AbstractLepidium castellanum,L. juvencumandL. oleraceumare threatened coastal cresses endemic toNewZealand. These three species were selfed and interspecific hybrids generated for examination of hybrid fitness and inbreeding depression. In controlled glasshouse experiments, the interspecific hybrids and selfed progeny were inoculated with a strain of the introduced Turnip mosaic virus (TuMV) previously isolated from wild populations ofL. aegrum. Experiments tested the hypothesis that heterosis in the interspecific hybrids provides a gain inTuMVresistance in comparison to selfed plants. We show that interspecific hybrids of three genetically distinct species ofLepidiumincreased plant performance and reduced susceptibility to the effects of theTuMV. We suggest that interspecific hybridization could be implemented as a conservation management strategy and that a broader outlook may be required to mitigate the negative impacts of introduced pathogens on threatened sp