The resistance of commercial cultivars of cotton to bacterial blight, caused by Xanthomonas campestris pv. malvacearum, in, is due to the interaction of resistance gene products in cotton and avirulence gene products in the pathogen. This interaction triggers a hypersensitive response at the site of infection that leads to localised cell death and hence containment of the pathogen. Associated with the localised hypersensitive response is a more generalised induced resistance that can be detected elsewhere in the plant. This induced resistance can be effective against a range of other pathogens. We are conducting experiments to determine if it is possible to utilise the interaction of bacterial avirulence genes expressed in transgenic plants already containing blight resistance genes to trigger defence responses including generalised induced resistance.