Ustilaginoidea Virens

Ustilaginoidea virens, perfect sexual stage Villosiclava virens, is a plant pathogen which causes the disease False Smut of rice which reduces both grain yield and grain quality. The disease occurs in more than 40 countries, especially in the rice producing countries of Asia. but also in the U.S. As the common name suggests, it is not a true smut (fungus), but an ascomycete. False smut does not replace all or part of the kernel with a mass of black spores, rather sori form erupting through the palea and lemma forming a ball of mycelia, the outermost layers are spore-producing. Infected rice kernels are always destroyed by the disease.

Of particular concern are the production of alkaloids in the grain as with the Claviceps spp. causing ergot.

Little is known of the exact life cycle of the pathogen. There is debate among plant pathologists at what time infection of the plant occurs. There are reports of early, systemic infections of seedlings and other reports of later infection at boot or flowering.