Tree Genetics and Molecular Breeding 2024, Vol.14, No.4, 185-193 http://genbreedpublisher.com/index.php/tgmb 188 estimation, allows for the identification of heritable phenotypes and linked genetic markers, facilitating the discovery of novel genetic targets for crop improvement (Kumar et al., 2024). These phenotypic assessments are crucial for validating gene functions and understanding the biological processes that contribute to desirable traits in loquat. 5 Genetic Transformation in Loquat 5.1 Methods for gene introduction Genetic transformation in loquat (Eriobotrya japonica) involves several methods for introducing new genes into the plant genome. One common approach is the use of Agrobacterium-mediated transformation, which exploits the natural ability of Agrobacterium tumefaciens to transfer DNA to plant cells. This method has been widely used in various Rosaceae species, including loquat, due to its efficiency in stable gene integration (Gisbert et al., 2009a). Another method involves the use of biolistic or particle bombardment techniques, which physically introduce DNA into plant cells by shooting microscopic particles coated with DNA into the plant tissue. This method is particularly useful for species that are recalcitrant to Agrobacterium-mediated transformation (Gisbert et al., 2009a; Zhao, 2024). 5.2 Applications of CRISPR-Cas systems The CRISPR-Cas system has emerged as a powerful tool for precise genome editing in plants, including loquat. This technology allows for targeted modifications of specific genes, enabling the development of loquat varieties with improved traits such as disease resistance, fruit quality, and stress tolerance. The application of CRISPR-Cas in loquat is still in its early stages, but it holds significant promise for accelerating breeding programs and enhancing genetic improvement efforts (Song et al., 2016; Jing et al., 2022). The ability to precisely edit genes involved in key metabolic pathways could lead to breakthroughs in loquat breeding, particularly in enhancing fruit development and ripening processes (Song et al., 2016). 5.3 Challenges and solutions in loquat transformation Transforming loquat presents several challenges, including low transformation efficiency and difficulties in regenerating transformed plants. These challenges are often due to the complex genetic makeup and recalcitrant nature of loquat tissues to in vitro culture conditions (Gisbert et al., 2009a). To overcome these obstacles, researchers are exploring the optimization of transformation protocols, such as improving tissue culture techniques and selecting more responsive explant types. Additionally, the use of advanced molecular tools like CRISPR-Cas systems can help bypass some of the limitations associated with traditional transformation methods by allowing for more precise and efficient gene editing (Song et al., 2016; Jing et al., 2022). Another solution involves the use of polyploidy manipulation, which has shown potential in improving genetic diversity and transformation success rates in loquat breeding programs (Wang et al., 2021). 6 Molecular Markers in Loquat Breeding 6.1 Marker development The development of molecular markers has significantly advanced loquat breeding by providing tools for genetic analysis and cultivar identification. Single nucleotide polymorphism (SNP) markers have been identified from transcriptome sequences of loquat cultivars, offering a high-resolution tool for genetic studies. These SNPs are instrumental in cultivar identification and genetic diversity analyses, which are crucial for marker-assisted selection breeding in loquat (Li et al., 2015). Additionally, random amplified polymorphic DNA (RAPD) markers have been used to fingerprint loquat cultivars, aiding in the management of germplasm resources and the estimation of genetic similarity among cultivars (Vilanova et al., 2004). Furthermore, microsatellite markers, or simple sequence repeats (SSRs), have been developed from loquat genomic libraries, providing a robust method for assessing genetic diversity and facilitating genetic studies (Gisbert et al., 2009b). 6.2 QTL mapping for key traits Quantitative trait loci (QTL) mapping in loquat has been facilitated by the development of genetic linkage maps using AFLP and SSR markers. These maps have been constructed for different loquat cultivars, such as 'Algerie' and ‘Zaozhong-6’, and have been used to map traits like self-incompatibility, which is crucial for breeding
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