International Journal of Horticulture, 2024, Vol.14, No.6, 414-425 http://hortherbpublisher.com/index.php/ijh 417 A specific case study of hybrid breeding involves the improvement of red-skinned red-fleshed and yellow-skinned white-fleshed dragon fruit varieties. The nutritional analysis of red-purple and white-fleshed pitaya species grown in Turkey provides insights into the biochemical differences between these varieties, with red-fleshed fruits showing higher antioxidant capacity and phenolic content compared to white-fleshed ones (Attar et al., 2022). This information is valuable for hybrid breeding programs aiming to combine the high nutritional value of red-fleshed varieties with the desirable traits of other varieties. Furthermore, the study on dragon fruit cultivation in India mentions the popularity and commercial potential of red-fleshed and white-fleshed pitaya, underscoring the economic benefits of developing superior hybrids (Perween et al., 2018). 3.2 Mutation breeding Mutation breeding involves the use of physical or chemical mutagens to induce genetic variations, which can lead to the development of new dragon fruit varieties with desirable traits. This technique has been employed to introduce novel characteristics that are not present in the existing gene pool. For example, the study on dragon fruit cultivars in Puerto Rico demonstrates significant variability in fruit yield and quality among different cultivars, suggesting that mutation breeding could further enhance these traits by creating new genetic variations (Goenaga et al., 2020). Additionally, the transcriptome analysis of pitahaya reveals numerous differentially expressed genes, indicating the potential for mutation breeding to target specific genes associated with stress tolerance and other beneficial traits (Oltehua-Lopez et al., 2023). An example of mutation breeding is the development of disease-resistant dragon fruit varieties through radiation-induced mutation. This method involves exposing plant tissues to radiation to induce mutations that may confer resistance to diseases. The study on the nutritional analysis of pitaya species in Turkey highlights the importance of disease resistance in maintaining fruit quality and yield, as healthier plants are more likely to produce high-quality fruits (Attar et al., 2022). Moreover, the transcriptome analysis of pitahaya identifies genes related to hormone-mediated signaling pathways, which are known to play a role in plant defense mechanisms. By targeting these pathways, radiation-induced mutation can potentially enhance disease resistance in dragon fruit varieties (Oltehua-Lopez et al., 2023). 3.3 Molecular breeding and marker-assisted selection (MAS) Marker-assisted selection (MAS) has revolutionized the breeding of dragon fruit by enabling the selection of disease-resistant and high-quality varieties through the integration of molecular markers and genomic information. MAS allows for the indirect selection of traits, making the breeding process more efficient and precise. This technique is particularly useful for traits with low heritability, such as abiotic stress resistance and horizontal disease resistance, which are challenging to improve through conventional breeding methods (Torres, 2010; Singh et al., 2015; Pathania et al., 2017). By utilizing molecular markers linked to resistance genes, breeders can identify and select resistant individuals early in the breeding process, thereby streamlining the development of new cultivars (Torres, 2010; Migicovsky and Myles, 2017). The application of MAS in dragon fruit breeding has been facilitated by advancements in genomic tools, including the development of a draft genome for Hylocereus undatus, which provides valuable insights into the genetic basis of important traits (Chen et al., 2021; Tel-Zur, 2022). MAS has been successfully employed to improve various traits in dragon fruit, including sweetness, stress tolerance, and coloration. For instance, the use of molecular markers has enabled the selection of hybrids with enhanced sweetness by targeting genes involved in sugar metabolism (Chen et al., 2021; Tel-Zur, 2022). Additionally, MAS has been used to develop dragon fruit varieties with improved stress tolerance by selecting for genes associated with drought and heat resistance (Oltehua-Lopez et al., 2023). The coloration of dragon fruit, which is primarily determined by betalain biosynthesis, has also been improved through MAS by identifying and selecting for genes involved in the betalain biosynthetic pathway (Chen et al., 2021). These advancements demonstrate the potential of MAS to accelerate the breeding of high-quality dragon fruit varieties with desirable traits.
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