Basidiomycetes are characterised by all given features, except :

Options

A. presence of dolipore septum
B. conidia formation
C. dominant dikaryotic mycelium
D. basidium as the site of karyogamy and meiosis

Answer

To solve the question regarding the characteristics of Basidiomycetes, we will analyze each option provided and determine which one does not belong to the defining features of this group of fungi.

### Step-by-Step Solution:

1. **Understanding Basidiomycetes**: Basidiomycetes are a class of fungi that are characterized by their reproductive structures called basidia, where karyogamy and meiosis occur.

2. **Evaluating the First Option - Presence of Dolipore Septum**:
- Dolipore septa are specialized structures found in the hyphae of Basidiomycetes. They are indeed a characteristic feature of this group.
- **Conclusion**: This option is true for Basidiomycetes.

3. **Evaluating the Second Option - Conidia Formation**:
- Conidia are asexual spores that are typically formed in fungi like Penicillium, which belongs to the Ascomycetes group, not Basidiomycetes.
- **Conclusion**: This option is false for Basidiomycetes.

4. **Evaluating the Third Option - Dominant Dikaryotic Mycelium**:
- In Basidiomycetes, the dikaryotic phase (where two nuclei coexist in the same cell) is indeed the dominant phase of their life cycle.
- **Conclusion**: This option is true for Basidiomycetes.

5. **Evaluating the Fourth Option - Basidium as the Site for Karyogamy**:
- The basidium is the structure where karyogamy (fusion of nuclei) occurs, followed by meiosis to produce basidiospores.
- **Conclusion**: This option is true for Basidiomycetes.

6. **Final Conclusion**:
- The only option that does not characterize Basidiomycetes is "Conidia formation." Therefore, the correct answer to the question is that Basidiomycetes are characterized by all given features except for conidia formation.

### Final Answer:
The characteristic that does not apply to Basidiomycetes is **Conidia formation**.

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