Question

The ‘witches’ broom of legumes is caused by a
A. Virus
B. Phytoplasma
C. Bacterium
D. Fungus

Answer 1

Witches broom of legumes is a type of disease that changes the natural structure of the plant or a tree. It mostly occurs in woody plants or trees. A witch of the broom is mainly caused by the basidiomycetes.

Step by step answer: Witches broom of legumes is a disease in which the structure of plant changes and gives the appearance of a broom. This disease is caused by Phytoplasma or basidiomycetes and is economically important in the number of crop plants, including the cocoa tree and the timber tree. Auxin is responsible for the tree's characteristic shape or habit and controls the growth of secondary apices. Auxin limits the growth of an offshoot while that of the parent branch is not. In cases of this witch's broom, the normal anatomy of buds is interrupted and apices grow indiscriminately. This condition can be caused by cytokinin, a phytohormone which interferes with growth regulation. The phenomenon can also be caused by other organisms, including oomycetes, insects, mites, nematodes, phytoplasmas. These broom growths may last for many years or can be throughout the life of the host plant. If twigs of witch's brooms are grafted onto normal rootstocks, freak trees result, showing that the attacking organism has changed the inherited growth pattern of the twigs.
So, the correct option is option B. Phytoplasma.

Note: Witches broom is of ecological importance. The witches’ broom of legumes provides a nesting habitat for many birds and mammals. An example of this is the northern flying squirrel which nests in them. It is a dense mass of shoots that grows from a single point with the resulting structure resembling a broom or a bird's nest.