Maturation of pseudothecia and discharge of ascospores of Leptosphaeria maculans on oilseed rape stubble

  • B. Naseri
  • J. A. Davidson
  • E. S. Scott


The effects of temperature, wetness and darkness on formation of pseudothecia and the effect of temperature on the release of ascospores of L. maculans on oilseed rape stubble were studied in a controlled environment in South Australia. Pseudothecia of L. maculans developed at 5–20°C and the time taken to reach maturity and discharge ascospores decreased from 58 days at 5°C to 22.2 days at 15°C. The optimum temperature of those tested for pseudothecium maturation was between 15°C and 20°C but fewer pseudothecia were observed at 20°C than at 15°C. Exposure to a 12 h photoperiod enhanced pseudothecium formation on the stubble compared with continuous darkness. No pseudothecia formed on stubble moistened once a day at 15°C, whereas three sprays of water per day decreased maturation time in comparison with two sprays per day. More ascospores were released for a longer duration at 20°C than at 5–15°C, although peak sporulation occurred earlier at 5–10°C than at 20°C. These findings highlight the importance of moisture, temperature and light for production and release of inoculum from stubble. This information, combined with field data, may help to predict the onset of inoculum release.


Blackleg Canola Darkness Phoma stem canker Temperature Wetness 



This research was a part of the PhD project of the first author, supported by a scholarship from the Iranian Ministry of Agriculture. The authors thank Mr T. Potter for providing canola stubble and Ms K. Dowling for assistance with statistical analyses.


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Copyright information

© KNPV 2009

Authors and Affiliations

  1. 1.School of Agriculture, Food and WineThe University of Adelaide, PMB1Glen OsmondAustralia
  2. 2.South Australian Research and Development InstituteAdelaideAustralia
  3. 3.Department of Plant ProtectionAgricultural Research InstituteZanjanIran

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