Utilizing a new target gene, Ppinihp1, identified from genome sequences to detect Phytophthora pini

Phytophthora pini is a globally distributed plant pathogen of the Phytophthora genus. This fungus-like organism was recently associated with foliage blight and shoot dieback disease of Rhododendron pulchrum Sweet, which threaten the health of natural ecosystems and horticultural crops in China. Early and accurate detection of P. pini is critical for effective disease prevention and management. In this study, a new target gene Ppinihp1, which is a hypothetical protein, identified from the whole-genome sequence of P. pini was used to establish a conventional polymerase chain reaction (PCR) assay for the detection of this pathogen. PCR results were proved to be positive for P. pini, but negative for other Phytophthora, Pythium, fungal isolates and Bursaphelenchus species. The test was sensitive enough to detect 100 pg of P. pini purified genomic DNA in a 50 μL reaction mixture. P. pini was also detected in artificially inoculated R. pulchrum samples. Finally, this novel Ppinihp1-PCR-assay was able to detect P. pini in 15 of 40 soil samples collected from R. pulchrum fields in Jiangsu, China. This method established the specificity, sensitivity, accuracy and convenience for P. pini detection, offering a dependable tool for the rapid screening of Phytophthora root and stem rot in R. pulchrum.