Tree Genetics and Molecular Breeding 2024, Vol.14, No.4, 185-193 http://genbreedpublisher.com/index.php/tgmb 189 programs (Gisbert et al., 2009b). The transferability of SSR markers from related species in the Rosaceae family, such as apple and pear, has enhanced the mapping efforts in loquat, allowing for the identification of key genomic regions associated with important agronomic traits (Gisbert et al., 2009b). 6.3 Marker-assisted selection Marker-assisted selection (MAS) in loquat breeding leverages molecular markers to accelerate the selection of desirable traits. The use of SNPs and SSRs has enabled the identification of genetic markers linked to traits such as fruit quality, size, and flesh color, which are critical for improving loquat cultivars (Figure 1) (Li et al., 2015; Wang et al., 2021). The integration of these markers into breeding programs allows for the efficient selection of superior genotypes, reducing the time and resources required for traditional breeding methods. The development of high-density genetic linkage maps and the identification of QTLs further support the application of MAS in loquat breeding, providing a framework for the systematic improvement of this fruit species (Gisbert et al., 2009b). Figure 1 Schematic flew diagram of qPCR genotyping. DNA of loquat leaves was extracted for qPCR genotyping. qPCR genotyping was amplified by allele-specific primers, and the relative copy number of each allele was calculated by 2−ΔΔCt method, and then parameter b [b = a1/(a1 + a2); 0 ≤ b ≤ 1] was calculated to determine the genotype of the tested material. We can select tetraploids of the appropriate genotype as backbone parents according to the breeding goal. More genetic information was obtained by MAS and ploidy analysis (Adopted from Wang et al., 2021) 7 Case Study Sharing 7.1 Genetic improvement for disease resistance The genetic improvement of loquat for disease resistance has been significantly advanced through the study of genetic diversity and the identification of key genes. Research has shown that wild loquat populations, particularly those from Guizhou Province in China, offer a rich genetic resource for breeding disease-resistant varieties. These populations exhibit a high level of genetic diversity, which is crucial for developing cultivars with enhanced resistance to diseases (Wu et al., 2014). Additionally, the heterosis observed in triploid loquats, which includes improved disease resistance, suggests that manipulating ploidy levels can be an effective strategy for enhancing disease resistance in loquat breeding programs (Liu et al., 2019). 7.2 Enhancing fruit quality traits Enhancing fruit quality traits in loquat has been a major focus of genetic improvement efforts. The identification of differentially expressed genes (DEGs) involved in carbohydrate metabolism, hormone signaling, and cell-wall
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