Abstract: The complete sequences of rDNA ITS1 and ITS2 were determined for the brown planthopper Nilaparvata lugens, the white-backed planthopper Sogatella furcifera and the small brown planthopper Laodelphax striatellus in order to explore the molecular identification method for them. The flanking regions of rDNA-ITS1 and ITS2 of the three planthoppers showed only limited variation, but the sequences of rDNA-ITS1 and ITS2 differed significantly. There are 294 variable sites in the 438 analyzed sites for the ITS1 region, and 177 variable sites in the 403 analyzed sites for the ITS2 region. Species-specific primers of N. lugens, S. furcifera, and L. striatellus were designed based on their rDNA-ITS1 and ITS2 sequences. The results of PCR amplification of rDNA-ITS1 in the three species indicated that the species-specific primers were not applicable. However, the species-specific primers based on the rDNA-ITS2 sequences proved to be useful diagnostic primers for the three planthoppers. It is so concluded that molecular identification of N. lugens, S. furcifera and L. striatellus using the species-specific primers from the rDNA-ITS2 region is feasible.

Key words: Nilaparvata lugens, Sogatella furcifera, Laodelphax striatellus, rDNA, ITS1, ITS2, diagnostic primers, molecular identification