Chromosome-scale diploid unphased assembly of horsemint (Mentha longifolia)

Mint oils are essential oils with many commercial applications. Mint oils are harvested from peppermint or spearmint plants. Spearmint (Mentha spicata) is an allotetraploid, hybrid between diploid parents Mentha suaveolens (apple mint) and Mentha longifolia (horse mint). Peppermint comes from a second hybridization event between spearmint and octoploid Mentha aquatica (water mint). Here we present a chromosome-scale diploid unphased assembly of a clone of a Mentha longifolia. Combined with the previously assembled M. suaveolens and a previous consensus assembly of a genetically more distant clone of M. longifolia, these assemblies provide valuable tools for trait mapping and understanding the genomic composition of commercial hybrid genomes and their relative contribution to traits important to the mint industry.

A two haplotypes Hifiasm assembly of the genome of M. longifolia was generated from 105 x consensus coverage of PacBio long reads. The hifiasm assembly included 346 contigs and exhibited an N50 of 30.5 Mb. Two sets of pseudochromosomes were constructed by comparison to the previously published genome of Mentha suaveolens, resulting in 20 superscaffolds and 8 partial scaffolds, for an overall genome size of 734 Mb. Illumina RNA-Seq libraries from a mixed set of Mentha species were used to annotate the genome.