Q.Who discovered viroids, and in which year were they discovered?

Viroids and prions are infectious agents even simpler in structure than viruses, sitting at the very boundary of what is considered living.

In 1971, T.O. Diener discovered viroids while studying the causal agent of potato spindle tuber disease, finding an infectious particle smaller than the smallest known virus. A viroid consists only of a free RNA molecule of low molecular weight, entirely lacking the protein capsid that always surrounds a virus's genetic material; despite this stripped-down structure, the naked viroid RNA can still infect a host cell and replicate using the host's own cellular machinery. …