A simple and versatile authenticity assay of coffee products by single-nucleotide polymorphism genotyping

Interspecific single-nucleotide polymorphisms (SNPs) in the <i>rbcL</i> DNA barcode have been strictly validated and adopted as a designed SNP genotyping maker to discriminate between two major coffee species, <i>Coffea arabica</i> and <i>C. canephora</i>, and to estimate the mixing ratio of DNA from <i>C. arabica</i>/<i>C. canephora</i> in this study. The SNP genotyping is applicable to not only green (unroasted) coffee beans, but also processed coffee products (roasted coffee beans and instant coffee powder), in which genomic DNA is degraded, because the genotyping developed in this study requires only 10 copies of 63-bp-long DNA fragments of <i>rbcL</i> gene. The authenticity assay established in this study has several advantages: a high versatility to DNA sample conditions; simple and rapid procedures (only two steps; DNA extraction and SNP genotyping); the feasibility in coffee business for practical use to prevent false advertising and provide quality control. <b>Abbreviations:</b> SNP: single-nucleotide polymorphism; SBS: single base substitution; ISR: intergenic spacer region; INDEL: insertion-deletion. SNP Genotyping: Required only 10 copies of 63-bp-long DNA fragment of rbcL gene.