International Journal of Horticulture, 2024, Vol.14, No.6, 438-450 http://hortherbpublisher.com/index.php/ijh 442 ddRA has been used to identify an ideal sex-linked site, MSL4, which can distinguish male and female Eucommia seedlings (Wang et al., 2020). These markers enhance the precision of sex identification and provide a robust method for genetic studies and breeding efforts aimed at improving the species. Amplified Fragment Length Polymorphism (AFLP) and SCAR markers have also been employed for early sexual identification in E. ulmoides. These molecular markers offer reliable and efficient means to determine the sex of plants, which is crucial for optimizing breeding strategies and ensuring the production of high-quality plant material (Wang et al., 2011; Razumova et al., 2023). Figure 2 The use of dioecious plants depending on its sex (Adopted from Razumova et al., 2023) 4 Comparative Analysis of Sex Determination Pathways 4.1 Common genetic markers across dioecious species Sex determination in dioecious plants often involves conserved sex-linked genes that play crucial roles across different species. For instance, in Eucommia ulmoides, genes such as EuAP3 and EuAGhave been identified as key regulators of sex differentiation (Du et al., 2023). Similarly, MADS-box genes, particularly B-class genes, have been implicated in the sex determination pathways of various dioecious plants, suggesting a convergent mechanism where distinct sex-determining genes regulate these floral genes (Mai et al., 2022; Zhang et al., 2022). Additionally, the presence of sex-linked molecular markers, such as the MSL4 locus in E. ulmoides, further underscores the conservation of sex-linked genes across dioecious species (Wang et al., 2020). Marker-assisted selection (MAS) is a powerful tool in breeding programs for dioecious plants. In E. ulmoides, the identification of sex-linked markers like MSL4 enables early sex identification, which is crucial for breeding and commercial production (Wang et al., 2020). The use of molecular markers has also shown advantages in other dioecious crops, such as papaya, whose molecular marker W11 can identify male/hermaphrodite sex in papaya seedling populations with 100% accuracy (Thanh et al., 2024). These markers help to verify sex before phenotypic expression, thus simplifying the breeding process (Heikrujam et al., 2014). 4.2 Differences in sex determination pathways between species While there are conserved elements in sex determination pathways, significant divergence exists between species. For example, the sex determination system in E. ulmoides involves specific MADS-box transcription factors that
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