Mitochondrial Genome Resources for <i>Peronospora sparsa</i> from a 19th-Century Herbarium Specimen and a Modern Isolate

Peronospora sparsa is an oomycete pathogen causing downy mildew in species of Rosa and Rubus, including economically important fruit crops. Despite its agricultural significance, genomic resources for this pathogen remain limited. Here we report the first complete mitochondrial genomes of P. sparsa, assembled from a historical herbarium specimen collected in 1899 and from a contemporary isolate obtained in 2021. The circular mitochondrial genomes were 36,924 bp and 36,980 bp in length and contained 64 annotated genes, including 40 protein-coding genes, 22 transfer RNAs, and two ribosomal RNA genes. Comparative analysis revealed only 41 single-nucleotide polymorphisms and three small insertions–deletions between the genomes, indicating extremely low mitochondrial divergence over more than a century. These mitogenomic resources provide a foundation for improved molecular diagnostics, enable reliable discrimination among species within the Sparsa clade, and facilitate molecular surveillance and epidemiological studies of this economically important plant pathogen.