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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.