A new species, Malenchus sexlineatus n. sp., discovered from the Philippines, is described based on morphological and molecular data. The new species is unusual in the genus by having six lateral lines. Malenchus sexlineatus n. sp. is distinguished from M. williamsi, the only other species in the genus with six lateral lines (based on currently available SEM data), by a shorter body of 278 (270-288) vs 452 (425-495) mu m, shorter stylet (7.0 (6.2-7.5) vs 11-12 mu m), narrower annulations (0.8 (0.7-0.8) vs 1.2-1.6 mu m), lateral field comprising one elevated ridge in LM vs six well-separated incisures (resembling the lateral lines in Cephalenchus) in LM, the presence of S-shaped vs straight amphidial apertures, and vulval flaps absent or only one annuli long vs distinct. By having an exceptionally short body, M. sexlineatus n. sp. comes close to M. parvus, M. bryanti and M. acarayensis. However, there are significant differences in the lateral lines, annuli width and most morphometric ratios. Three known species, namely M. exiguus, M. nanellus and M. pachycephalus, all being first records and first representative from China, are characterised by morphological data. The new species was placed in a robustly supported clade containing two other Malenchus spp. and M. exiguus. Interestingly, M. pressulus was placed in a separate, unresolved phylogenetic position. However, the phylogenetic position of these clades could not be resolved within Tylenchidae. The shapes of the amphidial aperture and fovea within Malenchus are also compared and its possible developmental process is illustrated and discussed

Few Aphelenchoides spp. are facultative plant-parasites (foliar and bulb nematodes); three of them are well known in agricultural systems, namely Aphelenchoides besseyi, A. fragariae and A. ritzemabosi. Ten other plant-parasitic species, A. arachidis, A. bicaudatus, A. blastophthorus, A. dalianensis, A. ensete, A. nechaleos, A. paranechaleos, A. saprophilus, A. sphaerocephalus and A. subtenuis, have been reported from a limited number of plant species. We compiled a new database of the associated plants for these thirteen species, a comprehensive list that includes 1104 reports from 126 botanical families. A. besseyi, A. fragariae and A. ritzemabosi represent 94% of the reports, circa 83% and 16% of the total reports correspond to flowering plants and ferns, respectively, with three records on conifers and two from other botanical groups also listed. Most plant-parasitic Aphelenchoides show a remarkably broad diversity of associated plants. Most species appear to have no specific plant hosts (i.e. are generalists). The broad host ranges of these species and absence of more intimate interactions with the associated plants highlights the primitive mode of parasitism in Aphelenchoides species, making them potentially interesting in the study of the evolution of plant parasitism. Even though the compiled list of associated plants is long, it probably only represents a fraction of the potential range. The complete compilation has been uploaded to http://nematodes.myspecies.info/.

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