Viroids are subviral, submicroscopic low molecular weight covalently closed ssRNA. They are possibly smallest pathogens on Earth. They cause many diseases in plants like PSTVd, Cdang Cdang disease of coconut, tamato bunchy top disease etc. T.O. Diener first time discovered viroids while working on Potato Spindle Tuber Disease (PSTVd). To know more about Viroids, watch the video..............
