Assessment Of Molecular Markers As Molecular Taxonomy For Diaspididae

Diaspididae is one of the most abundant taxa in Coccoidea. According to the statistics from ScaleNet, Diaspididae have about 2429 species worldwide and more than 600 species which accounted for about 25% of the world in China. All of insects in this taxa are an important agricultural and forestry pests. Currently, the identification for this pest is based on published characteristic of female adult, as small individual, high similarity. However, by reason of its small body, high similarity, there are few features are used for identification between related species and that will make some difficult or confusion. So, it will be necessary to develop a rapid method of identification and pest control. This research studies the identifation of Diaspididae based on molecular techniques, and it will provide a technical support for rapid identification of species.We evaluate the markers COI, ITS2, two 28 SrRNA and18SrRNA, based on a large number of Diaspididae specimens.Firstly, we conduct the PCR amplification and sequencing about the five species respectively, which are Aulacaspis rosae, Aulacaspis tubercularis, Aulacaspis actinocaphnes, Aulacaspis megaloba and Aulacaspis fuzhouensis. By comparing the sequence amplification efficiency and success rate of sequencing, the intraspecific and interspecific genetic distance, and building Neighbor-joining trees, we valuate different sequences’ identification ability. And then, the selected suitable candidate sequences for identifying armoured scales have checked from these sequences. The results showed 28 SrRNA and ITS2 sequence are suitable for identifying the armoured scale.In order to further verify the 28 SrRNA and ITS2 identification ability, we expanded the scope of specimens to evaluate them. For the cover of the 28 species, 180 specimens, 28 SrRNA and ITS2 were evaluated by Distance-based and Tree-based methods.The experimental results show that: Overlapping in terms of intra- and inter- specific genetic divergence was observed for two molecular markers. In the species level and the family level, 28 SrRNA for the correct identification reached 89.3% and 92.3% respectively. Results based on the Best Match(BM) and Best Close Match(BCM) criteria are as follows: For the BM criteria, ITS2 showed 91.8% in identification, 28 SrRNA showed 91.9%. For the BCM criteria, ITS2 showed 86.25% in identification, 28 SrRNA showed 89.14%. Based on Tree-based DNA identification criteria, ITS2 with NJ method can correctly identify 66.67 % of species, and 28 SrRNA can correctly identify 78.57% of species. ITS2 with ML method can correctly identify 55.56 % species, and 28 SrRNA can correctly identify 75% of the species.Our research provides effective data support about molecular taxonomy for Diaspididae. Based on these results, the addition of 28 SrRNA as a supplementary marker in armoured scale identification is therefore recommended. Combined with the standard sequence COI can offer help to accurately identify armoured scale.