Genomic characterization, annotation, and comparative analysis of Ludisia discolor reveal its evolutionary and functional traits

MAIN CONCLUSION: The high-quality L. discolor genome clarifies orchid phylogeny and provides immediate targets for breeding and biosynthetic engineering of medicinal metabolites. Ludisia discolor is a valued orchid for ornamental veined foliage and documented medicinal uses, yet genomic resources are lacking. We generated the first chromosome-level assembly of 696.37 Mb with scaffold N50 33.14 Mb and 94.55% BUSCO completeness by integrating PacBio HiFi, Hi-C and Illumina reads; 91.86% of sequences were anchored to 22 chromosomes. Annotation yielded 20,552 protein-coding genes and 70.9% repetitive content dominated by LTR-retrotransposons. Comparative analysis revealed 157 species-specific gene families and significant expansion of terpenoid and flavonoid biosynthetic clusters, supporting its pharmacological potential. Phylogenomics placed Ludisia sister to Platanthera (Orchidoideae) with divergence ~ 39.5 Mya. Positive selection was detected in 123 genes enriched for chromatin remodeling and nuclear transport, reflecting adaptation to shaded, nutrient-limited habitats. This reference genome provides a foundational resource for understanding orchid evolution, molecular breeding, and metabolic engineering of bioactive compounds in L. discolor.