Covered smut of barley (Caused by Ustilago hordei) is/are

Covered smut of barley (Caused by Ustilago hordei) is Externally seed borne.
Covered smut of barley is caused by the fungus Ustilago hordei. The disease is found worldwide and it is more extensively distributed than either loose smut or false loose smut.
Kernels of infected plants are replaced by masses of dark brown smut spores. Smutted heads are hard and compact. Infected plants may be stunted.
Infection is seed-borne within the seed, the fungus penetrating the endosperm while the grain is being formed. Infected seeds give rise to systemically infected plants. The mycelium advances through the host tissue and becomes established behind the growing point.