Description about general characters of plant viruses

1. General characters of
Plant viruses
N. H. SHANKAR REDDY
Ph.D., Plant Pathology
Annamalai University

2. Properties of plant viruses
 The virus contains only one type of nucleic acid, either DNA or RNA but not both.
 Most of the plant pathogenic viruses contains RNA as genetic material (almost 78% of
plant viruses)
 Virus does not contain cell wall, but it contains protein coat as protective layer, and the
amount of protein coat and amino acids compositions may vary with viruses.
 Viruses neither have any sexual reproduction nor produce any resting structures as that
of fungi and bacteria.
 The major symptoms produced by viral diseases are yellowing off leaves, due to the
inhibition of chlorophyll production.

3.  The viruses produce symptoms like mosaic, leaf curl, crinkling, stunting, chlorosis, necrosis,
vein clearing, vein banding and enation.
 Viruses moves from cell to cell through ‘Plasmodesmata’
 Virus moves 8-10 cells/ day (1mm) in plant cells approximately
 Plant viruses may transmit through seeds, vectors, mechanical transmission (sap) and
vegetative propagative materials etc.
 Enzyme used for replication of virus is ‘RNA polymerase I’
 For short distances virus can moves through vectors, whereas long distances viruses move
through propagative material
 Capable to causes diseases in plants, animals and humans
 The maximum temperature required to kill almost all plant viruses ranges form 55-70 oC.
 Few viruses require the presence of other viruses for their replication.

4. They have both living and non-living properties.
 Living characters include their ability to cause disease, reproduce, mutate and have
genetic materials.
 Non-living characters are the lack of cellular structure; enzymatic activities, respiratory
activities and they can be crystallized

5. Shape may vary with virus to virus
 Rigid rod: (E.g.) Tobacco Mosaic Virus (TMV) and Tobacco rattle Virus (TRV)
o Flexuous rod: (E.g.) Potato virus X (PVX), Bean Common mosaic virus (BCMV).
o Filamentous rod: (E.g.) Tenuiviruses likes Rice grassy stunt (RGSV) and Rice stripe
virus (RSV).
 Isometric: (E.g.) Rice tungro spherical virus (RTSV), Cucumber mosaic Virus (CMV),
Tomato spotted wilt virus (TSWV).
 Bacilliform: (E.g.) Rice tungro bacilliform Virus (RTBV), Banana streak virus (BSV)
and Cocoa swollen shoot virus (CCSV).
 Eg - Tobacco mosaic virus (TMV), Cauliflower mosaic virus (CaMV) etc.

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