The parasitic fungus which destroys wheat plant is

The correct option is Puccinia.

Step-by-step Explanation:

1. Understanding the Role of Puccinia:
Puccinia is a genus of obligate parasitic fungi known for causing rust diseases in various agricultural crops. Specifically, Puccinia graminis (often referred to as stem rust or black rust) is a devastating pathogen that infects cereal crops, particularly the wheat plant. The fungus produces spores that invade the plant tissues, hindering nutrient transport and causing the stem and leaves to rupture, which ultimately destroys the plant.

2. Analyzing the Incorrect Options:
- Lice: These are ectoparasitic insects that live on the skin or hair of host animals (mammals and birds). They are animals, not fungi, and do not infect plants.
- Leech: Leeches are segmented predatory or parasitic worms belonging to the phylum Annelida. They reside primarily in aquatic habitats and feed on the blood of animals, making them unrelated to plant pathology.
- Cuscuta (Dodder): Cuscuta is a genus of parasitic flowering plants. Although it is a plant parasite that harms other host plants, it is not a fungus.

Thus, Puccinia is the correct parasitic fungus responsible for destroying the wheat plant.