Tree Genetics and Molecular Breeding 2024, Vol.14, No.6, 286-294 http://genbreedpublisher.com/index.php/tgmb 287 et al., 2022). The genetic diversity within loquat is notable, with wild loquats exhibiting higher levels of genetic variation compared to cultivated varieties. This diversity is crucial for understanding the domestication process and for breeding purposes (Wang and Paterson, 2021; Zhao, 2024). Studies have shown that loquat underwent a two-staged domestication process, initially in West-northern Hubei province and later refined in other regions of China, which has resulted in a rich genetic pool. The genetic diversity among loquat accessions has been further explored using microsatellite markers, revealing significant variation that is geographically structured (Blasco et al., 2014). 2.2 Current status of genomic resources in loquat The genomic resources for loquat have advanced significantly with the development of high-quality genome assemblies. The first chromosome-level genome assembly of wild loquat has been completed, providing a comprehensive resource with over 45 000 predicted protein-coding genes. This assembly has facilitated the identification of key genes involved in fruit quality and development, which are essential for molecular breeding efforts. Additionally, the development of genetic maps using AFLP and SSR markers has provided a framework for further genetic studies and breeding programs (Gisbert et al., 2009; Manghwar et al., 2019). The availability of genic SNP markers has also enhanced the ability to conduct genetic diversity analyses and marker-assisted selection in loquat (Li et al., 2015). 2.3 Comparison with genomic efforts in related species Comparative genomics has revealed that loquat shares a close evolutionary relationship with other Rosaceae species, such as apple and pear, with a divergence time of approximately 6.76 million years ago (Figure 1) (Jiang et al., 2020). The genomic efforts in loquat have paralleled those in related species, with similar approaches being used to map genetic traits and understand self-incompatibility mechanisms (Carrera et al., 2009; Gisbert et al., 2009). The transferability of SSR markers from apple and pear to loquat has been demonstrated, highlighting the potential for cross-species genomic studies within the Rosaceae family. Moreover, the identification of S-RNases in loquat has provided insights into the self-incompatibility systems that are common across Pyrinae species, further aligning loquat genomic research with that of its relatives (Wang et al., 2017). Figure 1 Picture of a loquat variety, Seventh Star (Eriobotrya japonica) (Adopted from Jiang et al., 2020) 3 Genome Mapping in Loquat 3.1 Early efforts and conventional mapping approaches Early efforts in loquat genome mapping primarily relied on conventional techniques such as quantitative trait locus (QTL) mapping and the use of simple sequence repeat (SSR) markers. These methods were instrumental in identifying genetic markers associated with key traits like fruit weight and flesh color. For instance, QTL mapping has been used to identify loci associated with fruit weight, providing a foundational understanding of the genetic basis of this trait in loquat (Yuan et al., 2020; Peng et al., 2022b). Additionally, SSR markers have been employed to study genetic diversity and relationships among loquat varieties, which are crucial for breeding programs (Wang et al., 2021).
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