Question:
In which of the following disease you will find both sign and symptoms together
In which of the following disease you will find both sign and symptoms together
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Whenever you see Sclerotium rolfsii or Athelia rolfsii, think of the coarse white mycelial fan and brown sclerotia (signs) appearing on the rotted collar (symptom) at the soil surface.
Updated On: Aug 13, 2026
- Southern blight incited by Athelia rolfsii
- Wilt incited by Fusarium
- Gall incited by Agrobacterium
- Blight incited by Xanthomonas
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The Correct Option is A
Solution and Explanation
Step 1: Understanding the Concept:
In plant pathology, it is critical to distinguish between a sign and a symptom.
A symptom is the host plant's visible reaction to the pathogen (e.g., wilting, chlorosis, necrosis, galls).
A sign is the physical presence of the pathogen or its structures (e.g., mycelium, spores, bacterial ooze, sclerotia).
Step 2: Detailed Explanation:
Let us evaluate the four diseases:
1. Southern blight (Athelia rolfsii): The pathogen is a soil-borne fungus (asexual stage Sclerotium rolfsii).
It causes sudden wilting, collar rot, and necrosis at the base of the stem (symptom).
Concurrently, a thick, white, fan-like mat of mycelium and small, brown, mustard-seed-like sclerotia develop on the surface of the infected collar region (sign).
Thus, both signs and symptoms are found together.
2. Fusarium wilt: This disease is characterized by leaf yellowing and wilting (symptoms).
The pathogen remains inside the vascular xylem vessels. Its mycelia and spores are not visible on the plant surface during early disease development.
3. Crown gall (Agrobacterium tumefaciens): This disease causes woody galls on stems or roots (symptom).
The bacterial cells are microscopic and do not form a macroscopic structure on the surface.
4. Bacterial blight (Xanthomonas): This causes leaf necrotic lesions (symptom).
Although bacterial ooze (sign) can sometimes appear, it requires highly humid conditions and is not as consistent or prominent as the mycelia and sclerotia in Southern blight.
Step 3: Final Answer:
Southern blight incited by Athelia rolfsii consistently shows both host symptoms and pathogen signs together. Therefore, the correct option is (A).
In plant pathology, it is critical to distinguish between a sign and a symptom.
A symptom is the host plant's visible reaction to the pathogen (e.g., wilting, chlorosis, necrosis, galls).
A sign is the physical presence of the pathogen or its structures (e.g., mycelium, spores, bacterial ooze, sclerotia).
Step 2: Detailed Explanation:
Let us evaluate the four diseases:
1. Southern blight (Athelia rolfsii): The pathogen is a soil-borne fungus (asexual stage Sclerotium rolfsii).
It causes sudden wilting, collar rot, and necrosis at the base of the stem (symptom).
Concurrently, a thick, white, fan-like mat of mycelium and small, brown, mustard-seed-like sclerotia develop on the surface of the infected collar region (sign).
Thus, both signs and symptoms are found together.
2. Fusarium wilt: This disease is characterized by leaf yellowing and wilting (symptoms).
The pathogen remains inside the vascular xylem vessels. Its mycelia and spores are not visible on the plant surface during early disease development.
3. Crown gall (Agrobacterium tumefaciens): This disease causes woody galls on stems or roots (symptom).
The bacterial cells are microscopic and do not form a macroscopic structure on the surface.
4. Bacterial blight (Xanthomonas): This causes leaf necrotic lesions (symptom).
Although bacterial ooze (sign) can sometimes appear, it requires highly humid conditions and is not as consistent or prominent as the mycelia and sclerotia in Southern blight.
Step 3: Final Answer:
Southern blight incited by Athelia rolfsii consistently shows both host symptoms and pathogen signs together. Therefore, the correct option is (A).
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