Reference Plant Ontologies are being developed in the context of the Planteome project and are being integrated with the Crop Ontology, which provides harmonized breeders’ trait names, measurement methods, scales and standard variables for many crops. The Bioversity Molecular Markers Ontology is one of these reference plant ontologies integrated within the Crop Ontology. It has been adapted from Descriptors for Genetic Markers Technologies (2004) by Carmen De Vicente, Thomas Metz and Adriana Alercia.