The trnL (UAA)-trnF (GAA) intergenic spacer is a robust marker of green pea (Pisum sativum L.) adulteration in economically valuable pistachio nuts (Pistacia vera L.).

Background: Pistachio (Pistacia vera L.) is an expensive culinary nut species; it is therefore susceptible to adulteration for economic profit. Green pea (Pisum sativum L.) kernels constitute the most common material used for adulterating chopped / ground pistachio nuts and pistachio paste. Food genomics enables the species composition of a food sample to be ascertained through DNA analysis. Accordingly, a barcode DNA genotyping approach was used to standardize a test method to identify green pea adulteration in pistachio nuts.

Results: The trnL (UAA)-trnF (GAA) intergenic spacer in the plastid genome was the target analyte in the present study. The barcode locus displayed a significant, discriminatory size difference between pistachio and pea, with amplicon sizes of 449 and 179 bp, respectively. Polymerase chain reaction-capillary electrophoresis (PCR-CE) analysis of the intergenic spacer resulted in the successful identification of species composition in the in-house admixtures, which contained 5% to 30% of green pea.

Conclusion: The present work describes a fast and straightforward DNA test that identifies green pea adulteration in pistachio nuts without requiring a statistical data interpretation process. The plastid trnL (UAA)-trnF (GAA) intergenic spacer length widely varies among plant taxa, so the PCR-CE protocol that operates on the intergenic spacer holds the potential to reveal adulteration with a plethora of adulterants. The PCR-CE assay described in the present work can be adopted readily by food-quality laboratories in the public sector or the food industry as an easy and reliable method to analyze pistachio authenticity. © 2020 Society of Chemical Industry.