| ’Huayou’ kiwifruit is a natural hybrid cultivar of yellow-fleshed Actinidia chinensis and green-fleshed Actinidia deliciosa.Yellow flesh is the consequences of natural development and matures,which attracts lots of consumers with high commercial value.In recent years,however,the flesh cannot degreen normally after cold storage and there is no way to solute,causing its commodity value affected seriously.In this paper,the effects of ethylene,controlled atmosphere storage,cold storage temperature and different cooling modes on the flesh color and relative expression quantity of chlorophyll-degradation-related enzyme genes of ’Huayou’kiwifruit during the shelf life were studied,with a view to providing methods to solute the problem that the flesh cannot degreen normally during shelf life;with a view to exploring the physiological and molecular mechanism of chlorophyll degradation of yellow-fleshed kiwifruit.The mail results were showed as follows:1.Influence of ethephon on the firmness,soluble solids content,ethylene release rate,flesh color,hue angle,pigment content of ’Huayou’ during shelf life of different harvest time were studied,exploring the relationship between flesh color and ethephon.(1)The change of flesh color is due to a significant reduction in the content of chlorophyll,and the content of carotenoid has been remained relatively stable.(2)Ethephon cannot turn from green to yellow during 7d shelf life time of 134 day after full bloom(134DAFB),but can promote from green to yellow during shelf life time of fruit harvested at 134-148 DAFB.In other words,Ethephon can turn significantly yellow when fruit grows to a certain stage.(3)134 DAFB was chosen as the optimal time.Flesh color treated with ethephon turn yellow to some degree in the 7d shelf life time,which could shorten yellowing process and meet early market demand.Meanwhile,firmness and ssc were maintained at 1.16kg/cm2 and 15%at the shelf life of 14d,which keeps commodity value.2.Influence of ethephon and 1-MCP on the fruit quality,pigment content and the expression of chlorophyll-degradation-related genes were studied;Influence of 1-MCP on the fruit refrigerated quality and the change of flesh color also were studied,revealing furtherly the relationship and mechanism of flesh color and ethylene.(1)In the early shelf life time,hardness decreasing treated with ethephon was accelerated,and hardness of ’Huayou’ post-harvest fruits and fruit refrigerated were delayed and inhibited by 1-MCP,respectivally.(2)The reduction of chlorophyll content of fruit treated with ethephon and 1-MCP in which harvested at optimal time was accelerated and reduced,respectively.Fruit treated with 1-MCP could turn from green to yellow in the end.(3)Fruit treated with 0.5μL/L 1-MCP in which harvested at optimal time could turn from green to yellow during the shelf life time of 30d and 126d(Spring Festival),although delayed nearly 4 d.(4)Influence of ethylene on the expression of chlorophyll-degradation-related enzyme genes:SGR2,PPH1 and PAO1 gene involved in regulating chlorophyll degradation of’Huayou’ kiwifruit.RCCR,CBR2 and CLH1 gene was likely to play a role in the early regulating chlorophyll degradation of ’Huayou’ kiwifruit.The expression of SGR2 gene was promoted by ethylene.The expressions of PAO1,PPH1 and RCCR gene were affected by ethylene.CBR2 and CLH1 gene could be affected by ethylene.3.Influence of CA(2.5%-3%O2+4%-4.5%CO2)on the fruit quality and change of flesh color during shelf life time of 30d and 126d(Spring Festival)were studied.(1)Hardness of fruit during storage and shelf life time was significantly inhibited by CA.(2)The yellowing of flesh color during shelf life time of 30d and 126d(Spring Festival)could be delayed 4d and 2d by CA,although flesh could turn yellow.(3)Influence of CA on the expression of chlorophyll-degradation-related enzyme genes:①The expression of SGR2 and CBR2 gene during shelf life time of one month and Spring Festival were inhibited by CA.②The expression of PAO1 gene during shelf life time of one month and Spring Festival was inhibited and postponed by CA.③The expression of PPH1 gene during middle shelf life time of one month and Spring Festival were inhibited obviously by CA.④The reduced expression of RCCR gene was likely to be inhibited during the late shelf life time of one month and Spring Festival.This effect could be increased with the extension of storage time.⑤The expression of CLH1 gene was inhibited by CA,but this effect could work in the 1d shelf life time with the extension of storage time.4.The influence of different refrigeration temperature on fruit quality and flesh color during the shelf life was studied.(1)’Huayou’ kiwifruit could turn yellow when stored at 0.5±0.2℃ during the shelf life time of 30d and 126d(Spring Festival),but the fruit cannot degreen normally in the same shelf life and there were some chilling injury when stored at-0.5±0.2℃.Hence,the fruit cannot be ripen when stored at-0.5±0.2 ℃.(2)Influence of low temperature on expression of chlorophyll-degradation-related enzyme genes:①The expression of SGR2,PPH1 and PAO1 gene were inhibited when stored at-0.5±0.2℃.This effect was increased with the extension of cold storage time as to both PPH1 and PAO1 gene.②The expression of CBR2 and RCCR gene were inhibited when stored at-0.5±0.2℃.This effect was increased with the extension of cold storage time.③The decline of expression of CLH1 gene was obviously inhibited during the early shelf life(3d)with the extension of cold storage time.5.Effect of comparison of different cooling modes on the fruit quality and flesh color was studied.The gradual cooling mode(postharvest→5℃→3℃2d→0.5±0.2℃)was chosen as the optimal cooling modes.The hardness and shelf life time and the yellowing of fruit harvested at optimal time were maintained by the gradual cooling.Though(postharvest put in the field in 2d→0.5±0.2 ℃)could turn significantly yellow(it reached the yellowing of flesh at 9d shelf life time,h≤103°),hardness was the lowest,causing the shorten of shelf life time.The yellowing of fruit treated(postharves→0.5±0.2℃)was the slowest.Flesh turned from green to yellow after at 9d shelf life;flesh turned yellow at 11 d(h*102°),but the degree of yellowing of flesh cannot reach the gradual cooling mode(postharvest→5℃→3℃d→0.5±0.2℃).Fruit quality and the change of flesh color were similar to both during shelf life time of 30d and 78d(New Years’ day). |
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