In agriculture sectors, when it comes to the issue of virus control, it simply means to prevention is the only steps that should be done. The ultimate goal is to prevent virus spread simply just by either controlling the vectors or through the eradication of infected plants. In this also is an important step to prevent the farmers, agriculture industry as well as the national and international trade. Viruses are sub-microscopic which is an infectious particles that multiply only inside living host cells. (Virology,
n.d.) The basic shape of the viruses found in plants are elongate which is either in rigid rods or flexuous threads, cylindrical rods such as Bacillus-like and in isometric or polyhedral which is spherical shape. They are made out of two components which is a protein coat and also the nucleic acid center. They are also an obligate parasites which means they live in living tissues of plants before they reproduce themselves. They require a wound to gain entrance to a plant cell. In general, they severely affect the host both in quantity, quality and longevity. There are a few symptoms to extinguish the viruses which depends on a couple of factors such as:
1) Symptoms are important indicators of a plant virus disease.
2) Symptoms on a diagnostic indicator plants assists in characterizing the virus.
3) The ability to cause symptoms confirms the biological activity of the virus.
Objective
1. To study the diseases caused by virus.
2. To observe the morphology of virus.
3. To understand the steps in mechanical inoculation of virus on a host plant.
Materials
Figure 1 shows mortar and pestle
Figure 2 shows carborundum
Figure 3 shows the host plants which is chili plant
Figure 4 shows distilled water
Figure 5 shows diseased leaf
Mortar and pestle, carborundum, test host plant which is chili plant, distilled water and diseased leaf.
Procedure
Activity: Mechanical inoculation of virus on chili host plant.
- The virus inculum was prepared by crushing the diseased leaf by using the mortar and pestle until a uniform extract was obtained.
- 0.5ml to 1ml of distilled water was added to the extract.
- The host plant was dusted with carborundum abrasive on the leaf surface of the host which virus mix was inoculated.
- The carborundum caused injuries on the leaf surface resulting in the minute opening on the leaf surface. The carborundum was used only in a small quantity.
- The virus mix that has been prepared was applied on the test leaf surfaces of the host plant using a soft piece of cloth.
- Inoculation on the leaves was done by gently wiping the inoculum across the upper epidermis about 3-4 times to ensure that the leaves appear to be uniformly wetted and not damaged.
- The leaves that was inoculated with the virus was then washed using water. This was to remove excess leaf pieces and sap from the leaf surfaces.
A. Virus Morphology
1. Chlorosis - An even change of colour which is yellow on the inside with the distinct spotting.
2. Necrosis - Cell death which appears as general necrosis or in the form of spots.
3. Mosaic - Characterized by light green, yellow or white areas intermingled with the normal green of the leaves or fruit. For example, mosaic of chili, tobacco and ground nuts.
4. Ringspot - Chlorotic or necrotic rings on the leaves and fruits.
5. Veinclearing - Chlorosis or necrotic rings on the leaves and fruits.
6. Veinbanding - severe chlorosis of the leaf veins. Example; Ageratum conzyzoides.
7. 'Penyakit Merah' of paddy.
Result and Discussion
The host plant of virus which is the chili plant was left within 24 hours in open air. After a day, observation and recording was done regarding the result of the infected chili host plant.
Chili host plant before inoculation
After 24 hours of inoculation
Left side - infected host plant
Right side - controlled host plant
Between the controlled chili host plant and the inoculated chili host plant, it was clear to state that the inoculation was experiment was successful as the infected host shows signs of inoculation. One of the obvious symptoms that can be seen is the curling up of leaves as compare to the control host.
As shown in the picture above, the leaves that was inoculated with disease started to shows symptoms by curling up the leaves. The infection also doesn't seem to be spreading to other parts of the plants Other than that, the leaves started to turn yellow as shown in the picture but due to a day observation, the symptoms can't really be observe as the virus that was inoculated was a disease symptoms called mosaic.
Conclusion
In conclusion, virus can be seen through their morphology using the naked eyes such as chlorosis, necrosis, mosaic, ringspot, veinclearing and also 'penyakit merah' of paddy plant. This makes it easier for farmer to directly ifdentify the symptoms of viruses through the morphology of the symptoms. Other than that, we were able to understand the stages that is needed to be done to proceed the mechanical inoculation of virus on the chili host plants. It was clear that the virus require a wound to gain enterance to the plant cell. And also virus inoculation is fast thus the symptoms can already be seen within 24 hours after inoculation. The symptoms that can been seen through the inoculation was the curling of the leaves on the areas that was inoculated with viruses.
Reference
Plant Virology. (n.d.). Retrieved from FABI:
https://fabinet.up.ac.za/research-groups/plant-virology
Virology, P. (n.d.). Plant
Virology . Retrieved from Agricultural Research Council:
http://www.arc.agric.za/arc-ppri/Pages/Plant%20Pathology%20and%20Microbiology/PLANT-VIROLOGY-.aspx
