Question

Choose the correct answer from the options given below:
(A) Ralstonia causes wilt disease
(B) Fusarium causes wilt disease
(C) Verticillium causes wilt disease
(D) Pseudomonas causes wilt disease

• A. (A), (B), (C), (D)
• B. (A), (B), (C)
• C. (B), (A), (D)
• D. (C), (B), (D)

Hint:

Vascular wilt pathogens are highly destructive because they target the plant's water-transport system.
Once the xylem is colonized and blocked by fungal mycelia, bacterial cells, or their extracellular slime, the plant cannot transport water, causing it to wilt and die even if soil moisture is abundant.

Answer 1

The Correct Option is A

Step 1: Understanding the Concept:
Vascular wilt is a severe type of plant disease where pathogens colonize and clog the plant's water-transporting xylem vessels.
This blockage restricts water movement, leading to leaf yellowing, wilting, and eventual death of the host plant.
Both bacterial and fungal pathogens can cause vascular wilt diseases.

Step 2: Detailed Explanation:
Let us analyze the disease-causing capabilities of each listed genus:
(A) Ralstonia:
Ralstonia solanacearum is a well-known soil-borne bacterium that causes bacterial wilt (also known as brown rot in potato) in solanaceous crops and bananas.
The bacteria enter the roots, multiply rapidly in the xylem, and produce extracellular polysaccharides (EPS) that clog the water-transporting vessels, causing the plant to wilt.
Thus, (A) is correct.
(B) Fusarium:
Fusarium oxysporum is a soil-borne fungus with many host-specific forms (*formae speciales*).
It causes vascular wilt (Fusarium wilt) in a wide range of crops, including banana (Panama disease), cotton, tomato, and pigeonpea.
Thus, (B) is correct.
(C) Verticillium:
Verticillium dahliae and Verticillium albo-atrum are soil-borne fungi that cause Verticillium wilt in many broadleaf crops, including cotton, potato, and mint.
Like *Fusarium*, the fungus invades the roots and colonizes the xylem vessels.
Thus, (C) is correct.
(D) Pseudomonas:
Certain species of the genus *Pseudomonas* (such as *Pseudomonas syringae* or species historically classified under this genus) can cause bacterial wilting and blight in various host crops under specific environmental conditions.
Thus, (D) is correct.
All four genera contain pathogens that cause wilt diseases.

Step 3: Final Answer:
All the listed genera (A, B, C, and D) contain pathogens that cause wilt diseases.
This corresponds to Option (A).