EFFECT OF GIBBERELLIC-ACID AND 2-(3,4-DICHLOROPHENOXY)TRIETHYLAMINE ON NOOTKATONE IN GRAPEFRUIT PEEL OIL AND TOTAL PEEL OIL CONTENT

The nootkatone content in grapefruit peel oil extracted from flavedo and the peel oil content of fruit receiving preharvest treatment with 20 or 50 ppm gibberellic acid (GA) and/or 50, 125, or 250 ppm 2-(3,4-dichlorophenoxy)triethylamine (DCPTA) were determined. Treatment by GA reduced the rate of increase in nootkatone concentration observed in control fruit with maturation, and the effect was dose-dependent. When DCPTA was used alone as the growth regulator, nootkatone content increased significantly. When 50 ppm GA followed DCPTA treatment at the three levels used above, the effect of GA predominated and nootkatone content was significantly lower than that found in untreated fruit. Treatment by GA generally increased peel oil concentration. © 1990, American Chemical Society. All rights reserved.