Rapid detection of <i>Phytophthora nicotianae</i> by simple DNA extraction and real‐time loop‐mediated isothermal amplification assay

<jats:title>Abstract</jats:title><jats:p><jats:italic>Phytophthora nicotianae</jats:italic> is a phytopathogenic oomycete with a wide host range and worldwide distribution. Rapid detection and diagnosis at the early stages of disease development are important for the effective control of <jats:italic>P. nicotianae</jats:italic>. In this study, we designed a simple and rapid loop‐mediated isothermal amplification (LAMP)‐based detection method for <jats:italic>P. nicotianae</jats:italic>. We tested three DNA extraction methods and selected the Kaneka Easy DNA Extraction Kit version 2, which is rapid and robust for LAMP‐based detection. The designed primers were tested using mycelial DNA from 35 species (81 isolates) of <jats:italic>Phytophthora</jats:italic>, 12 species (12 isolates) of <jats:italic>Pythium</jats:italic>, one isolate of <jats:italic>Phytopythium</jats:italic> and one isolate each from seven other soil‐borne pathogens. All of the 42 <jats:italic>P. nicotianae</jats:italic> isolates were detected by these primers, and no other isolates gave positive results. Three isolates were tested for the sensitivity of the reaction, and the lowest amounts of template DNA that could be detected were 10 fg for two isolates and 1 fg for the third. The target was detected within 25 min in all tested samples, including DNA extracted from both inoculated and naturally infected plants. In contrast, PCR assays with <jats:italic>P. nicotianae</jats:italic>‐specific primers failed or showed weakened detection in several samples. Thus, we found that the rapid DNA extraction and LAMP assay methods developed in this study can be used to detect <jats:italic>P. nicotianae</jats:italic> with high sensitivity, specificity and stability.</jats:p>