Paratrichodorus teres. [Distribution map].

A new distribution map is provided for Paratrichodorus teres (Hooper) Siddiqi. Enoplea: Dorylaimida: Trichodoridae. Hosts: sugarbeet (Beta vulgaris var. saccharifera), potato (Solanum tuberosum), onion (Allium cepa) and various bulbs. Information is given on the geographical distribution in Africa (South Africa), Asia (Iran), Europe (Belgium, Denmark, France, Germany, Greece, Italy, Netherlands, Poland, Russia, Spain, Canary Islands, Sweden, United Kingdom, England), North America (United States, Florida, Oregon, Washington), Oceania (Australia, South Australia), South America (Chile).

First Report of the Stubby-Root Nematode, Paratrichodorus teres, from Potato in the Columbia Basin of Washington State

Stubby-root nematodes of the genus Paratrichodorus are migratory ectoparasites that cause stunted and deformed roots. They also transmit Tobacco rattle virus, the causal agent of corky ringspot disease in potato. Thus, they are important to the potato industry in the Pacific Northwest, including the Columbia Basin of Washington state, which is one of the largest potato-producing regions in the United States. Stubby-root nematode species are difficult to identify because the morphological differences between the species are very small (4). Paratrichodorus teres is a morphologically similar species and has been reported mainly from temperate regions within Europe. P. teres has also been reported in potato fields in eastern Oregon (3). The morphological similarity between P. allius and P. teres creates problems for routine identification because trichodorid species have a conservative morphology and are separated by the following primary characteristics: females, type of genital system and vulva position; males, number of ventromedian precloacal supplements and cervical papillae and habitus (2). As with most soil nematodes, females are more prevalent than the males. Unfortunately, in the generic key (2), female P. allius and P. teres belong to subgroup 1–12 and are separated by a secondary characteristic, vaginal shape that could be affected by fixation or handling. Male P. allius and P. teres are separated by the former species having one fewer ventromedian precloacal supplement. Thus, the morphological similarity between P. allius and P. teres creates problems for routine identification. This might be one of the reasons that P. teres has not been diagnosed in Washington until now. Using nematode morphological diagnostic keys (1,2) and comparing 18S rDNA sequence data obtained from specimens with those listed on public sequence databases, e.g., NCBI GenBank, stubby-root nematodes from two potato fields close to Moses Lake, Grant County, WA, were diagnosed as P. teres. The two adjacent potato fields are irrigated and are situated approximately 100 miles from the eastern Oregon site where P. teres was first described (3). Soil samples were collected from several Columbia Basin potato fields that had corky ringspot disease and stubby-root nematodes. Corky ringspot disease is an emerging disease in Washington, and the presence of a new viruliferous nematode species might be of concern to the potato industry. References: (1) W. Decraemer. Page 615 in: Manual of Agricultural Nematology. W. R. Nickle, ed. Marcel Dekker, Inc., New York, 1991. (2) W. Decraemer and P. Baujard. Fundam. Appl. Nematol. 21:37, 1998. (3) H. J. Jensen et al. Plant Dis. Rep. 58:269, 1974. (4) S. MacFarlane et al. Adv. Bot. Res. 36:169, 2002.

First Report of the Stubby-Root Nematode Paratrichodorus teres Associated with Artichoke (Cynara scolymus) in Greece

The polyphagous stubby-root nematode species, Paratrichodorus teres (Hooper) Siddiqi, was first described from soil under lettuce near Norwich, UK and subsequently reported from South Africa and the United States, but predominantly from temperate regions within Europe (4). P. teres is one of 13 economically important trichodorid species known to be vectors of Tobacco rattle virus (TRV) (4). Artichokes planted during 2000 in a field located in the Kandia area of the Argolis Region, Greece (37°32′N, 22°56′E) exhibited symptoms of a virus infection. Sampling was done to ascertain the presence of Longidorus fasciatus, a vector of artichoke Italian latent nepovirus known to occur in the area (1,4). In addition to L. fasciatus, an unknown trichodorid species and Tylenchorhyncus sp. were recovered from the root zone of artichoke at a number of sites within the field. Measurements and morphological examination of the female (n = 13, body length = 741.7 ± 25.5 μm, onchiostyle = 43.7 ± 0.8 μm, and position of vulva from anterior region relative to total body length V% = 53.8 ± 0.4 μm) and male (n =1, body length = 720.5 μm, onchiostyle = 43.5 μm, spicule length = 51.7 μm, and number of ventromedian precloacal supplements = 3) trichodorids isolated from soil samples conformed to the original description of P. teres and the generic polytomous key (2). Furthermore, morphological identification was supported by molecular data. DNA was extracted from seven individual trichodorids, each of which were placed into separate 0.5-ml micro-centrifuge tubes containing 20 μl of 0.25 M NaOH and incubated at 25°C overnight. Thereafter, samples were incubated at 99°C for 3 min and 10 μl of 0.25 M HCl, 5 μl of 0.5 M Tris-HCl, (pH 8.0) and 5 μl of 2% Triton X-100 were added to each tube. Samples were incubated at 99°C for a further 3 min and stored at -20°C. Template DNA was amplified using polymerase chain reaction with primers specific for 18S rDNA and sequenced (3). The resultant consensus sequence had 99.8% homology to P. teres populations isolated from Portugal and good homology (95 to 98%) with five other Paratrichodorus spp. listed on public sequence databases, e.g., NCBI GenBank. This constitutes a new geographic record and a possible association of P. teres on artichoke. References: (1) D. J. F. Brown et al. Eur. J. Plant Pathol. 103:501, 1997. (2) W. Decraemer. Fundam. Appl. Nematol. 21:37, 1998. (3) C. M. G. Oliveira et al. J. Nematol. 36:153, 2004. (4) C. E. Taylor and D. J. F. Brown. Nematode Vectors of Plant Viruses, CAB International Mycological Institute, Wallingford, UK, 1997.