Journal of Tea Science Research, 2024, Vol.14, No.4, 225-237 http://hortherbpublisher.com/index.php/jtsr 233 genetic diversity within tea plant populations to prevent the emergence of new pathogen strains that could overcome the resistance. The genomic differentiation observed in various plant species, such as the two-spotted spider mite, highlights the importance of maintaining genetic diversity to ensure the adaptability and resilience of crops (Xue et al., 2023). Moreover, the genomic studies on tea plants have revealed significant signatures of domestication and modern breeding, emphasizing the need to balance these efforts with the conservation of genetic diversity to support ongoing adaptation and resistance (Xia et al., 2020) (Figure 3). By integrating genomic research with traditional breeding practices, it is possible to develop tea plant varieties that are both resistant to diseases and genetically diverse, ensuring the sustainability and ecological balance of tea farming. Figure 3 Population Structure of Tea Plants and Gene Flow (Adopted from Xia et al., 2020) Image caption: (A) Sample collections. (B) Phylogenetic relationships of all the accessions. The accessions from Laos, Iran, Azerbaijan, and Russia are indicated in the tree by colored stars. Hollow circle represents landrace accessions. (C) Population structure of the tea plant collections. The dashed rectangle represents the best inferred K value with lowest cross-validation errors. (D) Principal component analyses (PCA) of the collected populations. (E) LD decay in all collected tea plant accessions and different subpopulations. (F) Nucleotide diversity (θπ) and genetic differentiation (Fst) within different tea plant subpopulations calculated using the sliding-window approach (1-Mb windows with 1-Mb steps). The circle size represents the mean value of θπ in each subpopulation. The numbers marked between each subpopulation indicate the Weir and Cockerham weighted Fst values. (G) Tajima's D estimation in tea plant subpopulations. Only the sites in genic regions were included in the calculations. (H) Population splits and migrations between the ancient, landrace, elite, and wild tea plant accessions. (I) Population splits and migrations between accessions from different countries. (J) Population splits and migrations among accessions from different provinces of China. The provinces with fewer than one accession were excluded.In (H) to (J), the line between each branch indicates possible migration events. Color scale indicates the weight of migration edges. Red color indicates strong migration weight and yellow indicates low or moderate weight. The drift parameter is a relative temporal measure, and the scale bar indicates 10 times the average SE of the relatedness among populations based on the variance–covariance matrix of allele frequencies (Adopted from Xia et al., 2020)
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