Question

Witches Broom of potato tree is caused by
A) Mycoplasma
B) Bacteria
C) Viruses
D) All of the above

Answer 1

Hint: In this disease, the natural structure of the tree is changed and the tree has bushy outgrowth in the shoot. The witches broom can also be the result of the interruption of the growth by the cytokinins which plays a major role in growth regulation. The disease pathogen also attacks cocoa, jujube etc.

Complete answer:
Witches' brooms are a kind of symptom of plant disease. In this, the plant appears abnormal. Brush-like clusters develop in the weak shoots at the same point. The branches may die. It can be caused by a number of pathogens including mites, fungi, viruses etc but in the case of potato, it is caused by Mycoplasmas. In the case of pine trees, it is caused by rust fungus.

The symptoms of the disease in potatoes include narrowing of the leaf, formation of hairy sprouts on the plant, formation of aerial tubers, the size of the potato tubers may get reduced. The stunted growth and the yellowing of the plant are also seen in many cases.

Bacteria- The bacteria cause brown rot, pink eye or ring rot or scab type of diseases in potato plants.
Virus- Potato blackspot, leaf roll, potato spindle tuber, yellow rot are the major virus-caused diseases in potatoes.

Therefore the correct answer is option ‘B’.

Note: Mycoplasma is also known as jokers of the biological park as they do not have a definite shape. These are closely related to bacteria and lack cell walls. It is the smallest known free-living organism. The mode of nutrition can be parasitic or saprotrophic.