Plant Gene and Trait 2024, Vol.15, No.6, 285-294 http://genbreedpublisher.com/index.php/pgt 291 6.3 Identification of promising markers Promising markers identified in the studies include the 247 bp SCAR marker for male plants and the 569 bp SCAR marker for female plants. These markers are particularly valuable because they allow for early sex identification, which can significantly reduce the time and resources required for breeding programs. The identification of these markers represents a significant advancement in the genetic study and practical breeding of Eucommia ulmoides (Xu et al., 2004; Wang et al., 2011). 6.4 Statistical relationships between markers and sex phenotypes The statistical relationships between the identified markers and sex phenotypes were robust. The male-specific 247 bp SCAR marker and the female-specific 569 bp SCAR marker showed consistent segregation patterns that aligned with the sex phenotypes of the plants. This consistency underscores the reliability of these markers in practical applications, such as breeding and early selection of desired plant sexes (Xu et al., 2004; Wang et al., 2011; Liu et al., 2020). Furthermore, the high-density genetic maps constructed using SNP markers provided additional insights into the genetic architecture of Eucommia ulmoides, although these maps were more focused on growth traits rather than sex determination (Li et al., 2014; Liu et al., 2022). In summary, the identification and validation of sex-specific markers in Eucommia ulmoides have significant implications for breeding programs. These markers not only facilitate early sex identification but also contribute to a deeper understanding of the genetic basis of sex determination in this economically important species. 7 Discussion on the Role of Sex-Specific Markers inEucommia ulmoides Improvement 7.1 Impact of identified markers on understanding sex determination The identification of sex-specific markers in Eucommia ulmoides has significantly advanced our understanding of sex determination in this dioecious species. For instance, the discovery of a male-specific AFLP marker and its conversion into a SCAR marker allows for early sexual identification, which is crucial for breeding programs (Wang et al., 2011). Similarly, the identification of the MSL4 locus through ddRAD-seq provides a reliable marker for distinguishing male from female seedlings, further supporting the genetic basis of sex determination in E. ulmoides (Wang et al., 2020). Additionally, transcriptome analyses have revealed differentially expressed genes (DEGs) between male and female plants, including genes related to floral organ identity and sex differentiation, such as the APETALA3-like gene (Wang and Zhang, 2017; Du et al., 2023). These findings collectively enhance our understanding of the genetic mechanisms underlying sex determination in E. ulmoides. 7.2 Comparison with other dioecious plants When compared to other dioecious plants, the identification of sex-specific markers in E. ulmoides shows both similarities and unique aspects. In many dioecious species, sex determination is often linked to specific genetic markers or regions. For example, in Silene latifolia, sex determination is associated with sex chromosomes, and specific markers have been identified for early sex identification (Wang et al., 2011; Wang et al., 2020). In E. ulmoides, the use of AFLP, SCAR, and ddRAD markers parallels the approaches used in other species, but the specific markers identified, such as the 247 bp SCAR marker and the MSL4 locus, are unique to E. ulmoides. This highlights the species-specific nature of sex determination mechanisms and the importance of tailored approaches for each species. 7.3 Conservation and commercial implications The identification of sex-specific markers in E. ulmoides has significant conservation and commercial implications. Early sex identification using these markers can optimize breeding programs by ensuring the selection of desired sexes, particularly the economically valuable pistillate plants (Xu et al., 2004; Meng et al., 2023). This can lead to more efficient cultivation and higher yields of medicinal and industrial products derived fromE. ulmoides. Additionally, understanding the genetic basis of sex determination can aid in the conservation of this species by facilitating the management of genetic diversity and the maintenance of balanced sex ratios in natural populations (Wang et al., 2018). The ability to distinguish between male and female plants at an early stage can also enhance the sustainable use and commercial production of E. ulmoides (Wang et al., 2020; You et al., 2023).
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