Genomic Resequencing and Phylogenetic Analysis in Plant Sample Traceability

Botanical evidence left at the crime scene can provide important assistance to scene reconstruction. For example, some plant materials, such as fruits and pollen, easily adhere to human hair or clothing, and the identification of the plant material and the tracing of its origin can assist in deducing the original location of the crime and identifying the perpetrators. However, some plant materials are not easily recognized by phenotypic characteristics and become even more difficult to identify as preserved for longer time. Therefore, we attempted to utilize genome-wide molecular genetic information to infer the kinship and origin of the plant materials left at the crime scenes (here is a piece of long-preserved peach bark), trying to provide new ideas for the identification and origin-tracing of botanical evidence. First, a genetic information database of peaches from all over China was constructed by searching for previously published papers and databases. Then, DNA was extracted from the peach materials collected at the crime scene and those from where the suspect came from. Whole genome DNA library was constructed for the following next generation sequencing, and genome-wide SNPs were called with strict control. By constructing a phylogenetic tree based on the data, the relationships between individuals were revealed, and it provided evidence to characterize and speculate on their origins. In this study, DNA of all 21 collected samples was successfully extracted and used for library construction, including those preserved for decades and highly degraded. After genome resequencing and by comparing to the published complete peach genome, a total of 9938 SNPs were obtained. Phylogenetic analyses indicated that the cultivated peach trees in China, to some extent, showed a pattern of clustering in consistent with geographical distributions. Especially, those individuals from Xinjiang and Xizang were well clustered. And the peach material appeared at the crime scene was inferred to come from Zhejiang province, where the case occurred. In summary, by combining genome resequencing technology with phylogenetic analysis, we can obtain information from poorly characterized and/or long-preserved plant materials, supporting the investigation of cases efficiently and accurately.