Potato virus Y - Курсовая работа

Content 1. Referat 2. Introductory part 3. Virus characteristics 3.1 Nomenclature 3.2 Physical and biochemical properties 3.3 Reproduction 3.4 Virus(es) with serologically related virions 4 Symptoms 5 Transmission 6 Diagnostic techniques for detection of Potato Virus Y 6.1 ELISA 6.2 RT-PCR 6.3 qRT-PCR 7 Control 7.1 General Recommendations 7.2 The novel gene Ny-1 8 Additions 8.1 Images 8.2 Complete genome 8.3 Gene map 8.4 Plants transformed with a cistron of a potato virus Y protease (NIa) are resistant to virus infection 9 References 1. Referat This course work is devoted to widely known Potato virus Y. It contains 31 pages and 9 figures. 2. Introductory part Two of the 73 genera of plant viruses share equally more than 30% of all recognized species. Potyvirus is one of them and Begomovirus the other. Potyvirus is the largest of six genera in the family Potyviridae, and is named after its type species, potato virus Y. Many potyviruses are damaging crop pathogens. They infect species of most angiosperm taxa in all temperate and tropical climes. They are transmitted by aphids, especially species of Aphidinae, when aphids move from plant to plant and probe them in search of their preferred host species, and some are also transmitted in seeds to the progeny of infected plants.[3] Potato virus Y (PVY) is the type member of the potyvirus group. Potyviruses, like picorna-, como-, and nepoviruses, belong to the picornavirus-like supergroup. PVY infects many economically important plant species. These include potato (Solanum tuberosum L.), tobacco (Nicotiana tabacum L.), tomato (Lycopersicon esculentum Mill) and pepper (Capsicum frutescens L.). Potato virus Y (PVY) is a serious potato pathogen that affects potato seed and commercial production crops. In recent decades, novel PVY strains have been described that cause necrotic symptoms on tobacco foliage and/or potato tubers. The major PVY strains that affect potato include PVY(O) and PVY(N), which have distinct serotypes that can be differentiated by immunoassay. Other economically important strain variants are derived from recombination events, including variants that cause tuber necrotic symptoms (PVY(NTN)) and PVY(O) serotypes that cause tobacco veinal necrosis (PVY(N)-W, PVY(N:O)).[7] 3. Virus characteristics Data collated by C. Buchen-Osmond, 1987. potato virus detection genome 3.1 Nomenclature Synonyms brinjal mosaic virus[48], datura 437 virus, potato acropetal necrosis virus, potato severe mosaic virus, tobacco vein-banding virus [24]. Acronym PVY Strains potato C virus, tobacco veinal necrosis virus, potato virus Yo group (common strain), potato virus YN group (tobacco veinal necrosis strain), potato virus YC group (stipple streak strain, including potato virus C) [58]. ICTV decimal code 57.0.1.0.058 3.2 Physical and biochemical properties Properties of particles in sap TIP: 50-62 °C. LIV: 7-50 days. DEP: log10 minus 2-6. Infectivity of sap not changed by treatment with di-ethyl ether. Leaf sap contains few virions[18]. Particle morphology Virions consist of a capsid. Virus capsid is not enveloped. Capsid/nucleocapsid is elongated with helical symmetry (FIG 1). Virus preparations contain one particle component[60]. The capsid is filamentous, flexuous with a clear modal length with a length of 684 nm (from purified preparations (Delgado-Sanchez and Grogan, 1966)), or 730 nm and a width of 11 nm. Axial canal is indistinct; 2-3 nm in diameter. Basic helix is obscure. Pitch of helix is 3.3 nm [57]. Electron microscopic preparation and references: Virus preparation contains few virions. Physical properties One sedimenting component in purified preparations; sedimentation coefficient 145 S [32]. Density 1.323 g cm-3 in CsCl (strain Yo), or 1.326 g cm-3 in CsCl (strain YN[32]). A260/A280 ratio 2.3 (corrected for light-scattering (Leiser and Richter, 1978)), or 2.9 [32],[52]. Biochemical properties Features of the genome The Mr of the genome constitutes 5.4-6.4% of the virion by weight[32],[52]. The genome is monopartite, only one particle size is recovered of linear, positive-sense, single-stranded RNA. Minor species of non-genomic nucleic acid are not found in virions. The complete genome is 10400 nucleotides long. Is fully and partially sequenced, complete sequence is 10400 nucleotides long [24],[38]. Sequence has the accession number ;93.6-94.6 % protein; 0 % lipid. Genome consists of RNA; single-stranded; linear. Total genome size 10.4 kb. Genome unipartite; largest (or only) genome part 10.4 kb[39]. Hosts such as weeds and other crops serve as breeding grounds for these aphids and form a temporary area of colonization before the aphids migrate to the potato fields. In moderate climates, such as in South Africa, aphids are thought to reproduce asexually on weeds, other crops, indigenous plants and garden plants. This means that there are a number of aphids present year-round. Wingless aphids have not yet been linked to the spread of PVY in potato fields [33].