Preliminary Investigations on the Genetic Relationships and Origin of Domestication of the Tea Plant (Camellia sinensis (L.)) Using Genotyping by Sequencing

A Tea is the most popular non-alcoholic beverage in the world. Asia accounts for 85% of the global tea production. Comprehensive studies on the genetic diversity and origin of domestication of tea plant are scarce, while the studies carried out to date also used fewer number of markers narrowing down its scope. Genotyping by Sequensing (GBS) is a novel next generation sequensing technique which generates large amounts of Single Nucleotide Polymorphysms (SNPs) that are vital for modern genetic analysis. Therefore, 114 wild, landraces and cultivated tea samples collected across 14 countries in Asia were subjected to GBS analysis to study the genetic relationships and origin of domestication of tea plant in Asia. A set of 247,760 high quality SNPs were generated and used for the genetic analysis of 112 samples. Multiple analysis with SNPs revealed three independent domestication events for cultivated tea confirming the results of simple sequence repeat analysis. Most of the wild species clustered together while few species/samples clustered differently showing their gene flow with the cultivated tea or possible hybrid origins. Structure and neighbour joining tree analysis clearly showed a differential clustering of Assam tea collected from India, Sri Lanka and other South Asian countries with the Assam tea collected from China and neighbouring countries in East Asia. Future studies with the recently published tea genome possibly identify differentially selected genes/biochemical pathways during tea domestication. Based on the findings of this most comprehensive study done on tea plant to date, incorporation of Chinese Assam tea germplasm into the breeding programmes in India, Sri Lanka and other South Asian countries is recommended.