## 6 Molecular Markers for Detecting Invasive Plant Contaminants in Food Crops  
Involuntary ingestion of poisonous plants is a frequently reported issue worldwide, and the number of species involved is increasing due to the incorrect identification of toxic and edible plants. In the food supply chain, it is becoming more necessary to develop authentication systems that achieve more accurate identification and reliable plant classification. DNA-based markers are considered particularly reliable and stable for identifying plant species that are morphologically identical [79]. In the context of food contaminants, DNA molecular markers are specific DNA sequences that identify specifically the presence of unwanted plant species or adulterants by providing a specific genetic fingerprinting. The detection of these specific DNA sequences, in order to be useful in certification labs, must easily and quickly differentiate between the contaminant and the intended food source. In the last decade, several studies have emphasized the use of molecular markers in the authentication of plant-origin foods, focusing on species identification and discrimination [80; 81]. For example, sequence-characterized amplified region (SCAR) markers, developed from the older technique of random amplified polymorphic DNA (RAPD), have been employed to detect safflower (_Carthamus tinctorius_) adulteration in saffron (_Crocus sativus_ L.) [82]. Thanks to the increasing knowledge of the DNA sequences of several species, there is a greater possibility of establishing a database of invasive plant DNA barcode sequences [83]. DNA barcoding represents a highly effective method for species identification [84]. This technique uses a short section of DNA from specific genes to accurately identify species, especially when initial morphological identification provides only approximate results [85]. DNA barcoding has also been proven successful in detecting sources of phytotoxic pyrrolidine alkaloids (PAs) and other toxic compounds. For instance, herbal material from the _Heliotropium_ genus (Boraginaceae) has been detected in spice seeds using this method [86]. The most important aspects to consider when using DNA molecular markers to detect invasive plant contaminants are the efficacy in detecting low levels of contamination and the speed of the analysis. To this aim, DNA barcoding with high-resolution melting (Bar-HRM) analysis has been applied for species identification and authentication since it is a fast, reliable, less time-consuming, and inexpensive method. Bar-HRM analysis allows for the detection of single-base variants in a short region of DNA based on differences in the melting curve, i.e., the graphical representation of the relationship between temperature and the denaturation of DNA [87; 88]. For example, HRM analysis is capable of detecting saffron admixture with other plant materials, including _Carthamus tinctorius_ L., _Calendula officinalis_ L., _Curcuma longa_ L., _Zea mays_ L., and _Gardenia jasminoides_[89]. Also based on HRM, [PERSON] and colleagues [88] developed a method to detect a specific ITS2 for discriminating common toxic plants. Since it relies on small fragments detection, the authors showed that it could be applied to identify sources of intoxication even after digestion for forensic scopes. In particular, authors with Bar-HRM analysis tested successfully the presence of _Datura stramonium_ in simulated mixtures with the edible _Amaranthus retroflexus_. Molecular markers can even be used in food authenticity and traceability for end products that have undergone extensive and complex processing, as some DNA often remains intact after all industrial production steps thanks to its stability. Regarding efficacy in identifying small amounts of contamination, recent advancements in technology, such as digital PCR, have significantly enhanced detection capabilities. Digital PCR offers higher sensitivity and precision compared to traditional quantitative PCR methods.