Transmission of Tomato chlorotic dwarf viroid by Myzus persicae assisted by Potato leafroll virus

In this study, we have shown Myzus persicae transmissibility of Tomato chlorotic dwarf viroid (TCDVd) by exposing Potato leafroll virus (PLRV) plus TCDVd carrying aphids to tomato plants. The efficiency of PLRV-assisted TCDVd transmission by M. persicae was higher at 26–28 °C than that at 20–22 °C, with a rate of infection of 25% compared to that of 5%, respectively. Moreover, serial passages of PLRV + TCDVd into host plants and non-host plants showed that TCDVd infections still could be detected in host plants (tomato) even after passage over non-host plants Brassica oleracea (20% compared to 33% only host plant passages). This finding indicates that PLRV-assisted TCDVd transmission occurs in a circulative manner. The foliar responses of singly TCDVd and doubly TCDVd + PLRV-infected tomatoes developed similarly for the first 5 weeks after inoculation. From the sixth week onward, however, doubly infected tomatoes began to produce new sprouts with small and stunted leaves, whereas the singly TCDVd-infected tomatoes remained stunted without forming new sprouts.