檢防疫重要性象鼻蟲的分子鑑定

大多數的象鼻蟲爲植食性昆蟲，寄主範圍廣泛，許多種類的幼蟲會蛀食寄主植物，往往造成嚴重的農作損害與植株死亡。由於象鼻蟲之幼蟲與卵已在我國進口農作物當中檢出，對本土農業生態形成潛在嚴重威脅。因此，建立一套有效之分子鑑定系統來檢測外觀形態不易區辨之檢防疫重要性象鼻蟲之幼蟲與卵實屬必要。本研究已成功開發出檢測象鼻蟲之分子鑑定技術平台，含活體與浸漬酒精蟲體之DNA萃取、基因片段增幅以及序列分析等技術。我們已由細胞色素氧化酵素(cytochrome oxidasesubunit I, COI)基因序列在鞘翅目昆蟲中歧異度較高的區段設計可分辨六種不同屬象鼻蟲（李象鼻蟲(Conotrachelus nenuphar)、白緣粗吻象鼻蟲(Graphognathusleucoloma)、新幾內亞甘蔗象鼻蟲(Rhabdoscelus obscurus)等三種爲外來種；甘藷蟻象(Cylas formicarius)、粉綠象鼻蟲(Hypomeces squamosus)、台灣三月始灰象鼻蟲(Sympiezomias cribricollis)爲本土既存物種）之專一性引子對。其中，新幾內亞甘蔗象鼻蟲之專一性引子可進一步區辨同屬之亞洲棕櫚象鼻蟲(R. lineaticollis)。本研究開發的檢測技術與策略可作爲鑑定其他檢防疫象鼻蟲之重要參考。

Most weevils are polytrophic insects. The larvae of many weevils feed by boring into host plants which may be damaged or killed as a result. Weevil larvae and eggs regularly enter Taiwan through imported agricultural products and pose a serious threat to the local agricultural ecology. Identification of invasive weevils, particularly larvae and eggs with indistinct morphological features is only possible using molecular methods and species-specific DNA sequences. We extracted DNA from live or ethanol-immersed samples of adult weevils for use as templates for Polymerase Chain Reaction (PCR), and cloned target sequences of a region containing divergent sequences near the 3'-end of the COI (cytochrome oxidase subunit I) gene in the mitochondrial genome. Within this target region, we successfully designed species-specific primers for six weevil species belonging to different genera (foreign species: Conotrachelus nenuphar (plum curculio), Graphognathus leucoloma (whitefringed beetle), and Rhabdoscelus obscurus (New Guinea sugarcane weevil); local species: Cylas formicarius (sweet-potato weevil), Hypomeces squamosus (gold-dust weevil), and Sympiezomias cribricollis (gourd-waist weevil)). Using the same strategy, we also were able to discriminate two weevil species of the same genus, namely R. obscurus and the Asiatic palm weevil R. lineaticollis. Strategies and technologies developed in this study can be applied to molecular identification of other kinds of weevils of quarantine importance.