Improved methodology for extraction and amplification of DNA from single grains of charred wheat

Comparisons were made between two commonly used methods for the extraction of ancient DNA from charred plant remains. Using artificially charred wheat seeds, we show that silica-binding is the most efficient method for extraction of DNA. We describe a improved silica-binding procedure, including pre-incubation with N-phenacylthiazolium bromide and increased washing of bound DNA, which yields amplifiable DNA from seeds heated at 200 °C for up to 8 h, conditions which promote the formation of Maillard products which often copurify with aDNA and inhibit subsequent PCRs. We believe that this method will be effective in ancient DNA extraction with most types of charred archaeobotanical material. Both cold- and hot-start PCR procedures gave good amplicon yields with extracts prepared in this way, but cold-start PCRs also resulted in synthesis of short artefact products. Addition of bovine serum albumin to PCRs, an inert carrier substance thought to enhance amplification efficiency by binding contaminants, had no advantageous effect and in fact reduced amplicon synthesis.