Effects of (2-Chloroethyl)phosphonic Acid and Succinic Acid-2,2-dimethylhydrazide on Sex Expression in Muskmelon1

Abstract

Abstract The effects of (2-chloroethyl) phosphonic acid (ethephon) and succinic acid-2,2-dimethylhydrazide (SADH) on sex expression in muskmelon were tested through a series of greenhouse and field experiments employing 2 experimental monoecious hybrids and 1 andromonoecious cultivar. Plants treated with 4,000 to 5,000 ppm SADH were severely dwarfed and produced fewer male, and in monoecious hybrids, fewer female flowers than untreated controls. Ethephon treatments at 240 or 480 ppm in the greenhouse and 500 ppm in the field completely inhibited male flowering and promoted female flower initiation for an extended period. The combination of SADH and ethephon affected flowering in a manner similar to ethephon alone. Ethephon induction of a temporary gynoecious condition in monoecious muskmelons has potential for development of hybrid muskmelons. The results do not support the contention that ethylene, the active product of ethephon, acts as a gibberellin antagonist in regulating sex expression. It is suggested that natural endogenous levels of ethylene might be involved in sex expression in cucurbits, and that applied ethephon would augment that involvement.