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