This document describes a method for detecting viruses in potatoes using tuber grafting. The objective is to detect virus in potato tubers. It explains that viruses can pass from infected to healthy potato tubers if their tissues are joined. The method involves taking cores from virus-containing and healthy potato tubers and grafting them together, then growing the grafted tuber to see if symptoms develop, indicating the presence of a virus. The healthy and infected potato tissues serve as controls. If symptoms appear on the grafted tuber after 3-4 weeks, it indicates the healthy tuber was infected by the virus from the other tissue.

2. Presenter
Hem Raj Pant
frenndlyhem01234@gmail.com
Msc. Ag
Department of plant pathology
AFU- Agriculture and Forestry University
Rampur, chitwan
www.afu.edu.np
A Presentation on
VIRAL DETECTION IN POTATO BY TUBER
GRAFTING

3. OBJECTIVE
To detect virus in potato by tuber grafting

4. THEORY
Viruses are intracellular (inside cells) pathogenic particles that infect other
living organisms.
The total number of known viruses to date are around 2000. Nearly half of
known viruses causes diseases in plants.
Common characteristics of viruses:
 Obligate parasites, highly infectious and host specific
 Viruses are visible under electron microscope but not visible under light
microscope
 Each plant viruses consist of at least nucleic acid and a protein coat
 Multiplication, Infectiveness and Mutation are living characters
 Particle and Precipitation are non living characters

5.  Plant viruses are transmitted from plant to plant in a number of ways
1. Transmission of viruses by vegetative propagation
2. Mechanical transmission of viruses through sap
3. Transmission of viruses by seed
4. Transmission of viruses by Pollen
5. Transmission of viruses by dodder
6. Transmission by vectors
a. Insect transmission
b. Mite transmission
c. Nematode transmission
d. Fungus transmission
Contd….

6.  Transmission by Vegetative Propagation
 Plants are propagated vegetative by budding or grafting or by cutting or by
the use of tubers, corms, bulbs or rhizome.
 Viral detection by potato tuber grafting
 In Potato, viruses may pass from virus-containing tubers into healthy ones if
parts of the two are put together sufficiently long. Plants developing from
initially healthy component will be virus diseased.
Originally, cut parts of tubers were simply fixed together. For tuber forming
crops like potatoes the method of core grafting was developed by Murphy
and Mckay (1926). This method is described here.
Contd….

7.  Virus containing tubers (V-tubers)
 Healthy tubers (H-tubers)
 Cork borer, diameter 13 mm
 Cork borer, diameter 13.5 mm
 Sticks fitting in the cork borers and at least twice as long
 Small container with paraffin wax (low melting point: 42-45˚C)
 Pots with sterilized soils
 Labels
MATERIALS REQUIRED

8.  With the 13.5 mm cork borer take a core without eyes from the V-
shaped tuber. The core can be pushed out of the borer using a stick.
 With the smaller 13mm cork borer remove a core with an eye from
the H-tuber. Do not damage the eye when removing the core from
the borer. Push with the stick from the opposite side.
 Insert the core from the V-tuber into the bore-hole of the H-tuber
with rotating movements. The inserted core may be a few mm
shorter than the bore-hole but not longer, as this may prevent the
proper union of the cambial tissues. For the same reason the skin at
the ends of the core should be undamaged.
PROCEDURES

9.  Immerse the V-tuber with the bore-hole, the grafted tuber and the core
from the H-tuber in the melted paraffin wax. The temperature of the wax
should be just above the melting point. The wax layer should cover the
wounds to prevent bacterial rotting in the soil.
 Plant the two tubers and the core separately in three pots containing
sterilized soil. The core and the V-tuber will serve as healthy and
diseased controls, respectively.
 After 3-4 weeks in the glass house the shoots will have developed
sufficiently for evaluating the symptoms or determining their virus
content.
Contd….

10. Thus we became able to know the method of viral detection
in potato by tuber grafting
CONCLUSION