Submitted to: Proceedings of Plant Growth Regulation Society of America
Publication Type: Peer reviewed journal
Publication Acceptance Date: 3/1/2012
Publication Date: 11/1/2012
Citation: Petracek, P.D., Sun, D., Dou, H., Stover, E.W. 2012. Gibberellic acid (GA3) effects on late season grapefruit peel oil composition. In: Proceedings of the 38th Annual Meeting of the Plant Growth Regulation Society of America. 38:108-116. Interpretive Summary: Gibberellic acid (GA3) is a plant growth regulator that is commonly applied to citrus fruit in the late summer/early autumn to keep fruit peel attractive and extend acceptable late season quality. In this study, the effect of August/September GA3 application on oil composition of "Marsh" white grapefruit peels was investigated when fruit were harvested in March 18 and April 16 from each of three groves. GA3 significantly increased some oil components and decreased others with different responses seen on different harvest dates. GA3 applications significantly reduced postharvest pitting (a major cosmetic disorder of fresh grapefruit) incidence of the March 18 harvest, but not the April 16 harvest. Oil composition and postharvest pitting were significantly different between groves for both harvests. Levels of two oil components (sabinene and ocimene) were relatively low in the grove with the lowest postharvest pitting incidence, suggesting the possibility that occurrence of these compounds may be related to this postharvest disorder.
Technical Abstract: Gibberellic acid (GA3) is commonly applied to citrus fruit in the late summer/early autumn to delay peel maturation and extend late season quality. The effect of August/September GA3 application on oil gland composition of "Marsh" white grapefruit harvested in March 18 and April 16 from three groves was examined by capillary GC/MS analysis of 25 constituents. In the March harvest, GA3 significantly increased limonene and significantly decreased linalool and trans-caryophyllene. In the April harvest, GA3 significantly increased phellandrene, limonene, trans-linalool oxide and significantly decreased sabinene, ß-pinene, linalool, a-terpineol, trans-caryophyllene, and nootkatone. With respect to changes in percent composition, limonene increased and nootkatone decreased the most with GA3. Harvest date had the greatest effect on limonene levels in which levels decreased for the later harvest date. GA3 significantly reduced postharvest pitting incidence of the March 18 harvest, but not the April 16 harvest. Grove significantly affected both oil composition and postharvest pitting for both harvests. Sabinene and ocimene levels were relatively low in the grove with the lowest postharvest pitting incidence.