The wild beet B. vulgaris ssp. maritima accession WB42 originated from Denmark and was partly selfed at KWS SE, Einbeck, Germany, as described (Capistrano‐Gossmann et al., 2017 (link)). Seeds of B. patula accession BETA 548 and B. vulgaris ssp. maritima accessions BETA 1011 and BETA 2322 were obtained from the Genebank of the Institute of Plant Genetics and Crop Plant Research (IPK), Gatersleben, Germany. DNA was extracted from leaves using the NucleoSpin Plant kit (Macherey‐Nagel, Düren, Germany). All plants were grown in a greenhouse under long‐day conditions.