Multiplex polymerase chain reaction assays for the detection of the zearalenone chemotype of Fusarium species in white and brown rice

Early detection of the zearalenone (ZEA) chemotype of Fusarium species could be a precautionary measure for preventing ZEA contamination in rice. In this study, a multiplex polymerase chain reaction (mPCR) assay for detecting ZEA-producing fungi in rice was established using a set of four primers targeting the ZEA biosynthesis genes PKS3, PKS13, ZEB1, and ZEB2. Two mPCR approaches were used: one that amplified the DNA obtained from Fusarium isolates (conventional method) and another that directly amplified the target DNA from rice samples without time-consuming DNA isolation (direct method). The two mPCR methods showed high sensitivity in detecting ZEA-producing species, with a detection limit of 1.25 pg/μL of genomic DNA and 102 and 103 spores/g of white and brown rice, respectively. Both methods were specific for ZEA-producing species and gave four band patterns. The application of the two mPCR methods to 51 Fusarium isolates and 41 rice samples revealed that 31% (16 of 51) and 24% (10 of 41) of the samples were contaminated with ZEA-producing species, respectively. The mPCR results were further evaluated using high-performance liquid chromatography; in general, the two methods yielded similar results. These findings indicate that both mPCR methods are suitable for the detection of ZEA-producing Fusarium species in white and brown rice; however, the direct method yielded more rapid results.