SSR marker-based individual identification system to trace illegal logging and geographic origin of teak (Tectona grandis L.f.) wood in India

Illegal tree felling is one of the crucial problems in forestry worldwide. It is essential to develop adequate forensic techniques that can verify the origin of timber sourced at logging concessions. Teak wood-one of the most important timber species in India-is often illegally logged and also imported from other countries without certification. In our study, the best combination of Simple Sequence Repeat (SSR) markers identified was utilized for match testing the genetic profiles of seized and evidence woods. A genetic reference database was also developed to assign unknown wood samples to their source populations. Our results found a perfect match between the genetic profiles of seized wood and their respective evidence wood which ascertains the utility of genetic profiles as an efficient forensic tool. Further, efficiency of assignment tools based on different approaches such as distance-based, model-based and machine learning were tested. Mycorrhiza, a machine learning algorithm, was identified as the best assignment tool. However, only broad provenance-level assignment was possible due to the genetic admixture in a few natural teak populations. Mycorrhiza was then used to identify the origin of two plantations in India. The assignment test predicted that both the plantations had similar origin, having sourced seeds from multiple natural populations (through clonal seed orchards and seed production areas) and local populations in different ratio. The SSR markers and assignment tool from this study can be used as an effective forensic tool to curb illegal felling and to verify integrity of timber supply chains in India. Also, provenance-based assignment guarantees usage of these markers in a global scale. However, a collective global effort to develop and deposit a robust reference database in a common repository is a prerequisite to strengthen timber traceability worldwide.