Smut of maize caused by

Answer: Option B

Smut of maize caused by Ustilago maydis.
Corn smut is a plant disease caused by the fungus Ustilago maydis, which attacks corn (maize) and teosinte plants.
The fungus infects all parts of the host plant by invading the ovaries of its host. The infection causes the corn kernels to swell up into tumor-like galls, whose tissues, texture, and developmental pattern are mushroom-like. These galls are made up of hypertrophied cells of the infected plant, along with resulting fungal threads, and blue-black spores.