In nature, most plants establish mutual relationships with root fungi, so-called mycorrhiza. Mycorrhizal fungi facilitate the plants’ nutrient uptake and help them thrive under extreme conditions. Researchers at the Max Planck Institute for Chemical Ecology in Jena, Germany, discovered that certain leaf metabolites can be used as markers for mycorrhizal associations. The discovery of foliar markers provides scientists with an easy-to-conduct tool to screen large amounts of plants for mycorrhizal associations without having to destroy them. This new tool could contribute to breeding more efficient and stress-tolerant crop varieties for sustainable agriculture.