Effects of Rootstock/Scion Combinations on the Flavor of Citrus Fruit

We examined sensory quality, total soluble solids (TSS) and acidity levels, and aroma volatiles compositions of 'Or' and 'Odem' mandarins grafted on sour orange (SO), Volkamer lemon (Volka), and US-812 rootstocks; 'Valencia' oranges grafted on SO, Volka, and x639 rootstocks; and a new pummelo X grapefruit hybrid cv. 'Redson' grafted on SO, Volka, and macrophylla rootstocks. TSS and acidity levels of all species were lower in juice of fruits on Volka than on SO. Sensory quality evaluations revealed that 'Odem' mandarins and 'Redson' fruits grown on SO were preferred to those on Volka but the rootstocks had no notable effects on flavor perception of 'Or' mandarins and 'Valencia' oranges. Chromatographic analysis revealed that contents of aroma volatiles, especially terpenes, in homogenized segments of 'Odem' and 'Redson' but not of 'Or' and 'Valencia' were significantly lower on Volka than on SO. Overall, the effects of rootstocks on citrus fruit flavor depended on specific rootstock/scion interactions. Furthermore, the flavor of some varieties grown on Volka was inferior to that on SO because of lower TSS and acidity levels and lower aroma volatiles contents.