Since 1988 viroid infections have occasionally been detected in tomato crops in the Netherlands.

To identify these viroid isolates unequivocally, two novel universal primer sets were designed for ‘Reverse Transcription-Polymerase Chain Reaction’ (RT-PCR), a sensitive technique enabling detection and identification of pospiviroids.

Sequence analyses identified the viroids as Citrus exocortis viroid (CEVd), Columnea latent viroid (CLVd) and Potato spindle tuber viroid (PSTVd).

To find potential sources of infection, ornamental plants were screened for the presence of pospiviroids.

These surveys revealed many new pospiviroid host plants as well as high infection rates for PSTVd in some ornamental species.

Phylogenetic studies provided evidence that the PSTVd isolates from tomato originated from vegetatively propagated, solanaceous host plants.

This conclusion was further substantiated by showing a high stability of predominant pospiviroid genotypes after mechanical pospiviroid transmission from ornamentals to potato and tomato.

In addition, several experiments showed that mechanical inoculation is a likely way of pospiviroid transmission between these crops.

In addition, a new pospiviroid from pepper was characterized, i.e.

Pepper chat fruit viroid that also can infect potato and tomato.

The results of above findings on pospiviroids are discussed in a broader context addressing diagnostic and epidemiological aspects as well as risk assessment in relation to quarantine