The unavailability of adequate immunological reagents has prevented the use
of ELISA for the diagnosis of rupestris stem pitting disorder of grapevine
s. In this work, the performance of five primer pairs for broad-scale detec
tion of rupestris stem pitting associated virus-1 by RT-PCR using ds-RNA te
mplates was compared and contrasted with biological indexing. The virus was
widespread among the budwood of 35 Portuguese grapevine varieties assayed,
with a prevalence of 85%. The biological assay proved to be unreliable as
an index of infection due to the high number of false negatives. Five sets
of primers were assayed and compared by means of their relative sensitivity
and negative predictive value. The primer pair specific for the coat prote
in gene was excluded because of the difficulty in identifying the specific
amplified product. From the other four primer pairs, those specific for the
helicase domain of the putative polymerase gene had the highest sensitivit
y and negative predictive value. However, a high confidence in the assay, a
s desirable for a certification scheme, could not be obtained by the sole u
se of this primer pair. An additional pair should be used in a separate or
in a multiplex RT-PCR reaction.