Tree Genetics and Molecular Breeding 2024, Vol.14, No.5, 239-246 http://genbreedpublisher.com/index.php/tgmb 242 4.3 Stable vs. transient transformation In the context of genetic transformation, stable and transient transformations are two distinct approaches. Stable transformation involves the integration of foreign DNA into the host genome, resulting in heritable genetic changes. This method is crucial for developing new pitaya varieties with permanent trait enhancements. On the other hand, transient transformation allows for temporary expression of introduced genes without integration into the genome, which is useful for functional studies and rapid trait assessment (Figure 2) (Shah et al., 2023). The choice between stable and transient transformation depends on the specific objectives of the breeding program and the desired outcomes in terms of trait stability and expression. Figure 2 Fruit peel, pulp, and scale and areoles phenotype found in different Hylocereus species. (A) H. undatus; (B) H. polyrhizus; (C, D) hybridization offspring of H. polyrhizus and H. undatus; (E) H. megalanthus; (F) Golden pitaya (yellow clone of H. undatus), (G) H. stenopterus (Adopted from Shah et al., 2023) 5 Genomic Selection and Prediction 5.1 Principles of genomic selection Genomic selection (GS) is a modern breeding approach that utilizes genome-wide markers to predict the genetic value of individuals in a breeding population. This method leverages the entire genome to make predictions about complex traits, which is particularly useful for crops like pitaya where traditional phenotypic selection can be challenging due to long generation times and complex trait inheritance (Chen et al., 2021; Tel-Zur, 2022). The principle of GS is to use a training population with known phenotypes and genotypes to develop a prediction model, which can then be applied to a selection population to predict their genetic potential without phenotypic evaluation (Figure 3) (Zheng et al., 2020; Hua et al., 2021; Wu et al., 2021; Xu and Wang, 2024). Figure 3 Relative expression patterns of 11 candidate reference genes across fruit samples of red pitaya, based on the RNA-seq data. The relative expression level of each candidate was represented by the log10 (Adopted from Zheng et al., 2020)
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