Study On Identification Of Tetranychus Spider Mites Using Morphological Classification And Molecular Technology

Tetranychus spider mites, which belong to Arachnida, Acari, Acariformes, Trombidiformes, Prostigmata, Eleutherengonides, Tetranychidae, are important agricultural pests. They food on vegetables, fruit trees, legumes, ornamentals. In the quarantine process, the identification of species in the Tetranychus is very difficult. Spider mites in genus Tetranychus are generally identified by morphological character, which is based on the shape of the aedeagus knob in adult males. However, morphological identification is limited by the particular life stages, and it is difficult to distinguish between closely related or cryptic species, especially for species within the genus Tetranychus. For example, Tetranychus urticae Koch and Tetranychus cinnabarinus Boisduval have closely morphological characters, it is difficult to distinguish.To overcome the difficulty of identification, growing number of molecular diagnostic tools have been developed for economically important taxa. Polymerase chain reaction (PCR) followed by restriction fragment length polymorphism (RFLP) is a useful molecular diagnostic tool for species identification. The internal transcribed spacer (ITS) region in nuclear ribosomal DNA (rDNA), which consisted of partial ends of 28S and 18S rRNA genes,5.8S rRNA genes, and two internal transcribed spacers (ITS1 and ITS2), usually expresses high variation in interspecies, low variation in intraspecies. This character is useful for species diagnosis.In this study, we identified Tetranychus species by combining morphological classification with PCR-RFLP technology based molecular identification from different hosts and geographic. We aimed at judging whether the combining of two technologies can identify the six spider mites accurately. We also establish diagnostic DNA markers useful for discriminating the six species, Tetranychus ludeni, Tetranychus phaselus, Tetranychus kanzawai, Tetranychus urticae, Tetranychus truncatus, and Tetranychus piercei. We sequenced and analyzed on the ribosomal ITS region of these species. We found three useful restriction enzymes (RsaI, Ddel, MfeI) for use in diagnostic and propose the establishment of a catalogue of RFLP.The results showed that the combination of these two methods can identify these species accurately. And it revealed that ITS was well suited for interspecies identification because of its high degree of polymorphism. The results of the phylogenetic analysis strongly supported the results of identification. The identification of Tetranychus spider mites based on ITS sequences is simple, rapid and reliable.