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      Secondary seed dormancy and the seedbank ecology of Brassica napus L. in western Canada

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      GULDEN_PhD.pdf (397.3Kb)
      Date
      2003-08-28
      Author
      Gulden, Robert H.
      Type
      Thesis
      Degree Level
      Doctoral
      Metadata
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      Abstract
      The release of genetically modified, herbicide tolerant canola (Brassica napus L.) genotypes in western Canada has increased interest in the persistence of volunteer canola. B. napus seed may be induced into secondary dormancy in the laboratory, however, little is known of the seedbank ecology and the role of secondary dormancy as a persistence mechanism in this species in the region. The objectives of this research were i) to determine seedbank additions at the time of harvest, ii) determine the role of secondary seed dormancy in seedbank persistence under different management systems, iii) determine the relative importance of factors contributing to secondary dormancy potential and iv) evaluate the role of abscisic acid (ABA) during secondary dormancy induction in B. napus. On farms, average seedbank additions during harvest were approximately 20 times the normal seeding rate of canola. High secondary seed dormancy potential prolonged seedbank persistence in fields, irrespective of tillage system. B. napus exhibited seedling recruitment of a typical summer annual weed where seedling recruitment was only observed in the spring. Seasonal seedling recruitment was the result of two fates: seed death in the shallow seedbank, irrespective of dormancy potential, and increased ungerminability in buried seeds which was related to secondary seed dormancy potential. Among the factors that contribute to secondary seed dormancy potential, genotype was of greatest significance. Seed size was of lesser importance, while the contributions of pre-harvest factors including seed maturity, year, and location were negligible in comparison. Differences in ABA synthesis and the response to ABA application were related to secondary seed dormancy potential and correlated well previous reports linking ABA to seed dormancy. Conclusions that emerge from this research are i) that on some farms, seedbank additions may be lowered by more diligent harvest practices, ii) seedbank persistence of B. napus may be reduced by growing low dormancy genotypes and avoiding seed burial for one year after seedbank establishment and iii) ABA + ABA-glucose ester (ABA-GE) and the ability of seeds to respond to ABA application after seed dormancy induction may potentially be used to identify seed dormancy potential in this species.
      Degree
      Doctor of Philosophy (Ph.D.)
      Department
      Plant Sciences
      Program
      Plant Sciences
      Committee
      Shirtliffe, Steven J.; McGregor, D. I.; Lutman, P. J. W.; Gusta, Larry V.; Archibold, O. W. (Bill); Thomas, A. Gordon; Waterer, Douglas R.
      Copyright Date
      August 2003
      URI
      http://hdl.handle.net/10388/etd-09052003-101649
      Subject
      seed dormancy
      seed burial
      factors affecting seed dormancy
      canola
      Abscisic acid (ABA)
      tillage system
      hormone profile
      harvest losses
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      • Graduate Theses and Dissertations
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