Global Diversity of the Brachypodium Species Complex as a Resource for Genome Wide Association Studies Demonstrated for Agronomic Traits in Response to Climate

The development of model systems requires a detailed assessment of standing genetic variation across natural populations. The Brachypodium species complexhas been promoted as a plant model for grass genomics with translation to small grain and biomass crops. To capture the genetic diversity within this species complex, thousands of Brachypodium accessions from around the globe were collected and genotypedby sequencing. Overall 1,897 samples were classified into two diploidor allopolyploid species and then further grouped into distinct inbred genotypes. A core set of diverse B. distachyon diploidlines were selected for whole genome sequencingand high resolution phenotyping. Genome Wide Association Studies(GWAS) across simulated seasonal environments were used to identify candidate genes and pathways tied to key life history and agronomic traits under current and future climatic conditions. A total of 8, 22 and 47 QTLs were identified for flowering time, early vigour and energy traits, respectively. The results highlight the genomic structure of the Brachypodium species complex, and the diploidlines provided a resource that allowed complex trait dissection within this grass model species.