Medicinal Plant Research 2025, Vol.15, No.3, 99-109 http://hortherbpublisher.com/index.php/mpr 101 international studies have jointly enhanced the understanding of the genetic structure, ecological adaptability and climate change impact of Sapindus (Xue et al., 2022; Liu et al., 2025). The establishment of the core germplasm bank and the identification of reverse resistance genotypes are important achievements among them (Sun et al., 2019; Liu et al., 2022). Despite the progress made, there are still challenges in the comprehensive collection of wild germplasm, long-term preservation in the context of climate change, and the integration of phenotypic and genotype data in breeding (Liu et al., 2025). Insufficient research on some species and regions, as well as weak conservation strategies, remain gaps in this field (Liu et al., 2021; 2022). 3 Investigation and Analysis of Phenotypic Traits 3.1 Determination methods for phenotypic indicators The morphological traits of Sapindus and its related species are usually evaluated through standardized field measurement methods. During the mature stage, the height and crown width of the plants are measured using a tape measure or a laser rangefinder, while the growth rate is calculated by continuously tracking the annual increase in height or diameter over many years. These traits are important indicators for evaluating the adaptability, growth vigor and structural diversity of germplasm resources, and are often incorporated into comprehensive agronomic-morphological surveys (Sun et al., 2018; Liu et al., 2022). Economic traits are particularly crucial for breeding and commercial utilization. The size of fruits is usually measured by dimensions, including weight, length, width, and thickness, using calipers and electronic scales. The color of the fruit can be evaluated by visual inspection with the naked eye or a colorimeter, providing a basis for market selection and processing utilization. Saponin content, as one of the core economic traits, is generally quantified through chemical extraction and chromatographic analysis, like HPLC, to determine the concentration of its active components (Figure 1). These methods can identify excellent materials with high oil content or high saponin yield, providing support for directed breeding (Sun et al., 2018; 2019; Zhou et al., 2024). 3.2 Statistical analysis of phenotypic data Phenotypic data are typically quantified for diversity among and within different materials through range and coefficient of variation (CV) analysis. Previous studies have shown that there are variations in both morphological and economic traits, and the CV values of fruit size, saponin content and kernel oil content are relatively high. This diversity reflects the great potential of selection and improvement in breeding (Sun et al., 2019; Liu et al., 2022). For instance, the economic trait variations of S. mukorossi and S. rarak, were greater than those of S. delavayi (Liu et al., 2022). Principal component analysis (PCA) and cluster analysis, are important methods for identifying the sources of major phenotypic variations and grouping germplasm materials with similar trait combinations. These multivariate statistical techniques can reveal the association patterns among traits, and promote the screening of superior germplasms. For example, PCA can identify materials with high oil content or high saponin content, while cluster analysis can group materials based on comprehensive traits, improving the efficiency of resource management and breeding (Sun et al., 2018; 2019). Correlation analysis further revealed the trade-off relationships among traits, such as the possibility, that an increase in saponin content might lead to a decrease in kernel oil content (Liu et al., 2022). 3.3 Relationship between phenotypic traits and environmental factors Environmental factors (e.g., temperature, altitude and soil type, etc.) have a significant impact on the phenotypic traits of Sapindus. For example, under conditions of moisture, warmth and low altitude, the morphology of leaves and fruits is usually larger, longer and thicker (Wang et al., 2020). The weight and content of kernels are positively correlated with altitude and negatively correlated with longitude. However, an increase in sunshine duration may reduce the weight of seeds and the thickness of seed shells (Sun et al., 2018; Wang et al., 2020). These results emphasize that to achieve the best trait performance, it is necessary to match germplasm materials with suitable environments.
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