A fungal disease, called Black Sigatoka, is threatening banana crops worldwide. The reason for this is the lack of genetic diversity in commercial bananas – the Cavendish – as all of these bananas are clones. So any disease that can kill one of them can kill them all. And this is the case with Black Sigatoka. Farmers can protect their crops by applying chemicals that kill fungi but this raises production costs and is bad for the environment. To better understand the problem, we explored the relationship between bananas and its pathogen. We found that due to continuous chemical spraying, most of the tested strains of the fungus that causes Black Sigatoka have developed resistance to the chemicals that are supposed to control them. We showed that wild resistant bananas carry resistance genes to Black Sigatoka that work by detecting a specific protein in the fungus. This is a very exciting discovery: disease resistance genes could be used to save the banana industry.