Ben Hoyt
University of California, Riverside
Riverside, CA, USA
Aidan C. Shands, PhD
University of California, Riverside
Riverside, California, United States
Savannah Salas
University of California, Riverside
Riverside, California, United States
Vanessa Hua
University of California, Riverside
Riverside, California, United States
Jonathan Crane, PhD
Professor
Plant Pathology Department, Global Food Systems Institute, 3Emerging Pathogens Institute, University of Florida, Gainesville, FL, USA
Homestead, Florida, United States
Romina Gazis, PhD
Associate Professor
Tropical Research and Education Center, University of Florida, Homestead, FL, USA
Homestead, Florida, United States
Monica Navia-Urrutia, PhD
Assistant Professor
University of Florida - Belle Glade, FL
Belle Glade, Florida, United States
Liliana Cano, PhD
Assistant Professor
University of Florida
Fort Pierce, Florida, United States
Achyut R. Adhikari
University of Hawaii at Mānoa
Honolulu, Hawaii, United States
Miaoying Tian
University of Hawaii at Mānoa
Manoa, Hawaii, United States
John Jifon
Texas A&M University
College Station, Texas, United States
Luz Myriam Serrato
USDA-ARS-Tropical Agriculture Research Station, Mayaguez
Mayaguez, Puerto Rico, United States
Alejandra Mondragón-Flores
INIFAP, Instituto Nacional de Investigaciones Forestales
Cacahoatán, Chiapas, Mexico
Sylvia Fernández-Pavía
Instituto de Investigaciones Agropecuarias y Forestales
Morelia, Michoacan de Ocampo, Mexico
Nick Cauldron
Oregon State University
Corvalis, Oregon, United States
Niklaus Grünwald
USDA-Agricultural Research Service
Corvalis, Oregon, United States
James E. Adaskaveg, Professor
Professor
University of California, Riverside
Riverside, California, United States
Patricia M. Manosalva
Associate Professor
University of California, Riverside
Riverside, California, United States
A global population study of Phytophthora cinnamomi (Pc), the most destructive avocado pathogen, identified two A2 panglobal clonal lineages, PcG1-A2 and PcG2-A2, across all continents collected from various hosts. In California, the avocado Pc populations also grouped into two clonal A2 clades (I and II). The A2 clade II contains isolates that were more virulent in avocado, resistant to the major fungicide (potassium phosphite), and detected only in San Diego and Riverside Counties. We assessed the genetic structure and relationships of avocado Pc populations collected across the U.S.A. and Mexico using a whole genome resequencing approach. Principal component and phylogenetic analyses clustered the U.S.A. and Mexican Pc populations into the previously identified A2 clades. By including isolates corresponding to the two panglobal A2 lineages, we assigned the A2 clade I and clade II to the PcG1-A2 and PcG2-A2 lineages, respectively. The PcG1-A2 lineage contained the majority of U.S.A. isolates and a few isolates from Mexico, while the PcG2-A2 lineage contained isolates collected from Riverside, San Diego, Santa Barbara, Hawaii, and most of the Mexican isolates, providing support for the Mexican origin of this clade in California. Our study detected migration of PcG2-A2 isolates within California and between Mexico and California, highlighting pathways that should be monitored to prevent further spread. Monitoring and characterizing the Pc populations is critical for developing effective and durable control methods that ensures the global avocado industry sustainability.