A universal probe for simultaneous detection of six pospiviroids and natural infection of potato spindle tuber viroid (PSTVd) in tomato in China

Several viroids in the genus Pospiviroid can infect tomato (Solanum lycopersicum) and cause severe diseases, posing a serious threat to tomato production.  For simultaneous detection of six tomato-infecting pospiviroids - columnea latent viroid (CLVd), pepper chat fruit viroid (PCFVd), potato spindle tuber viroid (PSTVd), tomato apical stunt viroid (TASVd), tomato chlorotic dwarf viroid (TCDVd), and tomato planta macho viroid (TPMVd), we developed a universal probe based on a highly conserved 61 nt long sequence shared among them.  Compared with their specific probes, the universal probe has a similar, though slightly reduced, detection sensitivity and has the advantages of simple and cost-effective preparation and simultaneous detection of the six pospiviroids.  In addition, the universal probe was used in dot-blot hybridization assays for a large-scale survey of viroid(s) in tomato plantings in China.  Only PSTVd was detected in a few greenhouse-planted tomato plants.  Sequence analysis revealed that these tomato PSTVd isolates may have been introduced from tomato seeds imported from abroad.