Viroid

Viroids are infectious agents that consist of single-stranded RNA. They are much smaller and more simple than viruses and lack the protein cover that is typical for viruses. Viroids use higher plants (such as potatoes, tomatoes and cucumber?s) to reproduce, inserting themselves into the nucleus of a plant cell to be replicated there. Viroids are usually transmitted by seed? or pollen?. Infected plants can show distorted growth. The first viroid to be identified was the [potato spindle tuber viroid]?.