Take-all

Take-all
Wheat plants displaying symptoms of take-all root disease.
Scientific classification
Kingdom:	Fungi
Phylum:	Ascomycota
Class:	Sordariomycetes
Subclass:	Sordariomycetidae
Order:	Magnaporthales
Family:	Magnaporthaceae
Genus:	Gaeumannomyces
Species:	G. graminis var. tritici
Trinomial name
Gaeumannomyces graminis var. tritici J. Walker, (1972)
Synonyms
Ophiobolus graminis var tritici

Take-all is a plant disease affecting the roots of grass and cereal plants in temperate climates caused by the fungus Gaeumannomyces graminis var. tritici. All varieties of wheat and barley are susceptible. It is an important disease in winter wheat in Western Europe particularly, and is favoured by conditions of intensive production and monoculture.

The disease

The disease survives in the soil on infected cereal and grass residues. The fungus infects the root tissue of young plants and can spread from plant to plant in the form of hyphae growing through the soil which is why the disease is often seen in patches. The fungus blocks the conductive tissue of the plants and reduces water uptake. Early signs of the disease include yellowing and stunting, tillering is reduced and plants mature prematurely and often exhibit bleached seed heads. The affected roots are blackened and the plants are easy to pull from the soil.^[1] These symptoms give rise to an alternative name for the disease, "whiteheads". Yield loss levels of 40 to 50% are often recorded in severe attacks.

Control

Chemical control measures have traditionally had little success, although a modern seed treatment shows promise. Crop nutrition imbalances exacerbate the disease, as does excessive liming. Modern varieties are stiff and short-strawed which allows relatively high spring nitrogen applications without serious lodging. This can limit damage from the disease.

The most appropriate control measure is the use of a clean one-year break crop of a non-cereal crop. This reduces the fungus to an acceptably low soil contamination level in about 10 months although stray volunteer grasses may reduce any beneficial effects.

There exists a phenomenon known as "take-all decline". Experiments performed on the famous "Broadbalk" field at Rothamsted Experimental Station where continuous monoculture winter wheat is grown, show that take-all build-up occurs in successive crops to reach a peak in the 3rd to 5th cropping year, after which the disease declines, ultimately restoring yields to 80 to 90% of 1st and 2nd year levels. The decline cycle is destroyed by the introduction of a crop other than wheat or barley.

See also

• Genetic engineering
• Genetic engineering in the United States

References

• Biology and Control of Take-all. (Asher, M.J.C. and Shipton, P.J. (eds)) 1981 Academic Press, London ISBN 0-12-065320-6
• Cereal Pests and Diseases. (Gair, Jenkins, Lester) 1987 Farming Press ISBN 978-0-85236-164-1
• Take-All Disease of Cereals. A Regional Perspective. (Hornby et al.) 1998 CABI ISBN 0-85199-124-6

External links

• Index Fungorum
• USDA ARS Fungal Database