Metabolic Differences Between Fruits from Grafted and Non-Grafted P. mahaleb L

In the cherry-growing area of Apulia (Italy), sweet cherry (Prunus avium L.) cultivars are commonly grafted onto Prunus mahaleb L. rootstock. This study investigated the influence of the scion on the fruit quality of the rootstock, an aspect that remains largely underexplored in studies of stionic interactions. In an old sweet cherry orchard in the Bari area, several ‘Ferrovia’ trees grafted onto P. mahaleb L. rootstock were observed, where some rootstock individuals had developed fruiting branches below the grafting point. We collected fruits from those mahaleb rootstocks and compared them with fruits produced by non-grafted P. mahaleb L. trees growing in the same orchard. Extracts of grafted and non-grafted mahaleb cherries was analyzed by HPLC-DAD and 1H-NMR. Anthocyanins, coumaric acid derivatives, organic acids, and reducing sugars were identified in both extracts. Nongrafted mahaleb fruits were characterized by a higher relative content of malic acid, fructose, dihydro-coumaric acid derivatives, and anthocyanins and lower content of α/β glucose and sorbitol, with respect to the grafted mahaleb. The metabolic differences observed between fruits from grafted and non-grafted P. mahaleb L. were further supported by our preliminary NMR-based analysis conducted on fruit juice over two consecutive years. The results suggest that grafting may induce some physiological changes not only in the scion, but also in the rootstock, even in its vegetative (above-ground) organs, if developed. This work represents a novel finding and reinforces the broader understanding that grafting impacts physiological processes in plants.