Rapid detection of Passalora sequoiae causing needle blight on Japanese cedar

Needle blight, caused by Passalora sequoiae (Mycosphaerellaceae, Ascomycota), is an economically significant disease that commonly affects Japanese cedar (Cryptomeria japonica) in Japan. With the increasing production of cedar saplings as part of reforestation efforts, there is concern that needle blight will become more prevalent in nursery fields. However, when visually inspected, this disease is sometimes misdiagnosed as other diseases with similar symptoms. Therefore, a prerequisite to preventing the spread of this pathogen is the development of an accurate and rapid molecular diagnostic method. In this study, species-selective primers were designed for conventional PCR and recombinase polymerase amplification (RPA) and then successfully applied for rapid detection of the pathogen in laboratory-grown cultures and diseased needles. The detection methods developed in this study should improve the control and management of needle blight in Japanese cedar.