International Journal of Molecular Ecology and Conservation, 2025, Vol.15, No.1, 30-43 http://ecoevopublisher.com/index.php/ijmec 35 barren environment. In the wild environment of Central America, pitaya also often coexists with large trees, and its aerial roots are attached to the surface of tree trunks rich in mosses and algae, absorbing nutrients and water from rainwater and air. This epiphytic lifestyle is also an adaptation to resource-scarce environments. 5.3 Role of local selection and farmer preferences Yellow pitaya has formed a complete set of mechanisms to adapt to dry and hot climates and barren environments in its native Central America, including CAM photosynthesis, efficient water use, nutrient acquisition promoted by rhizosphere bacteria, flexible phenology, and biochemical mechanisms of self-protection. This set of "adaptation strategy packages" makes yellow pitaya often show tenacious vitality when introduced to similar environments. For example, in Sicily, Italy, which has a Mediterranean climate, the introduced pitaya grows well under high temperature and low rainfall conditions in the greenhouse, and each plant has a considerable annual fruit yield, which has been proven to be adapted to local production (Trivellini et al., 2020). This shows that making full use of the inherent adaptation mechanism of yellow pitaya and combining it with appropriate agricultural measures can achieve its successful cultivation in non-origin environments. 6 Breeding and Selection for Adaptation 6.1 Key agronomic traits targeted in breeding programs In response to the demand for yellow pitaya cultivation in different regions, adaptive breeding has been gradually carried out in recent years. The core goal of breeding is to enable new varieties to adapt to the climate and cultivation conditions of the target environment through genetic improvement, while having excellent yield and quality. Since yellow pitaya is introduced over a wide area and the environment varies significantly from place to place, the traits of concern in breeding in different regions are different. For example, in hot and arid areas (such as the dry and hot valleys in the northwest), the focus of breeding is on breeding varieties that are drought-resistant and heat-resistant and have a high self-flowering fruiting rate; while in rainy and humid areas (such as the southern monsoon area), it is necessary to cultivate disease-resistant and waterlogging-resistant varieties. For greenhouse protected cultivation, the varieties are also required to have strong adaptability to weak light and potted environments (Liu, 2020). 6.2 Traditional vs. modern selection techniques Conventional hybrid breeding is one of the main means. Through hybridization, the excellent traits of different parents can be recombined to obtain offspring with better comprehensive traits. For example, Taiwanese and Vietnamese breeders used red-fleshed self-incompatible varieties to cross with white-fleshed self-compatible varieties to breed a new "two-color" pitaya variety that has both red flesh and self-pollination, successfully combining the advantages of the two types. Shaanxi Yangling Vocational and Technical College and other institutions recently reported red-fleshed × white-fleshed hybrid offspring varieties such as "Qin Honglong", which are both adapted to the local climate and have the characteristics of large fruit and high yield. These results show that through distant or close hybridization, it is possible to break through the limitations of a single strain and integrate multiple target traits such as stress resistance, self-compatibility, high yield, and large fruit (Huang et al., 2021). Ploidy breeding is also an exploratory direction for pitaya breeding. Polyploid plants often show characteristics such as enlarged organs and enhanced stress resistance. Chinese researchers successfully induced pitaya tetraploid materials by treating bud tips with colchicine, and used them to cross with diploids to produce triploid seedless varieties (Ding et al., 2024). Although there are no commercial polyploid varieties available yet, studies have shown that tetraploid pitaya is superior to diploid in terms of stem thickness, flower and fruit size, and is more tolerant to high temperature and drought (presumably based on the polyploidy rules of other crops). This provides ideas for breeding varieties for special purposes. In terms of mutation breeding, some studies have used physical or chemical mutagenesis to create new variations of pitaya. For example, irradiating pitaya seeds with carbon ion beams has been shown to effectively produce mutant plant populations. The experiment found that after treatment with carbon ion beams at a dose of 15~30 Gy, the survival rate of pitaya seedlings decreased, and some traits mutated, some of which may have breeding value
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