Tracing the botanical origins of UK heather honey by relative quantification of plant DNA

Heather honey is an important honey type produced in the UK, valued for its unique flavour, thixotropic texture and health-promoting properties. Botanical authentication can be challenging due to the natural variability in honey composition and typical pollen analysis relies heavily on expert knowledge. As an alternative, real-time PCR (qPCR) can be a rapid and robust method to identify floral species in honey. In this work, species-specific markers for Calluna vulgaris and Erica cinerea were developed and used to quantify 266 honey samples relative to the plant trnL P6 loop. The method classed 96% of 234 heather honeys as containing > 3% heather DNA, with 68% classified as dominant (> 45%) for ling heather origin. Moreover, high specificity was achieved with negligible amplification in the 32 non-heather honeys. Our qPCR method offered comparable results to melissopalynology, DNA metabarcoding, and digital PCR, showing potential as an alternative and accessible method for botanical authentication of heather honeys.