High-Quality Draft Genome for Armillaria mexicana, a Recently Described Species in North America

The genus Armillaria is a broad group of basidiomycete (Agaricales, Physalacriaceae) plant pathogens that can have detrimental effects on woody hosts in forested, urban, and horticultural landscapes. Several species are known as aggressive root pathogens on both conifers and deciduous woody plants. Armillaria species are considered white rot fungi due to their capacity to degrade both lignin and cellulose in woody tissues. Armillaria mexicana was recently described as a new species found in peach (Prunus persica) orchards of Coatepec Harinas, State of Mexico. However, a subsequent study identified A. mexicana on avocado (Persea americana) and pine (Pinus sp.), suggesting that A. mexicana may be able to infect diverse hosts that are planted in disturbed areas following deforestation. We assembled a reference genome for A. mexicana consisting of 38 contigs constructed using PacBio and Illumina sequencing reads. Genome annotation and comparison with A. mellea, a phylogenetic sister taxon, revealed notable differences, including a larger number of interspersed repeats in A. mexicana and the absence of small RNAs, which were detected in A. mellea. While A. mexicana (49 Mb) has a roughly 30% smaller genome than A. mellea (70 Mb), it has a similar number of genes encoding pectinases and nonribosomal peptide synthetase (NRPS) and NPRS-like secondary metabolites, which may influence the pathogenicity of A. mexicana. This reference genome of A. mexicana allows future genomic comparisons that can help characterize the evolutionary history and enhance our understanding of the molecular mechanisms involved in pathogenicity and wood decomposition of Armillaria species.