First reports of Hemicycliophora poranga, Helicotylenchus dihystera and Tylenchorhynchus zeae (Tylenchomorpha) from Greece and further records of four other nematode species

(Fig. 1A–D, Table 1)

Figure 1:

Specimens of Hemicycliophora de Man, 1921 were found in a soil sample collected from the rhizosphere of Citrus sp. in Lakonia, Peloponnisos, at a density of 70 specimens per 300 cm³ soil.

Females: Females of the recovered Greek population were characterized by a rounded to hemispherical lip region (16.0–18.0 μm wide), with a raised labial disc. Lateral fields marked by breaks and anastomoses, vulval lips modified (1–2 annuli long) and tail tapering regularly to a narrow conical part with finely rounded terminus. The morphometrics and morphology of the Greek population were coincident with original and later descriptions and the species was identified as H. poranga (Monteiro & Lordello, 1978; Subbotin et al., 2014).

Blastn search of D2–D3 sequences of the Greek population of H. poranga showed 99 to 100% identity (differing in 0 to 5 bp, 0 indels) with other world populations. They were deposited in NCBI GenBank (accession numbers OR286399–OR286401).

This nematode has been reported as a serious pest to various cultivated plants (Chitambar, 1993; Emilse et al., 2011; Subbotin et al., 2014; Nguyen and Trinh, 2021). However, its damage to the Citrus trees was not assessed during the present study. This is the first report of H. poranga in Greece, and further research is necessary to investigate whether it is pathogenic to other crops.

(Fig. 1E–H, Table 2)

Specimens of Helicotylenchus Steiner, 1945 were found in soil samples collected from the rhizosphere of tomato grown in a commercial greenhouse in Patras, Peloponissos at a density of 150 specimens per 300 cm³ soil.

Females: Females of the recovered population were characterized by a rounded lip region, separated from body by a slight depression with 2–3 lip annuli. The stylet was well developed, with knobs slightly projected to anterior region; lateral fields marked by four smooth lines; and tail conical, dorsally convex, with a subterminal projection on the ventral side. The morphology and morphometrics of the Greek population fit with those of the original and later descriptions (Sher, 1966; Pour Ehtesham et al., 2021) and was identified as H. dihystera. This is the first report of the species from Greece.

Blastn search of D2–D3 sequences of the Greek H. dihystera population showed 99 to 100% identity (differing in 0 to 3 bp, 0 indels) to other populations. This species has a cosmopolitan distribution and has been detected in association with several crops (Castillo and Gomez-Barcina, 1993; Brücher et al., 2019; Baimey et al., 2009; Firoza and Maqbool, 1995; Pour Ehtesham et al., 2021). Samples were deposited in NCBI GenBank (accession numbers OR286402, OR286403).

(Fig. 1I–L, Table 2)

Specimens of Tylenchorhynchus Cobb, 1913 were found in soil samples collected from the rhizosphere of kiwi fruit grown in Pieria at a density of 50 per 300 cm³ soil.

Females: Females of Greek population of Tylenchorhynchus were characterized by a slightly offset lip region with four to five annuli. Stylet well developed, with anteriorly flattened knobs. Tail conoid to sub-hemispherical with smooth terminus. Males were common, spicules ventrally curved and gubernaculum was rod-shaped. The morphology and morphometrics of the Greek population of Tylenchorhynchus fit with those of the original and later descriptions identified as T. zeae (Sethi & Swarup, 1968; Geraert, 2011). Blastn search of D2–D3 sequences of the Greek T. zeae population showed they have 99 to 100% identity (differing in 0 to 2 bp, 0 indels) to other sequences of isolates of the species already deposited in GenBank (accession numbers OR286404, OR286405). This nematode has been found in association with maize and other crops, e.g. cabbage, cauliflower, olive, and grapevine (Chen et al., 2007; Hassan et al., 2009; Handoo et al., 2014; Xu et al., 2020), in different areas worldwide. To our knowledge, this is the first report of the species in Greece.

Other nematode populations, matching with the genera Nanidorus Siddiqi, 1974 and Helicotylenchus, were detected in this study. Specimens of Nanidorus were also found in soil samples (40/300 cm³) collected from tomato grown in a commercial greenhouse (Patras, Peloponissos), and those belonging to Helicotylenchus were found in soil samples collected from kiwi fruit (20/300 cm³) in Pieria and from pistachio (15/300 cm³) in Korinthia. The Nanidorus species was molecularly identified as Nanidorus minor (Colbran, 1956) Siddiqi, 1974. Its morphology and morphometrics fit with those given for previous descriptions (Decraemer, 1995; Hajihassani et al., 2018). This species has a worldwide distribution, is a tobravirus vector (Decraemer and Robbins, 2007), and has been already reported in Greece with its identification based on morphological characteristics (Karanastasi et al., 2006). Thus, no morphometrics of this population are provided herein. The current work is the first molecular identification of the species in Greece.

Blastn search of D2–D3 sequences of the Greek population of N. minor population showed 99 to 100% identity (differing in 0 to 7 bp, 0 indels) with other populations, and they were deposited in NCBI GenBank (accession numbers OR286411, OR286412).

The spiral nematode from kiwi fruit (Pieria) and pistachio (Korinthia) was identified as Helicotylenchus microlobus Perry, Darling & Thorne, 1959 using its D2–D3 regions (NCBI accession numbers OR286408–OR286410). This nematode has been found previously in association with olives (island of Crete) and walnut (island of Evia) (Tzortzakakis et al., 2018). Thus, no morphometrics are provided herein. The current records indicate a wider geographical distribution in mainland Greece.

Other nematode species were recovered and identified from Tyrnavos and Athens. Bitylenchus hispaniensis (Handoo et al., 2014) was found in a soil sample (25/300 cm³) from grapevine (Tyrnavos) and Scutellonema brachyurus (Steiner, 1938) Andrássy, 1958 was found in a pot (10/300 cm³) planted with gardenia in a home garden (Athens). Bitylenchus hispaniensis has been found and characterized previously in association with olives on Crete (Tzortzakakis et al., 2018), and this current record is the first report from mainland Greece. Scutellonema brachyurus has been found and characterized previously in a home garden in Heraklion, Crete (Tzortzakakis et al., 2016). This nematode has been already reported, mainly in greenhouses of some European countries, and it is hypothesized that it has been introduced by imported plant material (Tzortzakakis et al., 2016).

D2–D3 sequences from both species have been deposited in NCBI GenBank with accession numbers OR286406 and OR286407 for B. hispaniensis and OR286413–OR287347 and S. brachyurus. These sequences matched well (100% identical) with the accessions belonging to B. hispaniensis and S. brachyurus from Crete.