太平洋地區蔥薊馬(Thrips tabaci Lindeman)之 遺傳變異

Abstract

Onion thrips (Thrips tabaci Lindeman), the cosmopolitan pest, has distributed around Europe, Asia, pacific islands, America, east of Africa and Australia. Because of the tiny body size, short life cycle, and polymorphology with body color from light to dark, it is not only hard to be identified but also impossible to be distinguished their genetic variation among populations. In this study, both genes of nuclear internal transcribed spacer 2 (ITS2) region and mitochondrial cytochrome oxidase subunit I (COI) of onion thrips collected from Pacific Rim were used to detect and analyse their intraspecific genetic diversity. There are 86 sequences successfully to be detected in those onion thrips populations from 13 countries of Pacific Rim with 49 sub-populations. The sequences variation of ITS2 rDNA and COI mtDNA region were 0.4~3.0% and 0~3.1%, respectively. The comparison of sequences in 4 single sample areas, i.e. China, Hawaii, Peru, and Netherlands, showed that the largest variation of ITS2 rDNA region (0.7~0.9%) was found in China populations. The absolute haplotype diversity of ITS2 rDNA region were found in T. tabaci samples of Peru and China (1.00000) and following with America (0.87273), New Zealand (0.83333) and Australia (0.80300). The highest haplotype diversity of COI mtDNA region were found in samples of Netherlands (1.00000) and following with New Zealand (0.83333). The higher fixation index (FST) of ITS2 rDNA region were found between the thrips populations of Taiwan and Mexico (0.60630), and the higher FST of COI mtDNA region were Hawaii and Australia (0.64935), Taiwan and America (0.64739), Taiwan and Australia (0.60240). These indicated that higher frequencies in gene flow, and thus lower genetic diversity, occurring between those two populations. Cloning method was used to study the ITS2 rDNA region composition as the direct sequending of PCR products shown the overlapping at nucleotides positions of 170. The highest haplotype diversity of ITS2 rDNA region was found in populations of Japan (0.9684) with 17 haplotypes totally, in comparing the heterogeneous composition of all specimens. The genetic analyses of both genes indicated that different genetic variations occurring in different populations of T. tabaci from Pacific Rim. Thus, the unexpected introduction of foreign populations of this pest should be avoid to reduce the hybridization adaptation.