菸草粉蝨 B 與 Q 生物小種傳播兩種番茄捲葉病毒之傳播生物學

Abstract

Whitefly-transmitted tomato yellow leaf curl disease (TYLCD) usually causes tomato yield losses of up to 100 % in tomato production. TYLCD is associated with a group of phylogenetically related viruses named tomato yellow leaf curl viruses (TYLCVs). These viruses belong to the genus Begomovirus, family Geminiviridae and are transmitted by B. tabaci which is also a species complex with at least 28 biotypes. Among these biotypes, B. tabaci B and Q biotypes are predominant biotypes and cause great economic losses globally including Taiwan. Even though the transmission of TYLCVs by B. tabaci have been studied by several research groups, the transmission mode of TYLCVs still remains controversial. The first objective of my study was to determine transmission characteristics for Tomato yellow leaf curl Thailand virus (TYLCTHV) and Tomato leaf curl Taiwan virus (ToLCTWV), which are predominant viruses in tomato fields in Taiwan, by B. tabaci B and Q biotypes. The second objective was to investigate whether TYLCTHV/ToLCTWV is transovarially transmitted to the progeny of its insect vectors. The third objective was to examine the infection and dissemination of either virus in its insect vectors. The transmission and indirect immunofluorescence assays concluded that TYLCTHV was transmitted by B. tabaci in special type of persistent-propagative transmission mode that Tomato yellow leaf curl virus Israel isolate (TYLCV-Is) also belongs to. The transmission of TYLCTHV and ToLCTWV by B. tabaci B and Q biotypes occurred with a minimum 1-2 h acquisition access period (AAP). Bemisia tabaci B biotype had better transmission ability than Q biotype for both viruses. Bemisia tabaci B biotype transmitted TYLCTHV and ToLCTWV with a minimum 2-6 h inoculation access period (IAP); Q biotype transmitted both viruses with a minimum 2-h IAP but showed lower efficiency than those transmitted by B biotype. In addition, B. tabaci B biotype transmitted TYLCTHV and TolCTWV with a latent period of no more than 4-8 h; Q biotype transmitted both viruses with a latent period of no more than 10 and 40 h, respectively. Even both viruses persisted in viruliferous B. tabaci B and Q biotypes for lifelong, but only B biotype remained the infectivity of TYLCTHV. Interestingly, transovarial transmission also only occurred in TYLCTHV transmitted by B. tabaci B biotype. These results imply that B. tabaci B biotype was a more efficient vector for TYLCTHV. It may attribute the displacement of ToLCTWV by TYLCTHV in the tomato fields in Taiwan within a few years to the virus-vector interaction. We further examined the infection and dissemination of TYLCTHV and ToLCTWV in B. tabaci B and Q biotypes. The results suggest that both viruses infected the alimentary gut of B. tabaci B and Q biotypes. Both viruses infected the ovariole of B. tabaci B biotype, but not Q biotype. This study would like to provide a framework for future studies on different begomovirus transmission by different biotypes of B. tabaci. The knowledge and information will improve the development of better management practices for TYLCD.