Littérature scientifique sur le sujet « Bacterial, diseases, plants »
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Articles de revues sur le sujet "Bacterial, diseases, plants"
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Goychuk, A. F., M. V. Shvets, I. M. Kulbanska, F. F. Markov, N. А. Muljukina et V. P. Patyka. « Bacterial Diseases of Silver Birch (Betula pendula Roth.) ». Mikrobiolohichnyi Zhurnal 82, no 6 (30 novembre 2020) : 23–34. http://dx.doi.org/10.15407/microbiolj82.06.023.
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A significant role in the pathogenesis of diseases of woody plants belongs to phytopathogenic bacteria and fungi. It has been scientifically confirmed that the organs and tissues of woody plants have a certain myco- and microbiota, the components of which are systematically interconnected both with each other and with the plant. The species composition and quantitative ratio are constantly changing both in the process of ontogenesis of the tree and with changes in its physiology. The aim of the work was to study the species composition and the formation of diversity and systemic interactions of microbiota associated with bacterial dropsy in the pathology of Betula pendula Roth. Methods. Classical microbiological, phytopathological, biochemical, statistical methods were used in the work. Combined diagnostic methods were also used, in particular careful microscopic examination of the affected parts of plants, isolation and identification of the pathogen. Results. Bacterial origin of wet wood in the trunk of birches was detected. Samples of wood and exudate were taken for laboratory studies from plants that had pronounced signs of pathology (cracks, swellings). It has been experimentally proved that the causative agent of bacterial dropsy of silver birch is the phytopathogenic polybiotrophic bacterium Lelliottia nimipressuralis, which causes dropsy of coniferous and deciduous woody plants and experimentally found pathogenic properties to B. pendula. Xanthomonas campestris, Pantoea agglomerans and Bacillus subtilis are associated with bacterial dropsy pathology of B. pendula. The pathogenic properties of P. agglomerans and X. campestris on B. pendula are variable, which indicates the possibility of the expansion of the circle of plants sensitive for these species of bacteria. It was established that L. nimipressuralis both during spring and autumn inoculation showed high pathogenicity to B. pendula. In only one case, on isolated on the border of healthy and affected wood from young B. pendula (bast part) the results of artificial injury were less pronounced. Other bacteria isolated from bacterial dropsy, in particular X. campestris, were non-pathogenic for B. pendula. At the same time, we noted traces of artificial infection with X. campestris in the samples isolated on the border of healthy and affected wood from middle-age B. pendula (cambial part). This may indicate an expansion of the circle of sensitive plants or the increased sensitivity of certain forms of birch for the mentioned bacteria, which is quite likely, since the bacteria have a significant forms variety. In 10 places of inoculation no pathology caused by B. subtilis was found. Bacteria of the Bacillus genus were non-pathogenic for B. pendula in all experiment. Our studies have shown that they can be a regulatory factor in the development of bacterial dropsy. Conclusions. A certain variability of isolated strains in the assimilation of some carbohydrates and alcohols can be explained by the specific conditions of the existence of bacteria, including the influence of environmental factors on their biochemical properties. It is known that the ecological niche affects even the antigenic composition of bacteria; therefore, such an effect should also be expected on other properties. Our studies confirmed that causative agent of bacterial dropsy is L. nimipressuralis and clarified the information about this bacteria cells size.
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Islam, Roohul, Tahira Qamash, Syed Saoud Zaidi, Sobiya Mohiuddin Omar, Maryam Shoaib, Rimsha Riaz, Asmat Ullah Khan, Sobia Naeem et Muhammad Junaid Khan. « Bioactivities of Medicinal Plants Focused on Targeting Infectious Diseases ». Saudi Journal of Medical and Pharmaceutical Sciences 8, no 8 (4 août 2022) : 392–96. http://dx.doi.org/10.36348/sjmps.2022.v08i08.003.
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Infectious pathologic changes caused by pathogens, which are harmful that enter the body by bacteria, fungus, viruses, and parasites. Infectious-diseases can range in severity from very mild to very dangerous. Numerous human diseases are caused by bacteria such as Staphylococcus aureus, Pseudomonas aeruginosa, Proteus vulgaris and Bacillus subtilis. Capparis spp. that have anti-bacterial, anti-oxidant and anti-inflammatory properties, including spermidine, carotenoids, quercetin, tocopherol, and rutin by the anti-bacterial, anti-fungal, and anti-leishmanial action. Carrot seed oil (Daucus carota) and tea tree oil (Melaleuca alternifolia) both exhibit antibacterial action respectively. Curcumin and its derivatives were found to have more potent anti-bacterial activity against several strains of S. pneumonia. Oregano oil and carvacrol has revealed that they have anti-viral properties against respiratory-syncytial-virus (RSV), that causes respiratory disease, rotavirus, a frequent condition of diarrhea in theng children, and herpes simplex virus type 1 (HSV-1). Sweet basil extract, which contain ingredients like ursolic acid and apigenin, have powerful antiviral properties against hepatitis B, herpes and enterovirus. Candida infections have fewer severe side effects and less cost load than chemical medications, can be treated with new pharmaceuticals, plant, and herbal items.
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Kolomiiets, Yu, I. Hryhoriuk, L. Butsenko et L. Biliavska. « Systemic effect of microbial preparations on causative microorganisms of bacterial diseases of tomato plants ». Agroecological journal, no 3 (30 septembre 2016) : 83–89. http://dx.doi.org/10.33730/2077-4893.3.2016.248868.
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Biologicals Phytohelp, Phytocide and Ekstrasol, based on the bacteria Bacillus subtilis, showed different antibacterial activity to phytopathogens, due to the peculiarities of used strains, cells titer and concentration of biologically active products of microorganisms. Biologicals Phytohelp and Phytocide showed high antibacterial activity against the agents of bacterial cancer C. michiganensis subsp. michiganensis and bacterial black spotting X. vesicatoria, and the no growth zone diameter ranged from 73 to 80 mm. Under these conditions no growth zone diameter of the studied strains C. michiganensis subsp. michiganensis and X. vesicatoria for microbiological preparation Ekstrasol did not exceed 40 mm. Among these preparations more active against bacterial speck of tomatoes P. syringae pv. tomato was microbial preparation Ekstrasol no growth zone diameter of which was 23±3.0 mm. Biological Azotofit, based on cells of nitrogen-fixing bacteria Azotobacter chroococcum, showed high antibacterial activity against the agent of bacterial cancer C. michiganensis subsp. michiganensis, no growth zone diameter was 78±2.0 mm. This preparation was middle-active against the agent of bacterial black spotting X. vesicatoria and showed no activity against the agent of bacterial speck of tomato P. syringae pv. tomato. It was revealed that the most active against the agents of bacterial black spotting and bacterial cancer are biologicals Phytocide and Phytohelp, based on the bacteria Bacillus subtilis that are recommended by us for use in the manufacture.
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Goychuk, Anatolyj, Ivanna Kulbanska, Maryna Shvets, Lidiia Pasichnyk, Volodymyr Patyka, Antonina Kalinichenko et Larysa Degtyareva. « Bacterial Diseases of Bioenergy Woody Plants in Ukraine ». Sustainability 15, no 5 (25 février 2023) : 4189. http://dx.doi.org/10.3390/su15054189.
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In this study, the characterization of several bacterial diseases affecting silver birch (Betula pendula Roth.), common ash (Fraxinus excelsior L.), white poplar (Populus alba L.), and white willow (Salix alba L.) in Ukraine were described. The typical symptoms, features of pathogenesis, and characteristics of the causative agents of the most common bacterial diseases of these tree species were shown. The following types of bacterioses were noted to be especially dangerous, namely, bacterial wetwood, fire blight, bacterial canker, and tuberculosis. Bacterial necrosis of the bark was a less dangerous disease. At the same time, all of the listed types of bacterioses were registered within the forest areas of the investigated region. The study revealed that bacterial wetwood of birch and poplar was caused by Lelliottia nimipressuralis; the bacterial canker of poplar is Pseudomonas syringae (Pseudomonas syringae f. populi and Pseudomonas cerasi); the fire poplar blight is caused by Pseudomonas cerasi (P. syringae); the common ash tuberculosis is caused by Pseudomonas syringae pv. savastanoi; and the bacterial wilt of the willow is caused by Brenneria salicis. The phenomenon of the introduction of microorganisms of different functional orientations as well as the formation of conditions for their activity in the rhizosphere of plants have been studied. In the future, it will provide the development of effective methods for the rapid identification of causative agents of bacterioses and plant protection measures based on multi-functional microbiological preparations based on highly effective strains of microorganisms.
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Poudel, Nabin Sharma, et Subhas Neupane. « Bacterial Diseases of Plants in Nepal : A Review ». Asian Journal of Agricultural and Horticultural Research 2, no 1 (10 septembre 2018) : 1–10. http://dx.doi.org/10.9734/ajahr/2018/42455.
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Abdullayeva, Shahla. « INCIDENTAL BACTERIAL IN HOUSE PLANTS AND FUNGAL DISEASES ». SCIENTIFIC RESEARCH 3, no 1 (26 février 2023) : 16–18. http://dx.doi.org/10.36719/2789-6919/17/16-18.
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Sakr, Nachaat. « Silicon control of bacterial and viral diseases in plants ». Journal of Plant Protection Research 56, no 4 (1 décembre 2016) : 331–36. http://dx.doi.org/10.1515/jppr-2016-0052.
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AbstractSilicon plays an important role in providing tolerance to various abiotic stresses and augmenting plant resistance against diseases. However, there is a paucity of reports about the effect of silicon on bacterial and viral pathogens of plants. In general, the effect of silicon on plant resistance against bacterial diseases is considered to be due to either physical defense or increased biochemical defense. In this study, the interaction between silicon foliar or soil-treatments and reduced bacterial and viral severity was reviewed. The current review explains the agricultural importance of silicon in plants, refers to the control of bacterial pathogens in different crop plants by silicon application, and underlines the different mechanisms of silicon-enhanced resistance. A section about the effect of silicon in decreasing viral disease intensity was highlighted. By combining the data presented in this study, a better comprehension of the complex interaction between silicon foliar- or soil-applications and bacterial and viral plant diseases could be achieved.
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Tshikhudo, Phumudzo Patrick, Khayalethu Ntushelo et Fhatuwani Nixwell Mudau. « Sustainable Applications of Endophytic Bacteria and Their Physiological/Biochemical Roles on Medicinal and Herbal Plants : Review ». Microorganisms 11, no 2 (10 février 2023) : 453. http://dx.doi.org/10.3390/microorganisms11020453.
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Bacterial endophytes reside within the tissues of living plant species without causing any harm or disease to their hosts. These endophytes can be isolated, identified, characterized, and used as biofertilizers. Moreover, bacterial endophytes increase the plants’ resistance against diseases, pests, and parasites, and are a promising source of pharmaceutically important bioactives. For instance, the production of antibiotics, auxins, biosurfactants, cytokinin’s, ethylene, enzymes, gibberellins, nitric oxide organic acids, osmolytes, and siderophores is accredited to the existence of various bacterial strains. Thus, this manuscript intends to review the sustainable applications of endophytic bacteria to promote the growth, development, and chemical integrity of medicinal and herbal plants, as well as their role in plant physiology. The study of the importance of bacterial endophytes in the suppression of diseases in medicinal and herbal plants is crucial and a promising area of future investigation.
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Iwai, Takayoshi, H. Kaku, R. Honkura, S. Nakamura, H. Ochiai, T. Sasaki et Y. Ohashi. « Enhanced Resistance to Seed-Transmitted Bacterial Diseases in Transgenic Rice Plants Overproducing an Oat Cell-Wall-Bound Thionin ». Molecular Plant-Microbe Interactions® 15, no 6 (juin 2002) : 515–21. http://dx.doi.org/10.1094/mpmi.2002.15.6.515.
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Bacterial attack is a serious agricultural problem for growth of rice seedlings in the nursery and field. The thionins purified from seed and etiolated seedlings of barley are known to have antimicrobial activity against necrotrophic pathogens; however, we found that no endogenous rice thionin genes alone are enough for resistance to two major seed-transmitted phytopathogenic bacteria, Burkholderia plantarii and B. glumae, although rice thionin genes constitutively expressed in coleoptile, the target organ of the bacteria. Thus, we isolated thionin genes from oat, one of which was overexpressed in rice. When wild-type rice seed were germinated with these bacteria, all seedlings were wilted with severe blight. In the seedling infected with B. plantarii, bacterial staining was intensively marked around stomata and intercellular spaces. However, transgenic rice seedlings accumulating a high level of oat thionin in cell walls grew almost normally with bacterial staining only on the surface of stomata. These results indicate that the oat thionin effectively works in rice plants against bacterial attack.
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Mustafa, Mirik, Aysan Yesim et Baysal-Gurel Fulya. « Bacterial spot and blight diseases of ornamental plants caused by different Xanthomonas species in Turkey ». Plant Protection Science 54, No. 4 (25 août 2018) : 240–47. http://dx.doi.org/10.17221/10/2017-pps.
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Putative strains belonging to Xanthomonas spp. causing leaf spot and blight diseases on geranium (Pelargonium peltatum and P. hortorum), begonia (Begonia × tuberhybrida), anthurium (Anthurium andraeanum), Chinese hibiscus (Hibiscus rosa-sinensis), and English ivy (Hedera helix) growing in Turkey were isolated. All bacterial strains were classified as Gram-negative, oxidase negative, catalase, levan and starch hydrolysis positive, with hypersensitive reaction positive on tobacco and pathogenic to host plants. Identification of these strains was further confirmed by serological method using ELISA kits, conventional PCR, carbon utilisation, and FAME. Results of the identification showed that 28, 24, 10, 2, and 1 strains were identified as X. axonopodis pv. begoniae, X. hortorum pv. pelargonii, X. axonopodis pv. dieffenbachiae, X. hortorum pv. hederae, and Xanthomonas sp., respectively. This is the first report of X. hortorum pv. hederae on English ivy in Turkey.
Thèses sur le sujet "Bacterial, diseases, plants"
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Roberts, S. J. « Bacterial diseases of woody ornamental plants ». Thesis, University of Leeds, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.375533.
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Akiew, E. B. « Potato diseases in South Australia : studies in leafroll, early blight and bacterial wilt / ». Title page, contents and summary only, 1985. http://web4.library.adelaide.edu.au/theses/09PH/09pha315.pdf.
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Roberts, Daniel Paul. « Molecular mechanisms of pathogenesis incited by Erwinia carotovora subsp. carotovora ». Diss., Virginia Polytechnic Institute and State University, 1985. http://hdl.handle.net/10919/71251.
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Erwinia carotovora subsp. Carotovora (Ecc) incites soft-rot on many plants. It is believed that soft-rot is due to the concerted activity of extracellular enzymes. Recombinant DNA techniques were used to study the molecular basis of pathogenesis incited by Ecc. Specifically, a clone library of Ecc strain EC14 DNA in plasmid pBR322 was constructed and transformed into Escherichia coli strain HB101. Some of the E. coli strains that contain these hybrid plasmids produce pectinases or cellulase(s). Plasmid pDR1 contains a 3.4 kilobase (kb) EC14 DNA fragment and mediates the production of endo-pectate lyases with isoelectric points (pI) of 9.5 and 7.5 in strain HB101. The pI 9.5 enzyme is believed to be the major extracellular pectolytic enzyme in soft-rot while the pI 7.5 enzyme has no documented counterpart in EC14. Subclone and transposon tn5 analyses of pDR1 indicate that 1.5 kb is necessary for the production of the pI 9.5 and pI 7.5 enzymes and that these enzymes are produced independently of other EC14 pectate lyase enzymes. Plasmid pDR30 contains a 2.1 kb EC14 DNA insert that mediates the production of an endo-polygalacturonase and an exo-pectate lyase in HB101. The exo-pectate lyase encoded by pDR30 produces an inducer of endo-pectate lyase synthesis as a reaction product. The endo-polygalacturonase encoded by pDR30 is thought to play a role in plant cell wall pectic polymer degradation. Restriction endonuclease and Southern hybrididizatian analyses indicate that the EC14 genes on plasmids pDR1 and pDR30 are not part of the same operon. Escherichia coli strain HB101 containing plasmid pDR1 or plasmid pDR30 is unable to macerate potato tuber slices. However, HB101 containing plasmids pDR1 and pDR30 can cause limited maceration of potato tuber slices. There appears to be a genetic interaction between plasmids pDR1 and pDR30 in maceration of potato tuber tissue. However, the EC14 gene(s) contained on plasmid pDR1 are transcribed independently of the EC14 genes contained on plasmid pDR30. It is possible that transcription of certain pectolytic enzymes independent of other pectolytic enzymes provides a flexible system for plant cell wall pectic polymer degradation.Ph. D.
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Proto, Mariarita <1990>. « Essential oils and hydrolates as potential tools for integrated prevention of bacterial diseases in plants ». Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2022. http://amsdottorato.unibo.it/10292/1/TESI%20PhD%20MRP.pdf.
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The present work aims to investigate the potential use of natural substances against bacterial plant pathogens. Microdilution tests were therefore carried out in vitro to identify the minimum inhibitory and bactericidal concentrations (MIC and MBC) of several EOs and Hys against selected bacterial pathogens. Commercial products based on a mixture of EOs were in addition assayed with macrodilution experiments against Erwinia amylovora (Ea-causal agent of fire blight). Subsequently, using selected EOs, Hys, and commercial products, ex vivo tests on disease incidence and Ea population dynamics were carried out; the latter experiment was followed by SEM observations. In addition, in vivo resistance induction test was carried out against bacterial leaf of tomato, caused by Xanthomonas vesicatoria (Xv). EOs and Hys showed high bactericidal activity in vitro (MBC <0.1 and <10% for the most active EOs and Hys: Origanum compactum and Thymus vulgaris EOs and Citrus aurantium var. amara Hy, respectively), but they were not effective ex vivo, while resulted very active when used in vivo as resistance inducers in the tomato-Xv pathosystem (relative protection >40%). Differently, commercial products resulted active in all tests, but not as resistance inducers against Xv. An open field trial with commercial products was carried out on strawberry plants naturally infected with Xanthomonas fragariae; the results showed discrete relative protection, concerning that provided by the conventional products based on copper; mostly, the disease severity reduction on those plants treated with EOs commercial products was significant when disease severity resulted high. The papers already published described in the present work investigate (1)the activity of Hys in comparison to EOs with respect to their active volatile content; (2) the potential use of EOs and Hys in cultural heritage; for the restoration of paintings; (3) the induction of resistance caused by plasma-activated water-based root treatments.
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DeYoung, Robyn Merrilee. « Gall formation by Erwinia species on Douglas-fir ». Thesis, University of British Columbia, 1990. http://hdl.handle.net/2429/28980.
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Bacterial galls on Douglas-fir (Pseudotsuga menzeisii [Mirb.] Franco), collected from the southern tip of Vancouver Island, the Greater Vancouver area and the Hope region of British Columbia, were generally globose in shape with rough, irregular surfaces and measured between 0.5 and 2.0 cm in diameter. The galls were generally located on the tips of branches or twigs of 10- to 20-year old Douglas-fir trees.
The bacterial gall disease appeared to affect few Douglas-fir trees in the collection areas and bacterial galls were not found on any other coniferous species. Furthermore, there have been no reports of serious damage to natural forests in British Columbia due to bacterial gall disease. Young, greenhouse-grown Douglas-fir seedlings occasionally died if the tip of the main stem was artificially inoculated. Often new growing tips would be produced affecting the growth form of the seedlings.
Two types of gall-forming Erwinia spp. were isolated from Douglas-fir galls. Typical isolates, tentatively identified by fatty acid analysis as Erwinia salicis, produced galls which were rough and irregular in shape composed of multiple outgrowths marked by a single or cross-shaped fissure. The atypical isolate, tentatively identified by fatty acid analysis as Erwinia herbicola subsp. herbicola, produced galls which were smooth and generally round in shape with the surface cracking as the gall expanded.
Colonies of the typical isolates grown on casein-peptone-glucose media were characteristically round, slightly domed with
somewhat concentric ridging observed near the margins of the colonies. Three to 4 day old colonies of the atypical isolates grown on casein-peptone-glucose media were characteristically round and concave while older colonies produced an extracellular slime and were more irregular in shape. In Luria Broth, the typical isolates grew at temperatures of up to 32°C while the atypical isolate grew at temperatures of up 34°C. The typical isolate was resistant to a wider range of antibiotics than the atypical isolate.
Polyclonal antisera were produced against glutaraldehyde-fixed whole cells of both the typical T-2789 and atypical A-0181 gall-forming Erwinia isolates. The purified antisera were isolate specific as tested by immunodiffusion and an indirect ELISA against several different phytopathogenic bacteria including Pseudomonas syringae pv. syringae, Erwinia herbicola subsp. herbicola, Agrobacterium tumefaciens, Rhizobium leguminosarum and Erwinia carotovora subsp. carotovora.
Plasmid profiles of the typical Erwinia isolates contained one band while the atypical isolate characteristically contained 4 to 5 bands which appeared to be different forms of at least one plasmid. Restriction digests of the typical isolates suggested a size of approximately 50 kb while complex digestion profiles were obtained for the atypical isolates because of the difficulty in isolating individual plasmid types. From visual estimates against Hindlll-digested lambda DNA, a size of between 10 and 20 kb was suggested for the fastest moving plasmid band of the atypical isolate. No homology was observed between the different plasmid types characteristic of the two isolates. The
role of the plasmid DNA of the atypical isolate in pathogenesis was not determined because curing of the plasmid(s) was not successful using high temperature treatments plus chemical curing agents.
Heat treatment experiments, in which the pathogen was selectively killed at various times after inoculation, demonstrated that the bacteria are required to be present for gall induction and continued development of the gall for both of the gall-forming Erwinia isolate types.
Pathogenicity of the isolated bacteria was tested on 14 conifer species, other than Douglas-fir, including Abies, Chamaecyparis, Pinus and Thuja spp. The typical isolates were weakly pathogenic on Abies, Larix and Picea spp. The atypical isolate was weakly pathogenic on Abies, Chamaecyparis, Larix, Picea and Pinus spp. Due to the limited damage caused on the conifers tested and to their infrequent occurrence, these gall-forming pathogens do not appear to be of economic importance to the forestry industry.Land and Food Systems, Faculty of
Graduate
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Njom, Henry Akum. « Mechanism and synchronicity of wheat (Triticum aestivum) resistance to leaf rust (Puccinia triticina) and Russian wheat aphid (Duiraphis noxia) SA1 ». Thesis, University of Fort Hare, 2016. http://hdl.handle.net/10353/2700.
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Wheat (Triticum aestivum and T. Durum) is an extremely important agronomic crop produced worldwide. Wheat consumption has doubled in the last 30 years with approximately 600 million tons consumed per annum. According to the International Maize and Wheat Improvement Center, worldwide wheat demand will increase over 40 percent by 2020, while land as well as resources available for the production will decrease significantly if the current trend prevails. The wheat industry is challenged with abiotic and biotic stressors that lead to reduction in crop yields. Increase knowledge of wheat’s biochemical constitution and functional biology is of paramount importance to improve wheat so as to meet with this demand. Pesticides and fungicides are being used to control biotic stress imposed by insect pest and fungi pathogens but these chemicals pose a risk to the environment and human health. To this effect, there is re-evaluation of pesticides currently in use by the Environmental Protection Agency, via mandates of the 1996 Food Quality Protection Act and those with higher perceived risks are banned. Genetic resistance is now a more environmental friendly and effective method of controlling insect pest and rust diseases of wheat than the costly spraying with pesticides and fungicides. Although, resistant cultivars effectively prevent current prevailing pathotypes of leaf rust and biotypes of Russian wheat aphid from attacking wheat, new pathotypes and biotypes of the pathogen/pest may develop and infect resistant cultivars. Therefore, breeders are continually searching for new sources of resistance. Proteomic approaches can be utilised to ascertain target enzymes and proteins from resistant lines that could be utilised to augment the natural tolerance of agronomically favourable varieties of wheat. With this ultimate goal in mind, the aim of this study was to elucidate the mechanism and synchronicity of wheat resistance to leaf rust (Puccinia triticina) and Russian wheat aphid (Duiraphis noxia) SA1. To determine the resistance mechanism of the wheat cultivars to leaf rust infection and Russian wheat aphid infestation, a proteomics approach using two-dimensional gel electrophoresis was used in order to determine the effect of RWA SA1 on the wheat cultivars proteome. Differentially expressed proteins that were up or down regulated (appearing or disappearing) were identified using PDQuestTM Basic 2-DE Gel analysis software. Proteins bands of interest were in-gel trypsin digested as per the protocol described in Schevchenko et al. (2007) and analysed using a Dionex Ultimate 3000 RSLC system coupled to an AB Sciex 6600 TripleTOF mass spectrometer. Protein pilot v5 using Paragon search engine (AB Sciex) was used for comparison of the obtained MS/MS spectra with a custom database containing sequences of Puccinia triticina (Uniprot Swissprot), Triticum aestivum (Uniprot TrEMBL) and Russian wheat aphid (Uniprot TrEMBL) as well as a list of sequences from common contaminating proteins. Proteins with a threshold of ≥99.9 percent confidence were reported. A total of 72 proteins were putatively identified from the 37 protein spots excised originating from either leaf rust or Russian wheat aphid experiments. Sixty-three of these proteins were associated with wheat response to stress imposed by RWA SA1 feeding while 39 were associated with infection by Puccinia triticina. Several enzymes involved in the Calvin cycle, electron transport and ATP synthesis were observed to be differentially regulated suggesting greater metabolic requirements in the wheat plants following aphid infestation and leaf rust infection. Proteins directly associated with photosynthesis were also differentially regulated following RWA SA1 infestation and P.
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Mustafa, Bakray Nur Aqilah Binti. « Structure of root associated and soil fungal and bacterial communities in Southeast Asia tropical forest ». Thesis, University of Aberdeen, 2018. http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?pid=239153.
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The tropical rainforest has interested ecologists for hundreds of years because of its vast species diversity. The distribution and establishment of trees is related to soil properties and rootassociated microorganisms. The coexistence of hyper-diverse plant communities in tropical rainforests has resulted in associations being formed with belowground communities, mycorrhizas (particularly arbuscular mycorrhizal (AM), ectomycorrhizas (ECM)) and root associated bacterial communities. The rapid deforestation in Southeast Asia is causing the loss of the dominant and important tree species belonging to the family Dipterocarpaceae. It is important to understand whether different host species in the same environment maintain mycorrhizal and bacterial diversity, especially mycorrhizas with a restricted host range. In this study, I examine the ecology of mycorrhizas and bacteria associated with Dipterocarpaceae and also the plant community as a whole. The aim of this project is to understand the effect of host properties (e.g. species, size), soil factors (e.g. nutrient concentrations) and spatial factors on mycorrhizal fungi and bacterial diversity and community structure. The research took place in two Centre for Tropical Forest Science (CTFS) plots in Malaysia: Pasoh Forest Reserve (in Negeri Sembilan) and Danum Valley Conservation Area (in Sabah). Molecular protocols and a modern technique, Next Generation Sequencing (NGS), were adopted to quantify mycorrhizal and bacterial loads in tropical plants. ITS1 and ITS2 regions were used for ECM, 18S rRNA were used for AM, and 16S rRNA were used for bacteria. Mycorrhizas and bacteria present in the roots of Dipterocarpaceae from 60 individual plants belonged to 25 species within 6 genera were traced and sampled in 2015. To my knowledge, this study is the first attempt to study root-associated bacteria across multiple species within a single family, Dipterocarpaceae. Dipterocarpaceae's species was found to significantly influence root bacteria. Analyses showed that mycorrhizal communities are similar on the host, unlike the null model. Dipterocarpaceae was previously believed to solely host ECM, but this study disproves this. This study shows that Dipterocarpaceae can have dual colonization, as it iv can also associate with AM fungi. One soil core of 10 cm × 10 cm × 7.5 cm were collect randomly in three subplot and further divided at 2.5 cm each slice into 75 individual 'microcubes' of 2 cm × 2 cm × 2.5 cm depths enumerates a total of 192 fine root samples. Multivariate analysis revealed that AM fungi tend to associate with non-dipterocarp (as well as unidentified families) while ECM fungi tend to associate with dipterocarps. Data was also collected on host attributes, plant size, and root density. Dipterocarpaceae size does not influence the distribution of mycorrhizal or bacterial communities. The root density reduces as depth increases. Therefore, root density does have a significant influence on mycorrhizal community structure. The diversity of ECM and AM fungal communities within cubes decreased significantly with depth (p < 0.001), whereas the mycorrhizal communities did not change across horizontal distances within cubes. To investigate whether there is a relationship between belowground communities and soil properties, soil macro and micro nutrients were examined and a multivariate analysis was performed. The results showed that communities of belowground (mycorrhizal and bacterial) species correlate with soil parameters. Spatial scale also had an effect on community assembly, independent of environmental variation. These results demonstrate that mycorrhizal fungal communities can vary substantially over very fine spatial scales, and that the distribution of roots from different species do not reflect their proximity aboveground. This study clearly demonstrates the widespread presence of mycorrhizal fungi and root associated bacteria in tropical rainforest plants.
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Agustí, Alcals Lourdes. « Characterization and efficacy of bacterial strains for biological control of soil-borne diseases caused by Phytophthora cactorum and Meloidogyne javanica on Rosaceous plants ». Doctoral thesis, Universitat de Girona, 2008. http://hdl.handle.net/10803/7930.
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S'avaluaren 58 soques de Pseudomonas fluorescens i Pantoea agglomerans per la seva eficàcia en el biocontrol de la malaltia causada per l'oomicet Phytophthora cactorum en maduixera i pel nematode formador de gal·les Meloidogyne javanica en el portaempelt GF-677.Es desenvolupà un mètode ex vivo d'inoculació de fulla amb l'objectiu de seleccionar soques bacterianes com a agents de control biològic de P. cactorum en maduixera. Tres soques de P. fluorescens es seleccionaren com a soques eficaces en el biocontrol del patogen en fulles i en la reducció de la malaltia en plantes de maduixera. La combinació de soques semblà millorar la consistència del biocontrol en comparació amb les soques aplicades individualment.
Tres soques de P. fluorescens es seleccionaren per la seva eficàcia en la reducció de la infecció de M. javanica en portaempelts GF-677. La combinació d'aquestes soques no incrementà l'eficàcia del biocontrol, però semblà reduir la seva variabilitat.
58 Pseudomonas fluorescens and Pantoea agglomerans strains were evaluated for their biocontrol efficacy against the oomycete Phytophthora cactorum in strawberry and the root-knot nematode Meloidogyne javanica in GF-677 rootstocks.
An ex vivo detached leaf inoculation method was developed to select bacterial strains as biological control agents of P. cactorum in strawberry. Three P. fluorescens strains were selected as effective in biocontrol of the pathogens on leaves and in disease reduction in strawberry plants. Combination of strains improved biocontrol consistency compared to strains applied individually.
Three P. fluorescens strains were selected for their efficacy in M. javanica infection reduction in GF-677 rootstocks. Combination of these strains did not increase biocontrol efficacy, but reduced its variability.
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Gumede, Halalisani. « The development of a putative microbial product for use in crop production ». Thesis, Rhodes University, 2008. http://eprints.ru.ac.za/1352/.
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Pauw, Elizabeth Lita. « Evaluating the predictive value of a database of antimicrobial activities of leaf extracts of 537 southern African tree species against six important bacterial and fungal pathogens ». Thesis, University of Pretoria, 2014. http://hdl.handle.net/2263/40266.
Texte intégralRésumé :
Infectious diseases are the world’s leading cause of premature deaths in humans and animals. The resistance to antibiotics and the emergence of new infectious diseases has increased the need for additional effective antimicrobial products. Despite numerous publications investigating antimicrobial activity of plant extracts it appears that no effective single product antimicrobial has yet been developed from plants. In many cases, however crude plant extracts have excellent activity and may provide useful products.
Plants are frequently selected based on traditional use. Traditional healers usually use aqueous extracts of plants which in our experience generally have very low activities and it may be one of the reasons why no new products were developed from plants. Another approach to select plants for research is to use the taxonomic approach based on the premises that: (1) there is a correlation between active chemical compounds and antimicrobial activity; and (2) species in a family or order may have similar activities if the chemical precursors are inherited from a common ancestor. Future screening programmes could then concentrate on close relatives of species within these promising families and orders.
The main aim of this study was to randomly screen leaf extracts of several hundred southern African tree species against important microbial pathogens to determine which taxa have the highest activity and may yield useful products to treat infections in human and animal health markets. A wide selection of plant species improved the possibility of finding promising extracts and has the advantage that active compounds may be discovered from plants that are not used traditionally. To ensure sustainable use only leaves of trees were examined. A spin off of this study would also indicate the susceptibility of different organisms, correlate the antimicrobial activities of the different organisms and determine what minimum inhibitory concentration (MIC) represents a good activity based on investigating many extracts against many microbes.
The antimicrobial activity was determined by using a sensitive serial dilution microplate method. Acetone extracts were tested against two Gram-positive bacteria, two Gram-negative bacteria and two fungi, i.e. Staphylococcus aureus, Enterococcus faecalis, Escherichia coli, Pseudomonas aeruginosa, Candida albicans and Cryptococcus neoformans.
Small and mostly insignificant differences were found between the susceptibility of the microbial pathogens to the extracts. E. faecalis was the most sensitive bacterium and C. neoformans the most sensitive fungal organism. The strongest correlations in activities among the pathogens were between C. albicans and C. neoformans, and among the pathogen classes between Gram-positive and Gram-negative bacteria. The tree extracts analysed in the present study had a wide range of activities against the different pathogens. Twenty six per cent of the extracts inhibited the pathogens at MIC levels of 0.16 mg/ml. This clearly shows that 0.16 mg/ml is not low enough to discriminate between promising species. Some of the extracts inhibited the growth of more than one pathogen while other extracts had selective activities and could be the most promising to follow up.
The study identified families and orders with either statistically significantly higher or lower antimicrobial activities. Among the large families, Combretaceae and Fabaceae had high mean activities against all test pathogens. The families Anacardiaceae and Moraceae had high activities against both Gram-positive and Gram-negative bacteria whereas the families Proteaceae and Meliaceae had higher antifungal activities. Among the large orders, Fabales had relatively high activities against all the pathogen classes. Considering that plants in related taxa often contain similar compounds and therefore similar activities, future studies could analyse more representative species in the promising taxa.
Many tree species, genera, families and orders, including well-known and lesser known medicinal taxa in southern Africa, were identified with promising activities. To evaluate the potential use of these results, additional cytotoxicity, phytochemical and pharmacological studies should be carried out. The study, although still exploratory, underlined the potential of southern African tree extracts as sources of antimicrobial products. Application of these results within the Phytomedicine Programme has led to patents and products that were as good as commercial products in animal and field trials. We hope that our results will provided a starting point for discovering new products with useful activities.Thesis (PhD)--University of Pretoria, 2014.
gm2014
Paraclinical Sciences
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Livres sur le sujet "Bacterial, diseases, plants"
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Borkar, Suresh G., et Rupert Anand Yumlembam. Bacterial Diseases of Crop Plants. Boca Raton, FL : CRC Press, Taylor & Francis Group, 2017. | : CRC Press, 2016. http://dx.doi.org/10.1201/9781315367972.
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Janse, J. D. Phytobacteriology : Principles and practice. Wallingford, UK : CABI, 2009.
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Lelliott, R. A. Methods for the diagnosis of bacterial diseases of plants. Oxford [Oxfordshire] : Published on behalf of the British Society for Plant Pathology by Blackwell Scientific Publications, 1987.
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Goto, Masao. Fundamentals of bacterial plant pathology. San Diego : Academic Press, 1992.
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Fundamentals of bacterial plant pathology. San Diego : Academic Press, 1992.
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S, De Boer, dir. Plant pathogenic bacteria : Proceedings of the 10th International Conference on Plant Pathogenic Bacteria, Charlottetown, Prince Edward Island, Canada, July 23-27, 2000. Dordrecht : Kluwer Academic Publishers, 2001.
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Janse, J. D. Phytobacteriology : Principles and practice. Cambridge, MA : CABI Pub., 2006.
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Plant bacteriology. St. Paul, Minn : American Phytopathological Society, 2010.
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C, Harrison F. Some bacterial diseases of plants prevalent in Ontario. Toronto : Ontario Agricultural College, 1997.
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Microbiology, American Society for, dir. Bacteria as plant pathogens. Washington, D.C., USA : American Society for Microbiology, 1987.
Trouver le texte intégralChapitres de livres sur le sujet "Bacterial, diseases, plants"
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Thind, B. S. « Diagnosis of Bacterial Diseases of Plants ». Dans Phytopathogenic Bacteria and Plant Diseases, 23–35. Boca Raton : Taylor & Francis, 2020. : CRC Press, 2019. http://dx.doi.org/10.1201/9780429242786-3.
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Narayanasamy, P. « Diagnosis of Bacterial Diseases of Plants ». Dans Microbial Plant Pathogens-Detection and Disease Diagnosis :, 233–46. Dordrecht : Springer Netherlands, 2010. http://dx.doi.org/10.1007/978-90-481-9769-9_5.
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Sletten, A. « Diagnosis of Bacterial Infections by Immunological Methods ». Dans Vascular Wilt Diseases of Plants, 107–11. Berlin, Heidelberg : Springer Berlin Heidelberg, 1989. http://dx.doi.org/10.1007/978-3-642-73166-2_6.
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Thind, B. S. « Plants as Carriers of Human Enteric Bacterial Pathogens ». Dans Phytopathogenic Bacteria and Plant Diseases, 95–109. Boca Raton : Taylor & Francis, 2020. : CRC Press, 2019. http://dx.doi.org/10.1201/9780429242786-6.
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Trigalet, A. « Virulence and Avirulence of Bacterial Pathogens and Designation of Races ». Dans Vascular Wilt Diseases of Plants, 291–302. Berlin, Heidelberg : Springer Berlin Heidelberg, 1989. http://dx.doi.org/10.1007/978-3-642-73166-2_21.
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Burr, T. J. « Future Development of Chemical and Biological Controls for Bacterial Diseases of Plants ». Dans Plant Pathogenic Bacteria, 19–23. Dordrecht : Springer Netherlands, 2001. http://dx.doi.org/10.1007/978-94-010-0003-1_3.
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Skipp, R. A., et J. G. Hampton. « Fungal and Bacterial Diseases of Pasture Plants in New Zealand ». Dans ASA, CSSA, and SSSA Books, 213–36. Madison, WI, USA : American Society of Agronomy, Crop Science Society of America, Soil Science Society of America, 2015. http://dx.doi.org/10.2134/1996.pastureforagecroppathol.c11.
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Strittmatter, Günter, Koen Goethals et Marc Van Montagu. « Strategies to Engineer Plants Resistant to Bacterial and Fungal Diseases ». Dans Subcellular Biochemistry, 191–213. Boston, MA : Springer US, 1998. http://dx.doi.org/10.1007/978-1-4899-1707-2_6.
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Becker, J. O., R. W. Hedges et E. Messens. « Diverse Effects of Some Bacterial Siderophores on the Uptake of Iron by Plants ». Dans Iron, Siderophores, and Plant Diseases, 61–70. Boston, MA : Springer US, 1986. http://dx.doi.org/10.1007/978-1-4615-9480-2_8.
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Sofkova-Bobcheva, Svetla, Ivelin Pantchev, Ivan Kiryakov, Petar Chavdarov, Yordan Muhovski, Fatma Sarsu et Nasya Tomlekova. « Induced mutagenesis for improvement of bean (Phaseolus vulgaris L.) production in Bulgaria. » Dans Mutation breeding, genetic diversity and crop adaptation to climate change, 178–93. Wallingford : CABI, 2021. http://dx.doi.org/10.1079/9781789249095.0018.
Texte intégralRésumé :
Abstract Although historically a surplus food producer, Bulgarian agriculture has faced a downturn in recent decades. Local legume cultivars have lost favour with farmers and the canning industry, due to their low productivity in comparison with imported ones. Diseases and abiotic stresses are the most important factors limiting the production of edible legumes, costing farmers hundreds of euros in lost revenue each year. The overall objective of our ongoing bean mutation breeding programme was to enrich the gene pool of Phaseolus vulgaris L. and to develop genotypes resistant to Xanthomonas axonopodis pv. phaseoli (Smith) (Xap) and Pseudomonas savastanoi pv. phaseolicola (Burkh.) (Psp) using EMS. An elite line and common cultivar (an heirloom and a snap bean type) in Bulgaria, were selected as parents and the chemical mutagen EMS was used for generating mutations. In total, 1000 seeds were treated and the two generated M1 populations were grown in the field. All M2 mutant plants (1650 from initial line IP564 and 2420 from initial cultivar 'Mastilen 11b') were grown in field conditions and a number of phenotypic changes were observed on these mutated plants. They were also screened for Xap disease resistance via leaf artificial inoculation under greenhouse conditions. Individual plant selection was performed for the putatively resistant M2 plants. In the M3 generation these lines were screened using artificial inoculation with Xap and Psp pathogens (leaves and pods) under field conditions. Selected M3-M4 lines with confirmed disease resistance were tested for fresh pod quality. Yield tests were started in M4 and M5 generations and, according to their productivity performance, mutants were advanced to the M6/M7 generation for validation. The expression patterns of genes putatively involved in the resistance reactions towards two races of Psp were determined using qRT-PCR for the specific and reference genes. In conclusion, 50 plants with visible morphological changes and/or increased tolerance to the two targeted bacterial diseases were selected. A total of 20 advanced mutant bean lines are currently being evaluated for their competitiveness in multiple sites.
Actes de conférences sur le sujet "Bacterial, diseases, plants"
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Sidarenka, A. V., H. A. Bareika, L. N. Valentovich, D. S. Paturemski, V. N. Kuptsou, M. A. Titok et E. I. Kalamiyets. « Molecular diagnostics of bacterial and fungal plant diseases ». Dans 2nd International Scientific Conference "Plants and Microbes : the Future of Biotechnology". PLAMIC2020 Organizing committee, 2020. http://dx.doi.org/10.28983/plamic2020.229.
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Taxon-specific primers were developed and PCR conditions were optimized for diagnostics of bacterial and fungal plant pathogens. Methods for phytopathogens DNA isolation from plant material, soil and water were selected.
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Kumalasari, Yeni Indra, Agung Dian Kharisma et Sri Yuwantiningsih. « Potential of Karimunjawa Island’s Plants as Antibiotic-Producing Endophytic Bacteria Sources ». Dans The 2nd International Conference on Technology for Sustainable Development. Switzerland : Trans Tech Publications Ltd, 2022. http://dx.doi.org/10.4028/p-kv25ou.
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Endophytic bacteria have a great potential to be applied as biofertilizers and biopesticides, but their information as a source of antibiotics still needs to be developed and explored. The aim of this study was to investigate the potential sources of antibiotics in endophytic bacteria isolated from the stems of Setigi, Wahong, Bongko, Kalimosodo, Dewandaru, and Legundi plants on Karimunjawa Island. Molecular approaches were performed to isolate, characterize, and identify bacterial endophytes as potential antibiotic sources by plate assay and 16S rRNA gene sequence analysis. Dewandaru isolate was identified as gram-negative bacteria, whereas; gram-positive bacteria were detected in other isolates. Moreover, Setigi and Dewandaru isolates showed the highest level to inhibit the growth of Fusarium sp and displayed 99% similarity with antibiotic-producing bacteria, namely Bacillus pumilus and Bacillus cereus, respectively. These results indicate the possibility of antibiotic activities by Setigi and Dewandaru isolated. Therefore, it is assumed that both Setigi and Dewandaru isolates potentially appeared as new antibiotics sources from local plants. This study provides novel insight into the future production of novel antibiotics derived from plant-associated endophytic bacterial as a strategy for increasing the application of natural compounds to control plant diseases in agriculture.
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Trigubovich, A. M., F. A. Popov, A. A. Arashkova, I. G. Volchkevich et E. I. Kolomiyets. « Biopreparation "Vegetatin" for protection of cabbage from fungal and bacterial diseases during grows and storage ». Dans 2nd International Scientific Conference "Plants and Microbes : the Future of Biotechnology". PLAMIC2020 Organizing committee, 2020. http://dx.doi.org/10.28983/plamic2020.252.
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Effectiveness of usage biopreparation "Vegetatin" which is based on bacteria of the genus Bacillus to protect white cabbage from diseases was studied. Positive effect after treatments of seeds, seedlings and vegetative plants on the productivity and cabbage harvest has been established. Biological effectiveness of "Vegetatin" was at level of 48.9–53.6%, the stored yield –28.1 c/ha of cabbage heads. Processing of cabbage heads before storage reduced the damage of cabbage by mixed rots by an average of 30%.
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Arafath, Muhammad, A. Alice Nithya et Sanyam Gijwani. « Tomato Leaf Disease Detection Using Deep Convolution Neural Network ». Dans International Research Conference on IOT, Cloud and Data Science. Switzerland : Trans Tech Publications Ltd, 2023. http://dx.doi.org/10.4028/p-vph2n1.
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Plants are a major and important food source for the world's population. Smart and sustainable agriculture should be capable of providing precise and timely diagnosis of plant diseases. This helps in preventing financial and other resource loss to the farmers. Since plant diseases show visible symptoms which a plant pathologist will be able to diagnose through optical observations. But this process is slow and requires continuous monitoring as well as the availability and successful diagnostic capability of the pathologist. To overcome this, in smart agriculture, computer-aided plant disease diagnostic/detection model is used to help increased crop yield production. Common diseases are found in tomatoes, potatoes and pepper plants, some of them are bacterial spot, early blight etc. If a farmer can detect these diseases early, and can apply an appropriate treatment then it will improve crop yield and prevent the economic loss. In this work, we train the dataset on three different deep convolution neural network architecture and found the best suitable model to detect tomato leaf diseases. In order to avoid overfitting of the mode, batch normalization layer and a drop out layer has been included. The proposed Deep CNN is trained with various dropout values and a suitable dropout value is identified to regularize the model. The experimental methodology tested on plant village dataset showed improved accuracy of 96%, even without performing pre-processing steps like noise removal. By introducing batch normalization and dropout layer training accuracy improved to 99% whereas validation and testing accuracy is found to be 98%.
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Belyakova, N. V., E. A. Vorobyova et V. A. Sivolapov. « MOLECULAR-GENETIC ANALYSIS OF PHYTOPATHOGENS IN STANDS OF THE VORONEZH REGION ». Dans Modern machines, equipment and IT solutions for industrial complex : theory and practice. Voronezh State University of Forestry and Technologies named after G.F. Morozov, Voronezh, Russia, 2021. http://dx.doi.org/10.34220/mmeitsic2021_29-33.
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This paper presents the results of DNA diagnostics of phytopathogens in the Voronezh region. DNA diagnostics was carried out step by step: isolation of total DNA from the sample by CTAB method, amplification of marker regions of phytopathogenic organisms using primers ITS1 and ITS4, electrophoretic separation of the obtained amplicons in 2% agarose gel followed by staining with ethidium bromide, determination of the nucleotide sequence of the amplified loci ABI Prism 310. The study identified the following plant diseases: Sphaeropsis sapinea, Rhizoctonia solani, Cladosporium herbarum. Along with this, we identified the Neocatenulostroma pathogen, which had not previously been found in the territories under its jurisdiction. This disease cannot be determined by phenological signs. The degree of infection by pathogens ranged from 15 to 40%. At present, the problem of protecting plants from diseases is especially urgent. It has been established that the greatest damage to forestry activities is caused by fungal and infectious diseases. At the same time, among phytopathogens, about 97% are fungal infections, 2% are bacterial and 1% are viral.
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TOADER, Elena Violeta, George TOADER, Daniela TRIFAN, Emanuela LUNGU et Alin-Ionel GHIORGHE. « INNOVATIVE ECOLOGICAL TECHNOLOGIES FOR SOIL RESTORATION : BACTERIAL BIOPREPARATIONS ». Dans Competitiveness of Agro-Food and Environmental Economy. Editura ASE, 2022. http://dx.doi.org/10.24818/cafee/2021/10/09.
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The use of fertilizer products in agricultural crops is a beneficial source of supplementing the nutrients needed for the growth and development of both plants and an increase in agricultural production. However, often the fertilizer doses applied per hectare to agricultural crops are not respected. Failure to comply with the applied fertilizer doses will lead to the occurrence of negative phenomena for soil, environment and agricultural crops, implicitly for human and animal health. Increasing the fertilizer doses per hectare and not respecting them will lead to the occurrence of soil acidification. The decrease of the bacterial colonies in the soil will bring with it a decrease of the humification processes, of the decomposition and solubilization processes of the complex compounds in the soil as well as favoring the leaching and appearance of the complex compounds in the soil (in large quantities). The increase of complex compounds in the soil will lead to a decrease in pH (below pH 7), which will lead to an increase in soil acidity. On acidic soil, crops will not reach their maximum potential in productivity. The use of bacterial biopreparation technologies in agricultural crops plays an important role in plant protection. Some bacterial cultures give plants a protection against pedo-climatic stress, a resistance to the attack of diseases and pests as well as conferring a protection on environmental factors (drought, heavy rainfall, cold, etc.). The use of these bacterial products as fertilizers as well as plant protection products has been shown to have great potential in growing, developing, maximizing agricultural production, in restoring and greening the soil and its beneficial flora, the role of these biological fertilizers being to address a green, sustainable, sustainable agriculture and achieving high, healthy, nutrient-rich productivity, beneficial to human and animal health.
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Pilipchuk, T. A., L. N. Valentovich et E. I. Kalamiyets. « Genome characterization of Pseudomonas phages BIM BV-45 and BIM BV-46 – the components of biopesticide Multiphage to control bacterial diseases of vegetable crops ». Dans 2nd International Scientific Conference "Plants and Microbes : the Future of Biotechnology". PLAMIC2020 Organizing committee, 2020. http://dx.doi.org/10.28983/plamic2020.197.
Texte intégralRésumé :
The conducted investigation resulted in full nucleotide sequencing of Pseudomonas phage BIM BV-45 and Pseudomonas phage BIM BV-46 (registration numbers in GenBank NCBI MT094430 and MT094431) – components of biopesticide Multiphage.
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Gabechaya, V. V., I. V. Andreeva, I. I. Vasenev et A. A. Neaman. « The impact of copper-containing pesticides on ecological attributes and agricultural value of soils. The need for monitoring and assessment ». Dans CURRENT STATE, PROBLEMS AND PROSPECTS OF THE DEVELOPMENT OF AGRARIAN SCIENCE. Federal State Budget Scientific Institution “Research Institute of Agriculture of Crimea”, 2020. http://dx.doi.org/10.33952/2542-0720-2020-5-9-10-127-1.
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Copper-based pesticides have been used around the world for more than 200 years to control bacterial and fungal diseases in a variety of crops. In our review, we found that copper content from cupric fungicides in vineyard soil surface horizons often exceeds 200 mg/kg. However, there are few studies on copper content in vineyard soils in Russia. The fact of the matter is that soil microorganisms have greater metal sensitivity than plants. Therefore, the use of copper-based pesticides may damage microbial communities in vineyard soils and disrupt litter decomposition processes, thus leading to a long-term deterioration of ecological attributes and agricultural value of soils. It is this fact that makes the need for constant monitoring and assessment of the impact of copper-based pesticides on vineyard soils in Russia so paramount.
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Ivanova, E. S., et I. S. Barashkova. « THE EFFECTIVENESS OF PROTECTIVE MEASURES AGAINST TOMATO BACTERIAL WILT IN PROTECTED SOIL CONDITIONS ». Dans Agrobiotechnology-2021. Publishing house of RGAU - MSHA, 2021. http://dx.doi.org/10.26897/978-5-9675-1855-3-2021-64.
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The article presents the results of production experience on evaluating the effectiveness of chemical and biological protective measures against tomato bacterial wilt in protected soil. During the research, the influence of biological agents and pesticides on the diseased plants growth rate in greenhouses, the disease manifestation intensity, and crop yield was revealed.
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Maksimov, I. V., M. Yu Shein et R. M. Khairullin. « Endophytic bacteria and plant immunity ». Dans 2nd International Scientific Conference "Plants and Microbes : the Future of Biotechnology". PLAMIC2020 Organizing committee, 2020. http://dx.doi.org/10.28983/plamic2020.160.
Texte intégralRésumé :
Diseases annually cause significant crop losses and reduced quality of agricultural products. The development strategy of new environmentally friendly plant protection products should consider the role of the microbiome in host defense.
Rapports d'organisations sur le sujet "Bacterial, diseases, plants"
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Hoitink, Harry A. J., Yitzhak Hadar, Laurence V. Madden et Yona Chen. Sustained Suppression of Pythium Diseases : Interactions between Compost Maturity and Nutritional Requirements of Biocontrol Agents. United States Department of Agriculture, juin 1993. http://dx.doi.org/10.32747/1993.7568755.bard.
Texte intégralRésumé :
Several procedures were developed that predict maturity (stability) of composts prepared from municipal solid wastes (MSW). A respirometry procedure, based O2 uptake by compost, predicted (R2=0.90) the growth response of ryegrass in composts and an acceptable level of maturity. Spectroscopic methods (CPMAS13-NMR and DRIFT spectroscopy) showed that the stabilizing compost contained increasing levels of aromatic structures. All procedures predicted acceptable plant growth after approximately 110 days of composting. MSW compost suppressed diseases caused by a broad spectrum of plant pathogens including Rhizoctonia solani, Pythium aphanidermatum and Fusarium oxysporum. A strain of Pantoea agglomerans was identified that caused lysis of hyphae of R. solani. Evidence was obtained, suggesting that thermophilic biocontrol agents also might play a role in suppression. 13C-NMR spectra revealed that the longevity of the suppressive effect against Pythium root rot was determined by the concentration of readily biodegradable carbohydrate in the substrate, mostly present as cellulose. Bacterial species capable of inducing biocontrol were replaced by those not effective as suppression was lost. The rate of uptake of 14C-acetate into microbial biomass in the conducive substrate was not significantly different from that in the suppressive substrate although specific activity was higher. The suppressive composts induced systemic acquired resistance in cucumjber roots to Pythium root rot and to anthracnose in the foliage. Composts also increased peroxidase activity in plants by the conducive substrate did not have these effects. In summary, the composition of the organic fraction determined bacterial species composition and activity in the substrate, which in turn regulated plant gene expression relative to biological control.
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Hoitink, Harry A. J., Yitzhak Hadar, Laurence V. Madden et Yona Chen. Sustained Suppression of Pythium Diseases : Interactions between Compost Maturity and Nutritional Requirements of Biocontrol Agents. United States Department of Agriculture, juin 1993. http://dx.doi.org/10.32747/1993.7568746.bard.
Texte intégralRésumé :
Several procedures were developed that predict maturity (stability) of composts prepared from municipal solid wastes (MSW). A respirometry procedure, based O2 uptake by compost, predicted (R2=0.90) the growth response of ryegrass in composts and an acceptable level of maturity. Spectroscopic methods (CPMAS13-NMR and DRIFT spectroscopy) showed that the stabilizing compost contained increasing levels of aromatic structures. All procedures predicted acceptable plant growth after approximately 110 days of composting. MSW compost suppressed diseases caused by a broad spectrum of plant pathogens including Rhizoctonia solani, Pythium aphanidermatum and Fusarium oxysporum. A strain of Pantoea agglomerans was identified that caused lysis of hyphae of R. solani. Evidence was obtained, suggesting that thermophilic biocontrol agents also might play a role in suppression. 13C-NMR spectra revealed that the longevity of the suppressive effect against Pythium root rot was determined by the concentration of readily biodegradable carbohydrate in the substrate, mostly present as cellulose. Bacterial species capable of inducing biocontrol were replaced by those not effective as suppression was lost. The rate of uptake of 14C-acetate into microbial biomass in the conducive substrate was not significantly different from that in the suppressive substrate although specific activity was higher. The suppressive composts induced systemic acquired resistance in cucumjber roots to Pythium root rot and to anthracnose in the foliage. Composts also increased peroxidase activity in plants by the conducive substrate did not have these effects. In summary, the composition of the organic fraction determined bacterial species composition and activity in the substrate, which in turn regulated plant gene expression relative to biological control.
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Sessa, Guido, et Gregory Martin. MAP kinase cascades activated by SlMAPKKKε and their involvement in tomato resistance to bacterial pathogens. United States Department of Agriculture, janvier 2012. http://dx.doi.org/10.32747/2012.7699834.bard.
Texte intégralRésumé :
The research problem: Pseudomonas syringae pv. tomato (Pst) and Xanthomonas campestrispv. vesicatoria (Xcv) are the causal agents of tomato bacterial speck and spot diseases, respectively. These pathogens colonize the aerial parts of the plant and cause economically important losses to tomato yield worldwide. Control of speck and spot diseases by cultural practices or chemicals is not effective and genetic sources of resistance are very limited. In previous research supported by BARD, by gene expression profiling we identified signaling components involved in resistance to Xcvstrains. Follow up experiments revealed that a tomato gene encoding a MAP kinase kinase kinase (MAPKKKe) is required for resistance to Xcvand Pststrains. Goals: Central goal of this research was to investigate the molecular mechanisms by which MAPKKKεand associated MAP kinase cascades regulate host resistance. Specific objectives were to: 1. Determine whether MAPKKKεplays a broad role in defense signaling in plants; 2. Identify components of MAP kinase cascades acting downstream of MAPKKKε; 3. Determine the role of phosphorylation-related events in the function of MAPKKKε; 4. Isolate proteins directly activated by MAPKKKε-associatedMAPK modules. Our main achievements during this research program are in the following major areas: 1. Characterization of MAPKKKεas a positive regulator of cell death and dissection of downstream MAP kinase cascades (Melech-Bonfil et al., 2010; Melech-Bonfil and Sessa, 2011). The MAPKKKεgene was found to be required for tomato resistance to Xcvand Pstbacterial strains and for hypersensitive response cell death triggered by different R gene/effector gene pairs. In addition, overexpression analysis demonstrated that MAPKKKεis a positive regulator of cell death, whose activity depends on an intact kinase catalytic domain. Epistatic experiments delineated a signaling cascade downstream of MAPKKKεand identified SIPKK as a negative regulator of MAPKKKε-mediated cell death. Finally, genes encoding MAP kinase components downstream of MAPKKKεwere shown to contribute to tomato resistance to Xcv. 2. Identification of tomato proteins that interact with MAPKKKεand play a role in plant immunity (Oh et al., 2011). We identified proteins that interact with MAPKKKε. Among them, the 14-3-3 protein TFT7 was required for cell death mediated by several R proteins. In addition, TFT7 interacted with the MAPKK SlMKK2 and formed homodimersin vivo. Thus, TFT7 is proposed to recruit SlMKK2 and MAPKKK client proteins for efficient signal transfer. 3. Development of a chemical genetic approach to identify substrates of MAPKKKε-activated MAP kinase cascades (Salomon et al., 2009, 2011). This approach is based on engineering the kinase of interest to accept unnatural ATP analogs. For its implementation to identify substrates of MAPKKKε-activated MAP kinase modules, we sensitized the tomato MAP kinase SlMPK3 to ATP analogs and verified its ability to use them as phosphodonors. By using the sensitized SlMPK3 and radiolabeled N6(benzyl)ATP it should be possible to tag direct substrates of this kinase. 4. Development of methods to study immunity triggered by pathogen-associated molecular patterns (PAMPs) in tomato and N. benthamiana plants (Kim et al., 2009; Nguyen et al. 2010). We developed protocols for measuring various PTI-associatedphenotypes, including bacterial populations after pretreatment of leaves with PAMPs, induction of reporter genes, callose deposition at the cell wall, activation of MAP kinases, and a luciferase-based reporter system for use in protoplasts. Scientific and agricultural significance: Our research activities discovered and characterized a signal transduction pathway mediating plant immunity to bacterial pathogens. Increased understanding of molecular mechanisms of immunity will allow them to be manipulated by both molecular breeding and genetic engineering to produce plants with enhanced natural defense against disease. In addition, we successfully developed new biochemical and molecular methods that can be implemented in the study of plant immunity and other aspects of plant biology.
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Sessa, Guido, et Gregory Martin. Role of GRAS Transcription Factors in Tomato Disease Resistance and Basal Defense. United States Department of Agriculture, 2005. http://dx.doi.org/10.32747/2005.7696520.bard.
Texte intégralRésumé :
The research problem: Bacterial spot and bacterial speck diseases of tomato are causedby strains of Xanthomonas campestris pv. vesicatoria (Xcv) and Pseudomonas syringae pv.tomato (Pst), respectively. These bacteria colonize aerial parts of the plant and causesignificant losses in tomato production worldwide. Protection against Xcv and Pst bycultural practices or chemical control has been unsuccessful and there are only limitedsources of genetic resistance to these pathogens. In previous research supported in part byBARD IS-3237-01, we extensively characterized changes in tomato gene expression uponthe onset of spot and speck disease resistance. A remarkable finding of these studies wasthe inducibility in tomato leaves by both Xcv and Pst strains of genes encodingtranscriptional activator of the GRAS family, which has not been previously linked todisease resistance. Goals: Central goals of this research were to investigate the role of GRAS genes in tomatoinnate immunity and to assess their potential use for disease control.Specific objectives were to: 1. Identify GRAS genes that are induced in tomato during thedefense response and analyze their role in disease resistance by loss-of-function experiments.2. Overexpress GRAS genes in tomato and characterize plants for possible broad-spectrumresistance. 3. Identify genes whose transcription is regulated by GRAS family. Our main achievements during this research program are in three major areas:1. Identification of tomato GRAS family members induced in defense responses andanalysis of their role in disease resistance. Genes encoding tomato GRAS family memberswere retrieved from databases and analyzed for their inducibility by Pst avirulent bacteria.Real-time RT-PCR analysis revealed that six SlGRAS transcripts are induced during theonset of disease resistance to Pst. Further expression analysis of two selected GRAS genesshowed that they accumulate in tomato plants in response to different avirulent bacteria orto the fungal elicitor EIX. In addition, eight SlGRAS genes, including the Pst-induciblefamily members, were induced by mechanical stress in part in a jasmonic acid-dependentmanner. Remarkably, SlGRAS6 gene was found to be required for tomato resistance to Pstin virus-induced gene silencing (VIGS) experiments.2. Molecular analysis of pathogen-induced GRAS transcriptional activators. In aheterologous yeast system, Pst-inducible GRAS genes were shown to have the ability toactivate transcription in agreement with their putative function of transcription factors. Inaddition, deletion analysis demonstrated that short sequences at the amino-terminus ofSlGRAS2, SlGRAS4 and SlGRAS6 are sufficient for transcriptional activation. Finally,defense-related SlGRAS proteins were found to localize to the cell nucleus. 3. Disease resistance and expression profiles of transgenic plants overexpressing SlGRASgenes. Transgenic plants overexpressing SlGRAS3 or SlGRAS6 were generated. Diseasesusceptibility tests revealed that these plants are not more resistant to Pst than wild-typeplants. Gene expression profiles of the overexpressing plants identified putative direct orindirect target genes regulated by SlGRAS3 and SlGRAS6. Scientific and agricultural significance: Our research activities established a novel linkbetween the GRAS family of transcription factors, plant disease resistance and mechanicalstress response. SlGRAS6 was found to be required for disease resistance to Pstsuggesting that this and possibly other GRAS family members are involved in thetranscriptional reprogramming that takes place during the onset of disease resistance.Their nuclear localization and transcriptional activation ability support their proposed roleas transcription factors or co-activators. However, the potential of utilizing GRAS familymembers for the improvement of plant disease resistance in agriculture has yet to bedemonstrated.
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Lindow, Steven, Isaac Barash et Shulamit Manulis. Relationship of Genes Conferring Epiphytic Fitness and Internal Multiplication in Plants in Erwinia herbicola. United States Department of Agriculture, juillet 2000. http://dx.doi.org/10.32747/2000.7573065.bard.
Texte intégralRésumé :
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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Coplin, David, Isaac Barash et Shulamit Manulis. Role of Proteins Secreted by the Hrp-Pathways of Erwinia stewartii and E. herbicola pv. gypsophilae in Eliciting Water-Soaking Symptoms and Initiating Galls. United States Department of Agriculture, juin 2001. http://dx.doi.org/10.32747/2001.7580675.bard.
Texte intégralRésumé :
Many bacterial pathogens of plants can inject pathogenicity proteins into host cells using a specialized type III secretion system encoded by hrpgenes. This system deliver effector proteins, into plant cells that function in both susceptible and resistant interactions. We have found that the virulence of Erwinia stewartii(Es; syn. Pantoea stewartii) and Erwinia herbicola pv. gypsophilae (Ehg, syn. Pantoea agglomerans), which cause Stewart's wilt of corn and galls on Gypsophila, respectively, depends on hrpgenes. The major objectives of this project were: To increase expression of hrpgenes in order to identify secreted proteins; to identify genes for proteins secreted by the type-III systems and determine if they are required for pathogenicity; and to determine if the secreted proteins can function within eukaryotic cells. We found that transcription of the hrp and effector genes in Es and Ehg is controlled by at least four genes that constitute a regulatory cascade. Environmental and/or physiological signaling appears to be mediated by the HrpX/HrpY two component system, with HrpX functioning as a sensor-kinase and HrpY as a response regulator. HrpYupregulateshrpS, which encodes a transcriptional enhancer. HrpS then activates hrpL, which encodes an alternate sigma factor that recognizes "hrp boxes". All of the regulatory genes are essential for pathogenicity, except HrpX, which appears only to be required for induction of the HR in tobacco by Es. In elucidating this regulatory pathway in both species, we made a number of significant new discoveries. HrpX is unusual for a sensor-kinase because it is cytoplasmic and contains PAS domains, which may sense the redox state of the bacterium. In Es, a novel methyl-accepting protein may function upstream of hrpY and repress hrp gene expression in planta. The esaIR quorum sensing system in Es represses hrp gene expression in Es in response to cell-density. We have discovered six new type III effector proteins in these species, one of which (DspE in Ehg and WtsE in Es) is common to both pathogens. In addition, Es wtsG, which is a homolog of an avrPpiB from P. syringae pv. pisi, and an Ehg ORF, which is a homolog of P. syringae pv. phaseolicola AvrPphD, were both demonstrated to encode virulence proteins. Two plasmidborne, Ehg Hop proteins, HsvG and PthG, are required for infection of gypsophilia, but interestingly, PthG also acts as an Avr elicitor in beets. Using a calmodulin-dependent adenylate cyclase (cyaA) reporter gene, we were successful in demonstrating that an HsvG-CyaA fusion protein can be transferred into human HeLa cells by the type-III system of enteropathogenic E. coli. This is a highly significant accomplishment because it is the first direct demonstration that an effector protein from a plant pathogenic bacterium is capable of being translocated into a eukaryotic cell by a type-III secretion system. Ehg is considered a limiting factor in Gypsophila production in Israel and Stewart’s Wilt is a serious disease in the Eastern and North Central USA, especially on sweet corn in epidemic years. We believe that our basic research on the characterization of type III virulence effectors should enable future identification of their receptors in plant cells. This may lead to novel approaches for genetically engineering resistant plants by modifying their receptors or inactivating effectors and thus blocking the induction of the susceptible response. Alternatively, hrp gene regulation might also provide a target for plant produced compounds that interfere with recognition of the host by the pathogen. Such strategies would be broadly applicable to a wide range of serious bacterial diseases on many crops throughout the USA and Israel.
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Sessa, Guido, et Gregory Martin. A functional genomics approach to dissect resistance of tomato to bacterial spot disease. United States Department of Agriculture, janvier 2004. http://dx.doi.org/10.32747/2004.7695876.bard.
Texte intégralRésumé :
The research problem. Bacterial spot disease in tomato is of great economic importance worldwide and it is particularly severe in warm and moist areas affecting yield and quality of tomato fruits. Causal agent of spot disease is the Gram-negative bacterium Xanthomonas campestris pv. vesicatoria (Xcv), which can be a contaminant on tomato seeds, or survive in plant debris and in association with certain weeds. Despite the economic significance of spot disease, plant protection against Xcvby cultural practices and chemical control have so far proven unsuccessful. In addition, breeding for resistance to bacterial spot in tomato has been undermined by the genetic complexity of the available sources of resistance and by the multiple races of the pathogen. Genetic resistance to specific Xcvraces have been identified in tomato lines that develop a hypersensitive response and additional defense responses upon bacterial challenge. Central goals of this research were: 1. To identify plant genes involved in signaling and defense responses that result in the onset of resistance. 2. To characterize molecular properties and mode of action of bacterial proteins, which function as avirulence or virulence factors during the interaction between Xcvand resistant or susceptible tomato plants, respectively. Our main achievements during this research program are in three major areas: 1. Identification of differentially expressed genes during the resistance response of tomato to Xcvrace T3. A combination of suppression subtractive hybridization and microarray analysis identified a large set of tomato genes that are induced or repressed during the response of resistant plants to avirulent XcvT3 bacteria. These genes were grouped in clusters based on coordinate expression kinetics, and classified into over 20 functional classes. Among them we identified genes that are directly modulated by expression of the type III effector protein AvrXv3 and genes that are induced also during the tomato resistance response to Pseudomonas syringae pv. tomato. 2. Characterization of molecular and biochemical properties of the tomato LeMPK3MAP kinase. A detailed molecular and biochemical analysis was performed for LeMPK3 MAP kinase, which was among the genes induced by XcvT3 in resistant tomato plants. LeMPK3 was induced at the mRNA level by different pathogens, elicitors, and wounding, but not by defense-related plant hormones. Moreover, an induction of LeMPK3 kinase activity was observed in resistant tomato plants upon Xcvinfection. LeMPK3 was biochemically defined as a dual-specificity MAP kinase, and extensively characterized in vitro in terms of kinase activity, sites and mechanism of autophosphorylation, divalent cation preference, Kₘand Vₘₐₓ values for ATP. 3. Characteriztion of molecular properties of the Xcveffector protein AvrRxv. The avirulence gene avrRxvis involved in the genetic interaction that determines tomato resistance to Xcvrace T1. We found that AvrRxv functions inside the plant cell, localizes to the cytoplasm, and is sufficient to confer avirulence to virulent Xcvstrains. In addition, we showed that the AvrRxv cysteine protease catalytic core is essential for host recognition. Finally, insights into cellular processes activated by AvrRxv expression in resistant plants were obtained by microarray analysis of 8,600 tomato genes. Scientific and agricultural significance: The findings of these activities depict a comprehensive and detailed picture of cellular processes taking place during the onset of tomato resistance to Xcv. In this research, a large pool of genes, which may be involved in the control and execution of plant defense responses, was identified and the stage is set for the dissection of signaling pathways specifically triggered by Xcv.
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Coplin, David L., Shulamit Manulis et Isaac Barash. roles Hrp-dependent effector proteins and hrp gene regulation as determinants of virulence and host-specificity in Erwinia stewartii and E. herbicola pvs. gypsophilae and betae. United States Department of Agriculture, juin 2005. http://dx.doi.org/10.32747/2005.7587216.bard.
Texte intégralRésumé :
Gram-negative plant pathogenic bacteria employ specialized type-III secretion systems (TTSS) to deliver an arsenal of pathogenicity proteins directly into host cells. These secretion systems are encoded by hrp genes (for hypersensitive response and pathogenicity) and the effector proteins by so-called dsp or avr genes. The functions of effectors are to enable bacterial multiplication by damaging host cells and/or by blocking host defenses. We characterized essential hrp gene clusters in the Stewart's Wilt of maize pathogen, Pantoea stewartii subsp. stewartii (Pnss; formerly Erwinia stewartii) and the gall-forming bacterium, Pantoea agglomerans (formerly Erwinia herbicola) pvs. gypsophilae (Pag) and betae (Pab). We proposed that the virulence and host specificity of these pathogens is a function of a) the perception of specific host signals resulting in bacterial hrp gene expression and b) the action of specialized signal proteins (i.e. Hrp effectors) delivered into the plant cell. The specific objectives of the proposal were: 1) How is the expression of the hrp and effector genes regulated in response to host cell contact and the apoplastic environment? 2) What additional effector proteins are involved in pathogenicity? 3) Do the presently known Pantoea effector proteins enter host cells? 4) What host proteins interact with these effectors? We characterized the components of the hrp regulatory cascade (HrpXY ->7 HrpS ->7 HrpL ->7 hrp promoters), showed that they are conserved in both Pnss and Fag, and discovered that the regulation of the hrpS promoter (hrpSp) may be a key point in integrating apoplastic signals. We also analyzed the promoters recognized by HrpL and demonstrated the relationship between their composition and efficiency. Moreover, we showed that promoter strength can influence disease expression. In Pnss, we found that the HrpXY two-component signal system may sense the metabolic status of the bacterium and is required for full hrp gene expression in planta. In both species, acyl-homoserine lactone-mediated quorum sensing may also regulate epiphytic fitness and/or pathogenicity. A common Hrp effector protein, DspE/WtsE, is conserved and required for virulence of both species. When introduced into corn cells, Pnss WtsE protein caused water-soaked lesions. In other plants, it either caused cell death or acted as an Avr determinant. Using a yeast- two-hybrid system, WtsE was shown to interact with a number of maize signal transduction proteins that are likely to have roles in either programmed cell death or disease resistance. In Pag and Pab, we have characterized the effector proteins HsvG, HsvB and PthG. HsvG and HsvB are homologous proteins that determine host specificity of Pag and Pab on gypsophila and beet, respectively. Both possess a transcriptional activation domain that functions in yeast. PthG was found to act as an Avr determinant on multiple beet species, but was required for virulence on gypsophila. In addition, we demonstrated that PthG acts within the host cell. Additional effector genes have been characterized on the pathogenicity plasmid, pPATHₚₐg, in Pag. A screen for HrpL- regulated genes in Pnsspointed up 18 candidate effector proteins and four of these were required for full virulence. It is now well established that the virulence of Gram-negative plant pathogenic bacteria is governed by Hrp-dependent effector proteins. However; the mode of action of many effectors is still unresolved. This BARD supported research will significantly contribute to the understanding of how Hrp effectors operate in Pantoea spp. and how they control host specificity and affect symptom production. This may lead to novel approaches for genetically engineering plants resistant to a wide range of bacterial pathogens by inactivating the Hrp effectors with "plantabodies" or modifying their receptors, thereby blocking the induction of the susceptible response. Alternatively, innovative technologies could be used to interfere with the Hrp regulatory cascade by blocking a critical step or mimicking plant or quorum sensing signals.
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Alfano, James, Isaac Barash, Thomas Clemente, Paul E. Staswick, Guido Sessa et Shulamit Manulis. Elucidating the Functions of Type III Effectors from Necrogenic and Tumorigenic Bacterial Pathogens. United States Department of Agriculture, janvier 2010. http://dx.doi.org/10.32747/2010.7592638.bard.
Texte intégralRésumé :
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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Ron, Eliora, et Eugene Eugene Nester. Global functional genomics of plant cell transformation by agrobacterium. United States Department of Agriculture, mars 2009. http://dx.doi.org/10.32747/2009.7695860.bard.
Texte intégralRésumé :
The aim of this study was to carry out a global functional genomics analysis of plant cell transformation by Agrobacterium in order to define and characterize the physiology of Agrobacterium in the acidic environment of a wounded plant. We planed to study the proteome and transcriptome of Agrobacterium in response to a change in pH, from 7.2 to 5.5 and identify genes and circuits directly involved in this change. Bacteria-plant interactions involve a large number of global regulatory systems, which are essential for protection against new stressful conditions. The interaction of bacteria with their hosts has been previously studied by genetic-physiological methods. We wanted to make use of the new capabilities to study these interactions on a global scale, using transcription analysis (transcriptomics, microarrays) and proteomics (2D gel electrophoresis and mass spectrometry). The results provided extensive data on the functional genomics under conditions that partially mimic plant infection and – in addition - revealed some surprising and significant data. Thus, we identified the genes whose expression is modulated when Agrobacterium is grown under the acidic conditions found in the rhizosphere (pH 5.5), an essential environmental factor in Agrobacterium – plant interactions essential for induction of the virulence program by plant signal molecules. Among the 45 genes whose expression was significantly elevated, of special interest is the two-component chromosomally encoded system, ChvG/I which is involved in regulating acid inducible genes. A second exciting system under acid and ChvG/Icontrol is a secretion system for proteins, T6SS, encoded by 14 genes which appears to be important for Rhizobium leguminosarum nodule formation and nitrogen fixation and for virulence of Agrobacterium. The proteome analysis revealed that gamma aminobutyric acid (GABA), a metabolite secreted by wounded plants, induces the synthesis of an Agrobacterium lactonase which degrades the quorum sensing signal, N-acyl homoserine lactone (AHL), resulting in attenuation of virulence. In addition, through a transcriptomic analysis of Agrobacterium growing at the pH of the rhizosphere (pH=5.5), we demonstrated that salicylic acid (SA) a well-studied plant signal molecule important in plant defense, attenuates Agrobacterium virulence in two distinct ways - by down regulating the synthesis of the virulence (vir) genes required for the processing and transfer of the T-DNA and by inducing the same lactonase, which in turn degrades the AHL. Thus, GABA and SA with different molecular structures, induce the expression of these same genes. The identification of genes whose expression is modulated by conditions that mimic plant infection, as well as the identification of regulatory molecules that help control the early stages of infection, advance our understanding of this complex bacterial-plant interaction and has immediate potential applications to modify it. We expect that the data generated by our research will be used to develop novel strategies for the control of crown gall disease. Moreover, these results will also provide the basis for future biotechnological approaches that will use genetic manipulations to improve bacterial-plant interactions, leading to more efficient DNA transfer to recalcitrant plants and robust symbiosis. These advances will, in turn, contribute to plant protection by introducing genes for resistance against other bacteria, pests and environmental stress.