Loose smut (Ustilago tritici) affects the entire inflorescence, except the rachis, is replaced by masses of smut spores. The materials in this subset contain known genes for loose smut resistance.

The black teliospores often are blown away by the wind, leaving only the bare rachis and remnants of other floral structures. The disease can occur wherever wheat is grown. Yield losses depend on the number of spikes affected by the disease; incidence is usually less than one percent and rarely exceeds thirty percent of the spikes in any given location.

Source: CIMMYT Wheat Germplasm Bank