Induction of Berry Abscission in Vitis Vinifera by Morphactins

¹ Department of Viticulture and Enology, University of California, Davis.

Two derivatives of fluorene-9-carboxylic acid, termed morphactins, were tested on both seeded Vitis vinifera `Muscat of Alexandria' and seedless `Thompson Seedless' and `Black Corinth' grapes. Berry abscission was induced when the compounds were applied at the fruit-set stage or two weeks later. When morphactins were applied near maturity, no berry drop occurred although the strength of berry attachment was reduced. An auxin (4-CPA) counteracted the morphactin response, indicating that it may involve auxin metabolism.