Metabolite Fruit Profile Is Altered in Response to Source–Sink Imbalance and Can Be Used as an Early Predictor of Fruit Quality in Nectarine

Abstract

Peaches and nectarines [Prunus persica (L.) Batsch] are among the most exported fresh fruit from Chile to the Northern Hemisphere. Fruit acceptance by final consumers is defined by quality parameters such as the size, weight, taste, aroma, color, and juiciness of the fruit. In peaches and nectarines, the balance between soluble sugars present in the mesocarp and the predominant organic acids determines the taste. Biomass production and metabolite accumulation by fruits occur during the different developmental stages and depend on photosynthesis and carbon export by source leaves. Carbon supply to fruit can be potentiated through the field practice of thinning (removal of flowers and young fruit), leading to a change in the source–sink balance favoring fruit development. Thinning leads to fruit with increased size, but it is not known how this practice could influence fruit quality in terms of individual metabolite composition. In this work, we analyzed soluble metabolite profiles of nectarine fruit cv “Magique” at different developmental stages and from trees subjected to different thinning treatments. Mesocarp metabolites were analyzed throughout fruit development until harvest during two consecutive harvest seasons. Major polar compounds such as soluble sugars, amino acids, organic acids, and some secondary metabolites were measured by quantitative 1H-NMR profiling in the first season and GC-MS profiling in the second season. In addition, harvest and ripening quality parameters such as fruit weight, firmness, and acidity were determined. Our results indicated that thinning (i.e., source–sink imbalance) mainly affects fruit metabolic composition at early developmental stages. Metabolomic data revealed that sugar, organic acid, and phenylpropanoid pathway intermediates at early stages of development can be used to segregate fruits impacted by the change in source–sink balance. In conclusion, we suggest that the metabolite profile at early stages of development could be a metabolic predictor of final fruit quality in nectarines.

Amino Acid Profiles in Peach (Prunus persica L.) Fruit

“…In addition, sorbitol changed less and remained relatively low throughout fruit growth. Early spring growth in peach trees was mostly dependent on stored carbohydrates that were mobilized after the release from dormancy and transported to the growing sinks through the xylem (as hexoses) [ 4 ]. Glucose and fructose concentrations were very close and lower than sucrose in all varieties.…”

“…Sorbitol appeared to be converted to glucose by sorbitol oxidase to support fruit growth. Glucose and fructose represent a transitory storage/metabolic pool [ 4 , 16 ]. High acid levels may provide the acid environment for anthocyanin and carotenoid stable and coloration in the flesh [ 17 ].…”

“…Previous studies about peaches mainly focused on accumulation of sugar, acids and phenolic and aroma compounds [ 4 , 5 ]. The total amino acid concentration in peaches increases during the fruit’s development [ 6 ].…”

Identifying sources of metabolomic diversity and reconfiguration in peach fruit: taking notes for quality fruit improvement

“…Among these preharvest factors, modifications of competition for resources among fruits on the same tree, the position of fruits on the tree, differential light exposure in the tree due to canopy management, among others, can affect sink strength and, therefore, are expected to affect the metabolome content of each fruit [48]. Nontargeted metabolite profiling was recently used for comparison of peach fruits at different developmental stages from unthinned or thinned peach trees [49,50]. Thinning is a widespread management that balances the source-sink relationship reducing the competition among fruits.…”

Transcriptome Remodeling in Response to Leaf Removal and Exogenous Abscisic Acid in Berries of Grapevine (Vitis vinifera L.) Fruit Cuttings

“…Modifying the source-sink ratio is a common manipulation that influences the sugar content in berries [6][7][8][9]. Different carbon supplies influence the central carbohydrate metabolites in primary metabolism pathways [10,11].…”