How many of the following are fungal diseases of plants?
Citrus canker, Late blight of potato, Mosaic disease of mustard, Downy mildew of grapes, Leaf curl of cotton, Rust of wheat, Tobacco mosaic disease, Loose smut of wheat, Leaf curl of tomato

Options

A. 6
B. 7
C. 4
D. 5

Explanation

To determine how many of the listed diseases are fungal diseases of plants, we will analyze each disease one by one:

1. **Citrus canker**: This is not a fungal disease; it is caused by bacteria.

2. **Late blight of potato**: This is a fungal disease caused by the pathogen *Phytophthora infestans*.

3. **Mosaic disease of mustard**: This is not a fungal disease; it is caused by a virus.

4. **Downy mildew of grapes**: This is a fungal disease caused by the pathogen *Plasmopara viticola*.

5. **Leaf curl of cotton**: This is not a fungal disease; it is caused by a virus.

6. **Rust of wheat**: This is a fungal disease caused by various species of fungi, including *Puccinia*.

7. **Tobacco mosaic disease**: This is not a fungal disease; it is caused by a virus.

8. **Loose smut of wheat**: This is a fungal disease caused by the fungus *Ustilago tritici*.

9. **Leaf curl of tomato**: This is not a fungal disease; it is caused by a virus.

Now, let's count the fungal diseases identified:

- Late blight of potato (Fungal)
- Downy mildew of grapes (Fungal)
- Rust of wheat (Fungal)
- Loose smut of wheat (Fungal)

Total fungal diseases = 4

Thus, the answer is **4**.