Integration of DNA barcoding and wood anatomy for the identification of selected timbers

Abstract

In the field of wood marketing, the accurate identification of species has greater importance. Traditional methods of wood identification are based on physical characters and anatomical features of the wood species concerned. But they have some major limitations which could be overcome by the integration of DNA barcoding with traditional wood taxonomy methods. This study was conducted to confirm the authenticity of certain wood samples based on their physical and anatomical characters and to create a DNA Barcode database of seven selected timber species that are regularly traded in Kerala. The wood samples of seven tree species viz., Indian Sal (Shorea robusta Gaertn), Mangium (Acacia mangium Willd), Indian sandalwood (Santalum album Linn), Western red cedar (Thuja plicata Donn), Red sanders (Pterocarpus santalinus L.F), Mulluvenga (Bridelia retusa Spreng) and Malabar neem (Melia dubia Cav) were collected from sawmills and timber traders across Kerala and their anatomical and physical properties were studied in detail. The identity of samples was confirmed using computer-aided wood identification software in addition to the use of dichotomous keys. The wood samples were then used for DNA isolation, amplification and sequencing. The detailed study on general features such as colour and odour, physical properties like moisture content and specific gravity and micro-anatomical properties such as the number and distribution of vessels and rays was appropriate to confirm the identity of species as the properties were highly comparable with the existing databases. In further procedures, the DNeasy Plant Mini Kit (Qiagen) with some in house modifications could yield the maximum quantity of DNA for the studied wood species in the current study. Also the samples which are soaked in water yielded maximum amount of DNA even if it was treated with wood chemicals during transits for longevity. PCR amplifications were carried out using COBOL Plant Working Group (2009) recommended universal primers for rbcL, matK, and trnH-psbA, from which the matK region showed reasonable amplification.