Medicinal Plant Research 2025, Vol.15, No.3, 99-109 http://hortherbpublisher.com/index.php/mpr 104 2019). Multiple regression models, including the Mixed linear Model MLM, are also used to identify marker-trait associations while controlling for population structure and kinship (Sun et al., 2019). These models are particularly effective in genome-wide association studies (GWAS), and have been used to locate gene loci related to important economic traits of Sapindus and other crops (Bahjat et al., 2025; Liu et al., 2025). 5.2 Association between key traits and genetic loci Association analysis using ISSR and SSR markers has identified specific loci associated with the fruit size and related economic traits of Sapindus. For example, 18 ISSR loci were identified to be associated with 13 fruit traits, including kernel oil content, fruit saponin content and fruit quality (Sun et al., 2019). These marker-trait associations provide genetic evidence for the selection of superior germplasms and marker-assisted breeding, which helps to improve target traits more efficiently. Genetic STRUCTURE analysis (STRUCTURE, principal component analysis PCA, etc.), revealed significant differentiation within different species and populations of the genus Sapindus (Sun et al., 2019; Liu et al., 2022). This group structure can affect the performance of key economic traits, so it must be taken into account when conducting association studies to avoid confounding effects. For instance, GWAS of Sapindus has identified candidate genes related to saponin biosynthesis and fatty acid quality of seed kernel, providing support for the genetic improvement of these traits (Liu et al., 2025). Population stratification, can also explain why certain marker-trait associations are only more obvious in specific subpopulations. 5.3 Implications for breeding and trait improvement The integration of phenotypic data and genotype data is conducive to the efficient screening of germplasm with superior character-genotype combinations. By establishing a core germplasm bank with both high genetic diversity and superior trait expression, the protection and utilization of superior germplasm can be promoted, and rich materials can be provided for the Sapindus breeding program (Sun et al., 2019; Liu et al., 2022). This method can accelerate the screening of breeding materials that perform excellently in oil content, saponin content and other economic traits. The identification of genetic markers associated with superior phenotypes (e.g., high oil content or high saponin content), provides conditions for the implementation of marker-assisted selection (MAS) strategies. This not only accelerates the breeding process, but enhances the potential of genetic improvement of Sapindus by targeting specific sites for selection (Sun et al., 2019; Bahjat et al., 2025; Liu et al., 2025). The combination of GWAS and core germplasm bank construction provides a robust framework for analyzing the genetic basis of complex traits and, applying this knowledge to actual breeding. 6 Case Studies on Sapindus Germplasm Correlation Analysis 6.1 Genetic diversity and adaptive evolution of Sapindus plants in China Sapindus is an important economic forest tree species in China, and has application value in biodiesel, biomedicine, biochemistry and forestry. To understand the genetic basis of its genomic evolution and important bioeconomic traits, Liu et al. (2025) conducted whole-genome resequencing on 100 core germplasm resources of Sapindus from different geographical sources in China, revealing the genetic structure and evolutionary history of this genus of plants. The results show that Sapindus is divided into six different populations in China. They are S. delavayi, S. rarak, North group, Southeast group, Guizhou group and hybrids group, respectively. These populations vary in species and geographical distribution (Figure 2). Phylogenetic analysis indicates that, the southeast population might be the ancestral population of Sapindus in China. Subsequent natural selection, gene flow and bottleneck effects led to the emergence of other populations. It also found that different Sapindus populations show differences in environmental adaptation. For instance, the population in Guizhou might have undergone the selection of drought and low-temperature stress, while the population in the north might have acquired cold resistance. GWAS revealed several homologues of fatty acid
RkJQdWJsaXNoZXIy MjQ4ODYzNA==