Question
Given below are two statements: one is labelled as Assertion A and the other is labelled as Reason R
Assertion A: Horizontal resistance is durable as it is non-race specific.
Reason R: Race specific resistance puts pressure on the pathogen to evolve more virulent races.
In the light of the above statements, choose the most appropriate answer from the options given below
This question was previously asked in
CUET PG 2026 Agri-Business Management Question Paper (25-Mar-2026) (Shift 2)
The correct answer is
Both A and R are correct but R is NOT the correct explanation of A.
Analysis of Assertion A
Assertion A states that horizontal resistance is durable because it is non-race specific.
- Horizontal resistance (also known as non-specific or quantitative resistance) involves multiple genes and provides a general defense against a broad range of pathogen strains.
- Because it targets multiple pathogen functions or is based on general plant defense mechanisms, it is much harder for the pathogen to overcome quickly.
- This makes horizontal resistance generally more durable over time compared to race-specific resistance.
Therefore, Assertion A is correct.
Analysis of Reason R
Reason R states that race-specific resistance puts pressure on the pathogen to evolve more virulent races.
- Race-specific resistance (often controlled by single R genes) provides defense against particular races or strains of a pathogen that possess matching avirulence genes.
- When such resistance is deployed widely, pathogen populations that happen to have mutations allowing them to overcome that specific resistance are strongly selected for.
- This selection pressure drives the evolution of new, potentially more virulent or aggressive pathogen races capable of overcoming the host's specific defense.
Therefore, Reason R is correct.
Relationship between Assertion A and Reason R
While both statements are factually correct:
- Assertion A explains the durability of horizontal resistance based on its non-race-specific nature.
- Reason R explains a consequence (pathogen evolution pressure) associated with race-specific resistance.
- Reason R does not explain *why* horizontal resistance is durable. The durability of horizontal resistance stems from its broad-acting, multi-gene nature, not from the evolutionary pressures exerted on pathogens by race-specific resistance.
Thus, Reason R is not the correct explanation for Assertion A, even though both are true statements.
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