Torradoviruses are transmitted in a semi-persistent and stylet-borne manner by three whitefly vectors

- Trialeurodes abutilonea was identified as a new vector of torradoviruses.
- Transmission by three whitefly species was demonstrated for ToTV, ToMarV and ToChV.
- Torradoviruses are transmitted in a semi-persistent manner by their whitefly vectors.
- Vector transmission of torradoviruses is stylet-borne.

Members of the genus Torradovirus (family Secoviridae, type species Tomato torrado virus, ToTV) are spherical plant viruses transmitted by the whitefly species Trialeurodes vaporariorum and Bemisia tabaci. Knowledge on the mode of vector transmission is lacking for torradoviruses. Here, the mode of transmission was determined for Tomato marchitez virus (ToMarV). A minimal acquisition access period (AAP) and inoculation access period (IAP) of approximately 2 h each was required for its transmission by T. vaporariorum, while optimal transmission required an AAP and IAP of at least 16 h and 8 h, respectively. Whiteflies could retain the virus under non-feeding conditions for at least 8 h without loss of transmission efficiency, but upon feeding on a non-host plant in between the AAP and IAP they retained the virus for no more than 8 h. Similar conditions supported transmission of isolates of ToTV and Tomato chocolàte virus (ToChV) by T. vaporariorum and B. tabaci. Additionally, similar experiments revealed the banded-winged whitefly (Trialeurodes abutilonea) as a vector for all three virus species. The results are congruent with acquisition and retention periods for semi-persistent virus transmission. RT-PCR detection analysis of ToTV and ToMarV in the vector's body revealed their presence in the stylet, but not in the head where the pharynx of the foregut is located. The results altogether indicate a semi-persistent stylet-borne mode of vector transmission for torradoviruses. Additionally, this is the first group of spherical viruses transmitted by at least three different species of whiteflies.