The Sugar-Acid-Aroma Balance: Integrating the Key Components of Fruit Quality and Their Implications in Stone Fruit Breeding

Improving fruit quality is one of the most critical core tasks in fruit tree breeding. However, the complexity of the constituent factors of fruit quality and their interrelationships, the significant influence of environmental factors on quality, and the diversity of consumer demands, among other factors, make quality breeding a more challenging endeavor than other breeding objectives. Essentially, fruit quality is defined by the delicate balance of sugar, acid, and aromas, which collectively influence the fruit’s flavor, consumer satisfaction, and economic value. While substantial progress has been made in the depiction of the metabolic pathways underlying these traits, the molecular mechanism coordinating carbon partitioning and competition between sugars, acids, and volatiles remains unknown. This review focuses on recent advances in understanding stone fruit metabolism and identifies key gaps in knowledge. We emphasize the need for integrated approaches combining spatial metabolomics, transcriptomics, genetics, and genomics to reveal the regulatory networks underlying metabolomic variation during fruit development and ripening. We also discuss the application of molecular tools, such as marker-assisted selection and metabolite-associated markers, to accelerate the breeding of flavor-balanced stone fruit cultivars. By adapting these advances in breeding practices, we can achieve coordinated improvement and precise regulation of various components of fruit quality, thereby developing elite stone fruit cultivars with improved flavor that meet prevailing consumer demands.