Pin nematodes of the genus Paratylenchus are obligate ectoparasites of a wide variety of plants that are distributed worldwide. In this study, individual morphologically vouchered nematode specimens of fourteen Paratylenchus species, including P. aculentus, P. elachistus, P. goodeyi, P. holdemani, P. idalimus, P. microdorus, P. nanus, P. neoamblycephalus, P. straeleni and P. veruculatus, are unequivocally linked to the D2-D3 of 28S, ITS, 18S rRNA and COI gene sequences. Combined with scanning electron microscopy and a molecular analysis of an additional nine known and thirteen unknown species originating from diverse geographic regions, a total of 92 D2-D3 of 28S, 41 ITS, 57 18S rRNA and 111 COI new gene sequences are presented. Paratylenchus elachistus, P. holdemani and P. neoamblycephalus are recorded for the first time in Belgium and P. idalimus for the first time in Europe. Paratylenchus is an excellent example of an incredibly diverse yet morphologically minimalistic plant-parasitic genus, and this study provides an integrated analysis of all available data, including coalescence-based molecular species delimitation, resulting in an updated Paratylenchus phylogeny and the corrective reassignment of 18 D2-D3 of 28S, 3 ITS, 3 18S rRNA and 25 COI gene sequences that were previously unidentified or incorrectly classified.

Summary: Pratylenchus rwandae n. sp., a root-lesion nematode associated with maize (Zea mays) from Rwanda, is described. This new species is characterised by females of medium to large size (469-600 μm) having an offset lip region with three annuli, stylet of 13-14.6 μm long with prominent rounded or anteriorly concave knobs, short to long pharyngeal gland overlap of 10.9-34.7 μm long, variable number of lateral lines (4-14) in different regions of the body, lateral field consisting of smooth bands, oval to slightly rounded spermatheca, vulva located at 75-80% of the total body length, post-vulval uterine sac (PUS) 20.3-26.5 μm long, tail subcylindrical to conoid with variation in tail tip shape from rounded to truncate or indented with generally smooth tip, and male unknown. The results of the phylogenetic analyses based on sequences of the D2-D3 expansion regions of 28S, partial 18S and ITS of rDNA and COI of mitochondrial DNA indicate that P. rwandae n. sp. is a species within the Penetrans group and appears as a sister species to a group comprising P. convallariae, P. dunensis, P. fallax, P. oleae, P. penetrans, P. pinguicaudatus, and three other unidentified species. A comparison of important morphological characters of the closely related Pratylenchus spp. is provided.

Summary: Root-lesion nematodes, Pratylenchus spp., are one of the most important nematode groups in economic terms. The combination of morphological analyses and molecular analyses based on D2-D3 of 28S rDNA, ITS rDNA, and COI mtDNA regions supported the establishment of a new Pratylenchus species, making a total of 103 valid Pratylenchus species. The females of P. horti n. sp. are characterised by the following traits: low labial region with two annuli continuous to the body, en face form belonging to group II sensu Corbett & Clark (1983) with submedian triangular-shaped segments fused with the oral disc and separated from the lateral segments, lateral field with four incisures at vulval level and lacking areolation, robust stylet 15-17 μm long with rounded knobs, and subcylindrical tail with smooth tail tip. The males are largely similar to the females but differ from the females by the partially areolated lateral field, slightly ventrally arcuate and weakly cephalated spicules (15-19 μm), and ventrally curved elongate conical tail with a poorly protruding, crenate bursa. The new species was recovered from soil and root samples from the rhizosphere of Hedychium greenii growing in the Botanical Garden, Ghent University, Belgium.

A survey for slug-associated nematodes in five locations of East and West Flanders in Belgium revealed the presence of one new and six known slug-parasitic nematodes,Agfa flexilis(Dujardin, 1845),Alloionema appendiculatum(Schneider, 1859),Angiostoma dentiferum(Mengert, 1953),Angiostoma limacis(Dujardin, 1845),Angiostoma norvegicum(Rosset al., 2017) andPhasmarhabditis hermaphrodita(Schneider, 1859).Angiostoma norvegicumandP.hermaphroditaare recorded for the first time in Belgium. The six known species are documented by light microscopy (LM) microphotographs and informative DNA sequences.Angiostoma gandavensisn. sp. (Angiostomatidae), discovered from arionid slugs, is described based on light microscopy, scanning electron microscopy (SEM) and molecular data. Based on analyses of D2D3 expansion segment of 28S and 18S rDNA sequences, this new species is found to be related toA.limacis,A.norvegicum,A.margaretae(Rosset al., 2011) andA.milacis(Ivanova and Wilson, 2009). The new species can be distinguished from these others based on morphological characters such as the distinctive mucronate structures at the tail tip of both sexes, presence of lateral ala, reflexed female ovaries and the number and arrangement pattern of male genital papillae.

During a survey in the Botanical garden of Ghent University, a new species Rotylenchus rhomboides n. sp. and a population of Rotylenchus buxophilus were found. Rotylenchus rhomboides n. sp. is characterized by the presence of a rhomboid-like widening of the mid-ridge of lateral field at the level of vulva, a feature previously unknown within the genus. The population of the new species, composed only by females, has a rounded labial region with 4 to 5 annuli, robust stylet (31-37 μm long), short dorsal esophageal gland (9-19 μm) overlap of the intestine, vulva located slightly posterior to mid-body, and hemispherical or rounded tail shape with large phasmids located 3 to 5 annuli anterior to the level of anus. The hierarchical cluster analysis based on morphological features indicated that the new species closely resembles R. corsicus, R. gracilidens, and R. rugatocuticulatus. The DNA analyses of the D2-D3 of 28S rDNA, ITS rDNA, and COI mtDNA sequences of Rotylenchus rhomboides n. sp. show a close relationship with R. buxophilus, R. goodeyi, R. laurentinus, R. pumilus, and R. incultus, all of which can also be differentiated from the new species by morphological features. The combination of morphological, morphometric, and molecular characteristics confirmed the new species and the first report of R. buxophilus on yam (Dioscorea tokoro) in Belgium. During a survey in the Botanical garden of Ghent University, a new species Rotylenchus rhomboides n. sp. and a population of Rotylenchus buxophilus were found. Rotylenchus rhomboides n. sp. is characterized by the presence of a rhomboid-like widening of the mid-ridge of lateral field at the level of vulva, a feature previously unknown within the genus. The population of the new species, composed only by females, has a rounded labial region with 4 to 5 annuli, robust stylet (31–37 μm long), short dorsal esophageal gland (9–19 μm) overlap of the intestine, vulva located slightly posterior to mid-body, and hemispherical or rounded tail shape with large phasmids located 3 to 5 annuli anterior to the level of anus. The hierarchical cluster analysis based on morphological features indicated that the new species closely resembles R. corsicus, R. gracilidens, and R. rugatocuticulatus. The DNA analyses of the D2-D3 of 28S rDNA, ITS rDNA, and COI mtDNA sequences of Rotylenchus rhomboides n. sp. show a close relationship with R. buxophilus, R. goodeyi, R. laurentinus, R. pumilus, and R. incultus, all of which can also be differentiated from the new species by morphological features. The combination of morphological, morphometric, and molecular characteristics confirmed the new species and the first report of R. buxophilus on yam (Dioscorea tokoro) in Belgium.

Heterodera dunensis n. sp. from the coastal dunes of Gran Canaria, Canary Islands, is described. This new species belongs to the Schachtii group of Heterodera with ambifenestrate fenestration, presence of prominent bullae, and a strong underbridge of cysts. It is characterized by vermiform second-stage juveniles having a slightly offset, dome-shaped labial region with three annuli, four lateral lines, a relatively long stylet (27-31 µm), short tail (35-45 µm), and 46 to 51% of tail as hyaline portion. Males were not found in the type population. Phylogenetic trees inferred from D2-D3 of 28S, partial ITS, and 18S of ribosomal DNA and COI of mitochondrial DNA sequences indicate a position in the ‘Schachtii clade’.