European maize genomes unveil pan-genomic dynamics of repeats and genes

The exceptional diversity of maize (Zea mays) is the backbone of modern heterotic patterns and hybrid breeding. Historically, US farmers exploited this variability to establish todays highly productive Corn Belt inbred lines from blends of dent and flint germplasm pools. Here, we report high quality de novo genome sequences of the four European flint lines EP1, F7, DK105 and PE0075 assembled to pseudomolecules with scaffold N50 ranging between 6.1 to 10.4 Mb. Comparative analyses with the two US Corn Belt genomes B73 and PH207 elucidates the pronounced differences between both germplasm groups. While overall syntenic order and consolidated gene annotations reveal only moderate pan-genomic differences, whole genome alignments delineating the core and dispensable genome, and the analysis of repeat structures, heterochromatic knobs and orthologous long terminal repeat retrotransposons (LTRs) unveil the extreme dynamics of the maize genome. Haplotypes derived from core genome SNPs demonstrate the tessellation of modern maize resulting from a complex breeding history. The high quality genome sequences of the flint pool are a crucial complement to the maize pan-genome and provide an important tool to study maize improvement at a genome scale and to enhance modern hybrid breeding.