The influence of rootstocks on the composition of oranges, with special reference to bitter principles

Abstract

A study was made of the effects of rootstock on the composition of Washington Navel oranges grown on eight rootstocks and Valencia Late oranges grown on three rootstocks in several regions during six seasons. Among the three major commercial rootstocks, trifoliate orange and rough lemon exerted contrasting influences on orange composition, while sweet orange occupied an intermediate position. The effects of rootstock were similar on both scion varieties but were more marked with Washington Navel oranges. Trifoliate orange stock tended to give high yields of juice which was high in acidity and soluble solids content but low in ascorbic acid content and in bitter taste when canned. Rough lemon stock tended to give low yields of juice which was lam- in acidity and soluble solids content but high in ascorbic acid content and in bitter taste. A positive correlation was demonstrated between the bitter taste of canned juices and the concentrations of limonoid bitter principles in the peel of Washington Navel oranges, and in the peel and seeds of Valencia Late oranges. Trifoliate orange stock promoted the disappearance of bitter principles from all parts of the fruit with advancing maturity, but rough lemon stock retarded this process. Tangelo and Cleopatra mandarin stocks resembled trifoliate orange in their effects on orange composition. while sweet lime, Kusaie lime, and East Indian lime stocks resembled rough lemon.