Exploring the genetic diversity of the IPK Medicago germplasm collection using GBS

The genus Medicago, which includes the widely cultivated forage crop alfalfa, is of significant agricultural and ecological importance. Understanding genetic diversity in Medicago is essential for the conservation of its germplasm and its utilisation in plant breeding. This study aimed to assess the genetic diversity and population structure of the Medicago germplasm collection at the German Federal Ex situ Gene Bank. Genotyping-by-sequencing was used to analyse 1234 accessions of the Leibniz Institute of Plant Genetics and Crop Plant Research (IPK), representing 40 Medicago species. After filtering, a high-quality dataset of 23,315 single nucleotide polymorphisms (SNPs) was generated. Our analyses revealed distinct genetic clusters corresponding to Medicago species and sections, with cultivated M. sativa L. and M. × varia Martyn clustering together with less genetic diversity compared to their wild counterparts. This reflects the shared genetic composition and extensive gene flow between M. sativa and M. × varia, commonly considered a hybrid between M. sativa and M. falcata L. Wild species displayed a more complex genetic structure, with polyphyletic patterns indicating higher genetic differentiation that reflects their diverse evolutionary histories and ecological adaptations. In conclusion, the comprehensive diversity analysis of the IPK Medicago collection provides valuable insights for gene bank management, targeted conservation efforts and strategic breeding initiatives.