Covered smut of Sorghum is caused by:
a. Sphaelotheca cruenta
b. Sphaelotheca reiliana
c. Sphaelotheca sorghi
d. Tolyposporium ehrenbergii

Hint: Covered smut of sorghum is a fungal disease. It mostly occurs in the regions where sorghum is grown. Maturing fungal fruiting structures known as sori rupture, it releases teliospores. Teliospores infect seeds on other plants. Infection is caused by only seed-borne spores. The rank of sorghum grain in cereals for global production is fifth. Individual grains of sorghum are replaced by oval or conical shaped spore-producing structures known as smut sori.

Complete answer:
- Covered kernel smut is caused by the fungus Sporisorium Sorgi (Sphaelotheca sorghi).
- It attacks all the groups of sorghums including johnsongrass.
- In Illinois, covered kernel smut is the most common disease of sorghum.
- This disease is also common in other states where farmers plant the untreated seed.
- A versatile crop that grows as a forage, sweet, or grain crop is sorghum.
- Sphaelotheca cruenta causes the loss of Sorghum.
- Sphaelotheca reiliana causes maize head smut and sorghum head smut.
- Tolyposporium ehrenbergii causes long smut of Sorghum.

Hence, the correct answer is option (C).

Additional information:
- Sphaelotheca sorghi belongs to the Ustilaginaceae family.
- The first time this disease was observed in 1890 in Russia.
- No biological control is available to treat this disease.
- Germination of fungus can be prevented by planting seeds in the soil at temperature 15°C-32°C.

Note: Covered smut of Sorghum is caused by Sphaelotheca sorghi belonging to the class Ustilaginaceae. It is a fungus that attacks all the groups of sorghum. Individual grains of sorghum are replaced by oval or conical shaped spore-producing structures known as smut sori. Infection is caused by only seed-borne spores. In this disease, branches are distorted and covered with large superficial smut sori, panicles can be twisted and inflorescence may be missing in smutted panicles.