Abstract:Phytophthora sojae is a devastating pathogen that causes soybean Phytophthora root rot. This paper reports the development of a loop-mediated isothermal amplication (LAMP) assay for detection of P. sojae based on Ypt1 gene. The Ypt1-LAMP assay efciently amplied the target gene within 60 min at 64°C and was evaluated for specificity and sensitivity. The specificity of the assay was evaluated against isolates of P. sojae, Phytophthora spp., Pythium spp., and some true fungi. Magnesium pyrophosphate resulting from the LAMP of P. sojae could be detected by real-time measurement of turbidity. Additionally, the DNA products of P. sojae were visualized as a ladder-like banding pattern on a 2% agarose gel electrophoresis, and a positive color (sky blue) was observed only in the presence of P. sojae by addition of hydroxynaphthol blue prior to the amplification, whereas none of the other isolates showed such a color change. The detection limit of Ypt1-specic LAMP assay was 100 pg·μL-1 of the genomic DNA per reaction, which was up to 10-fold more sensitive than that of the conventional PCR approach. P. sojae from diseased soybean tissues and residues was detected by the LAMP assay and the conventional PCR method. Moreover, the traditional isolation from these samples was also performed using a leaf disk baiting method. The positive-sample ratios were 71/130 (54.6%) by the LAMP assay, 61/130 (46.9%) by the conventional PCR approach, and 50/130 (38.4%) by the leaf disk baiting method, suggesting that the PsYpt1-LAMP assay reported here shows great potential for the rapid visual detection of P. sojae in the field and from the soybean production.