Acquisition of whitefly-transmitted Tomato yellow leaf curl virus through sexual and transovarial transmission

Tomato yellow leaf curl virus (TYLCV) is a persistently-transmitted, non-propagative virus transmitted by the sweet potato whitefly, Bemisia tabaci (Gennadius). Most evidence (five studies) points to little-to-no sexual transmission or transovarial transmission of infective TYLCV. However, one conflicting study shows both sexual and transovarial transmission of infective TYLCV in the Israeli isolate of Bemisia tabaci and TYLCV. The epidemiological impact of these modes of transmission is not known, so we would like to examine these modes of transmission with the whiteflies and TYLCV isolate present in Georgia. To test for sexual transmission, mating experiments were performed to see if a non-viruliferous whitefly could harbor the virus after mating with a viruliferous whitefly. After mating, whiteflies were then surface-sterilized and checked with PCR for TYLCV DNA. Also, after mating, the initially-non-viruliferous whiteflies were given an inoculation access period on tomato plants to determine infectivity to plants. To test for transovarial transmission of TYLCV, viruliferous female whiteflies were allowed to lay eggs on cotton. The resulting 4^th instar nymphs and adult offspring were surface-sterilized and checked for TYLCV DNA with PCR. Additionally, adult offspring were given an inoculation access period on tomato plants to determine infectivity to plants. Sequences from our isolates of Bemisia tabaci (COI) and TYLCV (full-length genome) were compared to those from around the world, including Israel, to determine similarity. Testing for sexual and transovarial transmission with both PCR detection and plant transmission assays provides a thorough investigation to examine the presence and significance of these phenomena.