Effect Of GA₃ And NAA On Postharvest Physiology And Expression Of CDK-Exp3 In Relation To Softening Of Persimmon Fruit

The persimmon fruit is not suitable for long-term storage and transportation for they tend to soften after harvest, which remarkably limit the storage and freshness and market circulation and restrict the economic value.Therefore,the research on the mechanism of fruit softening is the theory base of the application of storage technique.The research was performed with the fruit material of persimmon(Diospyros Kaki L. cv. Fuping Jianshi).After harvest the fruit was given the following treatment: (1)gibberellic acid(GA3), 60mg/L;(2)naphthylacetic acid(NAA),20mg/L;(3)1-MCP,1.0 ul·L-1;(4)propylene, 5000 ul·L-1. The changes of physiological indices of persimmon fruit treated with GA3 and NAA in relation to delayed-ripening and softening of persimmon fruit and the pectin metabolism were studied during the storage Meanwhile, the mRNA accumulation of CDK-Exp3 in persimmon fruit with the 4 treatment above was examined using SYBR Green I Real Time PCR to investigate the expression profile of CDK-Exp3. This study was conducted to investigate the possible relationship between expression of CDK-Exp3 and fruit softening and the influence of GA3,NAA,1-MCP and propylene on postharvest softening of persimmon fruit.Results showed that the storage time of groups treated with GA3 and NAA was delayed for 4 days and 10 days respectively, GA3 and NAA treatment significantly postponed the decrease in the flesh firmness and decreased the ethylene production and the respiration rates, of which the peak was retarded compared with the control group; GA3 and NAA treatment remarkably inhibited polygalacturonase (PG) activities, which delayed the depolymerization of protopectin and reduced the increase of water soluable pectin(WSP), thereby restraining the process of fruit softening. The expression of CDK-Exp3 rose dramatically after harvest and then drop gradually at the later stage of storage.The treatment of NAA , GA3 and 1-MCP inhibited the expression of CDK-Exp3 and retarded the appearance of the expression peak. The expression of CDK-Exp3 in persimmon fruit with propylene treatment was promoted and the expression peak occurred 4 days earlier than control group.As a conclusion , GA3 and NAA treatment can put off the delayed-ripening and softening of persimmon fruit and the effect of GA3 treatment was better than that of NAA; The expression of CDK-Exp3 had a close relationship with fruit softening.