Rupestris stem pitting associated virus-1 is consistently detected in grapevines that are infected with rupestris stem pitting

Rupestris stem pitting (RSP) appears to be the most widespread disease of t he rugose wood complex of grapevines. In previous work we showed that rupes tris stem pitting associated virus-1 (RSPaV-1), an agent that has similarit ies in genome structure to apple stem pitting virus is associated with RSP (Meng et al., 1997, 1998). To validate the association of RSPaV-1 with RSP, grapevines that had been indexed on the RSP indicator St. George (Vitis ru pestris Scheele) were collected from four major grape-growing countries and tested for RSPaV-1 by reverse transcription-polymerase chain reaction (RT- PCR) assay. Depending on the sets of primers used, we detected RSPaV-1- spe cific sequences from 85% to nearly 100% of the grapevines that had indexed positive for RSP. These data further demonstrate that RSPaV-1 is closely as sociated with, and likely to be the causal agent of RSP. We have also shown that RT-PCR is a fast and reliable alternative to biological indexing for the diagnosis of RSP.