Tree Genetics and Molecular Breeding 2025, Vol.15, No.1, 9-17 http://genbreedpublisher.com/index.php/tgmb 12 3.4 Population structure and evolutionary analysis Sun et al. (2018b) found that PCA can represent complex genetic data in the form of images, allowing the genetic differences between different populations to be visually observed, and also analyze whether these differences are related to ecological and environmental factors. Liu et al. (2022) indicated that the Fst value is used to measure the degree of genetic differentiation among different populations, and the higher the value, the greater the difference between populations. ISSR markers are widely used in the genetic analysis of Sapindus plants. They can effectively distinguish the genetic structure among different species and populations and reveal obvious genotype differences and evolutionary directions (Sun et al., 2018a; Sun et al., 2018b). Xue et al. (2022) demonstrated that these research results are helpful for understanding the evolutionary process and environmental adaptability of Sapindus mukorossi, as well as enabling breeders to identify superior germplasms with greater utilization value. 4 Mining and Functional Analysis of Superior Genes in Sapindus mukorossi 4.1 Functional genes related to saponin content The chromosome-level genome of Sapindus mukorossi has been assembled, providing a complete reference framework for identifying genes related to saponin synthesis. In the 2022 study by Xue et al., genomic data revealed that the Sapindus mukorossi contains many genes related to plant defense, growth and development, and these genes are very likely to include the key parts that control saponin synthesis. Liu et al. (2021a) and Xue et al. (2022) conducted gene expression analysis on germplasm with high saponin content using RNA-Seq technology and identified the core genes that might regulate saponin synthesis. This method is beneficial for a better understanding of the genetic basis of saponin content and also provides technical support for screening high-quality germplasm with higher saponin yield. 4.2 Genes related to stress resistance Identifying genes related to drought resistance, salt tolerance, heat tolerance and other stress resistance is crucial for breeding Sapindus mukorossi varieties with strong adaptability. Xue et al. (2022) have identified a number of candidate genes that may be involved in plant defense responses through genome-wide analysis. These genes may be crucial in enhancing plants' resistance to adverse environments. Studies have screened and verified the expression of candidate genes in Sapindus mukorossi germplasm with strong stress resistance, and found that these genes do have potential in enhancing the tolerance of plants to external environmental stress, highlighting the importance of genetic diversity and also indicating the key role of certain specific genes in adapting to different adverse conditions (Mahar et al., 2011; Ba, 2014; Sun et al., 2018b). 4.3 Validation technologies for functional genes RT-qPCR can quantify the expression of a certain target gene and verify whether it is really related to important economic traits such as saponin content or stress resistance. Sun et al. (2018a) and Xue et al. (2022) argued that these target genes are often preliminarily screened out in genome-wide analysis or selective dissection studies, and RT-qPCR is used to confirm whether these genes do play a role in key traits. Mahar et al. (2011a) and Xue et al. (2022) found that gene editing technology can precisely modify specific loci in the genome and knockout a gene involved in saponin synthesis or stress resistance pathways, thereby directly verifying its role in plant traits. The combined use of gene editing technology and traditional breeding methods can accelerate the breeding process of high-yield and stress-resistant Sapindus mukorossi varieties and enhance their commercial utilization and environmental adaptability. 4.4 Candidate gene association analysis Candidate gene association analysis is to obtain genotype data through molecular markers, and then conduct association analysis on these data with phenotypic traits such as saponin content and stress resistance in fruits. Sun et al. (2018a) and Liu et al. (2021a) demonstrated that in this way, genetic loci related to key economic traits can be identified, which is beneficial for locating the genes that play a role and providing a genetic basis for breeding work.
RkJQdWJsaXNoZXIy MjQ4ODYzNA==