56. Waretown, NJ : Apple Academic Press, 2017.: Apple Academic Press, 2017. http://dx.doi.org/10.1201/9781315366135-12.

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Kushwaha, Chanda, Neha Rani, and Arun P. Bhagat. "Nature, Dissemination And Epidemiological Consequences In Charcoal Rot Pathogen Macrophomina Phaseolina." In The Phytopathogen, 357–79. Waretown, NJ : Apple Academic Press, 2017.: Apple Academic Press, 2017. http://dx.doi.org/10.1201/9781315366135-13.

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Kumar, Santosh, Ravi R. Kumar, Mahendra Singh, Erayya, Mahesh Kumar, M. D. Shamim, Nimmy M. Subramanian, Vinod Kumar, and Amarendra Kumar. "Soil Microbial Community and Their Population Dynamics: Altered Agricultural Practices." In The Phytopathogen, 383–415. Waretown, NJ : Apple Academic Press, 2017.: Apple Academic Press, 2017. http://dx.doi.org/10.1201/9781315366135-14.

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Harish, S., R. Manikandan, D. Durgadevi, and T. Raguchander. "Population Diversity of Fusarium spp. and its Interaction with Plant Growth Promoting Rhizobacteria." In The Phytopathogen, 417–35. Waretown, NJ : Apple Academic Press, 2017.: Apple Academic Press, 2017. http://dx.doi.org/10.1201/9781315366135-15.

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Ansar, Mohammad. "Diversity and Variation in Major Insect Transmitted Viruses Infecting Various Crops." In The Phytopathogen, 437–61. Waretown, NJ : Apple Academic Press, 2017.: Apple Academic Press, 2017. http://dx.doi.org/10.1201/9781315366135-16.

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Kharayat, Bhupendra S., and Yogendra Singh. "The Process of Coevolution of Plants and Their Pathogens." In The Phytopathogen, 21–40. Waretown, NJ : Apple Academic Press, 2017.: Apple Academic Press, 2017. http://dx.doi.org/10.1201/9781315366135-2.

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Balodi, Rekha, Lajja Vati Ghatak, Sunaina Bisht, and Nandani Shukla. "Reproductive Fitness of Fungal Phytopathogens: Deriving Co-Evolution of Host–Pathogen Systems." In The Phytopathogen, 41–64. Waretown, NJ : Apple Academic Press, 2017.: Apple Academic Press, 2017. http://dx.doi.org/10.1201/9781315366135-3.

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Conference papers on the topic "Phytopathogen"

1

Diánez, F., M. Santos, I. Font, M. de Cara, and J. C. Tello. "New hosts for the enterobacterial phytopathogen Erwinia persicina." In Proceedings of the II International Conference on Environmental, Industrial and Applied Microbiology (BioMicroWorld2007). WORLD SCIENTIFIC, 2009. http://dx.doi.org/10.1142/9789812837554_0017.

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Liu, W., and J. H. Tang. "Research of two-component system genes in phytopathogen bacteria." In International Conference on Computer Science and Systems Engineering. Southampton, UK: WIT Press, 2015. http://dx.doi.org/10.2495/csse140521.

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Tsivileva, О. М., А. I. Perfileva, and А. G. Pavlova. "Biopreparations for plants produced with basidiomycetes." In 2nd International Scientific Conference "Plants and Microbes: the Future of Biotechnology". PLAMIC2020 Organizing committee, 2020. http://dx.doi.org/10.28983/plamic2020.255.

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Potentialities of the mushroom-originating preparations for potato recovery are shown. The metal(II) containing composites based on the metabolites of basidiomycetes exhibits the effect of enhancing the potato resistivity to phytopathogen.

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Zyubanova, T. I., O. M. Minaeva, and N. N. Tereshchenko. "Effect of bacterization with Pseudomonas extremorientalis PhS1 on photosynthesis processes in wheat plants (Triticum aestivum L.) under phytopathogenic load." In 2nd International Scientific Conference "Plants and Microbes: the Future of Biotechnology". PLAMIC2020 Organizing committee, 2020. http://dx.doi.org/10.28983/plamic2020.292.

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We found that bacterization of wheat with Pseudomonas extremorientalis increases the efficiency of open photosystem II reaction centers and reduces the photosynthesis losses dissipated as heat in the presence of a phytopathogen.

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Zhao, Jiehong, Degang Zhao, and Jie Han. "Isolation and Characterization of Dimethoate Degrading Phytopathogen Fungus from Soil." In 2009 3rd International Conference on Bioinformatics and Biomedical Engineering (iCBBE). IEEE, 2009. http://dx.doi.org/10.1109/icbbe.2009.5162993.

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Ibragimova, S. A., and K. A. Malafeeva. "Symbiosis of soil and rhizosphere bacteria." In 2nd International Scientific Conference "Plants and Microbes: the Future of Biotechnology". PLAMIC2020 Organizing committee, 2020. http://dx.doi.org/10.28983/plamic2020.105.

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The presence of symbiosis between different taxonomic groups of soil and rhizosphere bacteria is shown. In the mixed population, a high titer of active cells and the preservation of antagonistic activity against the phytopathogen were noted.

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Santoso, Iman, Qonita Gina Fadhilah, Andi Eko Maryanto, and Yasman. "The Potency of Bacillus siamensis LDR as Biocontrol Agent Against Fungal Phytopathogen." In 3rd KOBI Congress, International and National Conferences (KOBICINC 2020). Paris, France: Atlantis Press, 2021. http://dx.doi.org/10.2991/absr.k.210621.079.

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Petrova, O. E., O. I. Parfirova, J. P. Sergeeva, and V. Yu Gorshkov. "Stringent response is key player in plant-microbe interaction." In 2nd International Scientific Conference "Plants and Microbes: the Future of Biotechnology". PLAMIC2020 Organizing committee, 2020. http://dx.doi.org/10.28983/plamic2020.195.

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Bacterial SpoT-dependent SR was activated in Pectobacterium atrosepticum when pathogen infected potato as well as tobacco plants. Pba induced plastid stringent response in tobacco plants, but not in potato plants. Jasmonic acid defense pathway was activated in tobacco plants, provoking rapid maceration of plant tissues. Salicylic acid defense pathway was induced in potato plants, probably ensuring a more prolonged coexistence of the phytopathogen with its host.

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"Evaluating Resistance of Five Local Heirloom Tomato Cultivars to the Phytopathogen Fusarium oxysporum." In Nov. 16-17, 2020 Johannesburg (SA). Eminent Association of Pioneers, 2020. http://dx.doi.org/10.17758/eares10.eap1120116.

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Ehis-Eriakha, Chioma Bertha, Stephen Eromosele Akemu, and Azeeza Tiamiyu. "Formulation and Evaluation of Sugarcane-Bagasse-Based Biocontrol Agents for Sustainable Phytopathogen Management." In The 3rd International Electronic Conference on Agronomy. Basel Switzerland: MDPI, 2023. http://dx.doi.org/10.3390/iecag2023-15992.

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Reports on the topic "Phytopathogen"

1

Dickman, Martin B., and Oded Yarden. Role of Phosphorylation in Fungal Spore Germination. United States Department of Agriculture, August 1993. http://dx.doi.org/10.32747/1993.7568761.bard.

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Spore germination is a common and fundamental event in fungal development and in many instances an essential phase of fungal infection and dissemination. Spore germination is also critical for hyperparasites to function as biocontrol agents as well as in fermentation proceses. Our common objective is to understand the mechanisms which regulated spore germination and identify factors involved in pathogenicity related prepenetration development. Our approach is to exploit the overall similarity among filamentous fungi using both a plant pathogen (Colletotricum trifolii) and a model system that is genetically sophisticated (Neurospora crassa). The simulataneous use of two organisms has the advantage of the available tools in Neurospora to rapidly advance the functional analysis of genes involved in spore germination and development of an economically important fungal phytopathogen. Towards this we have isolated a protein kinase gene from C. trifolii (TB3) that is maximally expressed during the first hour of conidial germination and prior to any visible gene tube formation. Based on sequence similarities with other organisms, this gene is likely to be involved in the proliferative response in the fungus. In addition, TB3 was able to functionally complement a N. crassa mutant (COT-1). Pharmacological studies indicated the importance of calmodulin in both germination and appressorium differentiation. Using an antisense vector from N. crassa, direct inhibition of calmodulin results in prevention of differentiation as well as pathogenicity. Both cAMP dependent protein kinase (PKA) and protein kinase C (PKC) like genes have been cloned from C. trifolii. Biochemical inhibition of PKA prevents germination; biochemical inhibitors of PKC prevents appressorium differentiation. In order to analyze reversible phosphorylation as a regulatory mechanism, some ser.thr dephosphorylative events have also been analyzed. Type 2A and Type 2B (calcineurin) phosphatases have been identified and structurally and functionally analyzed in N. crassa during this project. Both phosphatases are essential for hyphal growth and maintenance of proper hyphal architecture. In addition, a first novel-type (PPT/PP5-like) ser/thr phosphatase has been identified in a filamentous fungus. The highly collaborative project has improved our understanding of a fundamental process in fungi, and has identified targets which can be used to develop new approaches for control of fungal plant pathogens as well as improve the performance of beneficial fungi in the field and in industry. In addition, the feasibility of molecular technology transfer in comparative mycology has been demonstrated.

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Barash, Isaac, Rosemary Loria, Giora Kritzman, Shulamit Manulis, and Yair Aharonowitz. Application of Recombinant DNA and Immunological Technologies for Development of Diagnostic Tools for Phytopathogenic Streptomyces Spp. United States Department of Agriculture, December 1990. http://dx.doi.org/10.32747/1990.7603799.bard.

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3

Watad, Abed A., Paul Michael Hasegawa, Ray A. Bressan, Alexander Vainstein, and Yigal Elad. Osmotin and Osmotin-Like Proteins as a Novel Source for Phytopathogenic Fungal Resistance in Transgenic Carnation and Tomato Plants. United States Department of Agriculture, January 2000. http://dx.doi.org/10.32747/2000.7573992.bard.

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The goal of this project is to enhance fungal resistance of carnation and tomato through the ectopic expression of osmotin and other pathogenesis-related (PR) proteins. The research objectives were to evaluate in vitro antifungal activity of osmotin and osmotin and other PR protein combinations against phytopathogens (including Fusarium oxysporum, Verticillium dahliae, Botrytus cinerea or Phytophthora infestans), develop protocols for efficient transformation of carnation and tomato, express PR proteins in transgenic carnation and tomato and evaluate fungal resistance of transgenic plants. Protocols for microprojectile bombardment and Agrobacterium-mediated transformation of carnation were developed that are applicable for the biotechnology of numerous commercial cultivars. Research established an efficient organogenetic regeneration system, optimized gene delivery and transgene expression and defined parameters requisite to the high frequency recovery of transgenic plants. Additionally, an efficient Agrobacterium-mediated transformation protocol was developed for tomato that is applicable for use with numerous commercial varieties. Rigorous selection and reducing the cytokinin level in medium immediately after shoot induction resulted in substantially greater frequency of adventitious shoots that developed defined stems suitable for rooting and reconstitution of transgenic plants. Transformation vectors were constructed for co-expression of genes encoding osmotin and tobacco chitinase Ia or PR-1b. Expression of osmotin, PR-1 and/or chitinase in transgenic carnation mediated a high level resistance of cv. White Sim (susceptible variety) to F. oxysporum f. sp. dianthi, race 2 in greenhouse assays. These plants are being evaluated in field tests. Comprehensive analysis (12 to 17 experiments) indicated that germination of B. cinerea conidia was unaffected by PR protein expression but germ tube elongation was reduced substantially. The disease severity was significantly attenuated by PR protein expression. Constitutive expression of osmotin in transgenic tomato increased resistance to B. cinerea, and P. infestans. Grey mold and late blight resistance was stable through the third selfed generation. The research accomplished in this project will have profound effects on the use of biotechnology to improve carnation and tomato. Transformation protocols that are applicable for efficient stable gene transfer to numerous commercial varieties of carnation and tomato are the foundation for the capacity to bioengineer these crops. The research further establishes that PR proteins provide a measure of enhanced disease resistance. However, considerations of PR protein combinations and conditional regulation and targeting are likely required to achieve; sustained level of resistance.

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Cytryn, Eddie, Mark R. Liles, and Omer Frenkel. Mining multidrug-resistant desert soil bacteria for biocontrol activity and biologically-active compounds. United States Department of Agriculture, January 2014. http://dx.doi.org/10.32747/2014.7598174.bard.

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Control of agro-associated pathogens is becoming increasingly difficult due to increased resistance and mounting restrictions on chemical pesticides and antibiotics. Likewise, in veterinary and human environments, there is increasing resistance of pathogens to currently available antibiotics requiring discovery of novel antibiotic compounds. These drawbacks necessitate discovery and application of microorganisms that can be used as biocontrol agents (BCAs) and the isolation of novel biologically-active compounds. This highly-synergistic one year project implemented an innovative pipeline aimed at detecting BCAs and associated biologically-active compounds, which included: (A) isolation of multidrug-resistant desert soil bacteria and root-associated bacteria from medicinal plants; (B) invitro screening of bacterial isolates against known plant, animal and human pathogens; (C) nextgeneration sequencing of isolates that displayed antagonistic activity against at least one of the model pathogens and (D) in-planta screening of promising BCAs in a model bean-Sclerotiumrolfsii system. The BCA genome data were examined for presence of: i) secondary metabolite encoding genes potentially linked to the anti-pathogenic activity of the isolates; and ii) rhizosphere competence-associated genes, associated with the capacity of microorganisms to successfully inhabit plant roots, and a prerequisite for the success of a soil amended BCA. Altogether, 56 phylogenetically-diverse isolates with bioactivity against bacterial, oomycete and fungal plant pathogens were identified. These strains were sent to Auburn University where bioassays against a panel of animal and human pathogens (including multi-drug resistant pathogenic strains such as A. baumannii 3806) were conducted. Nineteen isolates that showed substantial antagonistic activity against at least one of the screened pathogens were sequenced, assembled and subjected to bioinformatics analyses aimed at identifying secondary metabolite-encoding and rhizosphere competence-associated genes. The genome size of the bacteria ranged from 3.77 to 9.85 Mbp. All of the genomes were characterized by a plethora of secondary metabolite encoding genes including non-ribosomal peptide synthase, polyketidesynthases, lantipeptides, bacteriocins, terpenes and siderophores. While some of these genes were highly similar to documented genes, many were unique and therefore may encode for novel antagonistic compounds. Comparative genomic analysis of root-associated isolates with similar strains not isolated from root environments revealed genes encoding for several rhizospherecompetence- associated traits including urea utilization, chitin degradation, plant cell polymerdegradation, biofilm formation, mechanisms for iron, phosphorus and sulfur acquisition and antibiotic resistance. Our labs are currently writing a continuation of this feasibility study that proposes a unique pipeline for the detection of BCAs and biopesticides that can be used against phytopathogens. It will combine i) metabolomic screening of strains from our collection that contain unique secondary metabolite-encoding genes, in order to isolate novel antimicrobial compounds; ii) model plant-based experiments to assess the antagonistic capacities of selected BCAs toward selected phytopathogens; and iii) an innovative next-generation-sequencing based method to monitor the relative abundance and distribution of selected BCAs in field experiments in order to assess their persistence in natural agro-environments. We believe that this integrated approach will enable development of novel strains and compounds that can be used in large-scale operations.

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Lindow, Steven, Isaac Barash, and Shulamit Manulis. Relationship of Genes Conferring Epiphytic Fitness and Internal Multiplication in Plants in Erwinia herbicola. United States Department of Agriculture, July 2000. http://dx.doi.org/10.32747/2000.7573065.bard.

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Most bacterial plant pathogens colonize the surface of healthy plants as epiphytes before colonizing internally and initiating disease. The epiphytic phase of these pathogens is thus an important aspect of their epidemiology and a stage at which chemical and biological control is aimed. However, little is known of the genes and phenotypes that contribute to the ability of bacteria to grow on leaves and survive the variable physical environment in this habitat. In addition, while genes such as hrp awr and others which confer pathogenicity and in planta growth ability have been described, their contribution to other aspects of bacterial epidemiology such as epiphytic fitness have not been addressed. We hypothesized that bacterial genes conferring virulence or pathogenicity to plants also contribute to the epiphytic fitness of these bacteria and that many of these genes are preferentially located on plasmids. We addressed these hypotheses by independently identifying genes that contribute to epiphytic fitness, in planta growth, virulence and pathogenicity in the phytopathogenic bacterium Erwinia herbicola pv gypsophilae which causes gall formation on gypsophila. This species is highly epiphytically fit and has acquired a plasmid (pPATH) that contains numerous pathogenicity and virulence determinants, which we have found to also contribute to epiphytic fitness. We performed saturation transposon mutagenesis on pPATH as well as of the chromosome of E.h. gypsophilae, and identified mutants with reduced ability to grow in plants and/or cause disease symptoms, and through a novel competition assay, identified mutants less able to grow or survive on leaves. The number and identity of plasmid-borne hrp genes required for virulence was determined from an analysis of pPATH mutants, and the functional role of these genes in virulence was demonstrated. Likewise, other pPATH-encoded genes involved in IAA and cytokinin biosynthesis were characterized and their pattern of transcriptional activity was determined in planta. In both cases these genes involved in virulence were found to be induced in plant apoplasts. About half of avirulent mutants in pPATH were also epiphytically unfit whereas only about 10% of chromosomal mutants that were avirulent also had reduced epiphytic fitness. About 18% of random mutants in pPATH were avirulent in contrast to only 2.5% of random chromosomal mutants. Importantly, as many as 28% of pPATH mutants had lower epiphytic fitness while only about 10% of random chromosomal mutants had lower epiphytic fitness. These results support both of our original hypotheses, and indicate that genes important in a variety of interactions with plant have been enriched on mobile plasmids such as pPATH. The results also suggest that the ability of bacteria to colonize the surface of plants and to initiate infections in the interior of plants involves many of the same traits. These traits also appear to be under strong regulatory control, being expressed in response to the plant environment in many cases. It may be possible to alter the pattern of expression of such genes by altering the chemical environment of plants either by genetic means or by additional or chemical antagonists of the plant signals. The many novel bacterial genes identified in this study that are involved in plant interactions should be useful in further understanding of bacterial plant interactions.

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Alfano, James, Isaac Barash, Thomas Clemente, Paul E. Staswick, Guido Sessa, and Shulamit Manulis. Elucidating the Functions of Type III Effectors from Necrogenic and Tumorigenic Bacterial Pathogens. United States Department of Agriculture, January 2010. http://dx.doi.org/10.32747/2010.7592638.bard.

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Many phytopathogenic bacteria use a type III protein secretion system (T3SS) to inject type III effectors into plant cells. In the experiments supported by this one-year feasibility study we investigated type III effector function in plants by using two contrasting bacterial pathogens: Pseudomonas syringae pv. tomato, a necrotrophic pathogen and Pantoea agglomerans, a tumorigenic pathogen. The objectives are listed below along with our major conclusions, achievements, and implications for science and agriculture. Objective 1: Compare Pseudomonas syringae and Pantoea agglomerans type III effectors in established assays to test the extent that they can suppress innate immunity and incite tumorigenesis. We tested P. agglomerans type III effectors in several innate immunity suppression assays and in several instances these effectors were capable of suppressing plant immunity, outputs that are suppressed by P. syringae effectors. Interestingly, several P. syringae effectors were able to complement gall production to a P. agglomerans pthGmutant. These results suggest that even though the disease symptoms of these pathogens are dramatically different, their type III effectors may function similarly. Objective 2: Construct P. syringae mutants in different combinations of type III-related DNA clusters to reduce type III effector redundancy. To determine their involvement in pathogenicity we constructed mutants that lack individual and multiple type III-related DNA clusters using a Flprecombinase-mediated mutagenesis strategy. The majority of single effector mutants in DC3000 have weak pathogenicity phenotypes most likely due to functional redundancy of effectors. Supporting this idea, Poly-DNAcluster deletion mutants were more significantly reduced in their ability to cause disease. Because these mutants have less functional redundancy of type III effectors, they should help identify P. syringae and P. agglomerans effectors that contribute more significantly to virulence. Objective 3: Determine the extent that P. syringae and P. agglomerans type III effectors alter hormone levels in plants. Inhibition of auxin polar transport by 2,3,5-triiodobenzoic acid (TIBA) completely prevented gall formation by P. agglomerans pv. gypsophilae in gypsophila cuttings. This result supported the hypothesis that auxin and presumably cytokinins of plant origin, rather than the IAA and cytokinins secreted by the pathogen, are mandatory for gall formation. Transgenic tobacco with pthGshowed various phenotypic traits that suggest manipulation of auxin metabolism. Moreover, the auxin levels in pthGtransgenic tobacco lines was 2-4 times higher than the control plants. External addition of auxin or cytokinins could modify the gall size in gypsophila cuttings inoculated with pthGmutant (PagMx27), but not with other type III effectors. We are currently determining hormone levels in transgenic plants expressing different type III effectors. Objective 4: Determine whether the P. agglomerans effectors HsvG/B act as transcriptional activators in plants. The P. agglomerans type III effectors HsvG and HsvB localize to the nucleus of host and nonhost plants and act as transcription activators in yeast. Three sites of adjacent arginine and lysine in HsvG and HsvB were suspected to act as Nuclear localization signals (NLS) domains. A nuclear import assay indicated two of the three putative NLS domains were functional NLSs in yeast. These were shown to be active in plants by fusing HsvG and HsvB to YFP. localization to the nucleus was dependent on these NLS domains. These achievements indicate that our research plan is feasible and suggest that type III effectors suppress innate immunity and modulate plant hormones. This information has the potential to be exploited to improve disease resistance in agricultural crops.

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Prusky, Dov, Nancy P. Keller, and Amir Sherman. global regulation of mycotoxin accumulation during pathogenicity of Penicillium expansum in postharvest fruits. United States Department of Agriculture, January 2014. http://dx.doi.org/10.32747/2014.7600012.bard.

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Abstract:

Background to the topic- Penicilliumas a postharvest pathogen and producer of the mycotoxin PAT. Penicilliumspp. are destructive phytopathogens, capable of causing decay in many deciduous fruits, during postharvest handling and storage; and the resulting losses can amount to 10% of the stored produce and the accumulation of large amounts of the mycotoxinpatulin. The overall goal of this proposal is to identify critical host and pathogen factors that modulate P. expansummycotoxin genes and pathways which are required for PAT production and virulence. Our preliminary results indicated that gluconic acid are strongly affecting patulin accumulation during colonization. P. expansumacidifies apple fruit tissue during colonization in part through secretion of gluconic acid (GLA). Several publications suggested that GLA accumulation is an essential factor in P. expansumpathogenicity. Furthermore, down regulation of GOX2 significantly reduced PAT accumulation and pathogenicity. PAT is a polyketide and its biosynthesis pathway includes a 15-gene cluster. LaeA is a global regulator of mycotoxin synthesis. It is now known that patulin synthesis might be subjected to LaeA and sometimes by environmental sensing global regulatory factors including the carbon catabolite repressor CreA as well as the pH regulator factor PacC and nitrogen regulator AreA. The mechanisms by which LaeA regulates patulin synthesis was not fully known and was part of our work. Furthermore, the regulatory system that controls gene expression in accordance with ambient pH was also included in our work. PacC protein is in an inactive conformation and is unable to bind to the promoter sites of the target genes; however, under alkaline growth conditions activated PacC acts as both an activator of alkaline-expressed genes and a repressor of acid-expressed genes. The aims of the project- This project aims to provide new insights on the roles of LaeA and PacC and their signaling pathways that lead to GLA and PAT biosynthesis and pathogenicity on the host. Specifically, our specific aims were: i) To elucidate the mechanism of pH-controlled regulation of GLA and PAT, and their contribution to pathogenesis of P. expansum. We are interested to understanding how pH and/or GLA impact/s under PacC regulation affect PAT production and pathogenesis. ii) To characterize the role of LaeA, the global regulator of mycotoxin production, and its effect on PAT and PacC activity. iii) To identify the signaling pathways leading to GLA and PAT synthesis. Using state- of-the-art RNAseq technologies, we will interrogate the transcriptomes of laeAand pacCmutants, to identify the common signaling pathways regulating synthesis of both GLA and PAT. Major conclusions, solutions, achievements- In our first Aim our results demonstrated that ammonia secreted at the leading edge of the fungal colony induced transcript activation of the global pH modulator PacC and PAT accumulation in the presence of GLA. We assessed these parameters by: (i) direct exogenous treatment of P. expansumgrowing on solid medium; (ii) direct exogenous treatment on colonized apple tissue; (iii) growth under self-ammonia production conditions with limited carbon; and (iv) analysis of the transcriptional response to ammonia of the PAT biosynthesis cluster. Ammonia induced PAT accumulation concurrently with the transcript activation of pacCand PAT biosynthesis cluster genes, indicating the regulatory effect of ammonia on pacCtranscript expression under acidic conditions. Transcriptomic analysis of pH regulated processes showed that important genes and BARD Report - Project 4773 Page 2 of 10 functionalities of P. expansumwere controlled by environmental pH. The differential expression patterns of genes belonging to the same gene family suggest that genes were selectively activated according to their optimal environmental conditions to enable the fungus to cope with varying conditions and to make optimal use of available enzymes. Concerning the second and third Aims, we demonstrated that LaeA regulates several secondary metabolite genes, including the PAT gene cluster and concomitant PAT synthesis invitro. Virulence studies of ΔlaeAmutants of two geographically distant P. expansumisolates (Pe-21 from Israel and Pe-T01 from China) showed differential reduction in disease severity in freshly harvested fruit ranging from no reduction for Ch-Pe-T01 strains in immature fruit to 15–25% reduction for both strains in mature fruit, with the ΔlaeAstrains of Is-Pe-21 always showing a greater loss in virulence. Results suggest the importance of LaeA regulation of PAT and other secondary metabolites on pathogenicity. Our work also characterized for the first time the role of sucrose, a key nutritional factor present in apple fruit, as a negative regulator of laeAexpression and consequent PAT production in vitro. This is the first report of sugar regulation of laeAexpression, suggesting that its expression may be subject to catabolite repression by CreA. Some, but not all of the 54 secondary metabolite backbone genes in the P. expansumgenome, including the PAT polyketide backbone gene, were found to be regulated by LaeA. Together, these findings enable for the first time a straight analysis of a host factor that potentially activates laeAand subsequent PAT synthesis.

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