Characterization of a Dicistrovirus Taiwan Isolate, SINV-1 (TW), and its Impact on the Red Imported Fire Ant, Solenopsis invicta, in Taiwan

• Main Authors: Hung-Wei Hsu, 許弘瑋
• Other Authors: Cheng-Jen Shih
• Format: Others
• Language: zh-TW
• Published: 2010
• Online Access: http://ndltd.ncl.edu.tw/handle/42685110240839700378

碩士 === 臺灣大學 === 農藝學研究所 === 98 === The red imported fire ant, Solenopsis invicta, was first reported in Taiwan in late 2003, and no natural enemy, especially pathogen group, could be detected except two viruses, Solenopsis invicta virus-1 (SINV-1) and Solenopsis invicta virus-2 (SINV-2). An alternative control strategy that integrates virus with ongoing bait treatment therefore seems feasible and may have potential to long term suppress the fire ant in Taiwan. One core issue for this strategy is that how the virus transmits within or between colonies as well as how the virus impacts its host, which remains fairly unclear given most of studies focus on its molecular characterization. Hence, the present study aims to determine the infectivity and transmissibility of SINV-1, and characterize the symptom of infected colonies. Virus particles have been purified from infected colonies (confirmed by RT-PCR) and are consistent in size and shape under electron microscopic examination with those previously published. Subsequent sequence analyses confirmed these virus particles as SINV-1 by highly similar RdRp gene sequence identity. However, highly divergent capsid gene sequence was found in Taiwan. SINV-1 appears to be widespread in field with infection rate ranging from 30~ 45％. Furthermore, the healthy colony could be artificially infected by feeding SINV-1-infected individuals (homogenized with food source) for eight days, suggesting SINV-1 is transmissible at inter-colony level. However, the horizontal transmission was evident, most likely through trophallaxis from infected larvae to workers, in 3 of 5 replicates after 30 days. Forth instar larvae showed apoptosis in epithelial cell. Artificially infected larvae displayed serial cytopathologic effects through infective duration gradually. Induction of apoptosis by SINV-1 suggests significant association of SINV-1 infection with brood death. In future, combining SINV-1 and chemical controls for the integrated fire ant management, such as baits selection, mass production of virus and viral transmission are estimated. Hence, combination of SINV-1 and chemical pesticides to accomplish an end product of fire ant control strategy in Taiwan.