Identification of a cDNA clone specific to grapevine leafroll-associated virus 1, and occurrence of the virus in Australia

A cDNA clone derived from a leafroll infected low-yielding clone of Sultana grapevine (syn. Thompson Seedless, Sultanina) hybridized specifically to dsRNA from a number of grapevine varieties that reacted with grapevine leafroll-associated virus 1 (GLRaV-1) antibody. The cDNA was sequenced, and a set of specific primers was designed and used in a simple RT-PCR test using extracts from a range of grapevine varieties. The same vines were also tested by Western blotting or ELISA to assess the presence of GLRaV-1 coat protein. In every sample tested, the results of PCR tests were consistent with those of Western blots and ELISA, indicating that the cDNA clone was specific to GLRaV-1. The occurrence of GLRaV-1 strongly correlated with the low-yielding character of Sultana clones tested, suggesting that the virus may contribute to low yields in some leafroll-infected Sultana clones. The optimum time for detecting GLRaV-1 was determined to be early in summer. The DNA-based detection procedure reported here provides an alternative to detection by serology.