Hand pollination is a necessary aiding method for pitaya ( Hylocereus undatus ) production to achieve a high yield. With the cultivated area of pitaya going up exponentially in the recent years, a systematic study was carried out to understand the mechanism behind the high yield. In this study, we first developed an optimal medium for the in vitro germination of pitaya pollen. Upon testing the activity of the pollen collected from or stored for different time, we observed that the relative high pollen germination rates (27.2–65.1%) were those collected at between 2 h before blooming and 6 h after blooming, the highest activity was at 2 h after blooming, and that storing them for 24 h at 4°C reduces their germination rate from 65.2% to 35.5% and their production to about 82%. Therefore, it is not appropriate to pollinate plants with pollen that have been stored for more than 24 h, without bringing a breakthrough in pollen storage. We also observed that stigma receptivity and pollen activity are synchronous, which together determine fruit setting rate and fruit size. Pollination within 6 h after blooming provides the best fruit setting percentage and fruit size, the other favorable option being pollination at 6:00 pm, that is, 2 h before blooming; however, pollination at 6:00 am the next morning is expected to lead to 23% reduction in the production. These results will be useful for reproductive biology studies in this species. Moreover, this work set an important foundation for collecting pollen and selecting the right time of hand pollination to improve the yield and breeding efficiency in pitaya.

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.

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.