‘Ergot of rye’ is caused by

The correct option is C Claviceps purpurea
Ergot is the fungal disease mainly found in cereal crops, which is caused by the species of ascomycetes fungi, Claviceps purpurea. Ergot is commonly associated with rye.

Ergot symptoms become evident during kernel formation, when ergot bodies are formed in place of kernels.

Claviceps purpurea attacks rye and other cereal grasses, causing the plant disease ergot. This fungus is also the source of lysergic acid, the active component of the psychedelic drug LSD (Lysergic acid diethylamide).

Phytophthora infestans is an oomycete or water mold, a fungus-like microorganism that causes the serious potato and tomato disease known as late blight or potato blight.

Uncinula necator is a fungus that causes powdery mildew of grape.

Loose smut of barley is caused by Ustilago nuda . The fungus infects the growing barley plant during the flowering stage. The infected seed heads become sources of spores that infect other plants during flowering.

The correct option is Claviceps purpurea.