The metabolites in the tender shoots of the tea plant are the material basis for the determination of tea quality. The composition and abundance of these metabolites are affected by many key factors, and the tea plant’s age is one of them. However, the effect of plant age on the tender shoot metabolites of tea cultivars of different genotypes is poorly understood. Therefore, we used a combination of untargeted metabolomics and transcriptomics to analyze the differential mechanism behind the differences in the metabolites of the spring tender shoots of 7- and 40-year-old tea plants of two tea cultivars of different genotypes. We found that plant age could significantly change the metabolites in the spring tender shoots of tea plants and that flavonoids, and amino acids and their derivatives, were predominant among the differential metabolites. The quantities of most flavonoids in the aged tea plants of different genotypes were upregulated, which was caused by the upregulated expression of differential genes in the flavonoid biosynthesis pathway. We further discovered that 11 key structural genes play key regulatory roles in the changes in the flavonoid contents of tea plants of different plant ages. However, the influence of plant age on amino acids and their derivatives might be cultivar-specific. By characterizing and evaluating the quality-related metabolites of tea cultivars of two different genotypes at different plant ages, we found that whether an old tea plant (40 years old) can produce high-quality tea is related to the genotype of the tea plant.
The local tea plant population resources are rich in genetic variation, which is 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 still unknown. In this study, the genetic diversity and population structure of four main local tea plant populations in Jiangxi Province of China were explored by combining phenotypic characters identification and simple sequence repeats (SSR), and the loci associated with phenotypic characters were screened. The results of genetic diversity analysis of phenotype and SSR were consistent. It was found that the genetic diversity of population species was higher than that of wild species. The order of genetic diversity index of the four tea plant populations was Wuyuan > Fuliang > Suichuan > Ningdu. The single-plants of each population were heterozygotes, and Wuyuan had the highest heterozygosity. The clustering results of phenotypes and SSR on tea plant populations were not completely consistent. SSR could more effectively distinguish tea plant populations. Four tea populations could be clustered into three groups. Further analysis found that the geographical location of tea population distribution would affect its gene exchange. In addition, 9 SSR loci were screened and were significantly associated with 9 phenotypic characters (P < 0.01), and the interpretation rate of phenotypic variation ranged from 6.94–33.90%. These phenotypic characters related to the yield and mechanical harvest of tea varieties.
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