Dissemination and replication of tomato yellow leaf curl Thailand virus in Bemisia tabaci

Tomato yellow leaf curl viruses are a group of tomato infecting begomoviruses that are exclusively transmitted by Bemisia tabaci. Although tomato yellow leaf curl viruses are reported to be transmitted by B. tabaci in a persistent-circulative manner, some studies reported that the viruses replicate in B. tabaci. Therefore, whether tomato yellow leaf curl viruses replicate in whitefly is still a controversial issue. In this study, the dissemination and replication of tomato yellow leaf curl Thailand virus (TYLCTHV) in B. tabaci Middle East-Asia Minor 1 were investigated. Immunofluorescence assay revealed the virus infected the midgut, gastric caeca, and primary salivary glands, but not the oocytes of the viruliferous B. tabaci. A time-series analysis was conducted to examine the virus dissemination in B. tabaci. TYLCTHV was firstly detected in the midguts and hemolymph of B. tabaci 5 hours after the beginning of virus acquisition. TYLCTHV infection rate increased over time and reached 100% in the midgut, 80% in the hemolymph and 70% in the primary salivary glands 16 hours after the beginning of virus acquisition. The viral load of TYLCTHV in the viruliferous B. tabaci was quantified by qPCR daily for 10 days. The results showed that the viral load decreased with time in females but stayed constant in males. In conclusion, TYLCTHV is transmitted in a persistent-circulative manner and does not replicate in B. tabaci.