Detection of Southern tomato virus by molecular hybridisation

Southern tomato virus (STV) is a double-stranded RNA (dsRNA) virus belongingto the genus Amalgavirus from the family Amalgamaviridae. STV has beendetected in tomato plants showing symptoms of stunting, fruit discolorationand size reduction, although its role on symptom development is unclear. Also,little is known about the incidence and epidemiology of this virus and how itspreads in tomato crops. In this work, we developed a molecular hybridisationmethod by using a digoxigenin-labelled RNA probe based on the nucleotidesequence of the STV putative coat protein which was tested with differentprocedures for preparation of plant material. This technique was sensitiveenough to detect STV from sap extracts (obtained just by grinding in buffer)from different plant tissues such as leaves, fruits, roots and seeds. This procedureis suitable for field surveys since it allows a cheap and quick processing of a highnumber of samples. Surveys performed in three important tomato productionareas (Peninsular Spain, the Canary Islands and Sicily) showed that STV iswidely spread, with incidences ranging from 18% to 74% in different local andcommercial tomato varieties.