International Journal of Horticulture, 2025, Vol.15, No.4, 162-170 http://hortherbpublisher.com/index.php/ijh 163 production and motility are also very important and contribute to flower growth, suggesting that flower organ development in Pitaya is regulated by genetic mechanisms (Wu et al., 2022). Some studies found important genes called CONSTANS-LIKE and FLOWERING LOCUS T. These genes help control when pitaya flowers. They work together with other genes like CDF and TCP. These genes act like switches that turn other genes on or off. They respond to things like how long the day is and plant hormones. Because of this, the way genes control flowering in pitaya is not simple (Xiong et al., 2020). 2.2 Flowering time of pitaya Pitaya flowers open at night and close by early morning. This nocturnal habit matches well with the activities of pollinators that are active at night, like moths. This pattern helps ensure flowers are open when these pollinators visit (Ye et al., 2021). Environmental factors can affect when pitaya flowers bloom. For example, using extra lights during short winter days can encourage pitaya to bloom even out of its normal season (Xiong et al., 2020). The HuNIP6-1 gene helps control when flowers bloom. The researchers tested the gene in Arabidopsis thaliana, where overexpression of the gene promotes early flowering. HuNIP6; 1 gene may also help control the flowering time of pitaya, and this gene can be used to change the flowering time of pitaya, and also help to plant more fruit and improve the yield (Ye et al., 2021). 2.3 Differences among pitaya varieties Different kinds of pitaya flower in different ways. pitaya flowers can be larger or smaller, the opening time is also different, some early, some late. Researchers observed red pitaya and found that different genes play different roles in flower growth, so different pitaya types have different flower appearance and behavior (Wu et al., 2022). Different species of pitaya have different pollination methods, and Hylocereus undatus can grow fruit on its own without the help of insects or animals. If you want red meat pitaya (H. polyrhizus), you need pollinators to grow larger fruit. Not all pitayas flower or bear fruit in the same way (Muniz et al., 2019). Because of the variety of Pitaya flowering traits, optimizing these traits can produce more fruits and better quality Pitaya varieties. 3 Genetic Control of Flowering Time of Pitaya Fruit 3.1 Regulation of genes related to circadian rhythm Circadian rhythms work by integrating environmental signals with biological processes inside the plant, and it helps the plant decide the right time to bloom by matching internal signals with external conditions, such as light and dark. In Arabidopsis thaliana, this clock involves genes such as TOC1, CCA1 and LHY, several genes that work together to turn each other on and off, controlling when flowering genes are activated. Let the flowers open at the best time and grow in an environment suitable for reproduction. Through the interaction of multiple genes, such as PRR genes (such as PRR9, PRR7 and PRR5) help promote the key photoperiodic regulator CONSTANS (CO) genes, regulate the level of COexpression, to control the timing of flowering. This is also one of the functions of circadian rhythm regulation, and also shows the importance of synchronizing flowering with environmental signals. 3.2 Genes that respond to day length The length of day and night (called photoperiod) strongly affects when plants flower. A key gene that senses day length in pitaya fruit is called CONSTANS (CO). CO takes signals from the circadian clock and the amount of light and uses them to turn on another gene called FLOWERING LOCUS T (FT). FT then triggers the flowering process. Genes like TOC1, CCA1, and LHY, which are part of the circadian clock, also connect closely with the CO-FT pathway. Together, they make sure flowering happens at the right season. The EARLY FLOWERING 3 (ELF3) and GIGANTEA (GI), are also important. They help plants know how long the day and night are. These genes pass that information to the plant's internal clock, helping the plant decide exactly when to flower. This network of genes makes sure the timing of flowering matches the environment closely (Anwer et al., 2019).
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