Goji (fruits of Lycium spp.) is commonly consumed as food and medicine. The increasing market demand for goji has led to its wide cultivation and broad breeding, which might cause loss of genetic diversity. This study aims to uncover the genetic diversity of the cultivated and wild Lycium.

The chloroplast genome (CPG) of 34 accessions of Chinese food-medicinal Lycium spp., including the popular cultivars and their wild relatives, was re-sequenced and assembled, based on which the genetic diversity was evaluated.

Sequence structural comparison shows that CPG is comparatively conserved within species. Phylogenetic analysis indicates that CPG is sufficient for the discrimination of Lycium species; combined with nuclear ribosomal internal transcribed spacer (Nr ITS) sequences, materials with mixed genetic backgrounds can be identified. Nucleotide diversity analysis reveals that the modern cultivars are probably with a common maternal parent, while the wild accessions are with higher level of genetic diversity.

For the first time this study reveals the intraspecies genetic diversity of Lycium spp. using CPG, highlighting the urgent conservation demand of wild genetic resources of Lycium. Our study also demonstrates that CPG provides crucial evidence for identification of Lycium species with mixed genetic backgrounds and highlights the importance of the wild relatives in genetic diversity conservation. This CPG-based technology will contribute to the sustainable development of medicinal plants broadly.

For over one millennium, goji berries have been used traditionally as food and medicine in eastern Asia. In recent decades, it has become increasingly popular globally. However, the biocultural development of goji is poorly known. The botanical origin of goji is controversial: in many but not all modern regional or international quality standards, L. barbarum is accepted exclusively as the botanical origin of goji.

Focusing on historical, biogeographical, botanical, phytochemical and pharmacological data, the overarching aim is to understand the biological origin of goji's historical uses, as well as whether the two species can be used interchangeably.

The taxonomic literature on L. barbarum and L. chinense were analysed, followed by a study of botanical specimens and fieldwork. Historical herbals and gazetteers were employed to define the historical producing areas and medical properties of goji. An identification of the species used in history was carried out. In a final step the phytochemical and pharmacological literature on the species was compared.

Due to their morphological similarity and different accessibility, fruits of both L. barbarum and L. chinense have been used interchangeably as food and medicine at least since 682 CE. While the fruit of L. barbarum was recognized to be superior in quality, the fruit of L. chinense was commonly used as an equivalent because of its easier accessibility. Cultivation of L. barbarum in China since 1960s improved its availability, which likely lead to its exclusive use as source of goji in China. The long-term safe use with no reported major safety concerns supports that these two species both are useful sources for medicinal Lycium.

Medicinal plants had been used traditionally long before they were named in scientific nomenclature system. Therefore, the understanding of traditional herbal knowledge and the adequate use of those traditional medicines require a reliable identification based on archival records. This study developed an approach for the identification of species used historically, with an integrated analysis of specimens, historical herbals, and national gazetteers. Additionally, their different chemical profiles and pharmacological activities indicate that they should not be used interchangeably. Further scientific evidence is required for their safe and effective use.