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ARS Home » Northeast Area » Frederick, Maryland » Foreign Disease-Weed Science Research » Research » Publications at this Location » Publication #407965

Research Project: Discovery and Development of Microbial-Based Biological Control Agents for Use Against Invasive Weeds in the United States

Location: Foreign Disease-Weed Science Research

Title: Characterization of emerging Xanthomonas campestris isolates on the widespread, non-native weed Alliaria petiolata

item Tancos, Matthew
item HARNEY-DAVILA, GABRIELA - Wright State University
item CIPOLLINI, DON - Wright State University

Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/7/2024
Publication Date: 1/7/2024
Citation: Tancos, M.A., Harney-Davila, G., Cipollini, D. 2024. Characterization of emerging Xanthomonas campestris isolates on the widespread, non-native weed Alliaria petiolata. Plant Disease.

Interpretive Summary: Garlic mustard is an invasive weed that has quickly spread across North America. Garlic mustard is closely related to cabbage and other Brassica crops. Since garlic mustard is widespread and can support many plant pathogens, we wanted to determine if this weed could support a diverse group of bacterial pathogens known to infect cabbage. A pathogen survey of garlic mustard was performed across three Midwest states to identify diverse isolates of the bacterial pathogen Xanthomonas campestris. Numerous X. campestris isolates were identified from diseased garlic mustard populations. Sequence analysis and host range trials demonstrated the diversity of new X. campestris pathovars and genotypes. In addition to infecting garlic mustard, some isolates were capable of infecting cabbage. The emergence of new X. campestris strains infecting garlic mustard presents challenges as it increases the risks of pathogens moving between crops and nearby weeds.

Technical Abstract: Non-native 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 non-native plants acting as ancillary hosts and fostering microbial recombination and pathogen selection. Garlic mustard (Alliaria petiolata) is a widespread, non-native cruciferous weed that grows throughout North America and along the forested edges of diverse agricultural fields. The recent identification of a novel Xanthomonas campestris pv. incanae strain isolated from a diseased A. petiolata population led to the current investigation of the distribution and diversity of X. campestris isolates from naturally infected A. petiolata. A total of 14 diseased A. petiolata sites were sampled across three states, leading to the identification of diverse X. campestris pathotypes and genotypes. Pathogenicity assays and multilocus sequence analyses identified pathogenic X. campestris pv. incanae and X. campestris pv. barbareae isolates collected from disparate A. petiolata populations. Moreover, independently collected X. campestris pv. incanae isolates demonstrated broad cruciferous host ranges by infecting cabbage (Brassica oleracea var. capitata), garden stock (Matthiola incana), and the cover crop yellow mustard (Guillenia flavescens). This study highlights the genetic variability and host potential of natural X. campestris populations and the potential risks to Brassica crops via widespread, dense garlic mustard reservoirs.