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Classification of plant viruses
This document discusses the classification of plant viruses. It notes that viruses are sub-microscopic entities that can only multiply intracellularly and may be pathogenic. They contain either RNA or DNA and have a protein coat. Plant viruses are classified based on their structure, physicochemical properties, viral nucleoproteins, symmetry, number and arrangement of protein subunits, and size. Virus classification starts at the order level and includes family, sub-family, genus, and species, with the taxon suffixes given. Examples are provided of plant viruses classified by their nucleic acid type and structure, such as rod-shaped, filamentous, isometric, enveloped, and those with single or multipartite genomes.
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Classification of plant viruses
- 1. CLASSIFICATION OF PLANT VIRUSES MOHDSALIM 18-BTM-028 GK7985 DEPTT.OF BOTANY AMU.ALIGARH
- 2. WHAT IS PURPOSEOF CLASSIFICATION ❖Grouping of biological entities according to their resemblances and differences ❖To make structural arrangement for easy comprehension ❖To enable prediction of properties of new viruses ❖Possible evolutionary relationships ❖To be able to communicate with each other
- 3. VIRUSES ❖Viruses are ‘Sub-microscopic’infectiveentities that multiply only intracellularly and are potentially pathogenic ❖ Nucleic acid either-RNA or DNA ❖Genome enclosed within protein coat-Capsid ❖Different shapes (Helical,polyhedral,isometric,rod like or filamentous ) -size vary from 20-300nm ❖Nucleic acid 5-40% and protein 60-95% ❖These may enveloped or non enveloped
- 4. CRITERIA USED FORCLASSIFYING PLANT VIRUSES ❖Structure of the virus particle (monopartite,bipartite,tripartite) ❖Physiochemical properties of the virus particle ❖Properties of viral nucleo-protien ❖On the basis of symmertry ( eg.helical viruses) ❖Number and arrangement of protein sub-units (eg.isometric viruses) ❖Size of viruses
- 6. CLASSIFICATION OF VIRUSES •Virus classification starts at the levels of order and continues as follows ,with the taxon suffixes given in italics: ▪Order (-virales) ▪Family (-viridae) ▪Sub-family (-virinae) ▪Genus (-virus) ▪Species ✓Species –English common name
- 7. PLANT VIRUSES ❖ssRNA viruses-Non enveloped 1.Rod shaped viruses e.g Tobamovirus (300*18nm) Tobravirus (40-20*22nm) Hordeivirus (100-150*20nm) 2. Filamentous viruses e.g Potex virus (480-580*13nm) Carlavirus (610-700*13nm) Trichovirus (730*12nm)
- 8. 3.ISOMETRIC VIRUSES ❖Monopartite viruses e.gTobacco necrosis virus 30nm Turnip yellow mosaic virus 30nm Tomato bushy stunt virus 30nm ❖Bipartite viruses e.g Cowpea mosaic virus (25-30nm) Tobacco ring spot virus ❖ Tripartite viruses e.g Cucumovirus 29nm Tobacco streak virus 26-35nm ❖ Multipartite viruses e.g Alfamovirus 28-58*18nm
- 9. ❖ SSRNA VIRUSES(ENVELOPED VIRUSES) e.g Rhabdovirus( 70*170nm) Tospovirus 80nm ➢ dsRNA viruses (NON-ENVELOPED) e.g Wound tumour virus 70nm Oryzavirus 70nm ➢ ssDNA viruses e.g Geminivirus 28-30nm ➢dsDNA viruses e.g caulimovirus 50nm