Rapid and Quantitative Detection ofLeifsonia xylisubsp.xyliin Sugarcane Stalk Juice Using a Real-Time Fluorescent (TaqMan) PCR Assay

Abstract

Ratoon stunting disease (RSD) of sugarcane, one of the most important diseases seriously affecting the productivity of sugarcane crops, was caused by the bacterial agentLeifsonia xylisubsp.xyli(Lxx). A TaqMan probe-based real-time quantitative polymerase chain reaction (qPCR) assay was established in this study for the quantification ofLxxdetection in sugarcane stalk juice. A pair of PCR primers (Pat1-QF/Pat1-QR) and a fluorogenic probe (Pat1-QP) targeting thePart1gene ofLxxwere used for the qPCR assay. The assay had a detection limit of 100 copies of plasmid DNA and 100 fg ofLxxgenomic DNA, which was 100-fold more sensitive than the conventional PCR. Fifty (28.7%) of 174 stalk juice samples from two field trials were tested to be positive by qPCR assay, whereas, by conventional PCR, only 12.1% (21/174) were tested to be positive with a published primer pair CxxITSf#5/CxxITSr#5 and 15.5% (27/174) were tested to be positive with a newly designed primer pair Pat1-F2/Pat1-R2. The new qPCR assay can be used as an alternative to current diagnostic methods forLxx, especially when dealing with certificating a large number of healthy cane seedlings and determining disease incidence accurately in commercial fields.