臺灣小蠹蟲攜播線蟲族群調查

Abstract

小蠹蟲危害眾多森林樹種及經濟作物，由於該類昆蟲於植物組織內完成大半生活史，致使防治困難，故篩選可用於生物防治之天敵，對於開發此類害蟲防治措施至關重要。本研究針對台灣小蠹蟲攜播線蟲族群進行調查，並設計小蠹蟲蟲生線蟲的特殊誘釣裝置。自2015年10月至2018年4月間，由477隻自全國各地採集而得的小蠹蟲及具蛀食孔道段木中分離得的線蟲中，共完成45個樣本鑑定。其中，13個樣本鑑定至種，25個樣本鑑定至屬，7個樣本鑑定至科，另有1個樣本無法鑑定。對線蟲樣本之核醣體基因序列的28S區塊及18S 區塊進行族群分析，發現線蟲與小蠹蟲的攜播關係並無種類專一性；一種小蠹蟲能攜帶多種線蟲，一種線蟲亦能被多種小蠹蟲攜帶。其中，以Euwallacea屬小蠹蟲攜帶線蟲的頻度最高。進行線蟲生態之分析，觀察線蟲與寄主交互關係及線蟲食性，得自段木分離的Deladenus屬及自小蠹蟲分離的Howardula屬與Sphaerularia屬線蟲與小蠹蟲具有寄生交互關係；自小蠹蟲分離的Caenorhabditis屬與Rhabditolaimus屬線蟲對小蠹蟲同時為食腐及攜播；其餘8屬與小蠹蟲為攜播關係，包含Acrostichus屬、Aphelenchoides屬、Bursaphelenchus屬、屬Diplogasteroides屬、Halicephalobus屬、Neodiplogaster屬、Rhabditidoides屬與Ruehmaphelenchus屬。本研究亦嘗試建立以小蠹蟲誘釣蟲生線蟲之技術，以飼養小圓胸小蠹(Euwallacea fornicatus)作為誘釣模式之誘餌，設計出針對地上部蟲生線蟲篩選及具有方便觀察優點的誘釣裝置。試驗期間實際測試六個樣本，並進行多次調整。本研究之線蟲族群調查資料與誘釣系統建立，提供森林生態、昆蟲與微生物間交互作用研究資料，及未來小蠹蟲防治方法研擬之參考。

Scolytids are important pest of forest and economical important crops. The difficulty of scolytids management ties to their cryptic life cycle in host tissue. Therefore, screening for natural enemies with biological control potential is very important for management strategy developmemt. The purpose of this study were to investigate nematode population of scolytids in Taiwan and design emtomopathogenic nematode baiting system for scolytids. Nematodes isolated from 477 scolytid individuals and wood branches of their habitat were collected during October 2015 to April 2018, and fourty five nematodes have gone through the complete identification process. Among those, 13 samples could be identified to species, 25 samples could be identified to genera and 7 samples could only be identified to family level; however, one sample remains unknown. The phylogenetic analysis of the ribosomal gene 28S and 18S regions of the nematodes did not reveal specific interaction between certain scolytid and the nematodes they carry. Scolytids of same species could carry different nematodes and a given nematode species could be carried by several kinds of scolytids. The frequency of carriying neamtodes is higest for Euwallacea sp. among scolytids. Further ecological analysis of the relationships among the nematodes and scolytids through interaction and nematode feeding habits observation chaterized the relationship between the nematode and the scolytids. Deladenus spp. isolated from wood branches and the scolytids-isolated Howardula spp. and Sphaerularia spp. are with parasitism potencial; The Caenorhabditis spp. and Rhabditolaimus spp. isolated from scolytids are characterized as necronemic and phoretic. Eight genera isolated from scolytids belong to the phoresy category: Acrostichus spp., Aphelenchoides spp., Bursaphelenchus spp., Diplogasteroides spp., Halicephalobus spp., Neodiplogaster spp., Rhabditidoides spp. and Ruehmaphelenchus spp. In addition, the study attempt to construct a aboveground-nematode baiting system for scolytids-parasitic nematodes that uses reared Euwallacea fornicatus as lure. The system allows the extracted-nematodes be easily observed. Todate, 6 samples were examined to optimize the system. In sum, the outcome of this study provides valuable information of forest ecology and interaction between insect and microbe, the understanding of scolytids-related nematode population and the baiting system is useful insights for future scolytids management.