Fixation of heterosis can NOT be achieved by -
Show Hint
- Balanced lethal system
- Apomixis
- Pureline production
- Vegetative propagation
The Correct Option is C
Solution and Explanation
Heterosis (hybrid vigor) describes the superior performance of an $F_1$ hybrid compared to its homozygous parents.
Because heterosis depends on heterozygosity and gene interactions, it normally segregates and is lost in subsequent generations ($F_2, F_3$, etc.) due to inbreeding.
Fixing heterosis means preserving this superior heterozygous state across generations.
Step 2: Detailed Explanation:
Let us evaluate the methods used to preserve or fix heterosis:
1. Vegetative Propagation (D): This clonal reproduction method preserves the exact genotype of the $F_1$ hybrid, maintaining heterozygosity and fixing heterosis indefinitely (common in sugarcane, potato, and fruit crops).
2. Apomixis (B): This is asexual reproduction through seeds without fertilization. The embryo develops directly from maternal tissues, preserving the heterozygous maternal genotype in the seeds.
3. Balanced Lethal System (A): This genetic mechanism maintains structural heterozygosity by killing any homozygous recombinants, ensuring that only the heterozygous individuals survive.
4. Pureline Production (C): Purelines are developed through continuous self-pollination (inbreeding), which leads to complete homozygosity.
Because purelines are completely homozygous, any heterosis—which requires heterozygosity—is lost.
Therefore, pureline production cannot be used to fix heterosis.
Step 3: Final Answer:
Fixation of heterosis cannot be achieved by pureline production, corresponding to option (C).
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