Plant Gene and Trait 2024, Vol.15, No.5, 243-252 http://genbreedpublisher.com/index.php/pgt 245 genes that could be targeted for enhancing disease resistance. Additionally, the role of miRNAs in stress response processes has been highlighted, with several miRNAs identified as potential regulators of genes involved in disease resistance (Wang et al., 2016; Ye et al., 2019). By leveraging these genetic insights, it is possible to develop transgenic E. ulmoides varieties with enhanced resistance to pests and diseases, thereby reducing the reliance on chemical pesticides and improving overall plantation health. Figure 1 a) Somatic chromosome number of the haploids (2n=x =17); b) Ploidy levels obtained from 3-week-old first leaf samples from haploid plants by flow cytometric analysis; c) Ploidy levels obtained from 3-week-old first leaf samples from a mixture of haploid and diploid plants by flow cytometric analysis; d) A haploid plant (left) and diploid plant (right) of E. ulmoides (Adopted from Li et al., 2020) 3.3 Growth and biomass: modifications aimed at increasing growth rate and biomass production Increasing the growth rate and biomass production of E. ulmoides is essential for maximizing rubber yield and other industrial applications. Studies have shown that the application of growth regulators can significantly enhance biomass yield, tree height, and leaf size, which are directly correlated with increased rubber production. Researchers have utilized a high temperature-induced spore chromosome doubling method to breed new triploid varieties of Eucommia ulmoides with significant advantages such as rapid growth, gigantic leaves, and high content of effective components. These triploid Eucommia varieties have demonstrated the potential to provide excellent and low-cost raw materials for the development of rubber industry, pharmaceutical industry, and feed additive industry (Li et al., 2016). Furthermore, the phenotypic trait analysis of different E. ulmoides clones has revealed that both genotype and environmental factors play significant roles in growth traits, suggesting that selective breeding and optimized cultivation practices can further improve growth and biomass production (Deng et al., 2022). These findings provide a comprehensive framework for developing high-yielding E. ulmoides varieties through both genetic and agronomic interventions. 3.4 Secondary metabolites: improvement of medicinal and other valuable compounds Eucommia ulmoides is a valuable medicinal plant containing various bioactive secondary metabolites like iridoids, lignans, phenolics, and terpenoids. These compounds have demonstrated anti-oxidative, anti-inflammatory, anti-cancer, and other pharmacological activities beneficial for human health. E. ulmoides is not only valued for its rubber production but also for its medicinal properties, primarily due to the presence of secondary metabolites such as chlorogenic acid. The high-quality genome assembly has identified key enzymes involved in the chlorogenic acid biosynthesis pathway, which are predominantly expressed in the leaves. This provides a genetic basis for enhancing the production of chlorogenic acid and other valuable secondary metabolites through targeted genetic modifications. Meanwhile, studies have shown that treatment with different growth regulators and trace elements can significantly increase the content of secondary metabolites in Eucommia ulmoides. Additionally, the phenotypic trait analysis has shown that environmental factors such as annual mean temperature and sunshine duration significantly affect the content of secondary metabolites, indicating that optimized cultivation practices can also play a crucial role in improving the medicinal value of E. ulmoides (Deng et al., 2022). 4 Molecular Tools and Techniques Used in Transgenic Development 4.1 Gene editing technologies Gene editing technologies have revolutionized the field of plant biotechnology, enabling precise modifications to the genome of Eucommia ulmoides to enhance its industrial traits. One of the key advancements in this area is the
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