This study investigated the effects of different thinning treatments on yield, fruit quality, and leaf photosynthesis for ‘Xiahui 5’ peach [Prunus persica (L.) Batsch]. The suitable thinning period and loading capacity of ‘Xiahui 5’ peach were explored in production and a theoretical basis for efficient and high-yield cultivation of ‘Xiahui 5’ peach is provided, including blossom-thinning + fruit-thinning at 20 days after full bloom (DAFB) + fruit thinning at 40 DAFB, blossom-thinning + fruit-thinning at 40 DAFB, fruit-thinning at 20 DAFB + fruit-thinning at 40 DAFB, and fruit-thinning at 40 DAFB, with neither blossom-thinning nor fruit-thinning as control. The yield, fruit quality, and leaf photosynthesis were detected. The thinning treatments were carried out between April and May 2012 in Nanjing City, Jiangsu Province, China. The intensity of thinning with spacing was about 20 cm between fruit. Thinning fruit twice (20 DAFB + 40 DAFB) saved labor (260.4 h/ha) and improved the weights (186.45 g) of individual fruit, the yield (980.55 kg/ha), and the internal and external fruit quality (red saturation, the ratio between red and yellow saturation), as well as enhancing the water-use efficiency (8.19 mmol/mol) and apparent CO₂-use efficiency (140.58 mmol/mol) values of leaves. The effect of thinning fruit twice was better than blossom thinning + fruit thinning, or fruit thinning only once. Collectively, thinning blossoms and fruit is a blossom- and fruit-management method suitable for peach production areas in the middle and lower reaches of the Yangtze River in China. In addition, thinning fruit twice (20 DAFB + 40 DAFB) during the young fruit period and before entering the core-hardening period is suitable for achieving a reasonable load of ‘Xiahui 5’ peach. The treatment including flower thinning was not the recommended strategy of ‘Xiahui 5’ peach in terms of reasonable load.

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.

Yellow- and white-fleshed peach fruits are favored for their diverse flesh colors. While carotenoid accumulation primarily dictates flesh color differences, the influence of volatile compounds on their aromas remains largely unexplored. Here, multiple analytical methods including odor importance assessment, hierarchical clustering, and aroma characterization analysis were employed to investigate volatile compositions and aroma characteristics of the two types of peach, as well as the offspring with identical parentage. Dihydro-β-ionone was the sole volatile exhibiting content and odor importance disparities between the two types of peach, and in descendant cultivars such volatiles encompassed theaspirane additionally. Respectively 16 and 30 important volatiles were identified in the two peach types and in the offspring cultivars, and subsequently overview of their aroma characteristics was obtained from a graphical perspective. The two peach types and offspring cultivars all revealed prevalent floral, fruity and caramel notes, whereas the higher odor activity values and especially the woody odors in the white-fleshed cultivars, as well as the differential balance degrees of the main odor directions defined the distinct aromas. By delving into the pivotal differences in odor directions and aroma profiles between the two types of peach, this research elucidates the aroma distinctions rooted in flesh color variations and paves the way for uncovering aroma formation mechanisms in fruits with varied flesh colors.