| In general,peach belongs to climacteric fruits.Its ripening process was accompanied by a strong respiration and ethylene release.Fresh peaches are seasonal fruits,they have only 2 to 5 days' shelf life under normal temperature with poor storage transportation performance.People usually adjust market supplies and demands with different maturities of peaches.The flesh texture are divided into four categories which are softmelting,hardmelting,non-melting and wooliness.In recent years,Japanese scientists proposed a new type of flesh texture in peaches,named Stonyhard.In order to compare the storage characteristics of different flesh texture of peaches,understand the relevant information of the ethylene biosynthesis and signal transduction pathways,this study investigated the changes of ethylene production,fruit firmness,soluble solid content,main sugar and organic acid of soft melting,hard melting,non-melting and Stonyhard peaches,conbined the expression of some genes in the ethylene biosynthetic,singnal transduction and soften pathways.The results showed as follows:1.In order to identify the flesh texture and genotype of 'Xiacui',fruits of 'Yinhualu','Hujingmilu','Babygold 6','Yumyeong' and 'Xiacui'(Prunuspersica)were harvested in 8 tenth maturity and then stored at 25 ?.The ethylene production and flesh firmness were measured during storage.The results showed that fruit ethylene production of 'Yinhualu','Hujingmilu' and 'Babygold 6' appeared a rise then falling trend with significant peaks,the flesh firmness of them decreased with time going on,and were lower than 1.0 kg/cm2 with'Yinhualu' and 'Hujingmilu' by the end of storage.While only a little of ethylene production were detected after harvest with 'Yumyeong' and 'Xiacui',and the treatment of endogenous ethylene failed to induce a rapid loss of flesh firmness of the latter,it could retain more than 3.5 kg/cm2 in the last period of storage.All these proved that the flesh texture of 'Xiacui' peach cultivar is Stonyhard,and its genotype could be hdhdmm.2.In order to compare the storage characteristics of different flesh texture and maturity of peach,three cultivars of 'Xiahui 1' soft-melting peaches,'Xiahui 6' hard-melting peaches and non-melting 'Jinhui' peaches were used to analyze the changes of flesh firmness,ethylene production,soluble solid content,main sugar and organic acid of two harvest maturities,including 7 tenth and 8 tenth.The results showed that all fruits of three peach cultivars have normal ethylene release peaks.The non-melting cultivar peaches possessed the longest shelf-life,accompanied with lower soluble solid and main sugar content,compared to that of the soft-melting and hard-melting cultivars.However,'Xiahui 6' fruits of 8 tenth maturity had higher amount of soluble solid and main sugar content,and had better flavor during storage.The hard-melting cultivar peaches had better effect during shelf-life storage,and fruits of 8 tenth maturity kept better shelf-qualities.3.To study temperature modulate peach ripening and ethylene biosynthetic pathways,different cultivars of 'Xiacui' and 'Yumeyong' with Stonyhard,'Yinhualu' with soft-melting,'Hujingmilu' with hard-melting,and 'Baby gold 6' with non-melting in 8 tenth maturity were collected as test materials.The ethylene production and firmness analysis showed that only a little ethylene production were detected after harvest with fruits of'Yumeyong' and 'Xiacui',under either room temperature(25 ?)or low temperature(4 ?).The fruit firmness of Stonyhard cultivars retain at high level under room temperature with time going on,whereas low temperature induced 'Yumeyong' fruit to soften.Real-time quantitative PCR results indicated that PpACS1 gene was highly expressed in soft-melting,hard-melting and non-melting cultivars,but extremely low in Stonyhard peaches.However,PpACS2 or PpACS3 could not be detected in all five cultivars.Moreover,cold treatment induced the expression level of PpACO1 gene in 'Xiacui' and 'Yumeyong' peaches,and significantly enhanced endo-PG expression in 'Yumeyong' peaches.In conclusion,this study revealed that fruit softening of peaches with different flesh textures were closely related to ethylene biosynthesis during the storage period,which were controlled via regulating relevant gene expression levels under different temperatures.4.Taking the fruit of peach cultivar 'Yinhualu' with soft-melting,'Hujingmilu' with hard-melting,'Babygold 6' with non-melting,'Xiacui' and 'Yumeyong' with Stonyhard in 8 tenth maturity as test materials to study different postharvest conditions modulate ethylene signal transduction pathways in peaches.The results showed that the expression of PpERS1 in soft-melting,hard-melting and non-melting peachs appeared a rise then falling trend 25?,in association with changes in ethylene biosynthesis,the PpCTR1 and PpEIN2 mRNA increased with starting time of storage,then decresed but increased again by the end of the storage.These two gene's expreesion trend in 'Xiacui' decresed firstly and then up-regulated,but maintained at a stable level in 'Yumeyong'.Moreover,cold treatment induced the expression level of PpCTR1 and PpEIN2 gene in all fruits of five peach cultivars.In conclusion,the expression of PpERSl was closed related to ethylene biosynthesis,PpCTR1 and PpEIN2 may participate the regulation of senescence process. |
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