A haplotype-resolved chromosomal reference genome for the porcini mushroom Boletus edulis

Abstract

Haplotype-resolved chromosomal reference genomes are increasingly available for many fungi, offering insights into the evolution of pathogenic and symbiotic lifestyles. However, these resources remain scarce for ectomycorrhizal fungi (EMF), which play crucial roles in forest ecosystems. Here, we used a combination of chromatin conformation capture (Hi-C) and PacBio sequencing to construct a haplotype-resolved chromosomal genome assembly for Boletus edulis, an emerging model for EMF research and a prized edible fungus. Our new reference assembly, "BolEdBiel_h2", derives from a sporocarp sampled in Bielefeld, Germany. The genome assembly spans 41.8 Mb, with a scaffold N50 of 4.1 Mb, and includes 11 chromosome-level scaffolds, achieving near telomere-to-telomere coverage across multiple chromosomes. We annotated 15,406 genes, with a Benchmarking Universal Single-Copy Orthologs (BUSCO) score of 96.2%. Key genomic features such as mating loci, CAZymes, and effector proteins, were mapped across the assembly. As a first application of this new genomic resource, we mapped whole genome resequencing data from 49 genets to investigate the population structure and genetic diversity of the European lineage of B. edulis. We identified five distinct genetic clusters and found that high-latitude populations from Iceland and Fennoscandia exhibited greater nucleotide diversity than populations from the United Kingdom and central Europe. Additionally, we discovered a 0.4 Mb inversion on chromosome three and identified several regions of locally elevated nucleotide diversity, which may represent candidates for ecological adaptation. This genomic resource will facilitate a deeper understanding of this ecologically and commercially important wild fungus.