P-012 - Beyond the grove: Unveiling the ecology and diversity of X-disease, ‘Candidatus Phytoplasma pruni’, strains in extra-orchard environments

Tuesday, August 5, 2025

9:30 AM - 10:15 AM HST

Location: Exhibit Hall 3

Presenting Author(s)

MH

Mason C. Hoskins (he/him/his)

Graduate Student
Department of Plant Pathology, Washington State University
Bozeman, Montana, United States

Author(s)

CM

Cody Molnar

Department of Plant Pathology, Washington State University
Prosser, Washington, United States
SC

Sarah Jane Cowell

Department of Plant Pathology, Washington State University
Prosser, Washington, United States
MS

Madalyn Shires, PhD

Assistant Professor and Extension Plant Pathology Specialist
South Dakota State University
Brookings, SD, USA
SH

Scott Harper, PhD

Associate Professor
Department of Plant Pathology, Washington State University
Prosser, Washington, United States

Abstract Text: Commercial cherry growers throughout North America are suffering losses to their crops over the last few decades due to an outbreak of X-disease, caused by ‘Candidatus Phytoplasma pruni’. In previous epidemics, this phytoplasma was thought to have originated in free-living Prunus spp. adjacent to the orchard environment. Taking advantage of recent research into the diversity of ‘Ca. P. pruni’, which identified seven distinct strains, five associated with commercial Prunus spp. and two specific to wild Prunus, we aimed to test that hypothesis by determining which strains were present in cultivated vs. free-living Prunus across the western and mountain states of the United States during the growing seasons of 2023 and 2024. Chokecherry (Prunus virginiana) were sampled, 518 total, across 13 states, tested for ‘Ca. P. pruni’ presence using a species-specific real-time qPCR, then multi-locus sequence analysis performed using the 16S, secY, secA, imp, and Ef-Tu genes. Initial analysis suggests geographic segregation of ‘Ca. P. pruni’ strains present in wild Prunus spp., but not in commercial orchards in most states suggesting the introduction of strains into the orchard environment separate from potentially native strains. Additional new strain populations were also observed through MLSA, suggesting that this phytoplasma is more diverse than previously thought.