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Geminivirus
''Geminiviridae'' is a family of plant viruses that encode their genetic information on a circular genome of single-stranded (ss) DNA. The family contains 15 genera. Diseases associated with this family include: bright yellow mosaic, yellow mosaic, yellow mottle, leaf curling, stunting, streaks, reduced yields. They have single-stranded circular DNA genomes encoding genes that diverge in both directions from a virion strand origin of replication (i.e. geminivirus genomes are ambisense). According to the Baltimore classification they are considered class II viruses. It is the largest known family of single stranded DNA viruses. Mastrevirus and curtovirus transmission is via various leafhopper species (e.g. maize streak virus and other African streak viruses are transmitted by '' Cicadulina mbila''), the only known topocuvirus species, ''Tomato pseudo-curly top virus'', is transmitted by the treehopper '' Micrutalis malleifera'', and begomoviruses are transmitted by the white ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Begomovirus
''Begomovirus'' is a genus of viruses, in the family ''Geminiviridae''. They are plant viruses that as a group have a very wide host range, infecting dicotyledonous plants. Worldwide they are responsible for a considerable amount of economic damage to many important crops such as tomatoes, beans, Squash (plant), squash, cassava and cotton. There are 464 species in this genus. Morphology Virus particles are non-enveloped. The nucleocapsid is 38 nanometers (nm) long and 15–22 nm in diameter. While particles have basic icosahedral symmetry, they consist of two incomplete icosahedra—missing one vertex—joined together. There are 22 capsomeres per nucleocapsid. Genome Single stranded closed circular DNA. Many begomoviruses have a bipartite genome: this means that the genome is segmented into two segments (referred to as DNA A and DNA B) that are packaged into separate particles. Both segments are generally required for successful symptomatic infection in a host cell bu ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mastrevirus
''Mastrevirus'' is a genus of ssDNA viruses, in the family ''Geminiviridae''. Mostly monocotyledonous plants serve as natural hosts. They are vectored by planthoppers. There are 50 species in this genus. Diseases associated with this genus include: maize streak virus: maize streak disease (MSD). Capsid proteins ''Mastreviruses'' have an unusually diverse range of capsid proteins among the Geminiviridae. While all other genera have species with essentially identical proteins (and their producing genetic sequences) among themselves, ''Mastrevirus'' has seven protein clusters and three species that each constitute their own. Structure Viruses in ''Mastrevirus'' are non-enveloped, with icosahedral geometries, and T=1 symmetry. The diameter is around 22 nm, with a length of 38 nm. Genomes are circular and non-segmented, around 2.6-2.8kb in length. Life cycle Viral replication is nuclear. Entry into the host cell is achieved by penetration into the host cell. Replication ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Maize Streak Virus
Maize streak virus (MSV) is a virus primarily known for causing maize streak disease (MSD) in its major host, and which also infects over 80 wild and domesticated grasses. It is an insect-transmitted pathogen of maize in the genus ''Mastrevirus'' of the family ''Geminiviridae'' that is endemic in sub-Saharan Africa and neighbouring Indian Ocean island territories such as Madagascar, Mauritius and La Reunion. The A-strain of MSV ( MSV-A) causes sporadic maize streak disease epidemics throughout the maize-growing regions of Africa. MSV was first described by the South African entomologist Claude Fuller who referred to it in a 1901 report as "mealie variegation". The development of conventionally resistant maize varieties has been a priority since the 1950s in Kenya, Nigeria, South Africa and elsewhere, with a good deal of success: however, there are several genes associated with resistance, and breeding is complex. Transgenically resistant or genetically modified maize variet ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Grablovirus
''Grablovirus'' is a genus of plant viruses in the family ''Geminiviridae ''Geminiviridae'' is a family of plant viruses that encode their genetic information on a circular genome of single-stranded (ss) DNA. The family contains 15 genera. Diseases associated with this family include: bright yellow mosaic, yellow mosa ...''. The genus has three species. Taxonomy The genus contains the following species, listed by scientific name and followed by the exemplar virus of the species: * ''Grablovirus pruni'', Prunus geminivirus A * ''Grablovirus silvestris'', Wild Vitis virus 1 * ''Grablovirus vitis'', Grapevine red blotch virus References Geminiviridae Virus genera {{virus-plant-disease-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Whitefly
Whiteflies are Hemipterans that typically feed on the undersides of plant leaves. They comprise the family Aleyrodidae, the only family in the superfamily Aleyrodoidea. More than 1550 species have been described. Description and taxonomy The Aleyrodidae are a family in the suborder Sternorrhyncha and at present comprise the entire superfamily Aleyrodoidea, related to the superfamily Psylloidea. The family often occurs in older literature as "Aleurodidae", but that is a junior synonym and accordingly incorrect in terms of the international standards for zoological nomenclature. Aleyrodidae are small insects, most species with a wingspan of less than 3 mm and a body length of 1 mm to 2 mm. Many are so small that their size complicates their control in greenhouses because they can only be excluded by screening with very fine mesh; in fact they can enter mesh so fine that many of their natural enemies cannot come in after them, so that unchecked whitefly population ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cell (biology)
The cell is the basic structural and functional unit of all life, forms of life. Every cell consists of cytoplasm enclosed within a Cell membrane, membrane; many cells contain organelles, each with a specific function. The term comes from the Latin word meaning 'small room'. Most cells are only visible under a light microscope, microscope. Cells Abiogenesis, emerged on Earth about 4 billion years ago. All cells are capable of Self-replication, replication, protein synthesis, and cell motility, motility. Cells are broadly categorized into two types: eukaryotic cells, which possess a Cell nucleus, nucleus, and prokaryotic, prokaryotic cells, which lack a nucleus but have a nucleoid region. Prokaryotes are single-celled organisms such as bacteria, whereas eukaryotes can be either single-celled, such as amoebae, or multicellular organism, multicellular, such as some algae, plants, animals, and fungi. Eukaryotic cells contain organelles including Mitochondrion, mitochondria, which ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Icosahedra
In geometry, an icosahedron ( or ) is a polyhedron with 20 faces. The name comes . The plural can be either "icosahedra" () or "icosahedrons". There are infinitely many non- similar shapes of icosahedra, some of them being more symmetrical than others. The best known is the (convex, non- stellated) regular icosahedron—one of the Platonic solids—whose faces are 20 equilateral triangles. Regular icosahedra There are two objects, one convex and one nonconvex, that can both be called regular icosahedra. Each has 30 edges and 20 equilateral triangle faces with five meeting at each of its twelve vertices. Both have icosahedral symmetry. The term "regular icosahedron" generally refers to the convex variety, while the nonconvex form is called a ''great icosahedron''. Convex regular icosahedron The convex regular icosahedron is usually referred to simply as the ''regular icosahedron'', one of the five regular Platonic solids, and is represented by its Schläfli symbol , containi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Diameter
In geometry, a diameter of a circle is any straight line segment that passes through the centre of the circle and whose endpoints lie on the circle. It can also be defined as the longest Chord (geometry), chord of the circle. Both definitions are also valid for the diameter of a sphere. In more modern usage, the length d of a diameter is also called the diameter. In this sense one speaks of diameter rather than diameter (which refers to the line segment itself), because all diameters of a circle or sphere have the same length, this being twice the radius r. :d = 2r \qquad\text\qquad r = \frac. The word "diameter" is derived from (), "diameter of a circle", from (), "across, through" and (), "measure". It is often abbreviated \text, \text, d, or \varnothing. Constructions With straightedge and compass, a diameter of a given circle can be constructed as the perpendicular bisector of an arbitrary chord. Drawing two diameters in this way can be used to locate the center of ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Becurtovirus
''Becurtovirus'' is a genus of viruses, in the family ''Geminiviridae ''Geminiviridae'' is a family of plant viruses that encode their genetic information on a circular genome of single-stranded (ss) DNA. The family contains 15 genera. Diseases associated with this family include: bright yellow mosaic, yellow mosa ...''. Dicotyledonous plants serve as natural hosts. There are three species in this genus. Taxonomy The genus contains the following species, listed by scientific name and followed by the exemplar virus of the species: * ''Becurtovirus betae'', Beet curly top Iran virus * ''Becurtovirus exomis'', Exomis microphylla associated virus * ''Becurtovirus spinaciae'', Spinach curly top Arizona virus Structure Viruses in ''Becurtovirus'' are non-enveloped, with icosahedral geometries, and T=1 symmetry. Genomes are circular and non-segmented, around 3.0kb in length. Life cycle Viral replication is nuclear. Entry into the host cell is achieved by penetration into the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
