Abstract
Peel puffing of Satsuma mandarin (Citrus unshiu Marc.) is a serious problem in the citrus industry. High temperature and high humidity during ripening are known to enhance peel puffing. The puffy fruits are easily damaged to fall in value during storage and transportation. It is required that stably effective methods are developed. It has been found that combined application of gibberellin (GA) and prohydrojasmon (PDJ) in September or early October reduces peel puffing in a late maturing cultivar, 'Aoshima-unshu'. In this study, to develop the method for early or medium maturing cultivars, time for combined application of GA (5ppm) and PDJ (50ppm) was examined in extremely early maturing 'Iwasaki-wase', early maturing 'Okitsu-wase', and medium maturing 'Silver hill-unshu'. As a result, by the application in September for those cultivars, the alleviatory effects on peel puffing were very influential, but the delay of peel coloring was serious. Overall, the application in August or before that was considered to be practical for those cultivars. On the other hand, quantitative changes of endogenous phytohormone were investigated in order to elucidate the mechanism of peel puffing alleviation by the application. The combined application of GA and PDJ in September 20 for 'Aoshima-unshu' significantly suppressed the increase of abscisic acid in the peel of fruits. It is possible that the suppression may be related to the effects of the application.
