Diseases

Ustilago nigra Tapke - False Loose Smut.

Synonyms.

U. avenae (Pers.) Rostr.; U. medians Biedenk.

Systematic position.

Class Basidiomycetes, order Ustilaginales, family Ustilaginaceae, genus Ustilago.

Biological group.

Obligate parasite, attacks cultivated barley and species in the genus Hordeum.

Morphology and biology.

Teliospores of U. nigra are olive brown, globose, ovoid to elongate, 5.5-7.5 x 6-8 um (more often 6.5 x 7 um) in diameter, and minutely echinulate. The teliospore germinates to form a basidium bearing four ovate to oblong basidiospores. After the fusion of conjugation tubes formed of sporidia of opposite mating types the dikaryotic hyphae are formed, and are the infective phase. The fungus readily hybridizes with U. hordei, the Barley Covered Smut fungus. Teliospores survive on or under the hull of barley seeds, where they can remain viable for years. Hyphae of germinated spores may spread under the hull and then remain dormant until seeds begin to germinate. Seedlings become infected between germination and emergence above the soil. Infecting hyphae can arise from mycelia in or under the hull or from teliospores on or under the seed surface. Infection occurs through the coleoptile, and the mycelium advances through the host tissue and becomes established within the growing point. When the plant enters the boot stage, the smut fungus grows rapidly into the floral tissues, converting them into masses of dark brown teliospores. The smutted head eventually emerges at about the same time as healthy heads. Teliospores are dispersed by wind.

Distribution.

Disease is widely distributed throughout the world. In CIS countries it is found in the European part, the Caucasus, Ural, West Siberia, also in Kazakhstan and Ukraine.

Ecology.

Soil temperature of 15-21 degrees C and relatively dry soil are most favorable for U. nigra infection.

Economic significance.

The U. nigra is most important in Central part of Chernozem Region, in North-East of Non-Chernozem Region, South Ural, Volga Basin Region, also in North Kazakhstan. Local epiphytotic can take place in any agroclimatic zone at infringement of agronomical norms (e.g., untreated seeds). Therefore, it is impossible to designate an epiphytotic zone.

Reference citations:

Andreev P.S. 1977. About species of causal agents of Barley Loose Smut in conditions of Kuibyshev Region and some its morphological and biological features. In: Agrotehnic and Biology of Field Cultures. Ufa. 66-68 pp. (In Russian)
Ishkova T.I., Berestetskaya L.I., Gasich E.L., Levitin M.M., Vlasov D.Yu. 2000. Diagnostic of the main diseases of cereals. Saint Petersburg: VIZR. 76 p. (In Russian)
Kozhevnikova L.M. 1970. Species of Barley Loose Smut in Voronezh Region. Plant Protection against pests and diseases, 2: 19-20. (In Russian)
Mathre D.E., ed. 1997. Compendium of barley diseases. St. Paul, Minnesota: APS PRESS. 90 p.
Stepanovskikh A.S. 1970. Studies of species structure of Barley Loose Smut in virgin region, Kurgan and Chelyabinsk Regions. In: Proceedings of Kurgan Agricultural Institute "Plant Protection of Agricultural Cultures Against Pests and Diseases". Kurgan: KSKhI. 17-26 pp. (In Russian)
Tulina L.R., Maltseva A.I. 1976. False Loose Smut of Barley in North-East region of Non-Chernozem Region of RSFSR. Mycology and Phytopathology, 10(5): 397-402. (In Russian)
Tyunin V.A., Kushnirenko I.U. 1981. Species structure and distribution of causal agents of Barley loose Smut in Chelyabinsk Region. In: Regional Systems of Plant Protection Against Pests and Diseases in Siberia. Novosibirsk. 29-31 pp. (In Russian)

© Afanasenko O.S.