Worldwide Core Collections of Tea (Camellia sinensis) Based on Genome-Wide Simple Sequence Repeat (SSR) Markers

Tea (Camellia sinensis (L.) O. Kuntze) is one of the most popular beverage crops originated in Asia, and tea products are widely consumed all over the world. However, no core collection has been selected from world-wide germplasm resources based on genome-wide genotype data. In this study, we analyzed 788 tea germplasm accessions using 23 simple sequence repeat (SSR) markers. Our population structure analysis showed that the tea germplasms could be classified into two groups: a Japanese group and an exotic group. The exotic group consisted of two ancestral genome types: var. sinensis and var. assamica. The genetic diversity was higher for germplasms from China, Taiwan, India, and Sri Lanka than for those from other countries, and Japanese germplasms had low genetic diversity. Using the allele number as a measure of genetic diversity, we developed four core collections (with 24, 48, 96, and 192 accessions) from the 788 accessions. Though these results might be affected by a marker-selection bias, the Core 192, which contains 192 accessions, adequately covered the range of variation of the 788 accessions in terms of phenotype, floral morphology, and the chemical composition of the first-flush tea leaves. These collections will be powerful tools for breeding and genetic research in tea.