REDUCTION IN ETHYLENE SYNTHESIS IN PARTHENOCARPIC ACTINIDIA-DELICIOSAFRUIT INDUCED BY N-(2-CHLORO-4-PYRIDYL)-N'-PHENYLUREA

Parthenocarpic kiwifruit Actinidia deliciosa was produced and inductio n of ethylene synthesis in response to ethylene treatment studied. At anthesis, flowers were treated with N-(2-chloro-4-pyridyl)-N'-phenylur ea (CPPU). CPPU-treated parthenocarpic fruit and pollinated normal fru it were harvested in early November, and then treated with 1000 mu l l (-1) ethylene at 20 degrees C for 24 h. Ethylene production following ethylene treatment was reduced and delayed in the parthenocarpic fruit . To investigate the mechanism of this reduction in ethylene synthesis , 1-aminocyclopropane-1-carboxylic acid (ACC) concentrations, and gene expression of ACC synthase (using a cDNA probe, AD-ACS1) and of ACC o xidase (with a cDNA probe, AD-ACO1) were analyzed. ACC concentrations and levels in ACC synthase transcripts increased in the pollinated fru it 2 days after the 24 h ethylene treatment, but not in the parthenoca rpic fruit. Accumulation of ACC oxidase transcripts was stimulated imm ediately by the 24 h ethylene treatment in both pollinated and parthen ocarpic fruit. These results suggest that suppression of ethylene synt hesis in parthenocarpic fruit resulted mainly from suppressed expressi on of ACC synthase. (C) 1998 Elsevier Science B.V. All rights reserved .