Influence of rootstock genotype on individual metabolic responses and antioxidant potential of blood orange cv. Tarocco Scirè

In fruit crops, tree rootstock plays a relevant role in the tolerance of biotic and abiotic factors, various qualitative traits and biochemical profiles of the juice. In this work, the fruit quality characteristics of sweet orange Tarocco Sciré grafted onto ten rootstocks were evaluated. Analyses were performed on the fruit juice, coupling the quantification of phenolic compounds (anthocyanins, flavanones, flavones and hydroxycinnamic acids) through hyphenated chromatographic techniques and the assessment of antioxidant potential (measured in vitro). The study was conducted for two consecutive years in which the different minimum temperatures recorded during fruit ripening determined a higher accumulation of polyphenols, especially anthocyanins (63.6 %), and higher levels of antioxidant activity (48.92) in the colder year. The analyses allowed the identification and quantification of 24 phenolic compounds (6 anthocyanins, 5 flavanones, 1 flavone and 12 hydroxycinnamic acids). The results highlighted a significant effect of both rootstocks and the environment (and their interaction) on the metabolic profile of the juice, with low temperatures being directly involved in juice pigmentation and significant differences among the rootstocks within each year of analysis. In addition to temperature, a significant effect of rootstocks on the metabolic profile of the juice was revealed, with C35 and Bitters being the most effective in enhancing anthocyanin accumulation in the fruit of the grafted variety. Altogether, the data presented shed light on the significant role exerted by the rootstock on fruit quality, providing useful insights to guide the selection of rootstocks in novel implants.