Trichodorus Species Research Articles

Trichodorus orientalis n.sp. (Nematoda: Trichodoridae) from Jordan and Iran

A new species ofTrichodorus is described from the rhizosphere of vegetables (Lycopersicon esculentum Mill. andPhaseolus vulgaris L.) in Jordan and from the rhizosphere of grape-vine (Vitis sp.) in Iran.

Two New Species of Trichodorus (Nematoda: Diphtherophorina) From Africa*)

Soil samples collected during expeditions in Kenya (1975) and Ivory Coast (1979) yielded two new species of Trichodorus Cobb, 1913. T. coomansi n. sp. can easily be distinguished by the two cervical papillae with the excretory pore between them and by the shape of spicules (males); and by the shape of the sclerotized thickenings at the vulva (females). T. eburneus n. sp. can be distinguished by having one cervical papilla, only the posterior supplement opposite the head of spicules and the head of the spicules inclined ventrally (males); by the shape of the sclerotized thickenings at the vulva and the subventral position of the pair of body pores posterior to the vulva (females). Both species are differentiated from all other known Trichodorus species by the presence on the tail of one medioventral papilla (males) or one medioventral pore (females). Both species are found in soil samples from natural vegetation. T. coomansi n. sp. probably represents an endemic species in Kenya, T. eburneus n. sp. is probably more widespread occurring at various sites in Ivory Coast.

Soil disinfection to prevent transmission of tobacco rattle virus to potatoes and flower bulbs

Up to the present time, the ability of Tobacco Rattle Virus (TRV) transmission has been proved for 12 species of Trichodorus. Species of this cosmopolitan genus are found only in light-textured and organic soils. TRV occurs in Europe, North America, South America and Japan and has a wide host range that includes many crop and weed species. The economically most important disease caused by TRV is spraing or corky ringspot and stem mottle in potatoes in Great Britain, Continental Europe and the United States. In The Netherlands, serious damage caused by TRV is also known to occur in bulbflowers such as Gladiolus, tulips, daffodils, hyacinths, Allium, Ornithogalum, Scilla and Crocus. Although some resistant or tolerant potato cultivars are known, these are only of regional importance with regard to their ability to escape spraing disease, because of the occurrence of different strains of TRV. In potatoes, the disease is more important for ware potatoes than for seed potatoes, because it is usually only transmitted to a minor extent from mother tuber to progeny plants. In flower bulbs, the disease is carried over to the greater part of the vegetative progeny of infected plants. Effective control by crop-rotation cannot be expected, because TRV can be retained by the nematodes for about 3 years, even when the latter have no access to plant roots. Moreover many weed hosts, in some of which TRV is seed-borne, play an important role in the ecology of the disease. The best prospects of controlling transmission of TRV may be expected from preventive soil treatments. Systemic nematicides may affect the nematodes which feed on the roots before the treated plants reach a stage susceptible to TRV infection. Therefore, correct timing of application of such materials should be investigated. Soil fumigation provides the best prospect for control of transmission of TRV. In the case of virus vectors, complete nematode control to a great depth in the soil may be necessary. Almost undetectable populations of Trichodorus were found to transmit TRV to a relatively high proportion of tulips. Highest Trichodorus population densities are to be found regularly below the tilth and specimens have been found down to a depth of 120 cm in the soil. These nematodes in the subsoil may constitute a reservoir of virus-carrying individuals that may escape from soil disinfection. A comparison of DD and Metam-Na showed no difference in efficiency. In loamy sand soil and reclaimed peat sub-soil, insufficient control was obtained. Good control was obtained with 400 1 DD/ha in Gladiolus, but not consistently in tulips. In potatoes, good control was obtained with 250 1 DD/ha, but the tubers had a bad flavour which is unacceptable.

Taxonomy of the Trichodorus-Aequalis Complex (Diphtherophorina)

Comparison of type material of Trichodorus aerequalis Allen, 1957 and of T. sparsus Szczygiel, 1968 showed that these species can be distinguished by the spicules being setose in the latter and smooth in the former species, and by the shape of the male tail. The difference in arrangement of the ventral cervical pores in the male, which is suggested by the original descriptions, is non-existent. No clear-cut differences were found between females. Variation in these two species appears to be greater than in other Trichodorus species. A population from Plymouth, South England, shows aberrant characters: smooth, almost straight spicules; females with only one pair of lateral cuticular pores. This population is considered to represent a separate species, here described as T. hooperi.

Needle nematodes (Longidorus spp.) and stubby‐root nematodes (Trichodorus spp.) harmful to sugar beet and other field crops in England

SUMMARY Longidorus attenuatus produces galls at the tips of roots of field crops, including sugar beet, growing in alkaline, sandy soils in eastern England. L. elongatus produces similar, but often larger, galls on the roots of sugar beet and other crops in sandy soils in the W. Midlands and in Fen peats. Trichodorus spp. cause ‘stubby root’ of sugar beet and can feed on many field crops. Seven species of Trichodorus were found in sandy soils in eastern England. L. attenuatus, L. elongatus and Trichodorus spp. aggregate around roots and stunt sugar beet and other crop plants. L. attenuatus is commoner below plough depth than in the topsoil, whereas T. cylindricus, T. pachy‐dermus and T. anemones are more abundant in the topsoil. These nematodes cause some forms of ‘Docking disorder’.

Transmission of Tobacco Rattle Virus By Trichodorus Species

All nine species of Trichodorus which occur in the Netherlands proved to be potential vectors of tobacco rattle virus (TRV). T. nanus was least efficient in this respect. Non-viruliferous Tricbodorus populations could only rarely be made viruliferous by giving them access to infector plants inoculated with TRV.

Descriptive Notes on Three Species of Trichodorus (Dorylaimide : Trichodoridae) from Forest Nurseries in Japan

Three species of Trichodorus have been found in forest nurseries located at various regions in Japan. Trichodorus cedarus YOKOO, 1964 was the most widely distributed species out of three. The original description of this species was supplemented using specimens from a nursery in eastern Japan. T. cedarus is distinguished by a relatively long onchiostyle, male having three venromedian papillae located posterior to the onchiostyle base, cutinized vaginal pieces being conspicuous and characteristically triangular, and female having a pair of ventrosubmedian pores just behind the vulva. Females of T. minor COLBRAN, 1956 and T. porosus ALLEN, 1957 were collected with several species of forest tree seedlings.

Viruses of the tobacco rattle virus group in Northern Italy: Their vectors and serological relationships

Four species ofTrichodorus have been found in northern Italy, viz.Trichodorus viruliferus, T. teres, T. nanus and an undescribed species. In seven cases tobacco rattle virus (TRV) was isolated from soil samples by means of bait seedlings and in three of these cases the vector was found to beT. viruliferus. The seven virus isolates reacted with an antiserum against a Dutch TRV isolate and were divided into two groups according to their reaction with this serum. One isolate from each group was subjected to a more detailed examination. Of these, one was found to be closely related to a Dutch isolate from gladiolus with notched leaf symptoms, while the other showed a distinct relationship to the pea early-browning virus found in Britain. One of the isolates proved to be more closely related to the Dutch TRV than is the Dutch gladiolus isolate.

Transmission of raspberry ringspot virus by Longidorus elongatus (de Man) (Nematoda: Dorylaimidae)

Two groups of economically important plant viruses, nepoviruses and tobraviruses, are transmitted through the longidorids, Trichodorus and Paratrichodorus. Nepoviruses and tobraviruses are taxonomically different from each other, but both have RNA genetic material and contain two different types of genomic RNAs. Nepovirus particles are spherical in shape, while tobraviruses are rod-shaped. Nepovirus species have a single coat protein (CP), which is assembled in multiple copies to form the virus particles. Longidorids have been reported as vectors of nepoviruses, while trichodorids serve as vectors of tobraviruses. Of the 41 species of nepoviruses, 13 are transmitted by 11 species of Xiphinema and 10 are transmitted by 11 species of Longidorus in different crops. Different species of Trichodorus and Paratrichodorus have been reported to transmit pepper ringspot virus, tobacco rattle virus, and pea early-browning virus in different countries. Plant-parasitic nematodes acquire virus particles during feeding by sucking cell sap with a stylet. Most of the plant-parasitic nematodes transmit plant viruses by feeding ectoparasitically near the root tip on the outside of the root surface. Among them, some nematodes induce galls at the infection site of root surface after completion of the feeding process. The transmission process of the plant viruses by nematodes are completed by different phases, such as ingestion, acquisition, adsorption, retention, release, transfer, and establishment. Efficient transmission from infected host plants to healthy host plants by nematode vectors is an important biological feature for the development of epidemics of plant diseases incited by viruses. Both the adult and juvenile stages of the nematode vectors are capable of transmitting the associated plant viruses. Virus transmission by a vector is often characterized by some degree of specificity. Specific relationships exist between the serologically distinct viruses and their vector nematode species. Specificity is largely determined by the virus CP and by an inherited ability of the nematode to retain virus particles at specific sites within its esophagus. Numerous studies suggest the involvement of a virus–ligand interaction in transmission specificity. The CP and its derivatives readthrough CP and minor CP and nonstructural proteins, such as a helper component or a transmission factor, are major viral determinants of transmission specificity. A number of virion-binding vector proteins have been identified as potential receptors.

A Review of the Nematode Genus Trichodorus With Descriptions of Ten New Species 1)

Trichodorus primitivus (de Man 1880) is redescribed and ten new species of Trichodorus are described, including the species first reported to cause stubby-root disease in Florida, U.S.A. The species descriptions and illustrations present details of the morphology of both males and females and indicate the presence of two distinct species groups in the genus. The morphology of the onchiostyle is discussed and illustrated and evidence is presented to indicate that the onchiostyle in Trichodorus is not a hollow axial spear but is dorsal to the lumen of the esophagus. A key to the species is presented as an aid to identification.

On Trichodorus pachydermus n. sp. (Nematoda: Enoplida).

In soil samples taken from around trees of Primus serotina and shrubs near the writer's house at Ede, Holland, the nematode population proved to consist mainly of a hitherto undescribed species of Trichodorus. Small numbers of the same species were found in many other places including a strawberry field on light sandy soil near Beverwijk, where it occurred together with T. primitivus (de Man, 1884) Micoletzky, 1922; a garden at Middelharnis (sandy loam) and in arable land at Ottersum (sandy soil). No data could be collected on its food habits.