Genomes of Conopholis americana and Epifagus virginiana : Two holoparasitic plants (Orobanchaceae)

Abstract

Conopholis americana (American Cancer-Root) and Epifagus virginiana (Beechdrops) are sister genera of holoparasitic plants (Orobanchaceae) native to eastern North America, parasitizing oaks and American beech, respectively. Both have served as models for plastid genome reduction, yet no nuclear genomes exist for either genus or any New World holoparasitic Orobanchaceae. Here we present the first nuclear genome assemblies for both species using PacBio HiFi sequencing. The C. americana assembly totals 1.82 Gb and E. virginiana totals 440 Mb, representing an approximately four-fold difference in genome size between these sister genera. We observed a BUSCO completeness of 79-80% in both species, which is typical of holoparasites. While gene prediction identified 33,889 genes in C. americana and 21,031 in E. virginiana, repeat annotation revealed that LTR retrotransposons account for 78% of the genome size difference. These assemblies reveal contrasting mechanisms of genome evolution in sister holoparasitic genera and provide foundational resources for comparative genomics of parasitic plants.