Hand pollination is a necessary assisting method for pitaya (Selenicereus spp.) production to achieve a high yield. With the cultivated area increasing at an exponential rate in recent years, a comprehensive study of the pollination process was conducted. We developed an ideal medium for pitaya pollen in vitro germination in this study, then tested the activity of pollen collected from or stored for various time periods. We discovered that those collected between 2 h before blooming and 6 h after blooming had the higher germination rates (27.2–65.1%), the highest activity was at 2 h after blooming, and that storing them at 4°C for 24 hours reduces their germination rate from 65.2 percent to 35.5 percent and their production to about 82%. As a result, pollinating plants with pollen that has been held for more than 24 hours is not recommended unless a breakthrough in pollen storage is achieved. We also discovered that stigma receptivity and pollen activity are synchronized, which together determines the rate of fruit setting and the size of the fruit. Pollination within 6 hours after flowering offers the optimum fruit setting percentage and size, while pollination at 6:00 pm, 2 hours before blooming, is also a good alternative; however, pollination at 6:00 am the next morning is expected to result in a 23 % drop in productivity. These findings will be beneficial for reproductive biology research, as well as laying the groundwork for hand pollination to boost pitaya output and breeding efficiency.

Pitaya, (Selenicereus spp.), a fruit originating from North and Central America and extensively cultivated in China and Vietnam, holds significant economic value. Utilizing PacBio HiFi sequencing and Oxford Nanopore Technologies ultra-long sequencing, aided by Hi-C data, we have assembled a chromosome-level haplotype-resolved genome. The sizes of the two haplotype genomes were determined to be 1.477 Gb (hap1, contig N50 = 133.35 Mb) and 1.442 Gb (hap2, contig N50 = 132.57 Mb), with 96.7% (hap1) and 98.4% (hap2) respectively allocated to 11 pseudochromosomes. Hap1 comprises 58.94% repeat sequences and predicts a total of 29,139 protein-coding gene models and 18,378 non-coding RNAs. Hap2 comprises 58.37% repeat sequences and predicts a total of 28,538 protein-coding gene models and 19,458 non-coding RNAs. Notably, 93.5% and 93.6% of protein-coding genes were annotated for the two haplotypes. The high-quality genome assembly presented in this study provides a valuable resource for future ecological, evolutionary, biological, and breeding research in pitaya.

Combined drought and heavy metal stress are increasingly common in agricultural systems, yet the molecular basis of mitigation remains poorly resolved. We examined how exogenous melatonin modulates physiological and transcriptional responses of pitaya under drought, nickel stress, and their combination. Drought and nickel stress reduced growth relative to the control, increased antioxidant capacity, and decreased chlorophyll content. Melatonin application ameliorated these impairments and partially restored biomass and physiological traits. Transcriptome profiling identified treatment-specific changes in gene expression, indicating that melatonin reshapes responses under single and combined stress. Functional enrichment highlighted coordinated regulation of central carbon metabolism (starch/sucrose turnover, pyruvate-linked pathways), redox buffering (peroxisome and glutathione metabolism), and stress signaling. Transcription factor families displayed pronounced treatment-dependent shifts. Gene co-expression network analysis resolved multiple modules associated with elongation-related traits. Hub-gene analysis highlighted candidate associations with ubiquitin-mediated proteolysis, together with carbohydrate and secondary metabolism, in the melatonin response. Quantitative reverse-transcription PCR supported the transcriptome expression patterns. Collectively, these results suggest that melatonin helps sustain growth and physiological performance under drought and nickel stress, especially the combined drought-nickel treatment used here. These responses were associated with transcriptomic changes in carbon-energy metabolism, redox buffering, stress-responsive transcription factor families, and ubiquitin-mediated proteolysis.

Different pitaya cultivars (Selenicereus undatus) have unique aroma characteristics. For example, the “Vietnamese White Heart” pitaya fruit exhibits a distinct “herbaceous aroma”, while the new variety “Yuehong No. 6” exhibits a “fruity aroma”, but the underlying mechanisms remain unclear. This study aimed to characterize and compare the developmental changes in volatile organic compound (VOC) profiles between two pitaya cultivars at 25, 30, and 35 days after flowering (DAF), using GC × GC-TOF-MS combined with relative odor activity value (ROAV) analysis. The results show that the ROAVs of 2-pentylfuran and (E)-2-octenal increased progressively in “Vietnamese White Heart” but decreased during development in “Yuehong No. 6”. Although their ROAVs were higher in “Yuehong No. 6” at 25 and 30 DAF, this pattern was reversed at 35 DAF. At 35 DAF, 2-undecanone also showed a higher ROAV in “Vietnamese White Heart”, whereas 2-dodecenal showed a higher ROAV in “Yuehong No. 6”. This study reveals cultivar-dependent developmental trajectories of several potentially aroma-relevant VOCs, and provides a basis for future flavor-oriented molecular breeding, harvest timing optimization and fruit processing.