Heterodera amaranthusiae n. sp. (Nematoda: Heteroderidae), a new cyst nematode parasitising Amaranthus retroflexus L. in China

Y A new species of cyst-forming nematode, Heterodera amaranthusiae n. sp., is described and illustrated from the weed, Amaranthus retroflexus, in a potato field in Yunnan Province, China. It is characterised by having canary to russet-brown and asymmetric lemon-shaped cyst, distinct neck, bifenestrate vulval cone, relatively short vulval slit of 29 (28-32) mu m, bullae absent and underbridge absent or weak if present. Second-stage juveniles are characterised by a well-developed stylet of 23 (22-25) mu m with robust shaft and basal knobs concave anteriorly, tail conoid, 51 (48-58) mu m long and hyaline region comprising 48 (41-53)% of its length. Morphologically and morphometrically it most resembles H. vallicola in the Humuli group. The ITS, 28S and COI gene sequences of H. amaranthusiae n. sp. clearly differentiate it from other Heterodera species. For diagnostic purposes, restriction enzyme analysis of the ITS region and three restriction enzymes, AluI, BsuRI (HaeIII) and CfoI (HhaI), were selected, clearly distinguishing H. amaranthusiae n. sp. from representative species in the Humuli group. Phylogenetic relationships with other species of the genus, inferred from two ribosomal regions and the cytochrome oxidase c subunit 1 region, based on Bayesian analysis, consistently showed that H. amaranthusiae n. sp. clustered with high support with other Humuli group species but with separate species status.