The causative organism of downy mildew in cereals is

Options

A. Pythium debaryanum
B. Peronospora parasitica
C. Sclerospora glaminicola
D. Saprolegnia

Answer

To determine the causative organism of downy mildew in cereals, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Disease**:
- Downy mildew is a plant disease characterized by the presence of a white powdery substance on the leaves and yellow spots on the foliage.

2. **Identify Possible Organisms**:
- The question provides several organisms that could potentially cause downy mildew:
- Pythium Debrinum
- Peronospora parasitica
- Sclerospora gaminicola
- Saprolagnia

3. **Evaluate Each Organism**:
- **Pythium Debrinum**: This organism is known to cause grease spots but is not associated with cereals.
- **Peronospora parasitica**: This organism affects the leaves of plants, particularly pumpkin, and is not related to cereals.
- **Sclerospora gaminicola**: This organism is specifically known to produce downy mildew in cereals, making it a strong candidate.
- **Saprolagnia**: This organism causes spots in maize but is not the primary cause of downy mildew.

4. **Conclude the Correct Organism**:
- Based on the evaluation, the organism responsible for downy mildew in cereals is **Sclerospora gaminicola**.

### Final Answer:
The causative organism of downy mildew in cereals is **Sclerospora gaminicola**.

---