Write a short note on Viroids.

(N/A) Viroids were discovered by $T.O. Diener$ in $1971$ as a new infectious agent that is smaller than viruses.
$1$. Structure: They consist of a short strand of low molecular weight $RNA$ and lack the protein coat that is found in viruses,hence the name 'viroid'.
$2$. Genetic Material: The $RNA$ of the viroid is of low molecular weight.
$3$. Pathogenicity: They cause diseases in plants,such as the potato spindle tuber disease.
$4$. Replication: They replicate inside the host plant cells using the host's machinery.