Detection of Trace Level of cp4epsps Transgene on Sclerotia of Sclerotinia sclerotiorum Formed in Diseased Plants of Roundup Ready(superscript ®) Canola (Brassica napus)

The area seeded to genetically modified crops has been steadily increasing since their introduction in the early 1990s. However, there have been concerns relating to the persistence and stability of transgenic DNA from genetically modified crops and subsequent outflow into the environment. The cp4 5-enolpyruvylshikimate-3-phosphate synthase (cp4epsps) gene confers glyphosate resistance in Roundup Ready(superscript ®) (RR) canola (Brassica napus event RT73). Sclerotinia sclerotiorum is an important pathogen causing stem blight and pod rot of canola. The aim of this study was to detect cp4epsps transgenic DNA on sclerotia of Sclerotinia sclerotiorum formed in diseased stems of RR canola grown in the field. In this 2-year study, sclerotia collected from naturally infected stems of RR canola and conventional canola at the time harvest were screened for the presence of 1363bp cp4epsps and smaller transgene fragments by PCR (limit of detection 50 pg) and Southern hybridization (limit of detection ＜5 pg). The complete cp4epsps transgene could not be detected in any of the analyzed sclerotia: however, a transgene fragment was detected in a single sclerotium tissue recovered from a RR canola plant. This fragment was not stably integrated as the transgene fragment could not be detected in mycelia produced from was not stably integrated as the transgene fragment could not be detected in mycelia produced from the germination of this positive sclerotium. Thus, trace levels of transgene fragments may be detected, albeit at an extremely low incidence rate, from surface of sclerotia of S. sclerotiorum produced on the transgenic plants of canola.