Visual and PCR assessment of light leaf spot (Pyrenopeziza brassicae) on winter oilseed rape (Brassica napus) cultivars

Z. Karolewski, Bruce D.L. Fitt, A.O. Latunde-Dada, S.J. Foster, A.D. Todd, K. Downes, N. Evans

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10 Citations (Scopus)


Methods to assess light leaf spot (Pyrenopeziza brassicae) on winter oilseed rape cultivars were compared in laboratory, controlled-environment and field experiments. In controlled-environment experiments with seedling leaves inoculated at GS 1,4, the greatest differences in percentage area affected by P. brassicae sporulation were observed with inoculum concentrations of 4 x 10(3) or 4 x 10(4) spores mL(-1), rather than 4 x 10(2) or 4 x 10(5) spores mL(-1), but older leaves had begun to senesce before assessment, particularly where they were severely affected by P. brassicae. In winter oilseed rape field experiments, a severe light leaf spot epidemic developed in 2002/03 (inoculated, September/October rainfall 127.2 mm) but not in 2003/04 (uninoculated, September/October rainfall 40.7 mm). In-plot assessments discriminated between cultivars best in February/March in 2003 and June in 2004, but sometimes failed to detect plots with many infected plants (e.g. March/April 2004). Ranking of cultivar resistance differed between seedling experiments done under controlled-environment conditions and field experiments. The sensitivity of detection of P. brassicae DNA extracted from culture was greater using the PCR primer pair PbITSF/PbITSR than using primers Pb1/Pb2. P. brassicae was detected by PCR (PbITS primers) in leaves from controlled-environment experiments immediately and up to 14 days after inoculation, and in leaves sampled from field experiments 2 months before detection by visual assessment.
Original languageEnglish
Pages (from-to)387-400
Number of pages14
JournalPlant Pathology
Issue number3
Publication statusPublished - Jun 2006


  • cultivar resistance
  • disease assessment
  • PCR diagnostics
  • plant disease symptomatology
  • rapeseed
  • sporulation


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