First report of Heterodera vallicola, a Japanese elm parasitic cyst nematode species, in Japan

Abstract

During a nematological survey in a natural forest in Sapporo, Hokkaido, Japan, spherical to lemonshaped cysts thought to be Heterodera, were found in the rhizosphere of Japanese elm (Ulmus davidiana var. japonica). Considering the vegetation of the sampling place, the nematodes seemed to be an unreported cyst nematode species in Japan. A cyst nematode species that parasitizes Japanese elm in the Primorsky territory, the Russian Far East, was described in 2001 as H. vallicola. Therefore, we hypothesized that the cyst nematode population belonged to H. vallicola and examined its morphological features and nucleotide sequences to determine the species identity. The morphometrics of the cysts and second-stage juveniles were generally consistent with those of H. vallicola. In addition, the sequences of the mitochondrial cytochrome c oxidase subunit I gene and the internal transcribed spacer region of the ribosomal RNA gene were the most similar to those of H. vallicola. According to the results, we determined that this nematode belongs to H. vallicola.