Question

Potato spindle tuber disease is caused by
A) Prions
B) Viroid
C) Virus
D) Bacteria

Answer 1

Hint: The disease agent was characterized as an infectious ribonucleic acid (RNA) of low-molecular weight. This disease is said to be PSTVd.

Complete answer:
It is a serious disease that occurs in tomato and potato. This disease was first identified in North America as a potato disease, and first observed in South Africa as a tomato disease. Symptoms of nutritional imbalance, insect damage or other plant diseases can be confused with the symptoms of this disease.
In warm temperatures and under increased light intensity, symptoms become more noticeable.

Now, let us find the solution from the options-
- The first viroid to be described was the Potato spindle tuber viroid (‘PSTVd’) which contains a circular, small RNA molecule closely similar to the Chrysanthemum stunt viroid.
- The Pospiviroid RY motif stem loop is present inside the viroid RNA.
- Potatoes (Solanum tuberosum) and tomatoes (Solanum lycopersicum) are their natural hosts.
- PSTVd is susceptible to both potatoes and tomatoes and no sort of natural resistance exists.
- The disease of the potato spindle tuber is not caused by viruses, prions, or bacteria.

Thus, the correct answer is option (B) Viroid.

Note: Viroids are single-stranded RNA, a spherical molecule covalently closed, without any protein coating. These are the smallest known RNA-genome plant pathogen that ranges from 246 nucleotides to 399 nucleotides. There are some viroids which are found in the nucleus of plant cells called pospiviroidae and some are found in the chloroplasts called avsunviroidae.