International Journal of Horticulture, 2024, Vol.14, No.6, 438-450 http://hortherbpublisher.com/index.php/ijh 447 8 Applications in Breeding and Conservation 8.1 Breeding strategies for dioecious plants Breeding strategies for dioecious plants, such as Eucommia ulmoides, require a nuanced understanding of their sex determination mechanisms. The identification of sex-linked markers is crucial for early sex identification, which can significantly enhance breeding efficiency. For instance, the use of RAPD and SCAR markers has been shown to effectively distinguish between male and female E. ulmoides plants before they reach reproductive maturity, saving both time and resources (Xu et al., 2004). Additionally, the application of ddRAD-seq has identified stable and reproducible sex-linked loci, such as MSL4, which can be used to discriminate male from female seedlings, facilitating rapid breeding practices (Wang et al., 2020). These molecular tools are invaluable for developing superior varieties with desired traits, such as higher α-linolenic acid content, which is economically beneficial (Du et al., 2023). 8.2 Sex determination in conservation programs In conservation programs, understanding the sex determination pathways of dioecious plants is essential for maintaining genetic diversity and ensuring the survival of both male and female populations. The genetic mechanisms underlying sex determination in E. ulmoides, including the role of MADS-box genes and other sex-biased genes, provide insights that can be applied to conservation efforts (Wang and Zhang, 2017; Zhang et al., 2023). By utilizing molecular markers and transcriptome analyses, conservationists can monitor and manage the sex ratios within populations, ensuring that both sexes are adequately represented. This is particularly important for species like E. ulmoides, where the pistillate plants have higher economic value (Xu et al., 2004). Moreover, the identification of sex-determining regions (SDRs) and sex chromosomes in various dioecious plants can inform conservation strategies across different species (Leite Montalvão et al., 2021; Razumova et al., 2023). 8.3 Breeding practices inEucommia ulmoides Eucommia ulmoides, a dioecious tree with significant medicinal and economic value, serves as an excellent case study for breeding practices. The high-quality chromosome-level genome assemblies of both female and male E. ulmoides have provided a valuable resource for understanding sex differentiation and facilitating breeding programs. Transcriptome analyses have identified key genes, such as EuAP3 and EuAG, that regulate sex differentiation, which can be targeted in breeding strategies to develop superior varieties (Du et al., 2023). Additionally, the use of molecular markers, such as the 569 bp SCAR marker specific to pistillate plants, allows for early sex identification, streamlining the breeding process (Xu et al., 2004). The integration of these genetic tools into breeding programs can enhance the production of high-value pistillate plants, contributing to the economic viability of E. ulmoides cultivation (Wang et al., 2020; You et al., 2023; Zhang et al., 2023). 9 Concluding Remarks Research on sex determination pathways in Eucommia ulmoides has yielded significant insights into the genetic and molecular mechanisms underlying sexual differentiation in this dioecious plant. The high-quality chromosome-level genome assemblies for both female and male E. ulmoides have provided a valuable resource for understanding sex differentiation. Key genes such as EuAP3 and EuAG have been identified as crucial regulators of sex differentiation. Additionally, molecular markers like MSL4 and SCARmr have been developed for early sex identification, which is essential for breeding and commercial production. Comparative transcriptome analyses have revealed differentially expressed genes between male and female plants, further elucidating the genetic basis of sexual dimorphism. The findings from these studies have several practical applications in agriculture and industry. The ability to identify the sex of E. ulmoides plants at an early stage using molecular markers can significantly enhance breeding programs by allowing for the selection of desired traits before the plants reach reproductive maturity. This can lead to more efficient cultivation practices and improved yields. Additionally, understanding the genetic mechanisms of sex differentiation can aid in the development of superior varieties with enhanced medicinal and
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