Heterosis is

Options

A. Hybrid incompatibility
B. Hybrid vigour
C. Hybrid sterility
D. Inbreeding depression

Answer

**Step-by-Step Text Solution:**

1. **Understanding Heterosis**: Heterosis, also known as hybrid vigor, refers to the phenomenon where the offspring resulting from the crossbreeding of two genetically different individuals exhibit superior qualities compared to their parents.

2. **Exploring the Options**:
- **Hybrid Incompatibility**: This occurs when the offspring produced by mating two different species are not viable or unable to reproduce. This is not related to heterosis.
- **Hybrid Vigor**: This is the correct definition of heterosis. It indicates an increase in certain traits such as growth rate, fertility, and yield in the hybrid offspring compared to their parents.
- **Hybrid Sterility**: This refers to the inability of hybrids to reproduce, which is not the same as heterosis.
- **Inbreeding Depression**: This is the reduced biological fitness in a population due to inbreeding, which is also unrelated to heterosis.

3. **Conclusion**: Based on the definitions and explanations of the terms, heterosis is best defined as hybrid vigor, where the hybrid offspring show enhanced characteristics compared to their parental lines.

**Final Answer**: Heterosis is best described as hybrid vigor.

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