International Journal of Molecular Ecology and Conservation, 2025, Vol.15, No.1, 30-43 http://ecoevopublisher.com/index.php/ijmec 32 pitaya germplasm resources from Central America and Southeast Asia, including red meat, white meat and yellow skin types (Ding et al., 2024). Studies on the ploidy and genome of these resources show that pitaya germplasm has natural polyploidy on the basis of diploid, which provides a special way for genetic improvement. Figure 1 Two types of yellow peel pitayas. (A) H. megalanthus; (B) H. undatus (Adopted from Shah et al., 2023) 3.2 Pathways of germplasm flow across regions With the development of international trade and agricultural exchanges, yellow pitaya germplasm has achieved global dissemination. Since the 19th century, European colonists and missionaries first spread pitaya to Southeast Asia. Vietnam is one of the earliest and most successful Asian countries to accept pitaya germplasm. As early as around 1860, pitaya took root in Vietnam and developed rapidly in the second half of the 20th century. At present, Vietnam has become one of the major producers of pitaya in the world, with a rich variety of types (Trindade et al., 2023). China introduced pitaya cultivation from Taiwan and Southeast Asia in the early 1990s, and initially tried it in southern provinces such as Guangdong and Guangxi. Since then, through multiple germplasm exchanges and introduction trials, more than a dozen provinces and regions across the country, including Hainan, Yunnan, Fujian, Sichuan and even Shaanxi, have begun to plant pitaya, among which Hainan, Guangdong, Guangxi and Yunnan have become the main production areas. Many of the common cultivars in China, such as the red-fleshed "Red Dragon", "Big Red", the white-fleshed "Vietnam White", and the yellow-skinned "Qilin Fruit (Jindu No. 1)", are selected from foreign germplasms through hybridization or natural mutation. It can be said that the development of China's dragon fruit industry depends largely on the introduction and secondary innovative use of global germplasm resources. In addition to Southeast Asia, yellow pitaya has also been introduced and cultivated in other parts of the world: for example, Australia began to commercially cultivate red-skinned dragon fruit in the late 20th century and cultivated varieties suitable for the local climate (Adnan et al., 2011); Israel introduced multiple pitaya germplasms from Central America in the 1980s, and through hybridization breeding, successfully cultivated a number of excellent varieties adapted to Mediterranean climate conditions, and established dragon fruit orchards in arid areas (Mizrahi et al., 2010); the United States mainly uses greenhouses or orchards in California, Florida and Hawaii to cultivate pitaya on a small scale as an emerging specialty crop to supply the market. Due to climate restrictions, traditional open-field cultivation is rare in Europe, but in recent years, subtropical regions such as southern Spain and Sicily, Italy have also begun to try to plant it, and have achieved certain success. These introduction experiments show that as long as suitable germplasm is selected and cultivation measures are adjusted, yellow pitaya has the potential to grow in a wider range of regions around the world. 3.3 Institutional roles in germplasm collection and sharing The global flow of germplasm has greatly promoted the exploration and utilization of genetic diversity of yellow pitaya. For example, through SSR molecular marker analysis of 32 pitaya germplasms collected in Okinawa, Japan, it was found that there were significant allele differences between materials from different sources, and the germplasms could be divided into 6 genetic groups, which roughly corresponded to their species classification (Nashima et al., 2021). For another example, ISSR analysis of 76 yellow-skinned pitaya genotypes in Colombia
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