| Raspberry is a kind of small fruit tree with both nutritional and health values.Its fruit belongs to the aggregate drupelet,which is separated from the receptacle,extremely soft and not durable at maturity.Ethylene,as a plant endogenous hormone,plays an important role in regulating fruit ripening and development.In this study,the raspberry cultivar‘Heritage’was used as a test material,the raspberry fruits at different developmental stages(large green,white,mottled,ripe and overripe)were collected and the fruits at white stage were treated with ethephon and 1-MCP(an inhibitor of ethylene).The changes of ethylene production rate,the respiration rate,the activities of ACC synthase(ACS),ACC oxidase(ACO),the relative expressions of RiACSl and RiACO1 genes,fruit ripening related physiological indicators were measured in different parts(fruit with receptacle,drupelets and receptacle)of raspberry fruit at different developmental stages and different treatments.The aim was to further determining the respiration type of raspberry fruits,and to explore the possible role of ethylene in the development and maturity of raspberry fruits from both physiological and molecular aspects.The main results were as follows:(1)During fruit development and maturity,both respiration rate and ethylene production rate of raspberry drupelets changed steadily,while the ethylene in the fruit with receptacle was detected start at the mottled.And the ethylene production rate was the highest in the maturity Ⅱ.At this time,the ethylene production rate is 2.860 times than the mottled,however the respiration rate reaches the highest during the mottled,but the change range was not significantly.The respiratory rate and ethylene production rate of receptacle increased significantly from maturity Ⅰ to maturityⅡ,and then decreased significantly.Therefore,the receptacle was the main part for producing ethylene in raspberry fruit.According to the change characteristics of respiration rate and ethylene production rate in drupelets as edible part,at the same time,combining with the characteristics of ripening raspberry fruits without post-ripening after harvest and easy to rot after storage at room temperature,it was speculated that raspberry fruits should belong to non-climacteric fruits.(2)Treatment of ethephon significantly promoted the coloration of raspberry fruit and the appearance differences were the largest among different treatments 24 h after treatment;For the effect on hardness,fluoridone plus ethephon(F+E)treatment had no significantly difference to the treatment only by fluoridone(F)at 18 hours and 24 hours after treatment,however,the value of hardness was lower than fluoropyridone(F)treatment.It could be found that ethephon treatment promoted the softening of the fruit nevertheless.1-MCP significantly inhibited fruit coloring,slowed down the rate of hardness reduction,and delayed fruit ripening effectively.(3)After the treatment of raspberry fruit by ethephon,the changes in the physiological indicators of fruit with receptacle,drupelets and receptacle were consistent:It could increase the content of reducing sugar,soluble sugar,anthocyanin and reducing pectin,accelerate the accumulation of ABA content,and reduce the content of titrable acid,chlorophyll,protopectin and cellulose,while 1-MCP effectively suppressesed the above results.For the effects on the above physiological indexes,the promotion effect of ethylene and the inhibitory effect of 1-MCP on the fruit with receptacle,drupelets and receptacle could be clearly find at 18 h,24 h,especially 24 h after treatment.(4)The trend of changes in ACS,ACO activities and relative expressions of RiACO1 and RiACS1 genes in raspberry fruits at different development stages were basically the same as the respiratory rate and ethylene production rate.After ethylene treatment,the ethylene production rates in fruit with receptacle,drupelets and receptacle increased within a short time,which could increase the ACS and ACO enzyme activities and the transcription levels of RiACS1 and RiACO1 genes,but 1-MCP inhibited this process.Treated with ethephon had small effect on respiratory rate of fruit,but treated with 1-MCP significantly inhibited the respiratory rate in drupelets and receptacle. |
