Answer: Potato spindle tuber disease.
- A Tobacco mosaic disease
- B Potato spindle tuber disease
- C Mad cow disease
- D Rust of wheat
Correct answer: B. Potato spindle tuber disease
Explanation: Potato spindle tuber disease is caused by a viroid, discovered by T.O. Diener in 1971. Viroids lack the protein coat found in viruses.
Whittaker's five-kingdom system (1969) groups all cellular life by cell structure and nutrition; viruses, viroids, and lichens fall outside this system entirely since they aren't independently classifiable as one of the five.
Concept context
Whittaker's five kingdom system covering Monera, Protista, Fungi, plus viruses, viroids, and lichens. A foundational NEET chapter on how living organisms are grouped.