Pangeneric genome analyses reveal the evolution and diversity of the orchid genus Dendrobium

Orchids constitute one of the most diverse families of angiosperms, yet their genome evolution and diversity remain unclear. Here we construct and analyse chromosome-scale de novo assembled genomes of 17 representative accessions spanning 12 sections in Dendrobium, one of the largest orchid genera. These accessions represent a broad spectrum of phenotypes, lineages and geographical distributions. We first construct haplotype-resolved genomes for a Dendrobium hybrid and uncover haplotypic variations and allelic imbalance in the heterozygous genome, demonstrating the significance of diverse ancestry. At Dendrobium genus-wide scale, we further elucidate phylogenetic relationships, evolutionary dynamics, entire gene repertoire, and the mechanisms of preserving ancient genetic variants and rapid recent genome evolution for habitat adaption. We also showcase distinctive evolutionary trajectories in MADS-box and PEBP families over 28 Ma. These results considerably contribute to unearthing the mystery of orchid origin, evolution and diversification, laying the foundation for efficient use of genetic diversity in breeding.