disscussion on plant viruses

1. CLASSIFICATION OF
PLANT VIRUSES
MOHD SALIM
18-BTM-028
GK7985
DEPTT.OF BOTANY
AMU.ALIGARH

2. WHAT IS PURPOSE OF 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’infective entities 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 FOR CLASSIFYING 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.g Tobacco 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