Stinking smut of wheat is caused by
Common bunt, also known as stinking smut and covered smut is a disease of both spring and winter wheats. It is caused by two very closely related fungi, Tilletia tritici and Tilletia laevis. Plants with common bunt may be moderately stunted but infected plants cannot be easily recognized until near maturity and even then it is seldom conspicuous. After initial infection, the entire kernel is converted into a sorus consisting of a dark brown to black mass of teliospores covered by a modified periderm, which is thin and papery. The sorus is light to dark brown and is called as a bunt ball. The bunt balls resemble wheat kernels but tend to be more spherical. The bunted heads are slender, bluish-green and may stay greener longer than healthy heads. The bunt balls change to a dull gray-brown at maturity, at which they become conspicuous. Thus, the correct answer is option A.