Relevant bibliographies by topics / PLANT-VIRUS-DISEASES

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  1. Journal articles
  2. Dissertations / Theses
  3. Books
  4. Book chapters
  5. Conference papers
  6. Reports

Academic literature on the topic 'PLANT-VIRUS-DISEASES'

Author: Grafiati
Published: 9 March 2023

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Journal articles on the topic "PLANT-VIRUS-DISEASES"

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Nejidat, Ali, W. Gregg Clark, and Roger N. Beachy. "Engineered resistance against plant virus diseases." Physiologia Plantarum 80, no. 4 (December 1990): 662–68. http://dx.doi.org/10.1111/j.1399-3054.1990.tb05694.x.

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Nejidat, Ali, W. Gregg Clark, and Roger N. Beachy. "Engineered resistance against plant virus diseases." Physiologia Plantarum 80, no. 4 (December 1990): 662–68. http://dx.doi.org/10.1034/j.1399-3054.1990.800426.x.

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Komatsu, Ken. "Strategies to control plant virus diseases using plant activators." Japanese Journal of Pesticide Science 46, no. 2 (August 20, 2021): 117–21. http://dx.doi.org/10.1584/jpestics.w21-41.

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TSUCHIZAKI, Tsuneo. "Advances in Research of Plant Virus Diseases." Japanese Journal of Phytopathology 59, no. 3 (1993): 227–29. http://dx.doi.org/10.3186/jjphytopath.59.227.

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Van Regenmortel, M. H. V., E. L. Dekker, I. Dore, C. Porta, E. Weiss, and J. Burckard. "RECENT ADVANCES IN SERODIAGNOSIS OF PLANT VIRUS DISEASES." Acta Horticulturae, no. 234 (December 1988): 175–84. http://dx.doi.org/10.17660/actahortic.1988.234.20.

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Thottappilly, G. "Plant Virus Diseases of Importance to African Agriculture." Journal of Phytopathology 134, no. 4 (April 1992): 265–88. http://dx.doi.org/10.1111/j.1439-0434.1992.tb01236.x.

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Hull, Roger, and Jeffrey W. Davies. "Approaches to nonconventional control of plant virus diseases." Critical Reviews in Plant Sciences 11, no. 1 (January 1992): 17–33. http://dx.doi.org/10.1080/07352689209382328.

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Akhter, M. S., A. M. Akanda, K. Kobayashi, R. K. Jain, and Bikash Mandal. "Plant virus diseases and their management in Bangladesh." Crop Protection 118 (April 2019): 57–65. http://dx.doi.org/10.1016/j.cropro.2018.11.023.

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Walkey, D. G. A., A. A. Alhubaishi, and M. J. W. Webb. "Plant virus diseases in the Yemen Arab republic." Tropical Pest Management 36, no. 3 (January 1990): 195–206. http://dx.doi.org/10.1080/09670879009371471.

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Zaitlin, Milton, and Peter Palukaitis. "Advances in Understanding Plant Viruses and Virus Diseases." Annual Review of Phytopathology 38, no. 1 (September 2000): 117–43. http://dx.doi.org/10.1146/annurev.phyto.38.1.117.

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Dissertations / Theses on the topic "PLANT-VIRUS-DISEASES"

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Brown, J. K., D. Goldstein, and M. R. Nelson. "Plant Virus Diseases that Threaten Cucurbit Production in Arizona." College of Agriculture, University of Arizona (Tucson, AZ), 1986. http://hdl.handle.net/10150/214137.

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A number of plant viruses were isolated from diseased cucurbits in Arizona during 1982 -85. Watermelon mosiac virus 2, cucumber mosaic virus, and squash mosaic virus are previously recognized viral pathogens in Arizona and in most years are not considered economically threatening to cucurbit production. Three newly described plant viruses (lettuce infectious yellows, watermelon curly mottle and zucchini yellow mosaic) however, have the potential to, or already have, incited serious epidemics in Arizona. Losses are heaviest with these diseases when insect vector levels build up early in the growing season and plants become infected during critical developmental stages.
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Jeffries, Alex Craig. "The study at the molecular level of the New Zealand isolate of Lucerne transient streak sobemovirus and its satellite RNA." Title page, contents and summary only, 1993. http://web4.library.adelaide.edu.au/theses/09PH/09phj47.pdf.

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Király, Lóránt. "Interactions between cauliflower mosaic virus isolates and nicotiana species that determine systemic necrosis /." free to MU campus, to others for purchase, 1997. http://wwwlib.umi.com/cr/mo/fullcit?p9841160.

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Cole, Anthony Blaine Thomas. "Investigations into the hypersensitive response of Nicotiana species to virus infections /." free to MU campus, to others for purchase, 2001. http://wwwlib.umi.com/cr/mo/fullcit?p3012960.

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Balcı, Evrim Doğanlar Sami. "Genetic characterization of cucumber mosaic virus(CMV)resistance in tomato and pepper." [s.l.]: [s.n.], 2005. http://library.iyte.edu.tr/tezler/master/biyoloji/T000388.pdf.

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Yu, Weichang. "CAMV gene VI protein : a virulence factor and the host responses in Arabidopsis /." free to MU campus, to others for purchase, 2002. http://wwwlib.umi.com/cr/mo/fullcit?p3075411.

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Torok, Valeria Anna. "Biological and molecular variation among isolates of pea seed borne mosaic virus." Title page, contents and abstract only, 2001. http://web4.library.adelaide.edu.au/theses/09PH/09pht686.pdf.

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Corrigendum inserted at the back. Includes bibliographical references (leaves 133-158). Ch. 1. General introduction -- ch. 2. General materials and methods -- ch. 3. Biological characterisation of Australian PSbMV isolates -- ch. 4. Developing nucleic acid based diagnostics for PSbMV -- ch. 5. Detection of PSbMV isolates by RT-PCR and RFLP analysis -- ch. 6. Developing an internal control for PSbMV RT-PCR -- ch. 7. Molecular analysis of the PSbMV VPG -- ch. 8. PSbMV sequence and phylogenetic analysis -- ch. 9. General discussion Sixteen pea seed borne mosaic virus (PSbMV) isolates were collected between 1995 and 1998. These isolates were biologically distinct yet serologically indistinguishable. The conclusion is that PSbMV is widespread and occurs at a low incidence in Australia. Reports sequence information on new isolates of PSbMV which has allowed genomic regions to be identified which distinguish PSbMV pathotypes and isolates; and, to the development of PSbMV nucleic acid hybridisation and RT-PCR assays.
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PANNO, Stefano. "IDENTIFICATION OF THE MAIN DESTRUCTIVE PLANT-VIRUS-DISEASES OF HORTICULTURAL CROPS IN SICILY AND DEVELOPMENT OF NEW DIAGNOSTIC TECHNIQUES." Doctoral thesis, Università degli Studi di Palermo, 2014. http://hdl.handle.net/10447/91005.

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Chauhan, Ramola. "A study of filamentous viruses in maize and smallgrains." Master's thesis, University of Cape Town, 1985. http://hdl.handle.net/11427/22013.

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Bibliography: pages 175-184.
The occurrence of maize dwarf mosaic virus (MDMV) in field grown maize was investigated. For this purpose, maize showing mosiac symptoms was collected from different maize growing areas in South Africa by Prof. M.B. von Wechmar. These samples from Transvaal, Orange Free State and Natal were then investigated for the presence of MDMV and possible strains of this virus. Three virus isolates were purified and partially characterised. These isolates were serologically compared together with a fourth isolate SCMV 4975, obtained from the U.S., to establish strain relationships.
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Rechcigl, Nancy A. "Ultrastructural cytology of peanut infected with peanut stripe virus." Thesis, Virginia Polytechnic Institute and State University, 1986. http://hdl.handle.net/10919/91063.

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Two isolates of peanut stripe virus (PStV), stripe and blotch, were compared ultrastructurally in peanut (Arachis hypogaea L. 'Florigiant') at several stages of leaf expansion. Ultrathin sections of young leaves infected with either isolate of PStV revealed pinwheel inclusions attached to the cell wall near plasmodesmata. The cytoplasm of infected cells were highly vesiculated. Virus particles amassed in crystalline arrays were observed in blotch infected cells. Virus particles were observed along the arms of pinwheel inclusions. Scroll inclusions appeared in PStV infected cells at a later stage of leaf expansion. In more mature leaves, pinwheel and scroll inclusions occurred in the cytoplasm in association with mitochondria. Virus particles were observed free in the cytoplasm as well as concentrated in linear arrays along the inner surface of the tonoplast. Membrane and organelle degradation was evident in cells infected with either isolate of the virus. Numerous cytoplasmic inclusions and virus particles were observed in cells from light green areas of the leaf. Cells from dark green areas did not contain cytoplasmic inclusions and contained few if any virus particles. Particle measurements show stripe and blotch isolates to have a mean length of 753 nm and 747 nm for leaf dip preparations and 746 nm and 745 nm for partially purified preparations, respectively. Both isolates had a modal length of 750 nm, regardless of the extraction procedure. The relative virus titer of each isolate was determined in peanut leaves at five stages of leaf expansion and in dark green and light green areas of infected leaves. Virus titer increased significantly from the closed to the fully expanded stage, at which time the virus titer peaked and then decreased slightly. Virus titer was consistently higher in leaves infected with the blotch isolate at all expansion stages. Virus titer was also higher in cells from light green areas of the leaf than from dark green areas of the leaf, regardless of isolate.
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Books on the topic "PLANT-VIRUS-DISEASES"

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Matthews, R. E. F. 1921-, ed. Diagnosis of plant virus diseases. Boca Raton: CRC Press, 1993.

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Sastry, K. Subramanya. Seed-borne plant virus diseases. India: Springer India, 2013. http://dx.doi.org/10.1007/978-81-322-0813-6.

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Sastry, K. Subramanya. Plant Virus and Viroid Diseases in the Tropics. Dordrecht: Springer Netherlands, 2013. http://dx.doi.org/10.1007/978-94-007-6524-5.

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Sastry, K. Subramanya, and Thomas A. Zitter. Plant Virus and Viroid Diseases in the Tropics. Dordrecht: Springer Netherlands, 2014. http://dx.doi.org/10.1007/978-94-007-7820-7.

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Walkey, David G. A. Plant virus diseases of Yemen and associated areas. London: Overseas Development Administration, 1992.

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Plant virology. 3rd ed. San Diego: Academic Press, 1991.

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Matthews, R. E. F. Plant virology. San Diego: Academic Press, 1991.

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F, Harris Kerry, Smith Oney P. 1954-, and Duffus James E, eds. Virus-insect-plant interactions. San Diego, Calif: Academic, 2001.

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Breman, Lisa L. Dahlia mosaic virus. [Gainesville, Fla.]: Florida Dept. of Agriculture & Consumer Services, Division of Plant Industry, 1990.

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Applied plant virology. 2nd ed. London: Chapman and Hall, 1991.

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Book chapters on the topic "PLANT-VIRUS-DISEASES"

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Sastry, K. Subramanya. "Virus Transmission." In Seed-borne plant virus diseases, 75–83. India: Springer India, 2012. http://dx.doi.org/10.1007/978-81-322-0813-6_4.

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Sastry, K. Subramanya. "Introduction." In Seed-borne plant virus diseases, 1–53. India: Springer India, 2012. http://dx.doi.org/10.1007/978-81-322-0813-6_1.

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Sastry, K. Subramanya. "Future Strategies and Conclusions." In Seed-borne plant virus diseases, 307–15. India: Springer India, 2012. http://dx.doi.org/10.1007/978-81-322-0813-6_10.

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Sastry, K. Subramanya. "Identification and Taxonomic Groups." In Seed-borne plant virus diseases, 55–66. India: Springer India, 2012. http://dx.doi.org/10.1007/978-81-322-0813-6_2.

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Sastry, K. Subramanya. "Economic Significance of Seed-Transmitted Plant Virus Diseases." In Seed-borne plant virus diseases, 67–73. India: Springer India, 2012. http://dx.doi.org/10.1007/978-81-322-0813-6_3.

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Sastry, K. Subramanya. "Mechanism of Seed Transmission." In Seed-borne plant virus diseases, 85–100. India: Springer India, 2012. http://dx.doi.org/10.1007/978-81-322-0813-6_5.

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Sastry, K. Subramanya. "Detection of Plant Viruses in Seeds." In Seed-borne plant virus diseases, 101–63. India: Springer India, 2012. http://dx.doi.org/10.1007/978-81-322-0813-6_6.

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Sastry, K. Subramanya. "Ecology and Epidemiology of Seed-Transmitted Viruses." In Seed-borne plant virus diseases, 165–83. India: Springer India, 2012. http://dx.doi.org/10.1007/978-81-322-0813-6_7.

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Sastry, K. Subramanya. "Methods of Combating Seed-Transmitted Virus Diseases." In Seed-borne plant virus diseases, 185–284. India: Springer India, 2012. http://dx.doi.org/10.1007/978-81-322-0813-6_8.

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Sastry, K. Subramanya. "Plant Virus Transmission Through Vegetative Propagules (Asexual Reproduction)." In Seed-borne plant virus diseases, 285–305. India: Springer India, 2012. http://dx.doi.org/10.1007/978-81-322-0813-6_9.

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Conference papers on the topic "PLANT-VIRUS-DISEASES"

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Mitra, Debanjan, and Pradeep K. Mohapatra. "Effect of natural compounds to inhibit human respiratory syncytial virus." In 7th GoGreen Summit 2021. Technoarete, 2021. http://dx.doi.org/10.36647/978-93-92106-02-6.18.

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Current COVID-19 effects are forcing us to think about other deadly viral diseases. Respiratory syncytial virus (RSV) is one of them. Every year thousands of children lost their lives due to respiratory diseases which are occurred by this RSV. Nowadays, bioactive compounds show an enormous effect on many deadly diseases and show excellent therapeutic effects. In this study, we have identified five bioactive compounds from the plant which will be used in the treatment of RSV. Molecular docking on the protein was done by Autodock. Hydrogen was added and routable bonds were fixed in the preparation time of protein for docking. All those compounds show their non-toxic nature which is evaluated by Lipinski's Rule of Five. Molecular docking on RSV matrix protein and surface glycoprotein with those bioactive compounds shows very promising results. Between all those compounds Baicalein appears as a lead compound. It shows -8.1 Kcal/mol in the case of matrix protein and -7.9 kcal/mol in the case of the surface glycoprotein of RSV. Due to its availability and non-toxic nature, it can be used in the treatment of RSV. AS it is derived from plants, it also has very fewer side effects than chemical drugs.
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Novik, N. V., A. A. Lebedev, and I. A. Yakub. "Genetic sources of economically valuable characteristics for breeding yellow lupine." In Растениеводство и луговодство. Тимирязевская сельскохозяйственная академия, 2020. http://dx.doi.org/10.26897/978-5-9675-1762-4-2020-126.

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Screening of world gene bank is carried out to develop initial material for yellow lupin breeding. During 2018-2020 the following genetic sources have been selected: the Polish variety Parus (k-3371) as a semi-early ripened source for plant tallness, high growth tempo and high green mass productivity; the variety Puissant (k-2170) as a source for plant tallness, high seed productivity and seed protein content; the variety SV 01060 (k-2193) as a source for plant tallness, moderate period of ripening, high green mass productivity, seed protein content and their size; the lines Tromusillo-2 (k-3276), W 72 (k-2936), W 105 (k-2933), No. 1004 (k-3913) and the breeding line 07-20-240-2384-3 as sources for tolerance to virus diseases; the breeding line 11-11-02-2-4-3 as a source for high seed and green mass productivity; the hybrid Borluta x Zhitomirskii (k-3592) as a source for plant tallness and moderate period of ripening; k-3915 as a source for moderate period of ripening and high seed productivity.
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De La Garza, Cecilia, and Nora Oufi. "Health Crisis Management and Resilience Factors: A Comparative Study in Two Sectors." In 13th International Conference on Applied Human Factors and Ergonomics (AHFE 2022). AHFE International, 2022. http://dx.doi.org/10.54941/ahfe1001567.

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The objective of this study is to analyze the modalities of health crisis management in two different sectors during the Covid-19 crisis: the hospital and the nuclear industry. The aim is to:- Characterize the health crisis: similarities and differences compared to other known crises - nuclear, natural crisis (storm, earthquake, flood). - Identify elements of similarity between sectors in the modalities of crisis management and particularities related to the specificities of the socio-technical systems.- Identify the resilience factors and difficulties- Make proposals to enhance the robustness of crisis organizations.Study BackgroundBoth the hospital and the nuclear industry (EDF) have had to organize and adapt to continue their activities from the beginning of the crisis in March 2020.On the hospital side, an emergency plan (White Plan) provides a reconfiguration of the hospital in case of health crisis. On the nuclear side, a Business Continuity Plan exists as well as a pandemic emergency plan (support and mobilization plan).It was at La Pitié Salpêtrière Hospital, a reference hospital for infectious diseases, that the first death of Covid19 was recorded. The crisis unit was activated at that time. The hospital then opened its doors to us for human and organizational factors study of crisis management in April 2020. Concerning the nuclear sector, the health crisis management analysis could only be carried out from October 2020 at the national level and the nuclear power plants.Methodological approachWe applied a systemic approach combining ergonomics, cognitive psychology, and sociology to study socio-technical systems safety.The study focused on crisis management via an analysis of organizational resilience to identify the factors of success and difficulty. Given the temporality of this crisis, the study was carried out in three stages at the hospital.1. April and May 2020: i) a series of remote interviews with various hospital staff were conducted; ii) a passive listening follow-up of about 30 phone meetings of the crisis unit; iii) a documentary analysis of the planned crisis organization.2. November and December 2021: i) a second series of interviews in the hospital emergency unit.3. June and July 2021 in the intensive care unit: i) a third round of interviews; ii) field observations in the hospital; iii) a literature review.In the nuclear field we conducted two retrospective studies at different times, focused on the most critical phase of the crisis (from March to May 2020):1. October - November 2021: an analysis of the health crisis’ management at the national level via a series of interviews completed by an analysis of the crisis reference systems.2. August - September 2021: an analysis of the health crisis management in a Nuclear power plant via interviews and an analysis of site-specific documents. ResultsWe observed similarities in the way the crisis was managed, in terms of management, which proved to be factors of success both at the hospital and at EDF, for example,- A crisis management that integrates the business lines and is top-down, but that listens and takes into account proposals from the field.- Experience of crises and emergency situations, which facilitates crisis management and adaptation.- The habit of protocols facilitating the integration of new constraints.- Very strong collective mobilization of personnelHowever, there are linked difficulties in both sectors, for example, to the virus fear, the anxiety of contaminating one's family and friends, especially at the beginning, and then weariness and fatigue linked to the duration of the crisis.Particularities concerning the work activity in the hospital will be discussed especially in relation to the reconfiguration of the services and to the necessary adaptations and improvisations of patients care protocols and procedures, among others.These studies are source of learning, about crisis management and particularly long-term crises that have a lasting impact on socio-technical systems. Proposals in terms of crisis organization and preparedness for this type of crisis will be presented.
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Reports on the topic "PLANT-VIRUS-DISEASES"

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Bar-Joseph, Moshe, William O. Dawson, and Munir Mawassi. Role of Defective RNAs in Citrus Tristeza Virus Diseases. United States Department of Agriculture, September 2000. http://dx.doi.org/10.32747/2000.7575279.bard.

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This program focused on citrus tristeza virus (CTV), the largest and one of the most complex RNA-plant-viruses. The economic importance of this virus to the US and Israeli citrus industries, its uniqueness among RNA viruses and the possibility to tame the virus and eventually turn it into a useful tool for the protection and genetic improvement of citrus trees justify these continued efforts. Although the overall goal of this project was to study the role(s) of CTV associated defective (d)-RNAs in CTV-induced diseases, considerable research efforts had to be devoted to the engineering of the helper virus which provides the machinery to allow dRNA replication. Considerable progress was made through three main lines of complementary studies. For the first time, the generation of an engineered CTV genetic system that is capable of infecting citrus plants with in vitro modified virus was achieved. Considering that this RNA virus consists of a 20 kb genome, much larger than any other previously developed similar genetic system, completing this goal was an extremely difficult task that was accomplished by the effective collaboration and complementarity of both partners. Other full-length genomic CTV isolates were sequenced and populations examined, resulting in a new level of understanding of population complexities and dynamics in the US and Israel. In addition, this project has now considerably advanced our understanding and ability to manipulate dRNAs, a new class of genetic elements of closteroviruses, which were first found in the Israeli VT isolate and later shown to be omnipresent in CTV populations. We have characterized additional natural dRNAs and have shown that production of subgenomic mRNAs can be involved in the generation of dRNAs. We have molecularly cloned natural dRNAs and directly inoculated citrus plants with 35S-cDNA constructs and have shown that specific dRNAs are correlated with specific disease symptoms. Systems to examine dRNA replication in protoplasts were developed and the requirements for dRNA replication were defined. Several artificial dRNAs that replicate efficiently with a helper virus were created from infectious full-genomic cDNAs. Elements that allow the specific replication of dRNAs by heterologous helper viruses also were defined. The T36-derived dRNAs were replicated efficiently by a range of different wild CTV isolates and hybrid dRNAs with heterologous termini are efficiently replicated with T36 as helper. In addition we found: 1) All CTV genes except of the p6 gene product from the conserved signature block of the Closteroviridae are obligate for assembly, infectivity, and serial protoplast passage; 2) The p20 protein is a major component of the amorphous inclusion bodies of infected cells; and 3) Novel 5'-Co-terminal RNAs in CTV infected cells were characterized. These results have considerably advanced our basic understanding of the molecular biology of CTV and CTV-dRNAs and form the platform for the future manipulation of this complicated virus. As a result of these developments, the way is now open to turn constructs of this viral plant pathogen into new tools for protecting citrus against severe CTV terms and development of virus-based expression vectors for other citrus improvement needs. In conclusion, this research program has accomplished two main interconnected missions, the collection of basic information on the molecular and biological characteristics of the virus and its associated dRNAs toward development of management strategies against severe diseases caused by the virus and building of novel research tools to improve citrus varieties. Reaching these goals will allow us to advance this project to a new phase of turning the virus from a pathogen to an ally.
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Jordan, Ramon L., Abed Gera, Hei-Ti Hsu, Andre Franck, and Gad Loebenstein. Detection and Diagnosis of Virus Diseases of Pelargonium. United States Department of Agriculture, July 1994. http://dx.doi.org/10.32747/1994.7568793.bard.

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Pelargonium (Geranium) is the number one pot plant in many areas of the United States and Europe. Israel and the U.S. send to Europe rooted cuttings, foundation stocks and finished plants to supply a certain share of the market. Geraniums are propagated mainly vegetatively from cuttings. Consequently, viral diseases have been and remain a major threat to the production and quality of the crop. Among the viruses isolated from naturally infected geraniums, 11 are not specific to Pelargonium and occur in other crops while 6 other viruses seem to be limited to geranium. However, several of these viruses are not sufficiently characterized to conclude that they are distinct agents and their nomenclature and taxonomy are confusing. The ability to separate, distinguish and detect the different viruses in geranium will overcome obstacles te developing effective detection and certification schemes. Our focus was to further characterize some of these viruses and develop better methods for their detection and control. These viruses include: isolates of pelargonium line pattern virus (PLPV), pelargonium ringspot virus (PelRSV), pelargonium flower break virus (PFBV), pelargonium leaf curl (PLCV), and tomato ringspot virus (TomRSV). Twelve hybridoma cell lines secreting monoclonal antibodies specific to a geranium isolate of TomRSV were produced. These antibodies are currently being characterized and will be tested for the ability to detect TomRSV in infected geraniums. The biological, biochemical and serological properties of four isometric viruses - PLPV, PelRSV, and PFBV (and a PelRSV-like isolate from Italy called GR57) isolated from geraniums exhibiting line and ring pattern or flower break symptoms - and an isolate ol elderbeny latent virus (ELV; which the literature indicates is the same as PelRSV) have been determined Cloned cDNA copies of the genomic RNAs of these viruses were sequenced and the sizes and locations of predicted viral proteins deduced. A portion of the putative replicase genes was also sequenced from cloned RT-PCR fragments. We have shown that, when compared to the published biochemical and serological properties, and sequences and genome organizations of other small isometric plant viruses, all of these viruses should each be considered new, distinct members of the Carmovirus group of the family Tombusviridae. Hybridization assays using recombinant DNA probes also demonstrated that PLPV, PelRSV, and ELV produce only one subgenomic RNA in infected plants. This unusual property of the gene expression of these three viruses suggests that they are unique among the Carmoviruses. The development of new technologies for the detection of these viruses in geranium was also demonstrated. Hybridization probes developed to PFBV (radioactively-labeled cRNA riboprobes) and to PLPV (non-radioactive digoxigenin-labeled cDNAs) were generally shown to be no more sensitive for the detection of virus in infected plants than the standard ELISA serology-based assays. However, a reverse transcriptase-polymerase chain reaction assay was shown to be over 1000 times more sensitive in detecting PFBV in leaf extracts of infected geranium than was ELISA. This research has lead to a better understanding of the identity of the viruses infecting pelargonium and to the development of new tools that can be used in an improved scheme of providing virus-indexed pelargonium plants. The sequence information, and the serological and cloned DNA probes generated from this work, will allow the application of these new tools for virus detection, which will be useful in domestic and international indexing programs which are essential for the production of virus-free germplasm both for domestic markets and the international exchange of plant material.
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Whitham, Steven A., Amit Gal-On, and Tzahi Arazi. Functional analysis of virus and host components that mediate potyvirus-induced diseases. United States Department of Agriculture, March 2008. http://dx.doi.org/10.32747/2008.7591732.bard.

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The mechanisms underlying the development of symptoms in response to virus infection remain to be discovered in plants. Insight into symptoms induced by potyviruses comes from evidence implicating the potyviral HC-Pro protein in symptom development. In particular, recent studies link the development of symptoms in infected plants to HC-Pro's ability to interfere with small RNA metabolism and function in plant hosts. Moreover, mutation of the highly conserved FRNK amino acid motif to FINK in the HC-Pro of Zucchini yellow mosaic virus (ZYMV) converts a severe strain into an asymptomatic strain, but does not affect virus accumulation in cucurbit hosts. The ability of this FINK mutation to uncouple symptoms from virus accumulation creates a unique opportunity to study symptom etiology, which is usually confounded by simultaneous attenuation of both symptoms and virus accumulation. Our goal was to determine how mutations in the conserved FRNK motif affect host responses to potyvirus infection in cucurbits and Arabidopsis thaliana. Our first objective was to define those amino acids in the FRNK motif that are required for symptoms by mutating the FRNK motif in ZYMV and Turnip mosaic virus (TuMV). Symptom expression and accumulation of resulting mutant viruses in cucurbits and Arabidopsis was determined. Our second objective was to identify plant genes associated with virus disease symptoms by profiling gene expression in cucurbits and Arabidopsis in response to mutant and wild type ZYMV and TuMV, respectively. Genes from the two host species that are differentially expressed led us to focus on a subset of genes that are expected to be involved in symptom expression. Our third objective was to determine the functions of small RNA species in response to mutant and wild type HC-Pro protein expression by monitoring the accumulation of small RNAs and their targets in Arabidopsis and cucurbit plants infected with wild type and mutant TuMV and ZYMV, respectively. We have found that the maintenance of the charge of the amino acids in the FRNK motif of HC-Pro is required for symptom expression. Reduced charge (FRNA, FRNL) lessen virus symptoms, and maintain the suppression of RNA silencing. The FRNK motif is involved in binding of small RNA species including microRNAs (miRNA) and short interfering RNAs (siRNA). This binding activity mediated by the FRNK motif has a role in protecting the viral genome from degradation by the host RNA silencing system. However, it also provides a mechanism by which the FRNK motif participates in inducing the symptoms of viral infection. Small RNA species, such as miRNA and siRNA, can regulate the functions of plant genes that affect plant growth and development. Thus, this binding activity suggests a mechanism by which ZYMVHC-Pro can interfere with plant development resulting in disease symptoms. Because the host genes regulated by small RNAs are known, we have identified candidate host genes that are expected to play a role in symptoms when their regulation is disrupted during viral infections. As a result of this work, we have a better understanding of the FRNK amino acid motif of HC-Pro and its contribution to the functions of HC-Pro, and we have identified plant genes that potentially contribute to symptoms of virus infected plants when their expression becomes misregulated during potyviral infections. The results set the stage to establish the roles of specific host genes in viral pathogenicity. The potential benefits include the development of novel strategies for controlling diseases caused by viruses, methods to ensure stable expression of transgenes in genetically improved crops, and improved potyvirus vectors for expression of proteins or peptides in plants.
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4

Gal-On, Amit, Shou-Wei Ding, Victor P. Gaba, and Harry S. Paris. role of RNA-dependent RNA polymerase 1 in plant virus defense. United States Department of Agriculture, January 2012. http://dx.doi.org/10.32747/2012.7597919.bard.

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Objectives: Our BARD proposal on the impact of RNA-dependent RNA polymerase 1 (RDR1) in plant defense against viruses was divided into four original objectives. 1. To examine whether a high level of dsRNA expression can stimulate RDR1 transcription independent of salicylic acid (SA) concentration. 2. To determine whether the high or low level of RDR1 transcript accumulation observed in virus resistant and susceptible cultivars is associated with viral resistance and susceptibility. 3. To define the biogenesis and function of RDR1-dependent endogenous siRNAs. 4. To understand why Cucumber mosaic virus (CMV) can overcome RDR1-dependent resistance. The objectives were slightly changed due to the unique finding that cucumber has four different RDR1 genes. Background to the topic: RDR1 is a key plant defense against viruses. RDR1 is induced by virus infection and produces viral and plant dsRNAs which are processed by DICERs to siRNAs. siRNAs guide specific viral and plant RNA cleavage or serve as primers for secondary amplification of viral-dsRNA by RDR. The proposal is based on our preliminary results that a. the association of siRNA and RDR1 accumulation with multiple virus resistance, and b. that virus infection induced the RDR1-dependent production of a new class of endogenous siRNAs. However, the precise mechanisms underlying RDR1 induction and siRNA biogenesis due to virus infection remain to be discovered in plants. Major conclusions, solutions and achievements: We found that in the cucurbit family (cucumber, melon, squash, watermelon) there are 3-4 RDR1 genes not documented in other plant families. This important finding required a change in the emphasis of our objectives. We characterized 4 RDR1s in cucumber and 3 in melon. We demonstrated that in cucumber RDR1b is apparently a new broad spectrum virus resistance gene, independent of SA. In melon RDR1b is truncated, and therefore is assumed to be the reason that melon is highly susceptible to many viruses. RDR1c is dramatically induced due to DNA and RNA virus infection, and inhibition of RDR1c expression led to increased virus accumulation which suggested its important on gene silencing/defense mechanism. We show that induction of antiviral RNAi in Arabidopsis is associated with production of a genetically distinct class of virus-activated siRNAs (vasiRNAs) by RNA dependent RNA polymerase-1 targeting hundreds of host genes for RNA silencing by Argonaute-2. Production of vasiRNAs is induced by viruses from two different super groups of RNA virus families, targeted for inhibition by CMV, and correlated with virus resistance independently of viral siRNAs. We propose that antiviral RNAi activate broad-spectrum antiviral activity via widespread silencing of host genes directed by vasiRNAs, in addition to specific antiviral defense Implications both scientific and agricultural: The RDR1b (resistance) gene can now be used as a transcription marker for broad virus resistance. The discovery of vasiRNAs expands the repertoire of siRNAs and suggests that the siRNA-processing activity of Dicer proteins may play a more important role in the regulation of plant and animal gene expression than is currently known. We assume that precise screening of the vasiRNA host targets will lead in the near future for identification of plant genes associate with virus diseases and perhaps other pathogens.
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Dawson, William O., and Moshe Bar-Joseph. Creating an Ally from an Adversary: Genetic Manipulation of Citrus Tristeza. United States Department of Agriculture, January 2004. http://dx.doi.org/10.32747/2004.7586540.bard.

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Citrus is one of the major agricultural crops common to Israel and the United States, important in terms of nutrition, foreign exchange, and employment. The economy of both citrus industries have been chronically plagued by diseases caused by Citrus tristeza virus (CTV). The short term solution until virus-resistant plants can be used is the use of mild strain cross-protection. We are custom designing "ideal" protecting viruses to immunize trees against severe isolates of CTV by purposely inoculating existing endangered trees and new plantings to be propagated as infected (protected) citrus budwood. We crossed the substantial technological hurdles necessary to accomplish this task which included developing an infectious cDNA clone which allows in vitro manipulation of the virus and methods to then infect citrus plants. We created a series of hybrids between decline-inducing and mild CTV strains, tested them in protoplasts, and are amplifying them to inoculate citrus trees for evaluation and mapping of disease determinants. We also extended this developed technology to begin engineering transient expression vectors based on CTV as tools for genetic improvement of tree crops, in this case citrus. Because of the long periods between genetic transformation and the ultimate assay of mature tree characteristics, there is a great need for an effective system that allows the expression or suppression of target genes in fruiting plants. Virus-based vectors will greatly expedite progress in citrus genetic improvement. We characterized several components of the virus that provides necessary information for designing virus-based vectors. We characterized the requirements of the 3 ’-nontranslated replication promoter and two 3 ’-ORF subgenomic (sg) mRNA controller elements. We discovered a novel type of 5’-terminal sgRNAs and characterized the cis-acting control element that also functions as a strong promoter of a 3 ’-sgRNA. We showed that the p23 gene controls negative-stranded RNA synthesis and expression of 3 ’ genes. We identified which genes are required for infection of plants, which are host range determinants, and which are not needed for plant infection. We continued the characterization of native dRNA populations and showed the presence of five different classes including class III dRNAs that consists of infectious and self-replicating molecules and class V dRNAs that contain all of the 3 ’ ORFs, along with class IV dRNAs that retain non-contiguous internal sequences. We have constructed and tested in protoplasts a series of expression vectors that will be described in this proposal.
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Whitham, Steven A., Amit Gal-On, and Victor Gaba. Post-transcriptional Regulation of Host Genes Involved with Symptom Expression in Potyviral Infections. United States Department of Agriculture, June 2012. http://dx.doi.org/10.32747/2012.7593391.bard.

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Understanding how RNA viruses cause disease symptoms in their hosts is expected to provide information that can be exploited to enhance modern agriculture. The helper component-proteinase (HC-Pro) protein of potyviruses has been implicated in symptom development. Previously, we demonstrated that symptom expression is associated with binding of duplex small-interfering-RNA (duplex-siRNA) to a highly conserved FRNK amino acid motif in the HC-Pro of Zucchini yellow mosaic virus (ZYMV). This binding activity also alters host microRNA (miRNA) profiles. In Turnip mosaic virus (TuMV), which infects the model plant Arabidopsis, mutation of the FRNK motif to FINK was lethal providing further indication of the importance of this motif to HC-Pro function. In this continuation project, our goal was to further investigate how ZYMV and TuMV cause the mis-expression of genes in cucurbits and Arabidopsis, respectively, and to correlate altered gene expression with disease symptoms. Objective 1 was to examine the roles of aromatic and positively charged residues F164RNH and K215RLF adjacent to FR180NK in small RNA binding. Objective 2 was to determine the target genes of the miRNAs which change during HC-Pro expression in infected tissues and transgenic cucumber. Objective 3 was to characterize RNA silencing mechanisms underlying differential expression of host genes. Objective 4 was to analyze the function of miRNA target genes and differentially expressed genes in potyvirus-infected tissues. We found that the charged K/R amino acid residues in the FKNH and KRLF motifs are essential for virus viability. Replacement of K to I in FKNH disrupted duplex-siRNA binding and virus infectivity, while in KRLF mutants duplex-siRNA binding was maintained and virus infectivity was limited: symptomless following a recovery phenomenon. These findings expanded the duplex-siRNA binding activity of HC-Pro to include the adjacent FRNK and FRNH sites. ZYMV causes many squash miRNAs to hyper-accumulate such as miR166, miR390, mir168, and many others. Screening of mir target genes showed that only INCURVATA-4 and PHAVOLUTA were significantly upregulated following ZYMVFRNK infection. Supporting this finding, we found similar developmental symptoms in transgenic Arabidopsis overexpressing P1-HC-Pro of a range of potyviruses to those observed in miR166 mutants. We characterized increased transcription of AGO1 in response to infection with both ZYMV strains. Differences in viral siRNA profiles and accumulation between mild and severe virus infections were characterized by Illumina sequencing, probably due to the differences in HC-Pro binding activity. We determined that the TuMV FINK mutant could accumulate and cause symptoms in dcl2 dcl4 or dcl2 dcl3 dcl4 mutants similar to TuMV FRNK in wild type Arabidopsis plants. These dcl mutant plants are defective in antiviral defenses, and the results show that factors other than HC-ProFRNK motif can induce symptoms in virus-infected plants. As a result of this work, we have a better understanding of the FRNK and FKNH amino acid motifs of HC-Pro and their contributions to the duplex-siRNA binding functions. We have identified plant genes that potentially contribute to infectivity and symptoms of virus infected plants when they are mis-expressed during potyviral infections. The results establish that there are multiple underlying molecular mechanisms that lead viral pathogenicity, some dependent on HC-Pro. The potential benefits include the development of novel strategies for controlling diseases caused by viruses, methods to ensure stable expression of transgenes in genetically improved crops, and improved potyvirus vectors for expression of proteins or peptides in plants.
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Sessa, Guido, and 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.

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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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