Characterization of Emerging Isolates on the Nonnative Weed Garlic Mustard ().

Nonnative plant infestations provide unique opportunities to investigate pathogen emergence with evolutionarily recent plant introduction events. The widespread distribution of invasive plants and their proximity to genetically related crops highlights the risks of nonnative plants acting as ancillary hosts and fostering microbial recombination and pathogen selection. Garlic mustard () is a widespread, nonnative cruciferous weed that grows throughout North America and along the forested edges of diverse agricultural fields. The recent identification of a novel pv. strain isolated from a diseased population led to the current investigation of the distribution and diversity of isolates from naturally infected . A total of 14 diseased sites were sampled across three states, leading to the identification of diverse pathotypes and genotypes. Pathogenicity assays and multilocus sequence analyses identified pathogenic pv. and pv. strains collected from disparate populations. Moreover, independently collected pv. strains demonstrated a broad cruciferous host range by infecting cabbage ( var. ), garden stock (), and the cover crop yellow mustard (). This study highlights the genetic variability and host potential of natural populations and the potential risks to crops via widespread, dense garlic mustard reservoirs.