Extraction and amplification of DNA from aged and archaeological Populus euphratica wood for species identification

The wood samples of Populus euphratica Oliv. (Salicaceae) are common archaeological plant remains in the hot and arid regions of western China. However, it is difficult to identify P. euphratica wood based on traditional wood anatomical methods alone. DNA barcoding might provide a higher security for species identification. In this study, aged wood specimens stored for approximately 30, 60, and 80 years and archaeological wood up to 3600 years old were in focus to explore the potential of DNA extraction and PCR amplification for different-sized fragments, ranging between 100 and 800 bp, taken from wood stored for different periods. The results indicated that DNA fragments of more than 100 bp could be successfully retrieved from a wood specimen stored for about 80 years based on a modified Qiagen kit protocol. However, it was impossible to obtain DNA segments from the 3600-year-old wood according to the current extraction protocol. Moreover, it was deduced that two-stage PCR amplification could play a significant role in the analysis of DNA retrieved from aged wood materials. With the aid of phylogenetic analysis, based on the short DNA barcode rbcL-2 of 202 bp in length, it was possible to differentiate P. euphratica from the other species of the Populus genus.