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Thompson J.R.,Plant Virology Group
Advances in virus research | Year: 2010

Viral diseases of cultivated crops are responsible for the worldwide loss of billions of US dollars in agricultural productivity every year. Historically, this loss has been reduced or minimized principally by the implementation of specific agricultural/phytosanitary measures, and by the introduction of naturally occurring virus-resistance genes into appropriate cultivars by plant breeding. Since the first report of virus-resistant transgenic plants (VRTPs) in 1986, a remarkable diversity of virus-resistance transgenes has been developed. Despite this, to a large part due to controversy surrounding the use of genetically modified organisms, the number of commercially available VRTPs remains small. However, since the potential risks associated with VRTPs were first formulated in the early 1990s, fundamental research on plant-virus interactions and also research specifically aimed at resolving biosafety issues have greatly circumscribed the potential impact of the risks envisaged. Yet, in spite of the advances, both in strategies for creating VRTPs and in the assessment of potential risks, it remains remarkably difficult to weigh the risks/costs and benefits of different means to manage plant viral diseases, and even to make scientifically well-founded choices of the most appropriate strategy for creating VRTPs. Many of the outstanding issues concern the lack of sufficient knowledge of the breadth and durability of the resistance of VRTPs under field conditions. VRTPs will only take their appropriate place in modern agriculture when their potential users will be able to base their choices on realistic assessments of their efficacy, durability, and safety. Copyright © 2010 Elsevier Inc. All rights reserved.

Gaur R.K.,Plant Virology Group | Rao G.P.,Sugarcane Research Station
Archives of Phytopathology and Plant Protection | Year: 2010

Phytoplasma strain was detected in leaves of sugarcane in India exhibiting symptoms of yellowing of midribs. A phytoplasma characteristic 1.2 kb rDNA PCR product was amplified from DNAs of all diseased samples but not in healthy sugarcane plants tested using phytoplasma universal primer pairs P1/P7 and f5U/r3U. Restriction fragment length polymorphism (RFLP) analysis of amplified 16S rDNA indicated that diseased sugarcane was infected by phytoplasma. The 16S rDNA sequence of the Indian sugarcane yellow leaf phytoplasma (SCYLP) showed the closest identity (99%) to that of SCYLP in Cuba identified as Macroptilium lathyroides (AY725233), which belongs to 16SrXII (Stolbur group). This is the first record of the detection of SCYLP, and identification of the 16SrXII group of phytoplasma associated with yellow leaf syndrome (YLS) in India. © 2010 Taylor & Francis.

Matic S.,Plant Virology Group | Matic S.,CNR Institute of Plant virology | Pais da Cunha A.T.,University of Padua | Thompson J.R.,Plant Virology Group | And 3 more authors.
Journal of Plant Pathology | Year: 2012

SUMMARY Seventeen cassava plants showing strong cassava mosaic disease symptoms were sampled from three Angolan provinces. The DNA-A component of two isolates was amplified by rolling circle amplification (RCA) and characterized. The complete DNA-A of 2,778 nucleotides from sample AOS showed very high similarity to African cassava mosaic virus (ACMV), and that of 2,799 nu-cleotides from sample AO7 showed high identity to East African cassava mosaic virus (EACMV), particularly to EACMV-Uganda2 Severe strain. This represents the first report of complete ACMV and EACMV DNA-A sequences from Angola. PCR followed by direct sequencing of PCR products of a portion of DNA-A and DNA-B detected ACMV or EACMV in all 17 cassava plants. None of the five other cassava mosaic virus species were found. The presence of a mixed infection of ACMV and EACMV-Uganda2 Severe strain, associated with cassava mosaic disease pandemic, highlights the need for stricter controls on the importation of infected cassava stem cuttings from neighbouring countries and further investigations on the sanitary status of cassava plants in the presently unsurveyed provinces of Angola.

Morroni M.,Plant Virology Group | Morroni M.,Bioteck S.p.A. | Jacquemond M.,French National Institute for Agricultural Research | Tepfer M.,Plant Virology Group | Tepfer M.,French National Institute for Agricultural Research
Molecular Plant-Microbe Interactions | Year: 2013

Recombination is a major source of virus variability, and the question of whether novel recombinant viruses would emerge in transgenic plants expressing viral sequences has been a biosafety issue. We describe the results of pyrosequencing the recombinant viral RNAs appearing in transgenic plants expressing the coat protein (CP) gene and 3′ noncoding region of Cucumber mosaic virus RNA3, as well as in nontransgenic controls. The populations of recombinants in both transgenic and nontransgenic plants were similar to those previously described from Sanger sequencing but many more recombinant types were observed, including a novel class of large deletions removing all or nearly the entire CP gene. These results show that populations of recombinant viral genomes arising de novo can be characterized in detail by pyrosequencing, and confirm that the transgenic plants did not harbor novel recombinants of biosafety concern. © 2013 The American Phytopathological Society.

Friscina A.,Plant Virology Group | Chiappetta L.,Plant Virology Group | Jacquemond M.,Station de Pathologie Vegetale UR407 | Tepfer M.,Institut Universitaire de France
Molecular Plant Pathology | Year: 2016

Cacao swollen shoot virus (CSSV) is a major pathogen of cacao (Theobroma cacao) in Africa, and long-standing efforts to limit its spread by the culling of infected trees have had very limited success. CSSV is a particularly difficult virus to study, as it has a very narrow host range, limited to several tropical tree species. Furthermore, the virus is not mechanically transmissible, and its insect vector can only be used with difficulty. Thus, the only efficient means to infect cacao plants that have been experimentally described so far are by particle bombardment or the agroinoculation of cacao plants with an infectious clone. We have genetically transformed three non-host species with an infectious form of the CSSV genome: two experimental hosts widely used in plant virology (Nicotiana tabacum and N. benthamiana) and the model species Arabidopsis thaliana. In transformed plants of all three species, the CSSV genome was able to replicate, and, in tobacco, CSSV particles could be observed by immunosorbent electron microscopy, demonstrating that the complete virus cycle could be completed in a non-host plant. These results will greatly facilitate the preliminary testing of CSSV control strategies using plants that are easy to raise and to transform genetically. © 2016 BSPP AND JOHN WILEY & SONS LTD.

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