Affiliation:
1. Integrative Biology University of California, Berkeley, California, USA
2. Chan Zuckerberg Biohub, San Francisco, California, USA
Abstract
ABSTRACT
The
Pseudomonas syringae
species complex is a heterogeneous group of plant pathogenic bacteria associated with a wide distribution of plant species. Advances in genomics are revealing the complex evolutionary history of this species complex and the wide array of genetic adaptations underpinning their diverse lifestyles. Here, we genomically characterize two
P. syringae
isolates collected from diseased Callery pears (
Pyrus calleryana
) in Berkeley, California in 2019 and 2022. We also isolated a lytic bacteriophage, which we characterized and evaluated for biocontrol efficiency. Using a multilocus sequence analysis and core genome alignment, we classified the
P. syringae
isolates as members of phylogroup 2, related to other strains previously isolated from
Pyrus
and
Prunus
. An analysis of effector proteins demonstrated an evolutionary conservation of effectoromes across isolates classified in PG2 and yet uncovered unique effector profiles for each, including the two newly identified isolates. Whole-genome sequencing of the associated phage uncovered a novel phage genus related to
Pseudomonas syringae
pv.
actinidiae
phage PHB09 and the
Flaumdravirus
genus. Finally, using
in planta
infection assays, we demonstrate that the phage was equally useful in symptom mitigation of immature pear fruit regardless of the Pss strain tested. Overall, this study demonstrates the diversity of
P. syringae
and their viruses associated with ornamental pear trees, posing spill-over risks to commercial pear trees and the possibility of using phages as biocontrol agents to reduce the impact of disease.
IMPORTANCE
Global change exacerbates the spread and impact of pathogens, especially in agricultural settings. There is a clear need to better monitor the spread and diversity of plant pathogens, including in potential spillover hosts, and for the development of novel and sustainable control strategies. In this study, we characterize the first described strains of
Pseudomonas syringae
pv.
syringae
isolated from Callery pear in Berkeley, California from diseased tissues in an urban environment. We show that these strains have divergent virulence profiles from previously described strains and that they can cause disease in commercial pears. Additionally, we describe a novel bacteriophage that is associated with these strains and explore its potential to act as a biocontrol agent. Together, the data presented here demonstrate that ornamental pear trees harbor novel
P. syringae
pv.
syringae
isolates that potentially pose a risk to local fruit production, or vice versa—but also provide us with novel associated phages, effective in disease mitigation.
Funder
National Science Foundation
USDA | National Institute of Food and Agriculture
Fonds Wetenschappelijk Onderzoek
Chan Zuckerberg Initiative
Publisher
American Society for Microbiology