Molecular fingerprinting of peppermint (Mentha piperita) and some Mentha hybrids by sequencing and RFLP analysis of the 5S rRNA Non-Transcribed Spacer (NTS) region

Hybridization of species belonging to the genus Mentha is quite common. However, the indicators of hybridity are many and make difficult Mentha hybrids identification. By using the same molecular strategy that allowed us to unequivocally identify some Mentha species, we amplified the NTS (Not-Transcribed-Spacer) of the 5S-rRNA gene to characterise the industrial crop peppermint, M. x piperita, and some important Mentha interspecific hybrids: M. x dalmatica, M. x dumetorum, M. x rotundifolia, M. x maximilianea, M. x smithiana, M. x verticillata, M. x villosa. DNA amplification, sequence and cluster analysis revealed differences in the 5S-rRNA NTS region of Mentha hybrids. Peppermint and all other hybrids were unequivocally discriminated by RFLP analysis by using TaqI restriction enzyme, while a further discrimination between M. x dumetorum and M. x verticillata was obtained by XhoI restriction enzyme. Essential oil composition showed clustering patterns similar to DNA fingerprint, with a clear discrimination between plants producing menthofuran (e.g., M. aquatica and its related hybrids, including peppermint) and those containing piperitenone oxide (M. longifolia and its related hybrids).