Investigations On Mango Thrips In Hainan Island And Phylogenetic Researches Based On MtDNA CO Ⅰ Gene Sequences

Mango is one of the most ancient and important fruits. It is the second most important tropical fruit crop in the world only inferior to banana with a total production of about 25.1 MMT (million metric tons) per year. In recent years, as a result of pesticide abuse, thrips become one of the main pest insects while they are secondary pest insects in the past. The nymphs and adults of thrips damage mango flowers, leaves, buds and fruits using their mouthparts, seriously affect growth and fruit quality of mangos and cause serious economic losses.In this paper, the species of mango thrips in Hainan Island and their taxonomy were systematically studied. The results showed that the yellow tea thrip was the dominant species representing 75.51% of all specimens. Aeolothrips fasciatus was collected only in Danzhou and only two individuals were got. It is limited quantity and distribution showed that Aeolothrips fasciatus was not an effective pest control.In this study, mtDNA COâ… gene sequences of 10 species of mango thrips were amplified. The primers (LCO1490, HCO2198) can amplify well the gene fragments of the 10 species and PCR products obtained can be directly used for sequencing. All the lengths of PCR products were 655bp, with the exception of Haplothrips chinensis, which was 646 bp. Interspecific differences could be well revealed through sequence alignments. According to the genetic distances calculated by two models, genetic distances were relatively close among subfamilies. The largest genetic distances occured between Aeolothrips fasciatus and other thrips. And the smallest occurred between Stenchaetothrips victoriensis and Scirtothrips dorsalis. Phylogenetic trees were constructed using 3 different methods (NJ, MP, UPGMA). And the NJ method was possibly the simplist to construct genealogical tree quickly and simultaneously. Also it was quite suitable to analyse large data sets and the bootstrap tests were also time-saving. Furthermore, thrip individuals were successfully clustered by the NJ tree, which was consistent with the traditional classification system. The NJ tree based on the Kimura-2-Parameter (K2P) model was proved to able to meet the need of species identification.Moreover, mtDNA COâ… sequence analyses were conducted for Scirtothrips dorsalis on eleven different host plants. The results showed that genetic distances Scirtothrips dorsalis from different hosts ranged from 0 to 0.046 and the average genetic distance was 0.012, among which, the largest genetic distance (0.046) occurred between bombax malabaricum and Acacia confusa. Genetic distances among mango, litchi, avocado, annona squamosa, longan and coffee were 0. Maximum-Parsimony tree of Scirtothrips dorsalis from 11 hosts based on COâ… sequences showed mango, litchi, avocado, annona, longan, coffee, peanuts and tea were clustered together closely. And chillies, Taiwan acacia, kapok formed a branch, respectively.