Tree Genetics and Molecular Breeding 2024, Vol.14, No.4, 177-184 http://genbreedpublisher.com/index.php/tgmb 180 produced a fruit weighing 146.5 g (Figure 1I). This weight was substantially lower than the average fruit weight of (355.0±90.4) g observed in the donor plants, highlighting potential limitations in the reproductive capacity of the androgenic lines (Li et al., 2018). Figure 1 Reproductive parts of the diploid donor H. monacanthus and androgenic H. monacanthus lines (Adopted from Li et al., 2018) Image caption: (A) Flower bud from the androgenic line 007, showing an atypical folded end (scale bar 1 cm). (B) Aborted open flower bud from the androgenic line 011 (scale bar 1 cm). (C) Deformed anther detached from an aborted flower bud of androgenic line 011 (scale bar 200 μm). (D-G) Histological sections of flower buds having the same length (6 cm), as follows: (D) Androgenic line 007 showing abnormal ovules (scale bar 100 μm), with a close-up of a shrunken ovule in the upper right-hand inset (scale bar 10 μm), (E) Well-developed ovules of the diploid donor (scale bar 100 μm), (F) Anther of the androgenic line 007 showing aborted tetrads, and a few uninucleate microspores with an atypical triangular shape (scale bar 100 μm), with a close-up of aborted pollen grains in the upper right-hand inset (scale bar 10 μm) (G) Anther of the diploid donor showing well-developed and viable tetrads (scale bar 100 μm), with a close-up of viable grains in the upper right-hand inset (scale bar 10 μm). (H) Anthesis in the androgenic line 011 (scale bar 1 cm), and (I) Mature fruit from line 011 (scale bar 1 cm) (Adopted from Li et al., 2018) 4.2 Genomic and transcriptomic insights into betalain biosynthesis Recent genomic and transcriptomic studies have provided valuable insights into the biosynthesis of betalains in dragon fruit. The draft genome of Hylocereus undatus has revealed the co-localization of betacyanin biosynthetic genes on a specific chromosome region, suggesting a coordinated regulation of these genes that may enhance the efficiency of betalain production (Figure 2) (Zheng et al., 2021). Proteomic analyses have further identified key
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