Given below are two statements, one is labelled as Assertion A and the other is labelled as Reason R
Assertion A: Polycyclic diseases are known to cause plant disease epidemics.
Reason R: Polycyclic disease inciting pathogens produce multiplicity of infections in short time.
In light of the above statements, choose the correct answer from the options given below
Assertion A: Polycyclic diseases are known to cause plant disease epidemics.
Reason R: Polycyclic disease inciting pathogens produce multiplicity of infections in short time.
In light of the above statements, choose the correct answer from the options given below
Show Hint
Monocyclic = "Simple Interest" diseases (one cycle per season, e.g., Smuts).
Epidemics favor pathogens with high $r$ (rate of increase) values.
- Both A and R are true and R is the correct explanation of A
- Both A and R are true but R is NOT the correct explanation of A
- A is true but R is false
- A is false but R is true
The Correct Option is A
Solution and Explanation
This question deals with plant disease epidemiology, specifically the classification of diseases based on the number of infection cycles they complete in a single growing season.
Step 2: Detailed Explanation:
• Analysis of Assertion A: Polycyclic diseases are those where the pathogen undergoes multiple rounds of infection, colonization, and spore production (secondary cycles) within one crop season.
Examples include Potato Late Blight (Phytophthora infestans) and Cereal Rusts (Puccinia spp.).
Because the amount of inoculum increases exponentially with each cycle, these diseases are highly explosive and are the primary causes of large-scale epidemics. Thus, Assertion A is True.
• Analysis of Reason R: The defining characteristic of a polycyclic pathogen is its ability to produce a multiplicity of infections.
The "secondary inoculum" produced from the initial lesions can immediately infect neighboring plants or tissues.
Given the short generation time of many fungi (e.g., 7-10 days), a single lesion can lead to millions of new infections in a matter of weeks. This rapid, repetitive cycling is exactly what drives the epidemic. Thus, Reason R is True.
• Relationship: The reason directly explains the mechanism (rapid multiple infections) that leads to the outcome described in the assertion (epidemics).
Final Answer:
Both statements are correct, and the Reason provides the logical epidemiological justification for the Assertion.
The correct option is (A).
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