【作者】 许文平；

【导师】 张上隆； 陈昆松；

【作者基本信息】 浙江大学 ， 果树学， 2004， 博士

【摘要】 以跃变型果实‘湖景蜜露’桃[Prunus persica （L．） Batsch cv．‘Hujingmilu’]和‘布鲁诺’美味猕猴桃（Actinidia deliciosa cv‘Bruno’）果实为材料，研究1-甲基环丙烯（1-MCP）对果实后熟软化、乙烯代谢、冷害褐变等影响及相关的分子生物学基础。主要结果如下： 1．构建了猕猴桃Lambda FIX^?噬菌体基因组文库，并从文库中分离得到猕猴桃Expansins编码基因家族的新成员Ad-Exp3；采用RT-PCR从成熟桃果实中克隆到两个Expansins的cDNA片段，即Pp-Exp1和Pp-Exp3；一个ACO的cDNA片段Pp-ACO1，一个PPO的cDNA片段Pp-PPO和一个乙烯受体蛋白cDNA片段Pp-ETR1。 2．桃果实在20℃下后熟时，LOX活性和O₂^?产生速率在后熟软化的前期快速增加，并分别于处理后72h和120h达到峰值，先于乙烯合成相关酶和乙烯释放量高峰的出现；1-MCP处理抑制了LOX活性、O₂^?生成速率、ACS和ACO活性的上升，推迟乙烯跃变的出现，延缓了果实的后熟软化进程。 3．桃果实后熟软化进程中，Pp-Exp1和Pp-Exp3的表达随着成熟度的增加逐渐增强，在果实完熟时mRNA丰度达到最大，1-MCP处理可在一定程度上抑制Pp-Exp1和Pp-Exp3基因的表达；Pp-ACO1表达水平较低且变化不大，1-MCP处理有促进其表达的效应； 4．分别在采后猕猴桃果实的软化启动阶段（Stage Ⅰ）、快速软化前期（Stage Ⅱ）、快速软化阶段中期（Stage Ⅲ）进行1-MCP处理，发现随着果实成熟度的增加，1-MCP处理对乙烯合成的抑制和果实成熟的延缓效应逐渐减少以至消失。 5．桃果实经0℃冷藏40d后进入20℃货架期，果肉组织相对电导率显著性上升，果肉褐变加剧；虽然1-MCP处理对冷藏期间的相关品质及其生理变化的影响不是很明显，但在冷藏后的20℃货架期中，1-MCP处理可抑制了果实LOX活性的增加，减少O₂^?的积累和乙烯的释放，延缓组织相对电导率的增加，抑制了PPO活性的增加和减缓总酚含量的下降，显著减轻果肉组织的褐变程度；以Pp-PPO为探针的Northern杂交结果表明，1-MCP处理可以抑制货架期间Pp-PPO mRNA的积累，这与生理生化的研究结果相一致。果肉褐变指数上升与多酚氧化酶（PPO）活性增加呈极显著性正相关关系(r=0.9045^**)，与总酚含量减少呈极显著性负相关关系(r=-0.8324^**)。更多还原

【Abstract】 Climacteric fruits, "HujingmiltT peach [Prunus persica (L.) Batsch cv. ’Hujingmilu’] and "Bruno" kiwifruit (Actinidia delciosa cv. ’Bruno’) were used to study the effects of 1-MCP on postharvest fruit softening, ethylene biosynthesis and chilling injury-induced browning, whose regulation mechanism was also investigated in the present experiment. And the obtained results were described as following:1. Lambda genomic DNA library was constructed from young leaves of kiwifruit, and successfully used as template to mine gene Ad-Exp3 coding for Expansins. In ripening peach fruit, Pp-Expl, Pp-Exp3, Pp-ACOl, Pp-PPO and Pp-ETRl was cloned by RT-PCR.2. Under 20℃ storage, LOX activity and 62’ production rate increased rapidly at the initiation o f p each fruit s oftening, a nd r cached p eak v alue at72ha nd!20h, respectively. 1-MCP treatment inhibited LOX activity, slowed down O2-production rate, decreased ACS and ACO activities, suppressed ethylene biosynthesis, and thus delayed peach fruit senescence.3. In peach fruit, the mRNA levels of Pp-Expl and Pp-Exp3 accumulated during fruit softening, and could be allevated by 1-MCP treatment. The level of Pp-ACOl mRNA accumulation at 20℃ was relative low and could be enhanced by application of 1-MCP.4. 1 -MCP was applied at three stages of kiwifruit ripening including stage I (initial stage of softening), stage II (early stage of rapid softening) and stage III (middle stage of rapid softening). The results showed that the ability of 1-MCP in suppressing ethylene biosynthesis and delaying climacteric peak faded away with the fruit ripening.5. Peach fruit was transferred into 20℃ after 40 d storage at 0℃, which resulted in increase in relative electric conductivity significantly and led to flesh browning. The positive effects of 1-MCP treatment on fruit quality were not observed at 0℃ until fruit had been shifted to 20℃. 1-MCP treatment led to decrease in LOX activity, O2- accumulation, ethylene production, inhibited relative electric conductivity rise, suppressed PPO activity and declined total phenol content, andthus significantly alleviated flesh tissue browning. Northern blot of Pp-PPO showed that 1-MCP could inhibit Pp-PPO mRNA accumulation, which was consistent with that of the physiological changes. Furthermore, there existed significant positive relationship between flesh browning index and PPO activity (r= 0.9045**), and significant negative relationship between browning index and total phenol content (r= -0.8324**)更多还原