Molecular markers and phenotypic identification reveal the genetic diversity and structure of four local tea plant populations in China

Local tea plant population resources are rich in genetic variations, which are the natural treasure house of tea genes and the main source of breeding excellent tea cultivars. However, the genetic information of most local tea plant populations is unknown. In this study, the genetic diversity and population structure of the four main local tea plant populations from the Jiangxi Province of China were explored by combining the identification of phenotypic characters with simple sequence repeat (SSR). The loci associated with the phenotypic characters were also screened. The results of the genetic diversity analysis of the phenotypes and SSR were consistent. We observed that the genetic diversity of the population species in the four tea plant populations was higher than that of the wild species. The genetic diversity index was in the order Wuyuan > Fuliang > Suichuan > Ningdu. The single plants of each population were heterozygotes. The Wuyuan population had the highest heterozygosity. The clustering results of the phenotypes and SSR of the tea plant populations were not completely consistent. SSR could more effectively distinguish the tea plant populations. Four tea populations could be clustered into three groups. In total, nine SSR loci were screened and were significantly associated with nine phenotypic characters (P < 0.01). The interpretation rate of the phenotypic variation ranged from 6.94 to 33.90%. These phenotypic characters were related to the yield and mechanical harvest of the tea cultivars.