Loose smut of barley is/are

Loose smut of barley is internally seed-borne.
Loose smut of barley is caused by Ustilago nuda. It is a disease that can destroy a large proportion of a barley crop. Loose smut replaces grain heads with smut, or masses of spores that infect the open flowers of healthy plants and grow into the seed, without showing any symptoms.
Loose smut of barley and wheat are internally seed-borne and carried as a small colony of fungus inside the seed embryo rather than as spores on the seed coat.