An infectious agent associated with potato spindle tuber disease is smaller than viruses and lacks a protein coat. What
The agent is a viroid. Viroids consist of free RNA of low molecular weight and lack the protein coat found in viruses. T. O. Diener discovered them while studying potato spindle tuber disease.
Ref: NCERT Class 11 Biology Chapter 2: Biological Classification Viruses Viroids Prions and Lichens
