Polyphenolic Diversity and Genotypic Analysis of Tea Plants with Different Parents and Their F₁ Progeny

To investigate the genetic diversity of polyphenolic compounds in tea plant parents and their F₁ progeny, and to elucidate variations in polyphenolic composition among different hybrid combinations, as well as the population structure and genetic relationships of their genotypes, thereby providing support for parental selection and quality improvement in tea plant breeding.

Twelve parental tea plant samples and 87 F₁ progenies were used as experimental materials. Twelve polyphenolic polyphenolic indices were determined during 2024-2025, and multidimensional evaluations were performed using methods including systematic clustering, hybrid combination difference analysis, and population structure analysis.

The coefficients of variation for polyphenols varied between 14.50% and 89.34%. Notably, Strictinin (STR), 1,2,6-trigalloylglucose (1,2,6-TGG), epigallocatechin 3-O-(3-O-methyl) gallate (EGCG3″Me), gallocatechin gallate (GCG), and catechin gallate (CG) exhibited high coefficients of variation of 89.34%, 66.45%, 64.22%, 59.34%, and 58.12%, respectively. The Shannon Wiener indices ranged from 1.86 to 4.57, with the highest indices observed for epigallocatechin gallate (EGCG), trigalloyl quinuclidinic acid (TH), and gallocatechin gallate (GCG), which were 4.57, 4.45, and 4.23, respectively. In the differential analysis of polyphenolic compounds, the F₁ progeny resulting from the cross between HJC and AH demonstrated higher levels of catechin gallate (CG) and trigalloylquinic acid (TH) compared to both parental lines. While the levels of epicatechin 3-O- (3-O-methyl) gallate (EGCG3 "Me) were consistent with those of the parents. Using polyphenol cluster analysis, the 99 samples were grouped into five clusters: Group Ⅰ contained 49 samples, Group Ⅱ contained 26 samples, Group Ⅲ contained 20 samples, and Group Ⅳ and Ⅴ each contained 2 samples. Analysis of population structure based on SNP loci classified the 12 parental lines and 87 F₁ offspring into three groups: Group Ⅰ comprised 46 accessions, Group Ⅱ comprised 31 accessions, and Group Ⅲ comprised 22 accessions. Notably, Group Ⅰ consisted entirely of the parental line HJC and its F₁ offspring sired by this male parent. The levels of genetic diversity among the three groups were similar. The results of the kinship analysis show that the F₁ offspring are more closely related to their paternal parent (♂).

The 99 tea plant accessions exhibited rich genetic diversity. Biochemical component-based clustering divided the 99 tea plant accessions into five groups. CG and TH may exhibit overdominant heterosis, while EGCG3"Me exhibited a largely consistent accumulation pattern between the parental lines and their F₁ progeny, with no evident transgressive segregation or pronounced non-additive effects. Biochemical profiling grouped the 99 tea accessions into five groups, while SNP-based population structure identified three genetically similar subpopulations. Genome-wide analyses also revealed that, in the majority of crosses, F₁ progeny exhibited greater similarity to the paternal parent.