International Journal of Horticulture, 2024, Vol.14, No.6, 414-425 http://hortherbpublisher.com/index.php/ijh 416 Figure 2 The appearance, internal structure, and sugar content measurement of Selenicereus megalanthus 2.2 Main breeding objectives for dragon fruit The primary breeding objectives for dragon fruit include increasing yield and quality, enhancing disease resistance, and improving stress tolerance. High-yielding cultivars such as N97-17 and N97-20 have been identified, which produce significantly more fruit per hectare (Goenaga et al., 2020). Additionally, breeding efforts focus on extending the shelf life of the fruit to reduce post-harvest losses and improve marketability (Perween et al., 2018).Improving fruit texture and sweetness is crucial to meet consumer preferences. Varieties with higher soluble solids content, such as NOI-16 and N97-18, are particularly sought after for their sweetness (Goenaga et al., 2020). Enhancing the nutritional content, including increasing the levels of antioxidants and phenolic compounds, is also a key objective to boost the health benefits of the fruit (Huang et al., 2021; Attar et al., 2022). The red-fleshed varieties, in particular, are targeted for their higher nutritional value and bioactive compounds (Huang et al., 2021). 2.3 Challenges in breeding Breeding dragon fruit presents several challenges. One of the primary issues is the long breeding cycle, which can extend up to several years before new cultivars are ready for commercial production. The genomic complexity of dragon fruit, with its diverse genetic background, adds another layer of difficulty in achieving consistent breeding outcomes (Perween et al., 2018). Additionally, ensuring adaptability in various cultivation conditions, from dry to wet regions, is essential but challenging due to the plant's sensitivity to environmental changes (Perween et al., 2018; Goenaga et al., 2020). These challenges necessitate ongoing research and development to optimize breeding strategies and improve the resilience and productivity of dragon fruit cultivars. 3 Techniques in Varietal Improvement of Dragon Fruit 3.1 Hybrid breeding Hybrid breeding is a crucial technique in the varietal improvement of dragon fruit, aimed at enhancing both the quality and stress tolerance of the fruit. This method involves the cross-breeding of different dragon fruit varieties to combine desirable traits from each parent. For instance, the study on the yield and fruit quality traits of various dragon fruit cultivars grown in Puerto Rico highlights significant differences in fruit number, weight, and soluble solids among cultivars, indicating the potential for selecting superior hybrids for improved yield and quality (Goenaga et al., 2020). Additionally, transcriptome analysis of wild and cultivated pitahaya has identified differentially expressed genes related to drought stress, suggesting that hybrid breeding can also target stress tolerance by selecting for genes that enhance drought resistance (Oltehua-Lopez et al., 2023).
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