Virus
Definition
A virus is a particle consisting of hereditary material (DNA or RNA) enclosed within a protein shell. Unlike living organisms, viruses cannot reproduce independently; they require a living host cell to replicate. Because of this dependency, scientists debate whether viruses should be considered true life forms.
Host specificity
Viruses can infect a wide range of living cells, from single-celled organisms to plants and animals. However, not every cell is suitable for every virus. The protein coat of a virus enables it to recognise and attach to specific host cells. Once inside, the virus’s genetic material directs the host cell to produce new virus particles.
Viruses in plants
Approximately one quarter of known viruses are capable of infecting plants. A single plant may be infected by multiple viruses simultaneously, and even several isolates of the same virus can coexist within one plant. This complexity often makes plant virus management challenging.
Mechanism of disease
Viruses do not cause disease by consuming cells or poisoning them. Instead, they disrupt normal cellular processes by:
- Using cellular substances during replication
- Occupying space within cells
- Interfering with essential metabolic pathways
This interference weakens the plant and can lead to symptoms such as stunted growth, leaf distortion, or reduced yield.
