To investigate the peach fruit flesh types (soft-melting, hard-melting, stonyhard and non-melting) and harvest maturity level suitable for near-freezing temperature storage (NFTS), eight peach cultivars that had four flesh types were used as test materials. Changes in fruit respiration intensity and ethylene release rates, as well as the differences in quality indexes, such as soluble solids content (SSC), firmness, color difference, pigment content, soluble sugar and organic acid component content, of three fruit maturity levels (70%, 80% and 90% maturity) under NFTS conditions were analyzed and compared. The fruit quality indexes of peach having different maturity levels and flesh types changed little during NFTS. The SSC and total sugar content of hard-melting and stonyhard peach fruit were higher than those of other flesh types during NFTS. Those fruit maintained greater firmness at the end of the storage period. The differences in respiration intensity and ethylene release rate were small, but for fruit coloring, hard-melting fruit performed better than stonyhard fruit. The 80%, compared with the 90%, maturity stage maintained more fruit moisture, had less fruit mass loss and maintained a greater edible firmness. It effectively impeded the fruit senescence process and was the most suitable maturity for NFTS. Thus, the hard-melting peach maintained the highest commercial value and desirable storage characteristics under NFTS conditions, and its 80% maturity level was the most suitable for NFTS.

The effects of different fruit load treatments during peach growth and development on the internal and external quality of peach fruit were studied. At 47 days after full bloom, the plant materials were divided into four treatments: about 100%, 75%, 50% and 25% of fruit were retained. The results showed that as the fruit load was reduced during fruit growth and development, the fruit weight, size, soluble solid contents (SSC), total sugar content, sugar/acid ratio and color quality increased, while the flesh firmness, index of absorbance difference (IAD) and total acid content decreased. Compared with the control treatment in which the fruit were not thinned, the weight of individual mature fruit increased by 24.52%, 39.73% and 51.68% under three fruit thinning treatments (in which about 75%, 50% and 25% of the fruit were left on the tree). SSC increased by 30.78%, 37.63% and 49.69%; total sugar content increased by 13.58%, 22.33% and 31.42%; and the sugar-acid ratio increased by 13.25%, 13.59% and 19.47%, respectively, under the three conditions. In addition, the longitudinal, transverse and lateral diameters of fruit increased to varying degrees when the fruit load was reduced. Furthermore, the fruit firmness and IAD value of fruit skins decreased, and fruit ripening was advanced when the fruit load was reduced. The results showed that fruit quality and flavor were improved significantly by fruit thinning.

Peach (Prunus persica (L.) Batsch) is a highly desirable fruit that is consumed around the world. However, the peach fruit is highly perishable after harvest, a characteristic that limits the distribution and supply to the market and causes heavy economic losses. Thus, peach fruit softening and senescence after harvest urgently need to be addressed. In the current study, transcriptomic analysis was performed to identify candidate genes associated with peach fruit softening and senescence, comparing peach fruit from cultivars with different flesh textures, namely melting and stony hard (SH) flesh textures during storage at room temperature. The mitogen-activated protein kinase signaling pathway-plant and plant hormone signal transduction pathways were associated with peach fruit softening and senescence according to the Venn diagram analysis and weighted gene co-expression network analysis. The expression levels of seven genes, including Prupe.1G034300, Prupe.2G176900, Prupe.3G024700, Prupe.3G098100, Prupe.6G226100, Prupe.7G234800, and Prupe.7G247500, were higher in melting peach fruit than in SH peach fruit during storage. Furthermore, the SH peach fruit softened rapidly after 1-naphthylacetic acid treatment, during which the levels of expression of these seven genes, determined by a quantitative reverse transcription polymerase chain reaction, were strongly induced and upregulated. Thus, these seven genes may play essential roles in regulating peach fruit softening and senescence.

Plant plasma membrane H⁺-ATPase is a transport protein that is generally located on the plasma membrane and generates energy by hydrolyzing adenosine triphosphate (ATP) to pump hydrogen ions (H⁺) in the cytoplasm out of the cell against a concentration gradient. The plasma membrane H⁺-ATPases in plants are encoded by a multigene family and potentially play a fundamental role in regulating plant responses to various abiotic stresses, thus contributing to plant adaptation under adverse conditions. To understand the characteristics of the plasma membrane H⁺-ATPase family in peach (Prunus persica), this study analyzed the plasma membrane H⁺-ATPase family genes in peach. The results showed that there were 27 members of the plasma membrane H⁺-ATPase family in peach with amino acid sequences ranging from 943 to 1327. Subcellular localization showed that 23 of the 27 members were located on the cell membrane, and the phylogenetic tree analysis indicated that peach plasma membrane H⁺-ATPase members were divided into five groups. There were four genes with tandem repeat relationships, and six plasma membrane H⁺-ATPase genes were differentially expressed after 5 days of flooding and under non-flooding conditions based on the RNA-seq and RT-qPCR analyses. This study also investigated the characteristics and possible functions of the plasma membrane H⁺-ATPase family members in peach. The results provide theoretical support for further studies on their biological functions in peach.