Paratylenchinae: evaluation of diagnostic morpho-biometrical characters of females in the genus Paratylenchus Micoletzky, 1922 (Nematoda: Tylenchulidae)

Abstract

Examination of morphological variability within single female lines of Paratylenchus microdorus, P. straeleni, P. bukowinensis and P. projectus showed that females offer a limited number of characters useful for differentiation of similar species. The most stable were index V, followed by stylet length, conus length and index m. The most variable were tail length and shape, indices c¢ and c, and these are considered unreliable for separation of similar species. It is concluded that the description of a Paratylenchus species should be based on adults of both sexes as well as resistant juvenile stage. Résumé -Paratylenchinae: évaluation des caractères diagnostiques morpho-biométriques chez les femelles dans le genreParatylenchus Micoletzky, 1922 (Nematoda: Tylenchulidae) -L¢ étude de la variabilité morphologique dans des lignées issues d¢ une femelle de Paratylenchus microdorus, P. straeleni, P. bukowinensis et P. projectus a montré que les femelles possédaient un nombre limité de caractères utiles pour la différenciation d¢ espèces proches. Les plus stables sont le rapport V, puis la longueur du stylet, la longueur du cône et le rapport m. Les plus variables sont la longueur et la forme de la queue, les rapports c¢ et c, ces caractères étant considérés comme inutilisables pour séparer des espèces proches. Il en découle que la description d¢ une espèce de Paratylenchus devrait être fondée tant sur les adultes des deux sexes que sur les stades juvéniles résistants.

Description of Paratylenchus (Gracilacus) straeleni (De Coninck, 1931) Oostenbrink, 1960 (Nematoda: Criconematoidea, Tylenchulidae) from hazelnut in Turkey and its comparison with other world populations

“…Great variation in body length; tail length; and ratios b, c and c' is not a surprise. But, a relatively high degree of variation in the vulva position contrasts with results of study by Brzeski & Háněl (2000) and Ghaderi et al (2014) who found vulva position as the most stable characteristic. On the other hand, in accordance with their studies, the stylet and the cone length showed low variation across the populations compared in the present study.…”

“…Moreover, low variation in stylet length strongly suggests that this structure is genetically determined. The vulval positions that varied along the Factor 2 axis can be differentiated genetically rather than environmentally as low variation in the index V was established by Brzeski & Háněl (2000) and Ghaderi et al (2014). Thus, Paratylenchus abietis could be regarded as a subspecies or a cryptic species within a wide range of populations of Paratylenchus straeleni s.l.…”

“…Using a light microscope (Leica, DMLB), morphological and morphometric analyses were performed. Nematode identifi cation was based on observations of the main morphological features for the genus Paratylenchus particularly head, tail and spermatheca shape, presence of males and contents of sperm in spermatheca, number of incisures in the lateral fi eld, stylet and stylet cone length, position of vulva, and presence of advulval fl aps (Brzeski & Háněl 2000;Ghaderi et al 2014). Nematode morphological identifi cation was confi rmed by molecular analyses (sequencing of the 28S rDNA loci).…”

“…Details on the locality of CZ8 P. straeleni population were published by Háněl (1996Háněl ( , 2009) and details on the locality of SK P. straeleni population are in paper by Háněl & Čerevková (2010). Biometrical data on other populations were taken from previously published studies -populations: CZ1-6 (Brzeski & Háněl, 2000), CZ7 (Brzeski & Háněl, 1999), E (Castillo & Gomez-Barcina, 1988). PL1-5 and I (Brzeski, 1995) USA2 (Tarjan, 1960 -P. sarissus), USA3 (Raski, 1962 -P. sarissus) RO1,2 (Ciobanu et al, 2003), DK (Raski, 1976), CDN (Brown, 1959 -Paratylenchus andrilellus), B1 (De Coninck, 1931 -type specimens of P. straeleni), B2 (Geraert, 1965 -neotype of P. straeleni), RUS1 and RUS2 (Eroshenko, 1974 -P. abietis, type female and paratype females, respectively).…”

“…The type and neotype descriptions were based upon two and one females respectively (De Coninck, 1931;Geraert, 1965). However P. straeleni is a species spread worldwide known from North America (Raski, 1962, Van den Berg et al, 2014, Africa (Van den Berg & Tiedt, 2001), Europe (De Coninck, 1931;Brzeski & Háněl, 2000), Asia (Eroshenko, 1974;Ghaderi et al, 2014) and New Zealand (Raski, 1976) (Fig. 1).…”