Given below are two statements
Statement I: Horizontal and Vertical Resistance defend crop plants against pathogens
Statement II: Horizontal Resistance is more frequently exploited in resistance breeding programme than Vertical Resistance
In light of the above statements, choose the most appropriate answer from the options given below
Statement I: Horizontal and Vertical Resistance defend crop plants against pathogens
Statement II: Horizontal Resistance is more frequently exploited in resistance breeding programme than Vertical Resistance
In light of the above statements, choose the most appropriate answer from the options given below
Show Hint
Horizontal = Many genes, low effect, high durability (hard to breed).
Breeders often take the easy path (Vertical) until the pathogen evolves to break it.
- Both Statement I and Statement II are correct
- Both Statement I and Statement II are incorrect
- Statement I is correct but Statement II is incorrect
- Statement I is incorrect but Statement II is correct
The Correct Option is C
Solution and Explanation
The question tests the fundamental concepts of host-plant resistance (HPR) as defined by J.E. Vanderplank.
Step 2: Detailed Explanation:
• Analysis of Statement I: Vertical Resistance (monogenic/oligogenic) is race-specific and usually complete, while Horizontal Resistance (polygenic) is non-specific and usually partial. Both are valid biological mechanisms that defend plants against infection. Thus, Statement I is Correct.
• Analysis of Statement II: In traditional plant breeding, Vertical Resistance is much more frequently exploited. This is because it is controlled by single "R-genes," making it very easy to identify, track in crosses, and backcross into commercial varieties.
Horizontal resistance is complex to breed for because it involves many genes (quantitative inheritance) and requires extensive field screening. Despite its durability, it is less frequently used in breeding programs compared to the quick "all-or-nothing" success of vertical resistance. Thus, Statement II is Incorrect.
Final Answer:
Statement I is true, but Statement II is false as it incorrectly states the frequency of exploitation in breeding.
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