''Anguina agrostis'' (Bentgrass nematode, seed-gall nematode) is a plant pathogenic nematode.
at Nemaplex,

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History and significance

''Anguina agrostis'' was one of the first plant parasitic nematodes to be taxonomically described by J.G. Steinbuch in 1799. While on a “botanical walk”, Steinbuch collected samples from a grass that resembled ''Agrostis silvatica''. He examined the samples and discovered that the grass was not ''A. silvatica'' but was rather a degenerate form of ''

Agrostis capillaris ''Agrostis capillaris'', the common bent, colonial bent, or browntop, is a rhizomatous and stoloniferous perennial in the grass family (Poaceae). It is native to Eurasia and has been widely introduced in many parts of the world. Colonial ben ...

''; he further discovered that ''A. silvatica'' is not a true species (or variety) but that the misclassification of the grass was due to the formation of galls by ''A. agrostis'' parasitism.Bird, A.F. 1981. The ''Anguina''-''Corynebacterium'' Association. Pages 303-323 in: Plant Parasitic Nematodes, B.M. Zuckerman and R.A. Rohde, eds. Academic Press, New York, NY, USA. Galls caused by ''A. agrostis'' have glumes that are 4-5 times longer than normal and can cause yield losses of up to 40-70%.Lehman, P.S. (1979). Nematology Circular. In Seed and Leaf Gall Nematodes of the Genus ''Anguina'' occurring in North America (Gainesville, Florida: Florida Department of Agricultural and Consumer Services, Division of Plant Industry).Alderman, S., Bilsland, D., Griesbach, J., Milbrath, G., Schaad, N., and Postnikova, E. 2003. Use of a Seed Scarifier for Detection and Enumeration of Galls of ''Anguina'' and ''Rathayibacter'' Species in Orchard Grass Seed. Plant disease 87:320-323. In addition to crop loss, ''A. agrostis'' associates with pathogenic bacteria ''Rathayibacter rathayi'' (formerly ''Corynebacterium rathayi'') to cause

annual ryegrass toxicity Annual ryegrass toxicity (ARGT) is the poisoning of livestock from toxin contained in bacterially infected annual ryegrass (''Lolium rigidum''). The toxin is produced by the bacterium ''Rathayibacter toxicus'' (formerly ''Clavibacter toxicus''), wh ...

in Australia.

Hosts and distribution

''A. agrostis'' infects bentgrasses within the genus ''

Agrostis ''Agrostis'' (bent or bentgrass) is a large and very nearly cosmopolitan genus of plants in the grass family, found in nearly all the countries in the world. It has been bred as a GMO creeping bent grass. Species * '' Agrostis aequivalvi'' ...

'' as well as annual and perennial ryegrasses (''Lolium'' spp.). The nematode can also infect 14 other genera of grasses. ''A. agrostis'' has been found in

Australia Australia, officially the Commonwealth of Australia, is a Sovereign state, sovereign country comprising the mainland of the Australia (continent), Australian continent, the island of Tasmania, and numerous List of islands of Australia, sma ...

New Zealand New Zealand ( mi, Aotearoa ) is an island country in the southwestern Pacific Ocean. It consists of two main landmasses—the North Island () and the South Island ()—and over 700 smaller islands. It is the sixth-largest island count ...

, Western

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, former USSR,

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, and the

United States The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country primarily located in North America. It consists of 50 states, a federal district, five major unincorporated territorie ...

Morphology

The lip region is slightly offset (3-4 µm high) and the nematode has a very short stylet (10 µm). ''A. agrostis'' has a three-part esophagus. The procorpus is cylindrical with a swelling near its midsection. The metacorpus is ovoid in shape and the isthmus is long and narrow. The postcorpus has three glands and is highly developed, but does not overlap the intestine.Krall, E.L. 1991. Wheat and Grass Nematodes: ''Anguina'', ''Subanguina'', and Related Genera. Pages 721-760 in: Manual of Agricultural Nematology, W. Nickle, ed. CRC Press, New York, NY. On average, infective juveniles (J2) measure 530 µm and dauer juveniles measure 760 µm; the increase in size is due to feeding and the formation of lipid droplets or storage bodies. Females range from 1.5 to 2.7 mm in length, are curved ventrally, and are swollen. The vulva is located near the posterior end and one ovary is present. Males are smaller (1.1-1.7 mm in length), are not as swollen, and have a small bursae that extends subterminally. One testis is present.

Life cycle and reproduction

Infective second stage juveniles (J2) find a young host, migrate to areas of new growth and are carried up with the growing point of the plant.Goodey, T. 1932. The genus ''Anguillulina'' Gerv. & v. Ben., 1859, vel Tylenchus Bastian, 1865. Jour Helminthol 10:75-180. They may feed ectoparasitically until formation of the inflorescence, at which time the J2 invades the ovule, becomes sedentary, and a gall begins to form. Within the gall, nematodes progress through three molts to reach adulthood (J3, J4, male and female adults). Reproduction is amphimictic and females can lay up to 1000 eggs. The first molt occurs in the egg and the nematode hatches as a J2. These juveniles undergo anhydrobiosis and become the dormant dauer larvae to withstand the hot summer heat of Australia. Autumn rains rehydrate the dauer juveniles which become active to begin the life cycle over again. Only one generation is produced per year.

Host-parasite relationship

Infective second stage juveniles colonize plants during the vegetative growth stage and may feed ectoparasitically during this time. When the inflorescence begins to form, the J2s invade the flower ovule and begin to feed endoparasitically.Stynes, B.A., and Bird, A.F. 1982. Development of galls induced in ''Lolium rigidum'' by ''Anguina agrostis''. Phytopathology 72:336-346. Nematode feeding on floret primordia induces rapid cell division, cell enlargement, and subsequent cell degeneration and collapse. The continuation of this process results in the formation of a large central cavity (in which the now-sedentary nematodes reside) enveloped by a gall wall. Gall size increases rapidly as nematodes grow and reproduce. The gall wall is several cell layers thick. Inner cells of the gall wall (near the cavity) have dense cytoplasm with several mitochondria, indicating high levels of metabolic activity. These cells most likely provide nutrients to the nematodes. The outer layers of the gall wall are unmodified, thereby forming and maintaining the gall structure. As the plant senesces, the galls desiccate and the nematodes undergo anhydrobiosis.

Management

To mitigate the effects of annual ryegrass toxicity, farmers can move their livestock another, uninfected pasture at first sign of toxicity. Hot water treatments or chemical seed treatments have been used to produce clean seed. Infected pastures can be managed by mowing, herbicide treatments, or burning. These techniques eliminate the development of inflorescences and halt the life cycle of the nematode since they only mature to adulthood within the seed gall. ''A. agrostis'' cannot survive in the soil for more than one year and thus practices such as crop rotation or fallow have proven to be effective in managing the nematode.

References

{{DEFAULTSORT:Anguina Agrostis Agricultural pest nematodes Tylenchida Nematodes described in 1799