Plant Gene and Trait 2025, Vol.16, No.4, 182-193 http://genbreedpublisher.com/index.php/pgt 183 This study explores the genetic diversity of pitaya and its role in breeding, reviews different types of germplasm resources and their genetic structure, and focuses on research conducted using molecular markers. By integrating data from different sources for meta-analysis, the study evaluates the overall genetic diversity and varietal differences of pitaya, hoping to provide a reference for future research and variety improvement work, and help the long-term development of the pitaya industry. 2 Overview of pitaya germplasm resources 2.1 Germplasm types and classification characteristics Pitaya is a plant of the Cactaceae family, belonging to the “Hylocereus” category. In traditional classification, they are mainly divided into two genera: Hylocereus and Selenicereus (Li et al., 2024). In the past, due to inconsistent naming, sometimes the same plant had several names. Later, through molecular biological research, the original Hylocereus genus was actually included in the Selenicereus genus, so now the two genera have been merged into one, collectively known as the Selenicereus genus. After the merger, this genus has a total of about 33 species, of which 4 are the most common cultivated dragon fruit varieties: Selenicereus undatus with red skin and white flesh (formerly known as Hylocereus undatus, ‘David Boy’ is a variety of it); S. monacanthus with red skin and red flesh (formerly known as H. monacanthus, and some people call it H. polyrhizus); S. costaricensis with red skin and purple red flesh; S. megalanthus with yellow skin and white flesh (also known as H. megalanthus, both names refer to the same species). Among these species, the red skin and white flesh and red skin and red flesh dragon fruit are the most planted and occupy the largest area (Figure 1) (Chen et al., 2021; Li et al., 2024). In appearance, pitaya is a fleshy climbing plant that has no obvious leaves and relies on flat green stem nodes (also called stem segments) for photosynthesis. Different species have different stem segments and fruit appearances, which can be used to distinguish species (Silva et al., 2017). Figure 1 The phenotype of bud, flower and fruit of four main commercial dragon fruits (Adopted from Li et al., 2024) Image caption: (a) S. undatus has green buds; big, funnel-shaped, and white nocturnal flowers; and oblong fruits with pink peel, and white flesh and covered with green, long, and hard scales. (b) S. costaricensis has green buds along with lighter red edges on the outer perianth; big, funnel-shaped and white nocturnal flowers; and ovoid fruit with dark magenta peel and violet-red flesh, and covered with red, soft and short scales. (c) S. monacanthus has green buds along with bright red edges on the outer perianth; big funnel-shaped and white nocturnal flowers; and ovoid fruit with crimson peel and flesh covered with red, soft and short scales. (d) S. megalanthus has green buds along with dark brown outer perianth; big funnel-shaped (rounder than other species) and white (a little yellow) nocturnal flowers; and ovoid fruit with yellow peel and white (transparent) flesh covered with thorns on tuberculate skin instead of scales (Adopted from Li et al., 2024)
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