Question

Polycyclic diseases are usually caused by pathogens adapted

• A. on foliar plant parts
• B. in soil
• C. in rhizosphere
• D. in phloem

Hint:

Polycyclic diseases:
- Multiple infection cycles per season.
- Caused by foliar pathogens (produce many spores).
- Examples: Rusts, powdery mildews, leaf spots.

Answer 1

The Correct Option is A

Step 1: Understanding the Question:
This question tests knowledge of the epidemiology of polycyclic diseases.

Step 2: Detailed Explanation:
Polycyclic diseases are diseases that have multiple cycles of infection within a growing season.
These are usually caused by pathogens adapted on foliar plant parts (A).
Foliar pathogens produce many spores that can cause multiple infection cycles.
Examples: Rusts, powdery mildews, leaf spots, blights.
Other pathogens:
- Soil-borne pathogens (B): Usually cause monocyclic diseases (one infection cycle per season).
- Rhizosphere pathogens (C): Also cause monocyclic diseases.
- Phloem pathogens (D): Usually cause systemic diseases.
Thus, polycyclic diseases are caused by foliar pathogens.

Step 3: Final Answer:
Thus, polycyclic diseases are caused by pathogens adapted on foliar plant parts, which corresponds to option (A).
[0.5cm]