SYNTHETIC CYTOKININS CONTROL PERSIMMON FRUIT SHAPE, SIZE AND QUALITY

The effect of three synthetic cytokinins on fruit development of persi mmon (Diospyros kaki L.) 'Hiratanenashi' was studied by spraying flowe rs or young fruitlets with 10 or 100 ppm 4PU-30 and TDZ, and 100 or 10 00 ppm BA. The most effective for promoting fruit growth was 4PU-30 at 100 ppm, followed by TDZ at 100 ppm and 4PU-30 at 10 ppm. BA at 100 o r 1000 ppm and TDZ at 10 ppm had no effect on the fruit enlargement. A t 100 ppm, 4PU-30 produced flatter fruit, by promoting transverse grow th. Both 4PU-30 and TDZ retarded ripening, as evidenced by delayed chl orophyll degradation and low sugar accumulation. Comparison between pr ebloom and postbloom applications on cvs Tonewase and Saijo revealed t hat the former treatment produced flatter, heavier fruit than did the latter. The treated fruit also contained less sugars, especially the r educing sugars, than did the control fruits, indicating that the ripen ing process was also retarded in these cultivars.