Pests, diseases, and aridity have shaped the genome of Corymbia citriodora

<i>Corymbia citriodora</i> is a member of the predominantly Southern Hemisphere Myrtaceae family, which includes the eucalypts (<i>Eucalyptus</i>, <i>Corymbia</i> and <i>Angophora</i>; ~800 species). <i>Corymbia</i> is grown for timber, pulp and paper, and essential oils in Australia, South Africa, Asia, and Brazil, maintaining a high-growth rate under marginal conditions due to drought, poor-quality soil, and biotic stresses. To dissect the genetic basis of these desirable traits, we sequenced and assembled the 408 Mb genome of <i>Corymbia citriodora</i>, anchored into eleven chromosomes. Comparative analysis with <i>Eucalyptus grandis</i> reveals high synteny, although the two diverged approximately 60 million years ago and have different genome sizes (408 vs 641 Mb), with few large intra-chromosomal rearrangements. <i>C. citriodora</i> shares an ancient whole-genome duplication event with <i>E. grandis</i> but has undergone tandem gene family expansions related to terpene biosynthesis, innate pathogen resistance, and leaf wax formation, enabling their successful adaptation to biotic/abiotic stresses and arid conditions of the Australian continent.