Influence of graft compatibility on fruit quality and mineral nutrient profile in 'Dinosaur Egg' (

Introduction: 'Dinosaur Egg' is a premium interspecific hybrid cultivar of pluot, widely cultivated in Xinjiang, China. Its commercial production relies on grafting, for which the Siberian apricot is commonly used as the rootstock. However, this specific graft combination often develops symptoms of incompatibility (such as leaf chlorosis and graft-union cracking), several years after establishment, which ultimately impairs tree growth and fruit quality. To date, a comprehensive understanding of the effects of graft compatibility on the fruit quality and mineral nutrition of 'Dinosaur Egg' is still lacking. This study therefore aimed to investigate the influence of different compatibility grades on these traits using the 'Dinosaur Egg'/Siberian apricot combination, in order to provide a theoretical basis for fruit quality regulation and improved cultivation practices. Methods: Using eight-year-old 'Dinosaur Egg'/Siberian apricot grafted plants as experimental material, the trees were categorized into four distinct graft compatibility grades based on leaf and graft-union phenotypes: normal (control, CK), Grade I, Grade II, and Grade III (in descending order of compatibility). A total of 39 parameters encompassing fruit appearance, flavor, bioactive compounds, and mineral nutrition were measured for each grade. The data were subsequently subjected to significance analysis, correlation analysis, principal component analysis, and a comprehensive evaluation based on a membership function model. Results: The results demonstrated that graft compatibility significantly influenced both fruit quality and mineral nutrient accumulation in 'Dinosaur Egg'. High compatibility markedly increased fruit size, whereas lower compatibility, despite reducing individual fruit fresh weight, significantly enhanced fruit firmness and soluble solids content, while shifting peel coloration from red to bright yellow. Notably, the highest total soluble solids to titratable acidity ratio was recorded in Grade II fruits, corresponding to superior flavor quality. Furthermore, lower compatibility significantly increased the contents of soluble solids, total phenolic, and total flavonoid, but decreased total anthocyanin content. In terms of mineral nutrition, fruits under low-affinity conditions accumulated higher concentrations of B, P, K, and Mg, but lower concentrations of Fe, Mn, Cu, and Zn. Following correlation analysis, which reduced the 39 initial quality indicators to 20 key parameters, principal component analysis then categorized these parameters into five distinct dimensions. Finally, a comprehensive evaluation based on these dimensions yielded a fruit quality ranking of Grade II > CK > Grade III > Grade I. Discussion: Moderately low graft compatibility triggered a beneficial hormetic response, facilitating an optimal balance across multiple quality dimensions instead of the maximization of any single trait. Thus, this study demonstrates that pursuing an optimal, rather than the highest possible, compatibility represents a novel and effective strategy for enhancing the integrated quality of 'Dinosaur Egg' fruit.