Karnal Bunt (Partial Bunt)

Tilletia indica (syn. Neovossia indica)

Symptoms: Karnal bunt is not easily detected prior to harvest, since it is usual for only a few kernels per spike to be affected by the disease. Following harvest, diseased kernels can be easily detected by visual inspection: a mass of black teliospores replaces a portion of the endosperm, and the pericarp may be intact or ruptured kernels give off a fetid or fishy odor when crushed.

Development: Karnal bunt is a seed- or soil-borne, floral infecting disease. inoculum (teliospores) on or near the soil surface germinates, producing sporidia, which are carried by wind to the floral structures. These sporidia in turn germinate and penetrate the glumes, rachis, or the ovary itself. The fungus enters the newly formed kernel and develops in the intercellular space between the endosperm and seed coat. The degree of disease establishment and development depends on environmental conditions from spike emergence through grain filling.

Hosts/Distribution: Karnal bunt can affect wheat, triticale, rye, and several other related grasses, but not barley. The disease is endemic in the Asian Subcontinent and now in Mexico.

Importance: Karnal bunt is a relatively minor disease. Actual losses in yield are minimal, but the disease is on the quarantine lists of many countries and therefore of importance in world grain trade.