南黃薊馬 (Thrips palmi) 除了為葫蘆科作物重要害蟲外,亦傳播多種番茄斑萎病毒屬 (Tospovirus) 病毒,例如西瓜銀斑病毒 (Watermelon silver mottle virus, WSMoV) 。本研究確認南黃薊馬傳播 WSMoV 感染西瓜的傳播機制,研究結果指出南黃薊馬可於一齡幼蟲期、二齡幼蟲期及成蟲期獲得病毒及傳播病毒,但主要還是於一齡幼蟲期獲得病毒,待發育至成蟲期時傳播病毒。使用反轉錄聚合酶連鎖反應 (reverse transcription-polymerase chain reaction) 偵測到表現 WSMoV 非結構蛋白 (nonstructural protein) 之病毒互補 RNA (viral complementary RNA) 之 RT-PCR 產物,確認 WSMoV 在南黃薊馬體內進行複製。綜合以上結果證實南黃薊馬以持續性增殖型 (persistent-propagative) 傳播模式傳播 WSMoV。病毒與薊馬的交互作用方面,健康薊馬與感染 WSMoV 的薊馬之幼蟲存活率及發育速率沒有顯著差異,顯示 WSMoV 對南黃薊馬幼蟲存活率及發育速率沒有直接影響。當感染 WSMoV 薊馬幼蟲取食受 WSMoV 感染的西瓜葉時,其幼蟲存活率與取食健康西瓜者相比並無差別,但發育速率較於取食健康西瓜者高, 顯示 WSMoV 會透過寄主植物影響南黃薊馬幼蟲之發育速率。在不同性別薊馬成蟲的取食偏好性實驗中,雌、雄薊馬皆偏好取食遭薊馬取食的西瓜植株,但僅雄薊馬偏好薊馬接種感染 WSMoV 之西瓜植株。這樣的結果顯示,遭薊馬取食及 WSMoV 的感染可增加植株對南黃薊馬的吸引力。本研究闡述南黃薊馬傳播 WSMoV 感染西瓜的傳播機制及病毒與薊馬間交互作用,但有關 WSMoV 與南黃薊馬之間交互作用的細節,仍須進一步研究探討。
The melon thrips (Thrips palmi) is a pest on cucurbit crops but also a vector that transmits tospoviruses, for example Watermelon silver mottle virus (WSMoV). In this study, the transmission mode of WSMoV by T. palmi was clarified. The results of transmission assay indicate that first -instar larvae, second-instar larvae and adults of T. palmi acquired the virus and transmitted the virus. However, adults had the highest transmission efficiency when they acquired the virus at first -instar stage. Using reverse transcription-polymerase chain reaction, the WSMoV M RNA’s complementary RNA of which ecodes virus nostructural protein was detected in virus-infected thrips. These results suggest that T. palmi transmits WSMoV in a persistent-propagative manner. Further, the effect of WSMoV infection on survival rate and developmental time of T. pami larvae was examined. The developmental time and survival rate of WSMoV-infected T. palmi larvae were not different from those of healthy thrips. When T. palmi fed on the WSMoV-infected plants, either healthy thrips or virus -infected thrips grew faster than thrips fed on healthy plants. These results imply that WSMoV did not directly affect T. palmi, but WSMoV infection affects the developmental time indirectly through the WSMoV-infected plant. In feeding preference test of T. palmi adults, both male and female thrips prefered thrips-damaged plant and more males stayed on WSMoV-infected watermelon seedling, but females did not. Theese results indicate T. palmi is attracted by thrips damage and WSMoV infection. In this study, I not only exanined the transmission mode of WSMoV by Thrips palmi, but also studied on the interaction between virus and thrips vector. However, the effect of WSMoV infection on T. palmi should be studied in details to clarify the actual relationships between them.