Ben Hoyt
University of California, Riverside
Riverside, CA, USA
Savannah Salas
University of California, Riverside
Riverside, California, United States
Jocelyn Leos
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
Monica Navia-Urrutia, PhD
Assistant Professor
University of Florida - Belle Glade, FL
Belle Glade, Florida, United States
Romina Gazis, PhD
Associate Professor
Tropical Research and Education Center, University of Florida, Homestead, FL, USA
Homestead, 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
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
Phytophthora root rot (PRR) caused by Phytophthora cinnamomi (Pc) is the most devastating avocado disease worldwide. We previously characterized two genetically and phenotypically distinct avocado Pc populations in California (CA) with southern CA isolates being more virulent and resistant to potassium phosphite (PP), the most common fungicide used for PRR control. Here, we expanded our phenotypic characterization to isolates from other avocado producing states by comparing their growth rate at different temperatures, virulence, and in vitro sensitivities to ethaboxam, fluopicolide, mandipropamid, mefenoxam, oxathiapiprolin, and PP. Significant variability was detected among Pc populations for each phenotypic trait within and among states. Isolates from Hawaii, Florida (FL), and southern CA grew faster at 28°C, suggesting adaptation to warmer climates. More PP-resistant Pc populations were found in CA and FL, likely reflecting the continued overuse of PP applications in these states. We also detected significant variability regarding in vitro sensitivities to other Oomycota fungicides, possibly revealing natural variation since some of these fungicides are not heavily used or registered on avocados. Finally, significant variation in virulence was found among isolates using avocado seedlings and D’Anjou pear fruits. Our study highlights the adaptative capacity of clonal Pc populations to local environments and control measures suggesting the potential for emergence of new fungicide-resistant and more virulent populations threatening the national avocado industry.