International Journal of Molecular Ecology and Conservation, 2025, Vol.15, No.6, 294-302 http://ecoevopublisher.com/index.php/ijmec 295 2 Biological Characteristics and Breeding Foundations of Yellow Pitaya 2.1 Genetic background and current status of germplasm resources The current cultivated types of Yellow pitaya mainly include red skin and white flesh (such as Hylocereus undatus), red skin and red flesh (such as Selenicereus polyrhizus), and yellow skin and white flesh (such as Selenicereus megalanthus) (Figure 1) (Mizrahi, 2014; Shah et al., 2023; Zaman et al., 2024). These types have attracted great attention due to their bright peel color, rich nutritional composition and wide market appeal. Figure 1 Comparative genomics and phenomics of diploid and polyploid pitaya (Adopted from Zaman et al., 2024) Image caption: a) Phenotypic characteristics of yellow and b) red pitaya (white flesh) (Adopted from Zaman et al., 2024) Intergeneric hybridization provides an important way to improve yellow pitaya varieties, especially the sexual hybridization of Hylocereus and Selenicereus shows significant advantages. Many studies have confirmed that new germplasm with special fruit traits can be obtained through interspecific hybridization (Tel-Zur, 2022; Zaman et al., 2024). However, current breeding materials are mainly limited to a few cultivated varieties, and the long-term reliance on asexual reproduction has resulted in a lack of genetic diversity, which has seriously restricted the process of variety improvement and the improvement of environmental adaptability. Breakthroughs in modern molecular technology have brought a turning point to this dilemma. Molecular marker-assisted selection and genomic analysis are gradually being applied to the identification and evaluation of germplasm resources (Nashima et al., 2021; Chen et al., 2022; Shah et al., 2023; Li et al., 2025). Most Yellow pitaya show obvious self-incompatibility characteristics and usually rely on cross-pollination to achieve a high fruit setting rate and excellent quality. The short flowering cycle and the difficulty of flowering time between different varieties often increase the difficulty of natural pollination and the degree of dependence on pollination media or artificial pollination, making commercial production and breeding more complicated (Mizrahi, 2014). 2.2 Breeding goals and limiting factors Key breeding objectives for pitaya include high yield, improved storability, enhanced disease resistance, and superior fruit quality (flavor, color, texture, and nutritional value) (Tel-Zur, 2022; Shah et al., 2023). Additional goals are spineless stems, larger fruit size, and stable flowering for season regulation. Yellow pitaya breeding is deeply trapped in multiple technical shackles. The flowering period is short and erratic, and the pollination opportunity is fleeting; the seedling to fruiting cycle is long, and the breeding process is significantly slowed down. The genetic mechanism of quantitative traits is complicated, making breeding even more difficult (Tel-Zur, 2022). Excessive reliance on artificial pollination has caused uneven fruit size, and the current situation of scarce variety resources and vague genetic background has made the situation worse, together building a stubborn barrier in breeding practice. In terms of genetic basis, there is a clear phenomenon of limited genetic diversity in many key agronomic traits, and their genetic transmission patterns are also highly complex, which further limits the systematic selection and stable inheritance of excellent genotypes (Nashima et al., 2021; Tel-Zur, 2022; Shah et al., 2023; Zhang et al., 2024). These problems are intertwined and become the main challenges in the construction of an efficient breeding system.
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