Identification of zucchini varieties in commercial food products by DNA typing

DNA typing has been long proposed as a component of food traceability especially for the ability to provide genetic information on processed and/or mixed commercial products. However, the use of DNA testing to deliver legal evidence has been very limited in the agro-food chain, also because in this field, a genetic concordance is rarely sustained with indications on the interpretation and statistics of a DNA profile. Zucchini is the most important and diverse horticultural group belonging to Cucurbita pepo , a plant species that yields a large variety of edible fruits such as squashes and pumpkins. Challenges in genetic discrimination of zucchini material exiting the agro-food chain typify the problems in DNA typing of horticultural food products, because of limited allelic diversity, presence of common alleles, highly processed food and genetic similarity with other edible species. The aims of this work were to identify zucchini varieties in commercial products by a means of Simple Sequence Repeat (SSR) analysis and to provide indications for the statistical interpretation of a match. We assessed the efficacy of SSRs analyzing some of the most diffused hybrids and open pollinated zucchini varieties. SSRs were also screened for transferability in DNA isolated from edible organs of different plant species that are frequently present in food products containing zucchini. Moreover, we demonstrate the possibility to identify the variety in food products of different origins. The statistical evaluation on the rarity of DNA profiles in zucchini indicated that the genetic match presented in this work cannot be attributed to chance alone. Based on this evidence, the advantages and pitfalls of food DNA typing for variety identification of a horticultural crop are discussed.