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Poster: Diseases of Plants: Disease Detection & Diagnosis


Development of molecular diagnostic tools for the invasive oomycete pathogen Phytophthora tentaculata
N. Luecke (1), S. Koenig (1), T. Miles (2) (1) CSU Monterey Bay, U.S.A.; (2) California State University Monterey Bay, U.S.A.

Phytophthora basal rot (PBR) of plants is a disease recently observed in Central California Native plant nurseries and restoration locations. The primary causal agent of this disease is the oomycete pathogen Phytophthora tentaculata. Prior to 2012, P. tentaculata was among the ~30 Phytophthora species not known to be present in the US. Previous research had developed an isothermal diagnostic tool known as recombinase polymerase amplification (RPA), which had Phytophthora genus specific detection capability with results obtainable within as little as 15 minutes directly in the field without conventional DNA extraction. A P. tentaculata species-specific RPA assay was developed and specificity validated against pure DNA from 135 Phytophthora taxa. To test this technique for detection of the pathogen in PBR, 113 symptomatic samples were collected and evaluated with the new RPA assay as well as the previously validated TaqMan assay, Immunostrip and conventional culturing and baiting techniques. Results were similar across the various amplification platforms, with qPCR being the most sensitive in general. Finally, spatial models were created to test if elevation correlated with the presence of the pathogen. These results indicate that P. tentaculata is often present in low-lying areas when infected plant material is used for restoration. This information will assist in more efficient, rapid, specific pathogen detection for management decisions in a field.