A New Cyst Nematode <i>Heterodera luodingensis</i> n. sp. (Nematoda: Heteroderinae) from Rice in China

A unique cyst nematode population (<i>Heterodera</i> spp.) was collected from rice roots in Luoding County, Guangdong Province, China. Morphological and molecular analyses revealed that it is significantly different from all previously described cyst nematode species. It is described as <i>Heterodera luodingensis</i> n. sp. and classified in the Cyperi group. <i>H. luodingensis</i> n. sp. is characterized by its lemon-shaped cyst with a prominent terminal vulval cone that is ambifenestrate with abundant bullae and a relatively short vulval slit, measuring 31.3 (24.4 to 38.7) μm in length. The second-stage juveniles (J2s) are characterized by dumbbell-shaped labials, three lip annules, and a lateral field with three incisures. The J2 stylet is 18.7 (16.9 to 19.8) μm long with anterior concave or spherical knobs. The tail is elongate conoid, tapering to a rounded terminus or zig-tapering to a rounded terminus that is 54.9 (43.9 to 64.3) μm long with a hyaline region comprising 40.3 to 52.5% of the tail. Phylogenetic tree analysis based on rDNA 28S D2D3 and ITS fragments showed that <i>H. luodingensis</i> n. sp. is unique and clearly separated it from other cyst nematodes. It is most closely related to <i>H. oryzicola</i>, <i>H. fengi</i>, <i>H. elachista</i>, <i>H. oryzae</i>, and <i>H. guangdongensis</i>. <i>H. luodingensis</i> n. sp. can be distinguished from <i>H. oryzicola</i> by its shorter vulval slit and underbridge, from <i>H. elachista</i> by abundant bullae, shorter vulval slit, and fenestrate width, from <i>H. oryzae</i> by a shorter vulval slit and underbridge, from <i>H. fengi</i> by a shorter vulval slit, and from <i>H. guangdongensis</i> by a longer cyst length and abundant bullae. Based on PCR-RFLP of rDNA-ITS, <i>H. luodingensis</i> n. sp. can be clearly distinguished from <i>H. oryzicola</i>, <i>H. mothi</i>, <i>H. elachista</i>, <i>H. guangdongensis</i>, and <i>H. cyperi</i>. A parasitism test from a pure culture derived from a single cyst in a greenhouse showed that <i>H. luodingensis</i> n. sp. can successfully complete its life cycle on rice, and rice is its type host.