Detection of Roundup Ready soybean by loop-mediated isothermal amplification combined with a lateral-flow dipstick

LAMP–LFD, loop-mediated isothermal amplification (LAMP) combined with a lateral-flow dipstick (LFD), was developed and evaluated as a new method for the detection of Roundup Ready soybean (RRS). Biotinylated LAMP amplicons were produced by two sets of six designed primers that specifically recognized the endogenous gene (Lec1) and the event-specific 5′ -junction region (G35S) of RRS followed by hybridization with FITC-labeled probes and LFD detection. The following optimized conditions for the LAMP assay were used: deoxynucleotide triphosphate (dNTP) concentrations ranging from 0.6 to 3.2 mM, 6 mM Mg2+, 4 U Bst DNA polymerase and a 1:6 ratio of outer to inner primers. The LAMP–LFD results were generated within 50 min. The detection limit of LAMP–LFD was 2.4 copies of the linearized plasmid pTLH10 and was 20 times more sensitive than conventional PCR. We demonstrated the high specificity of LAMP–LFD by testing processed soybean products, genetically modified (GM) maize and Bt-cotton meal. The novel LAMP–LFD setup presented here is simple, rapid, and has the potential for future use in the detection of GM ingredients in feed and food products.