Hybrid breakdown is failure of :

Options

A. Hybrid zygote to develop into offspring
B. Hybrid adult to produce fertile offspring
C. Fusion failure of ova and sperms of two species
D. All the above

Answer

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

1. **Understanding Hybrid Breakdown**: Hybrid breakdown refers to a reproductive failure that occurs after the formation of a hybrid organism. This phenomenon typically happens when hybrids (offspring from two different species) are produced but fail to produce viable or fertile offspring in subsequent generations.

2. **Identifying the Options**: The question provides several options regarding what hybrid breakdown is a failure of:
- A) Hybrid zygote to develop into offspring
- B) Hybrid adult to produce fertile offspring
- C) Fusion failure of ova and sperm of two species
- D) All of the above

3. **Analyzing Each Option**:
- **Option A**: Hybrid zygote to develop into offspring. This is incorrect because hybrid zygotes can develop into offspring; the issue arises later.
- **Option B**: Hybrid adult to produce fertile offspring. This is correct because hybrid breakdown specifically refers to the failure of hybrids to produce fertile offspring.
- **Option C**: Fusion failure of ova and sperm of two species. This is also incorrect because fusion does occur; it is the subsequent stages that fail.
- **Option D**: All of the above. This option is incorrect as not all the statements are true.

4. **Conclusion**: The correct answer is **B) Hybrid adult to produce fertile offspring**. This option accurately describes the essence of hybrid breakdown, which is the failure of hybrids to produce viable offspring.