Diseases

Puccinia helianthi Schw. - Rust of Sunflower.

Systematic position.

Class Basidiomycetes, order Uredinales, family Pucciniaceae, genus Puccinia.

Biological group.

Obligate parasite.

Morphology and biology.

In its life cycle the fungus P. helianthi has several sporulations or stages of development varying in form and function. They all develop on sunflower. The pathogen is an autoecious species with a full cycle of development. It is known to affect common cocklebur (Xanthium strumarium), which may be an additional source of infection. In the spring, after over-wintering on sunflower, the teliospores produce basidiospores. The latter infect sunflower seedlings. Later, the spermagoniun stage of fungus appears as globular formations on the upper surface of leaves or cotyledons. There are small spores or spermatia. Dikaryotic mycelium occurs, forming aecia. Aecia with numerous spores develop on the lower surface of leaves. Aggregations of cinnamon-brown uredial pustuls with spores appear on the upper surface of leaves infected by aeciospores. In the uredia stage the pathogen forms several generations of spores which promotes mass accumulation of infection and intensive distribution of the disease on sunflower. Urediospores are unicellular, light brown, egg-shaped or spherical, 23-34 x 17-28 ., having high viability. They infect mainly leaves, but also petioles, bracts, back of head, and the upper part of stalks of sunflower. In the second half of sunflower vegetation the dark-brown teliospores occur on affected tissue; the teliospores are positioned on the lengthened colorless pedicel with a constriction in the center. In teliostage the causal agent winters in field, renewing its activity in spring. A line of physiological races have been revealed in the fungus P. helianthi. They have not yet been studied well in Russia and other countries of the former USSR.

Distribution.

Rust is spread throughout Russia and other countries of the former USSR on sunflowers everywhere.

Ecology.

High air temperature, short-term rains and dews are favorable for intensive development of Rust. Optimum temperature for urediospore germination and new urediopustules formation is 18-20 degrees C. Warmer weather reduces duration of urediospore generation, thus increasing their quantity during sunflower vegetation.

Economic significance.

Rust was harmful until the mid 1950's in the former Soviet Union. In some years the crop losses of sunflower caused by the disease reached 38%. Resistant varieties created by V.S. Pustovoit (1960) which use wild Texas sunflowers (Helianthus ruderalis) have solved the problem with Rust. Now the Rust of sunflower has no economic significance in Russia and other countries of the former USSR. However, gradual increase of occurrence and severity of the disease has taken place recently in those countries, in Russia in particular. In the Middle Volga Basin region, Northern Caucasus and southern part of Central Black Earth Zone of Russia, and also in Ukraine and Moldova the Rust damage is stronger than in other places. The most effective control measures used against the Rust is the use of resistant varieties and hybrids.

Reference citations:

Gulya T. 1996. Changes in sunflower disease incidence in the USA during the last decade. Proceedings of the 14th International Sunflower Conference; 1996. Beijing-Shenyang. V. 2: 651-657.
Peresypkin V.F. 1974. Rust. Agricultural phytopathology. Moscow: Kolos. 249-251 p. (In Russian)
Pustovoit V.S. 1960. Interspecific rust resistant hybrids of sunflower. Branch of hybridization of plants. Moscow. 376-378 p. (In Russian)
Sackston W.E. 1962. Studies on sunflower rust. Part III. Occurrence, distribution, and significance of races Puccinia helianthi. Can. J. Bot., 40: 1449-1458.
Tikhonov O.I. 1975. Diseases of sunflower. In: Sunflower. Moskow: Kolos. 401-409 p. (In Russian)
Transhel V.G. 1939. Review of rust fungi of the USSR. Moscow-Leningrad: AN SSSR. 426 p. (In Russian)
Tselle M.A. 1932. Diseases of sunflower. Leningrad. 31 p. (In Russian)
Yakutkin V.I. 2001. Diseases of sunflower in Russia and their control. Zaschita i karantin rastenii, 10: 26-29. (In Russian)

© Yakutkin V.I.