Occurrence of natural infection of tomato by Potato Spindle Tuber Viroid (PSTVd) in India

A field survey was carried out in districts of southern Karnataka to assess the pospiviroid infections on tomato crop. The tomato plants showing disease symptoms such as severe leaf curling, epinasty, chlorosis, purpling and stunted growth that are characteristics of viroid infection were collected along with asymptomatic plants and the infection was analysed by RT-PCR. A sample collected from the Mandya district showed an amplicon size of ~ 361 bp which confirmed PSTVd infection, while no other Pospiviroids were detected. The amplified PCR products were cloned, sequenced and the resultant sequences were deposited in GenBank. The PSTVd sample inoculated tomato plants also showed typical disease symptoms of viroid infection after four weeks of post-inoculation and was re-confirmed through RT-PCR. This is the first report of the occurrence of natural infection of tomato by PSTVd in India.