ONE OFTHE TOPIC IN CHAPTER 4 SEMESTER 2

1. Characteristics of VirusCharacteristics of Virus
Chapter 4 – AGR154

2. Overview of ChapterOverview of Chapter
Main characteristics of virus
Reproduction in virus
Virus mode of attack
Translocation and distribution if viruses in
plant
Detection of virus or virus disease

3. Main CharacteristicsMain Characteristics
Virus is a nucleoprotein (consist of nucleic acid and
protein) and has the ability to cause disease
The protein will form a protective coat around the
nucleic acid (capsid)
The nucleic acid has either DNA or RNA but not both
They may have two or more different proteins
Parasitic in cells
Multiplies only in living cells
Has many shapes such as rod shaped, polyhedral.

4. Structure of VirusesStructure of Viruses
Polyhedral VirusHelical Virus

5. Reproduction in VirusReproduction in Virus
Virus do not divide and do not produce spores
Do not have specialized reproductive
structures
Multiply by inducing host cell to make more
virus

6. Virus Mode of AttackVirus Mode of Attack
So how do viruses cause injury?
By utilizing cellular substances
During multiplication, they take up space in cells
and disrupting cellular processes
Viruses are small and transparent
They cannot be viewed and detected by
methods used for other pathogens
They are not cells nor do they consist of cells

7. How They Injured Plant?How They Injured Plant?
They do not produce toxins
They do not eat the host cell
But :
They utilize the host cellular substances
for multiplication
Conquer the host space
Disrupt the host cellular process

8. How Do Virus Enter PlantsHow Do Virus Enter Plants
Through wounds
By vectors
Infected plant parts/ seed
Example : Deposition of virus particle into
ovule by infected pollen grain.

9. Translocation & Distribution ofTranslocation & Distribution of
Virus in PlantVirus in Plant
1. Virus enter the host cell
2. Moves from one cell to another cell through
plasmodesmata (connecting the cell)
3. Multiply in each host parenchyma cell
4. Then, they will reach the phloem
5. In phloem, the virus will be transported
rapidly over long distance.
7. From phloem, they will enter the host
growing region (apical meristems and food
utilizing parts)

11. Detection of Virus or Virus DiseaseDetection of Virus or Virus Disease
1. Inclusion Bodies
Some infected plant will contain
inclusion bodies
Inclusion body : aggregation of virus
particle
The inclusion bodies can be seen under a
light microscope

12. Inclusion BodyInclusion Body

13. 2. Virus Particle
These can only be viewed under electron
microscope
Still it is not easy to identify and difficult to
prove that the particular virus cause the
disease
The virus particle can be seen under
electron microscope

15. 3. Transmission Method
Transmit the virus from infected plant
to healthy plant by:
Budding technique
Grafting
Rubbing the leaves of healthy plant
with the infected plant

16. 4. Serology
Most common method is using the ELISA
procedure
Enzyme-linked immunosorbent assay
5. DNA or RNA Probes
This is the most recent methods