Establishment Success and Potential Weediness of Oilseed Rape (Brassica napus L.) under Ruderal Conditions in View of GMO Risk Assessment

A comprehensive risk assessment is needed to evaluate whether genetically modified (GM) herbicide-resistant (HR) lines of oilseed rape (OSR) pose a threat to the environment. The probability for an unintended spread of transgenes is high: OSR can grow outside cultivation in feral (wild) populations, typically seen on disturbed ruderal sites. The aim of my thesis is to provide baseline data on the establishment success of ruderal OSR populations and to determine environmental factors of relevant impact focusing on the effects of soil quality. Several field experiments were carried out on ruderal sites in Northern Germany. Establishment success was compared with the success of weedy relatives. Dwarfing, intended as a method of transgenic mitigation, might lead to higher fitness under stressors relevant on ruderal sites, i.e. mowing and low soil quality. I therefore compared the fitness of a dwarfed OSR cultivar with that of a tall cultivar on a ruderal site. The potential for seed dormancy is important for long-term establishment success of OSR. The influence of soil quality and soil organisms on buried OSR seeds was therefore investigated.