Question

Identify the correct statement(s) with respect to plant disease:

• A. Hairy root disease in tobacco is caused by Agrobacterium tumefaciens.
• B. Loose smut of barley is caused by Ustilago nuda.
• C. Stem rust of grape is caused by Plasmopara viticola.
• D. Fire blight in pear is caused by Erwinia amylovora.

Hint:

Understanding the specific pathogen responsible for a plant disease is essential for choosing the appropriate control measures. For example, bacterial infections require different treatments compared to fungal diseases.

Answer 1

The Correct Option is B, D

- (A): Hairy root disease is a plant disease caused by the bacterium Agrobacterium rhizogenes, not Agrobacterium tumefaciens. Agrobacterium tumefaciens is responsible for crown gall disease, characterized by the formation of tumors on the roots and stems. Hairy root disease results in the formation of abnormal root structures and is caused by a different species of Agrobacterium. Hence, statement (A) is incorrect.
- (B): Loose smut of barley is indeed caused by the fungal pathogen Ustilago nuda. This disease is characterized by the formation of smut balls, which consist of fungal spores, in the heads of barley plants. Ustilago nuda is a common pathogen that affects barley and other grasses, making statement (B) correct.
- (C): Stem rust of grape is caused by the fungus Puccinia graminis, not Plasmopara viticola. Plasmopara viticola is the causal agent of downy mildew in grapevines, not stem rust. Therefore, statement (C) is incorrect.
- (D): Fire blight in pear is indeed caused by the bacterium Erwinia amylovora. This bacterial pathogen infects the flowers, twigs, and branches of pear trees, causing wilting and dieback. The disease is highly destructive and can spread rapidly under favorable conditions, making statement (D) correct.
Thus, the correct answers are (B) and (D), as they accurately describe the pathogens responsible for loose smut of barley and fire blight in pear.