MSc

Wood is one of the versatile and renewable natural resources, used extensively for diverse purposes. Its end uses are being improvised through technological advancements. An ever-increasing population has resulted in higher demand for this once plentiful resource. The conservation-oriented policy norms also augmented the widening gap between demand-supply in the timber markets which, in spite of this potential wealth, has led us to import timber from abroad. The remaining demand is met through plantation-grown timber including indigenous, and exotic species. Timber legality and assurance system demands a scientific method which guarantees the right timber for the right use. Scientific methods of wood identification involve conventional wood anatomy where the unique combination of wood elements (vessels, ray parenchyma, axial parenchyma etc.) derived from its natural growth in the living tree is used. This method is considered as modest, precise and feasible for different commercial timber species. However, distinguishing individuals within a species, which shows disparities due to local adaptation requires DNA profiling. DNA is barcoded to identify a species based on specific gene regions which are conserved and unique in every species. DNA barcoding has a tremendous scope in forestry enterprises including verifying forest trees and wild seedlings, population diversity studies, tracking adulterant species of timber as well as medicinal plants, and counteracting illegal logging of both wood and wood products. In this context, the present study titled “Development of DNA barcodes for the identification of selected timber species used in Kerala” aims at the development of a barcode database for the identification of the selected timber species integrated with the physical and anatomical properties of wood. The study was carried out during the period 2020-22 in the Department of Forest Products and Utilization, College of Forestry, Kerala Agricultural University, Vellanikkara and the Forest Genetics and Biotechnology division of Kerala Forest Research Institute (KFRI), Peechi. The wood samples include imported woods viz., Acacia auriculiformis A. Cunn. ex Benth (Acacia), Acrocarpus fraxinifolius Wight & Arn. (Acrocarpa), Albizia odoratissima (L.f.) Benth. (Ceylon rosewood), Intsia bujiga (Colebr.) Kuntze (Merbau), Martiodendron parviflorum (Amshoff) R. C. Koeppen (WPL- Witte Pinto Locus), Mesua ferrea L. (Mesua), Pterocarpus dalbergoides DC. (Andaman padauk), Ocotea rodiaei (R.H.Schomb) Mez (Greenheart), Salix babylonica L. (Weeping willow) and Salix tetrasperma (Indian Willow) were collected from timber sawmills in the Thrissur district and other timber dealers across Kerala. The general features of wood like colour, odour, weight and texture, and physical property like specific gravity were considered for the primary inspection of wood samples. Anatomical features were used to confirm the identity of the species along with the available wood identification databases like the “Inside wood” database. DNA barcodes were developed using three standard barcode loci viz., rbcL (ribulose bisphosphate carboxylase larger subunit), matK (maturase K) coding gene regions as well as non-coding region psbA-trnH from chloroplast region recommended by COBOL Plant Working Group (2009). Obtained sequences were edited, aligned and checked for similarity using our reference library as well as the Nucleotide BLAST tool in NCBI. The size of each sequence, homology per cent, frequency of each nucleotide, and conserved and variable sites for each gene region in all the species were recorded. For all the species under study, the maximum value for specific gravity was observed in Mesua ferrea whereas Salix spp. showed minimum value for specific gravity. The concentration of extracted DNA from all the leaf and wood samples was recorded and 100 per cent success rate was observed for DNA extraction from the processed wood samples using the kit method. Highly processed wood samples yielded a very less amount of amplifiable DNA but some in-house modifications which help in leaching phenolic compounds gave a high yield of intact DNA. Out of three gene regions considered for the study, rbcL amplified all 10 out of 10 species whereas matK and psbA-trnH amplified for 8 and 7 species respectively. The study concluded that the combination of wood elements in terms of their size and distribution pattern is essential to identify wood using anatomical tools. An integrated approach involving wood anatomy and DNA barcoding can identify any unknown wood specimen if the DNA barcode reference library is in place. The present study also recommends the creation of a DNA barcode reference library which can add more precision to the wood identification process, so as to counter the illegal trade and adulteration in the timber trade.