Rhizoctonia solani AG-3 causes considerable yield loss
in potato fields in eastern Canada and U.S.A. The accurate identification
of
AG-3 isolates is strategic prior to planting potatoes. To obtain a fast
and reliable identification method, RAPD experiments were
carried out to obtain specific genetic markers of AG-3 isolates. DNA from
various isolates of R. solani was submitted to RAPD
amplification using random 10 mers primers. One of the forty primers used
yielded a 2·6 kbp fragment present in all isolates of AG-3.
The specificity of this fragment was assessed by Southern blot analysis.
It was partly sequenced and DNA primers were designed
for PCR amplification experiments. A PCR-based restriction mapping method,
using one restriction endonuclease, Xho I, was
developed for specific detection of AG-3 isolates. Analysis of data showed
that AG-3 isolates were distinct to other AGs R. solani.
The detection method described here is very specific and reliable; it can
be applied on plant tissue and soil infected with R. solani AG-3.