Genomics and Applied Biology 2024, Vol.15, No.6, 320-332 http://bioscipublisher.com/index.php/gab 324 yield of white-fleshed dragon fruit to develop new varieties with superior comprehensive traits. In yellow pitaya (Selenicereus megalanthus), hybrid breeding has also yielded positive results. Through hybridization, breeders have enhanced its adaptability and fruit quality, such as improving sweetness and appearance to better meet market demand (Morillo-Coronado et al., 2021). Although hybrid breeding as a traditional method requires substantial time and labor, it plays a significant role in maintaining the diversity of Cactaceae plants and improving their traits. 4.2 Selection breeding Selection breeding is a method of improving varieties by selecting naturally occurring variants and reproducing them over multiple generations. In the breeding of cactus (Opuntia spp.), selection breeding is widely used to select individuals with higher cold resistance or better drought tolerance (De Jesus et al., 2023). As an important plant in desert areas, cactus has enhanced its survival ability in harsh environments and increased its nutritional value as a forage plant through selection breeding. After multiple generations of selection, the cold and drought tolerance of cactus has significantly improved, adapting to more diverse cultivation conditions. As an ornamental Cactaceae plant, queen of the night (Epiphyllum oxypetalum) is primarily bred for improving flower shape and color (Sampaio and De Almeida, 2021). Breeders select individuals with higher flowering frequency and more attractive flower colors to enhance the plant's appeal in the horticultural market. This selection breeding method effectively improves the traits of ornamental plants to meet the aesthetic needs of gardening enthusiasts. 4.3 Limitations of traditional methods Although hybrid and selection breeding have played important roles in the improvement of Cactaceae plants, traditional methods also have certain limitations. On the one hand, breeding cycles are long and unpredictable. Cactaceae plants grow relatively slowly, and the breeding process may take several years or even decades, making it challenging for traditional breeding methods to respond quickly to market changes and pest threats (Yusop et al., 2020). For example, the hybrid breeding of dragon fruit requires several generations of backcrossing and selection to stabilize genetic traits, limiting the speed of new variety development (Tel-Zur, 2022). Furthermore, traditional methods rely on natural variation and cannot precisely control target traits. In selection breeding, breeders often need to screen a large number of individuals to find variants that meet the target traits. This randomness not only consumes human and material resources but also makes it difficult to ensure that all desirable traits are stably passed on. Additionally, hybrid breeding may result in hybrid disadvantage, where some hybrid offspring perform worse than the parents, which is especially evident in breeding yellow pitaya and other species (Morillo-Coronado et al., 2021; Tel-Zur, 2022). 5 Biotechnological Advances in Cactaceae Breeding 5.1 Construction of high-density genetic maps based on molecular markers High-density genetic maps are indispensable tools in modern plant breeding, enabling precise localization of genes associated with target traits and assisting breeders in making efficient selections. In Cactaceae plants, genome-wide resequencing (WGrS) technology has facilitated the development of numerous single nucleotide polymorphism (SNP) markers and the construction of high-resolution genetic maps. For example, in Hylocereus undatus, high-throughput sequencing identified 6,434 polymorphic SNP markers distributed across 11 linkage groups, corresponding to the chromosome number of dragon fruit. The total map length reached 14 128.7 cM, with an average marker interval of 2.2 cM, providing a reference for gene mapping of traits such as disease resistance, drought tolerance, and fruit quality (Wu et al., 2021). Another study employed a hybrid assembly method combining long-read sequencing (PacBio) with short-read data to reassemble the genome of Carnegiae gigantea, significantly improving genome contiguity and accuracy (Copetti et al., 2023). This advancement lays the foundation for further genetic research on Cactaceae plants. Additionally, the integration of linkage and association analyses allows breeders to identify quantitative trait loci
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