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PLANT VIRUS PPT - SLIDE SHARE

Fully discription of PLANT VIRUS

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PLANT VIRUS PPT - SLIDE SHARE

  1. 1.  INTRODUCTION.  FEATURES.  HISTORY.  VIROIDS.  PRIONS.  CHEMICAL COMPOSITION OF PLANT VIRUS.  ARCHITECHTURE OF PLANT VIRUS.  TOBACCO MOSAIC VIRUS.  CAULIFLOWER MOSAIC VIRUS.  TOMATO YELLOW LEAF CURL VIRUS.  TRANSMISSION.  SYMPTOMS.  PROTECTION.  CONCLUSIONS.
  2. 2.  Plant viruses are viruses that affect plants.  Plant viruses are pathogenic to higher plants.  These are normally insects , but some fungi.  Plant viruses are harmless to human and other animals.
  3. 3.  Outside protein coat.  Consists of a single nucleic acid.  Non-living and Non-cellular structures.  Non-cellular sub microscopic entity.  Most viruses infect only SPECIFIC host cells.  May be transmitted in pollen.
  4. 4.  Beijerinck (1897) coined the Latin name “VIRUS” meaning Poison.He studied filtered plant juices and found they caused healthy plants to become sick.  Wendell Stanley (1935) crystallized sap from sick Tobacco plants. He discovered viruses were made of nucleic acid and protein.
  5. 5.  Small , circular RNA molecules.  Infect plants.  Have no protein coat.  Potato famine in Ireland.  Resemble introns cut out of eukaryotic.  Consist solely of small single-stranded RNA molecule.  Define group of pathogens much smaller and distinctly different from viruses.
  6. 6.  Prions are “Infectious Proteins”.  They have no DNA or RNA.  Causes neurons to rapidly degeneration.  Mad Cow Disease (Bovine Spongiform Encephalitis : BSE) is an example.  Inherited and transmissible diseases.
  7. 7.  Protein (capsid) - Capsomere.  Nucleic acids – DNA : - ssDNA , dsDNA. RNA : - +ve strand RNA , -ve strand RNA , ssRNA , dsRNA.
  8. 8. PROTEINS : -  60% - 95% of the virion.  Protein protects virus genome from – Degradation. Facilitates movement through the host. Transmission from one host to another.  Repeating subunits , identical for each virus type but varies from virus to virus and even from strain to strain.
  9. 9. NUCLEIC ACID : -  Nucleic acid represents the genetic material , indispensable for replication.  Nucleic acid is 5 – 40% of the virion. ssRNA : - About 540 plant viruses.eg. TMV. dsRNA : - About 40 pv. eg. Wound tumour virus. ssDNA : - About 50.eg. Beet curly top virus. dsDNA : - About 30. eg. Cauliflower mosaic virus.
  10. 10. ISOMETRIC : -  Apparently spherical and (depending on the species) from about 18 nm in diameter upwards.  Eg. –Tobacco necrosis virus.  Genus – Necrovirus , with particles 26 nm in diameter.  Geminate – Twinned isometric particles. ROD – SHAPED : -  Rigid rod. Eg. TMV.  Flexuous rod. Eg. Potato virus Y.
  11. 11. CLASSIFICATION : -  Family – Virgaviridae.  Genus – Tobamovirus.  Species – Tobacco mosaic virus.
  12. 12.  STRUCTURE : -  Rigid helical rods.  ssRNA.  Extremely stable structure.  95% protein and ~5% nucleic acid(RNA).  2130 copies of single 17kDa coat protein.  Simple regulatory elements.  300 nm long and 18 nm dia.  Rod-like appearance.  There are three RNA nucleotides monomer.
  13. 13. CLASSIFICATION : -  Family – Caulimoviridae.  Genus – Caulimovirus.  Species – Cauliflower mosaic virus.
  14. 14. STRUCTURE : -  CaMV is an icosahedral virus.  Diameter 52 nm.  Genome is circular dsDNA.  Capsid multilayered.  Arrangement of capsomere not clear.  The outermost layer is made up of a total of 420 coat protein subunits.
  15. 15. CLASSIFICATION : -  Family – Geminiviridae.  Genus – Begomovirus.  Species – Tomato yellow leaf curl virus.
  16. 16. STRUCTURE : -  TYLCV has a characteristic twinned morphology.  The TYLCV capsid , like that of other geminiviruses , consists of two joined , incomplete icosahedra.  TYLCV has a single 2787 nucleotides covalently closed genomic circular ssDNA.
  17. 17. There are two types of plant virus transmission –  Horizontal transmission.  Vertical transmission.  Horizontal transmission :- It is by vectors , human pruning shears and tools and other direct , external contamination.  Vertical transmission :- It occurs when a plant gets it from its parent plant. Either through asexual propagation (cuttings) or in sexual reproduction via infected seeds. -
  18. 18. Mechanical Transmission :-  Occure when plant come in contact with other plant and leaves rub together.  By the action of humans.
  19. 19. Nematode Transmission :-  Two ssRNA virus genera , Nepovirus and Tobravirus , have nematode vectors. NEPOVIRUSES – Comoviridae family. TOBRAVIRUSES – Family not yet assigned.
  20. 20. Seed Transmission :- It occurs in two ways –  Externally seed borne – Due to external contamination of the seed with virus particles (TMV , PVX).  Internally seed borne – Due to infection of the living tissues of the embryo.
  21. 21.  Mosaic.  Mottle.  Yellowing.  Chlorosis.  Vein clearing.  Vein banding.  Necrosis.  Wilt.  Ringspot.  Stunting.
  22. 22.  Discard virus infected plants.  Purchase virus-free plants.  Remove all crop debris from benches and the greenhouse structure.  Remove all weeds since these may harbor both viruses and insects.  Maintain strict insect and mite control.
  23. 23.  Plant viruses and viroids are unusual groups of plant pathogens that infect and cause disease in many crop plants.  Because these pathogens depend on the normal cellular machinery of their plant host for reproduction , it is difficult to eliminate them without damaging the host plant.
  24. 24. THANK YOU

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