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.