Dr Llewellyn is responsible for the development of Australia's first transgenic crop - insect resistnat cotton. He developed mechanisms for the successful release in Australia of a number of varieties of transgenic cotton. The current varieties contain transgenes for insect resistance and herbicide tolerance. He has also enhanced transformation methods for the introduction of valuable traits into cotton. Llewellyn's research also focuses on genes involved in the development of the cotton fibre and in mechanisms of host-plant resistance to insects. He has made important contributions to teh understanding of plant gene regulation, these discoveries being widely applicable in plant molecular biology.