Rapid and Specific Detection of the Poplar Black Spot Disease Caused by Marssonina brunnea Using Loop-Mediated Isothermal Amplification Assay

Marssonina brunneais the main pathogen that causes poplar black spot disease, which leads to the decrease of the photosynthetic efficiency and significantly affects the production and quality of timber. Currently, no in-field diagnostic exists forM. brunnea. Here, we described a loop-mediated isothermal amplification (LAMP) assay for the rapid and sensitive detection ofM. brunnea. A set of six oligonucleotide primers was designed to recognize eight distinct sequences of the internal transcribed spacer (ITS) region ofM. brunnea. The LAMP assay was optimized by the combination of high specificity, sensitivity, and rapidity for the detection of less than 10 pg/μL of target genomic DNA in 60 min per reaction at 65 °C, whereas with PCR, there was no amplification of DNA with concentration less than 1 ng/μL. Among the genomic DNA of 20 fungalisolates, only the samples containing the genomic DNA ofM. brunneachanged from violet to sky blue (visible to the naked eye) by using hydroxynaphthol blue (HNB) dye. No DNA was amplified from the eight other fungus species, including two otherMarssoninapathogens, three other foliar fungi pathogens of poplar, and three common foliar fungal endophytes of poplar. Moreover, the detection rates ofM. brunneafrom artificially and naturally infected poplar leaves were 10/16 (62.5%) and 6/16 (37.5%) using PCR, respectively, while the positive-sample ratios were both 16/16 (100%) using the LAMP assay. Overall, theITSLAMP assay established here can be a better alternative to PCR-based techniques for the specific and sensitive detection ofM. brunneain poplar endemic areas with resource-limited settings.Keywords:Marssonina brunnea;rapid detection;loop-mediated isothermal amplification;poplar black spot