Development of methods to distinguish between durum/common wheat and common wheat in blended flour using PCR

A PCR-based method was developed to distinguish between durum/common wheat and common wheat by leveraging slight differences of DNA sequence in Starch Synthase II (SS II) coded on wheat A, B and D genomes. A primer pair, SS II ex7-U/L, was designed to hybridize with a conserved DNA sequence region found in SS II-A, B and D genes. Another primer pair, SS II-D 1769U/1889L, was constructed to recognize a unique sequence in the SS II-D gene. The target region of SS II ex7-U/L with the size of 114 bp was amplified from durum and common wheat DNA, while no amplification was observed from any cereals other than those in the wheat genus. A DNA fragment with the size of 121 bp was specifically amplified from common wheat with SS II-D 1769U/1889L. In blended flour prepared from wheat and other cereals, the developed PCR system composed of two primer pairs effectively detected durum/common wheat and common wheat. These results suggested that PCR using two primer pairs is useful for detecting common and/or durum wheat in blended flour and could be utilized to ensure accurate food labeling.