Ustilago avenae

Oat smut ( Ustilago avenae )

The oat smut ( Ustilago avenae ) is a highly specialized parasitic smut fungus, the Oat, oat grass and related species infects and causes the same disease in him. The infested plants form fruits instead of a black mass of spores, which is spread by the wind.

Features

The sori are located in the spikelets, the ovaries are usually completely destroyed. Rarely, it occurs on the leaves. The spore mass is powdery and dark greenish - brown. The spherical spores are pale greenish- brown, but they are brighter on one side. You are kurzstachelig and 5-8 microns in size. Pure cultures can be grown on potato dextrose agar.

Artabgrenzung

The spiny spores distinguish the smut of oats from other smut fungi Ustilago hordei as having smooth spores.

Development cycle

Ustilago avenae, a kind of subdivision Ustilagomycotina is a haplo - Dikaryont, ie, the vegetative body is haploid and during fruiting body development, there are some dikaryotic stages. The haploid basidiospores are formed on the basidia, fall off and can reproduce by budding yeast-like. In this way, the fungus can survive saprotroph for a short time. If two of these haploid spores meet, it comes to somatogamy, where there are two mating types ( and -) are. After this somatogamy arise dikaryotic hyphae that can infect the host. There are two different ways:

The smut spores are mostly made of dikaryotic hyphae intercalary. After degenerate hyphae and the spores are released. It comes to karyogamy and right after the basidiospore germinates under meiosis with a Phragmobasidie ​​( septate ), which consists of four cells, which produce basidiospores again.

Hosts

The smut of oats growing on species of the genera Arrhenatherum, Avena and Hordeum, also on Meadow Gold oats. The oat smut occurs worldwide in a variety of breeds and varieties.

Combat

To combat the oat smut more resistant oat varieties were grown. In susceptible varieties an early sowing in spring, recommends the germination of infected seeds at 7 ° C has reduced disease incidence. A Seed treatment with systemic fungicides such as Vitavax ( carboxin ), Ceresan ( Methoxyethylquecksilbersilikat ) Chipcote ( Methylquecksilbercyanid ) or Panogen (2- Methoxyethylquecksilberacetat ) reaches a chemical control of oat smut. A hot-water treatment is recommended only for an infection rate of about 2%.