Production of transgenic plants, at laboratory level or commercially, has traditionally been mainly through expression of transgenes in the nucleus [24, 25] . Among the ecological concerns raised about genetically engineered organisms is that transgenes could move ("transgene flow", the process of transgene movement by recurrent hybridisation) via pollen from the crop and into relatives growing in natural or semi-natural communities [59] . Such concerns have led to a new field of transgene containment [60, 61] .