''Heterodera avenae'', the cereal cyst nematode or European cyst nematode, is a plant pathogen and an

obligate parasite An obligate parasite or holoparasite is a parasitic organism that cannot complete its life-cycle without exploiting a suitable host. If an obligate parasite cannot obtain a host it will fail to reproduce. This is opposed to a facultative parasite, ...

of cereal crops including

barley Barley (), a member of the grass family, is a major cereal grain grown in temperate climates globally. It was one of the first cultivated grains; it was domesticated in the Fertile Crescent around 9000 BC, giving it nonshattering spikele ...

oats The oat (''Avena sativa''), sometimes called the common oat, is a species of cereal grain grown for its seed, which is known by the same name (usually in the plural). Oats appear to have been domesticated as a secondary crop, as their seed ...

wheat Wheat is a group of wild and crop domestication, domesticated Poaceae, grasses of the genus ''Triticum'' (). They are Agriculture, cultivated for their cereal grains, which are staple foods around the world. Well-known Taxonomy of wheat, whe ...

and

rye Rye (''Secale cereale'') is a grass grown extensively as a grain, a cover crop and a forage crop. It is grown principally in an area from Eastern and Northern Europe into Russia. It is much more tolerant of cold weather and poor soil than o ...

. Cereal crops infected with this nematode are more susceptible to infection by fungal diseases such as

rhizoctonia ''Rhizoctonia'' is a genus of fungi in the family Ceratobasidiaceae. Species form thin, effused, corticioid basidiocarps (fruit bodies), but are most frequently found in their sterile, anamorph state. ''Rhizoctonia'' species are saprotrophic, ...

root rot.

Life cycle

This microscopic

nematode The nematodes ( or ; ; ), roundworms or eelworms constitute the phylum Nematoda. Species in the phylum inhabit a broad range of environments. Most species are free-living, feeding on microorganisms, but many are parasitic. Parasitic worms (h ...

exhibits

sexual dimorphism Sexual dimorphism is the condition where sexes of the same species exhibit different Morphology (biology), morphological characteristics, including characteristics not directly involved in reproduction. The condition occurs in most dioecy, di ...

. The female is rounded and white and measures 680 by 930 micrometres. The male is vermiform and transparent and measures 40 by 1300 micrometres. The

eggs An egg is an organic vessel in which an embryo begins to develop. Egg, EGG or eggs may also refer to: Biology * Egg cell, the female reproductive cell (gamete) in oogamous organisms Food * Eggs as food Places * Egg, Austria * Egg, Switzerland ...

are oval and the vermiform

larvae A larva (; : larvae ) is a distinct juvenile form many animals undergo before metamorphosis into their next life stage. Animals with indirect developmental biology, development such as insects, some arachnids, amphibians, or cnidarians typical ...

moult four times. The second

instar An instar (, from the Latin '' īnstar'' 'form, likeness') is a developmental stage of arthropods, such as insects, which occurs between each moult (''ecdysis'') until sexual maturity is reached. Arthropods must shed the exoskeleton in order to ...

larvae are mobile and can travel distances of up to thirty centimetres, looking for and invading roots of suitable host species. Here they develop, growing into sedentary bottle-shaped third instar larvae and rounded fourth instar ones. These then develop into either females or males and mating takes place. The female retains the majority of the several hundred eggs she produces inside her body. She turns into a brown

cyst A cyst is a closed sac, having a distinct envelope and division compared with the nearby tissue. Hence, it is a cluster of cells that have grouped together to form a sac (like the manner in which water molecules group together to form a bubb ...

by the end of plant growth season, as her external surface hardens and her internal parts die. The larvae may remain in anabiosis within this cyst for several years until suitable host plants become available.AgroAtlas
/ref> The cysts can withstand harsh conditions and can be spread in soil, by agricultural machinery, by animals, by wind, by dust storms or other means.

Economic significance

Infection with cereal cyst nematode is associated with a reduction in grain yield which may be of significant proportions. Thresholds of harmfulness depend on the population density of the nematode and differ among various cultivars and varieties. The weather conditions and soil types are also an important factor, with infections being increased in damp, warm growing seasons. The symptoms of infection include stunting and yellowing of the visible parts of the plant which may give the crop an uneven appearance. The presence of the disease can be established by inspecting the root system of plants and looking for abnormal development. The roots of infested plants develop a tangle of branches and swellings which are white when young but turn dark brown with age. It is the seedlings of cereals that are most readily infected with this nematode and damaged roots are often invaded by soil-borne pathogens such as root and crown rots. When nematode populations are high, significant losses in yield can occur. All wheat varieties are susceptible but some cultivars do not support cyst formation. It was found in trials that direct-drilling that did not disturb the soil below seeding depth reduced the incidence of cereal cyst nematode but did not have the same effect on the other serious cereal seedling diseases of rhizoctonia root rot and

take-all Take-all is a plant disease affecting the roots of grass and cereal plants in temperate climates caused by the fungus ''Gaeumannomyces tritici'' (previously known as ''Gaeumannomyces graminis ''var. ''tritici''). All varieties of wheat and barle ...

.Effect of sowing point design and tillage practice on the incidence of Rhizoctonia root rot, take-all and cereal cyst nematode in wheat and barley
/ref> Control is by crop rotation, fallowing and the use of less susceptible varieties.

References

External links

a
HYPP Zoology
{{Authority control avenae Cereal diseases Agricultural pest nematodes Nematodes described in 1924