Diseases

Ustilago hordei (Pers.) Lagerh - Covered Smut of Barley.

Synonym.

U. jensenii Rostr.

Systematic position.

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

Biological group

Obligate parasite, attacks cultivated barley.

Morphology and biology.

The characteristic symptom of Barley Covered Smut is the persistent membrane enclosing the smut sorus until the plant is mature. Smutted heads tend to emerge later than healthy heads, or in many cases they are trapped by the flag leaf sheath and fail to emerge completely. Plant dwarfing and peduncle compaction have been observed in severe cases. Smut sori sometimes develop as long strokes in leaf blades or in nodal tissue. Smutted heads are especially conspicuous at maturity. Teliospores are globose to subglobose, 3.6-7.2 microns (more often 4.5 microns in diameter), light olive brown, and smooth. The teliospore germinates to form a four-celled basidium bearing four ovate to oblong basidiospores. When sporidia of opposite mating types are in close proximity, as they would be following teliospore germination, the released pheromones induce the formation of conjugation tubes, which fuse. Later the infectious dikaryotic mycelium is formed. Smutted heads are broken and crushed during threshing. Teliospores survive on barley seeds. They germinate at the same time as barley seeds, when adequate moisture is available. Infection occurs through the coleoptile in the first 8 days following seed germination, and the mycelium advances through the host tissue. As the plant grows, the mycelium maintains its position within the meristem until flower formation, when it permeates the tissues of an ovary and forms the fungal mass in place of a seed. The teliospores are covered with a persistent membrane, being released at harvest.

Distribution.

Disease is widely distributed throughout the world. In CIS countries it is found everywhere in areas of barley cultivation.

Ecology.

Infection occurs at temperatures 14 to 25 degrees C (20-24 degrees C is optimal) in combination with a high extent of soil humidity. Teliospores germinate at 25-30 degrees C in 16 hours, at 20 degrees C in 24 hours, and at 5-10 degrees C in 3 days.

Economic significance.

Local epiphytotic of the Covered Smut can take place in any agroclimatic zone upon infringement of agronomical norms (e.g., untreated seeds). Therefore, it is impossible to designate an epiphytotic zone. Yield losses have been estimated in the Kurgan Region (Russia), where they can reach 7.7-14.12% loss depending on barley cultivar.

Reference citations:

Almuratov N. 1971. Features of teliospores germination of causal agent of covered Smut on the South-East of Kazakhstan. Alma-Ata: Vestnik sel.skokhozyaistvennoi nauki. N. 7: 40-43. (In Russian)
Chumakov A.E. 1962. Forecasting distribution of main diseases of field cultures for 1962. In: Plant Protection against pests and diseases, N. 3: 47-49. (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)
Kazenas L.D. 1974. Diseases of Agricultural Crops in Kazakhstan. Alma-Ata: Kainar. 366 p. (In Russian)
Mathre D.E., ed. 1997. Compendium of barley diseases. St. Paul, Minnesota: APS PRESS. 90 p.
Novozhilov K.V., Zakharenko V.A. 2000. Levels and tendencies of
variability of species composition and intrapopulation structure, areas of complexes of harmful and useful organisms and forecast of dangerous phytosanitary situations in zones of the country. St. Petersburg: VIZR. 100 p. (In Russian)
Rebenko V.P. 1968. Harmfulness of Barley Covered Smut and plant protection against it. In: Experimental station to practical agriculture. Donetsk. 125-129 p. (In Russian)
Stepanovskikh A.S. 1991. Smut Diseases of Barley. Abstract of PhD thesis. Novosibirsk. 44 p. (In Russian)

© Afanasenko O.S.