Question

Which of the following is not an air borne disease?
A. Black stem rust of wheat
B. Coffee rust
C. Blast of rice
D. Potato mosaic disease

Answer 1

Hint: The pathogens can affect the total yield of crops. It is more common in tropical climates because of high temperature and rainfall. Hence, disease resistant varieties are important to get high yield and food production. It also prevents the use of fungicides and bactericides .

Complete answer
The different pathogens cause different diseases in plants. It can be fungus, bacteria or virus that attacks plants and affects their yield. Specific pathogens attack specific species of plants. The different diseases in plants are-
Black stem rust of wheat- caused by the fungus Puccinia graminis, the disease is characterized by the presence of brick-red and long pustules on the stems and leaves of wheat. It is called black rust because at the end of growing season, telia are produced that are black in color. The disease spreads from one plant to another plant by air (hence, air borne disease). The diseased plant produces fewer grains and hence, low yield.
Coffee rust- the disease is caused by the fungus that belongs to the Phylum Basidiomycota. The Hemileia vastatrix causes the coffee rust in which the leaves of coffee plants are affected. The disease is characterized by the presence of small, oily spots that are initially yellowish and later turn brown. The disease spreads through the air.
Blast of rice- caused by the fungus Magnaporthe oryzae , the disease is characterized by the presence of lesions on the rice plant. Almost all parts of the plants are affected. It is transmitted through air. It causes serious damage to the rice plant.
Potato mosaic disease- Caused by the potato mosaic virus, the disease is characterized by mild symptoms. However, the yield is reduced. The symptoms include wrinkling of leaves, dwarfed plants etc. The virus mainly spreads through the mouth of aphids. It can also be spread mechanically.

Thus the answer of the above question is option (D) Potato mosaic disease as it spreads through aphids.

Note: To protect the plants from pathogen causing diseases, different crop varieties are developed by breeding methods. For example- the Pusa Komal is a variety of cowpea which is resistant to bacterial blight. Similarly, Pusa Sadabahar is a variety of chilli which is resistant to chili mosaic virus and tobacco mosaic virus.