Effects Of Calcium Chloride Treatment On Softening And Ethylene Biosynthesis Of Harvested Papaya Fruit

Papaya(Clausena lansium(Lour.)Skeels)belongs to the papaya genus of the papaya family.It is a breath-evolving fruit.It is easy to produce a large amount of ethylene during post-harvest storage,which is easy to soften and rot,causing quality fission and loss of commercial value.Therefore,the research on post-harvest storage and storage of papaya fruit is of great significance to the sustainable development of papaya industry.In this study,a variety of ’Sunrise’ papaya fruits was used as the test material.After calcium chloride treatment(CK,1%,3%,5%)was immersed for 15 minutes,the cell wall degradation genes and ethylene synthesis genes were studied to soften the papaya fruit after harvest Response mechanism,and its correlation with papaya fruit quality deterioration.The main results are as follows:1.The effects of calcium chloride treatment on the storage quality and post-harvest physiology of papaya fruits were studied.Using ’Rising’ papaya fruit as the test material,the post-harvest papaya fruit was placed in calcium chloride with a concentration of 0%,1%,3% and 5% for 15 minutes,and then transferred to a constant temperature incubator 20(±1)Store until 16 days,take samples every 4 days to determine texture changes,various quality and physiological indicators.The results showed that: compared with the control,during the storage of papaya fruit,the fruit texture changed,and its hardness was significantly positively correlated with chewability,adhesiveness,elasticity,cohesion,and recovery,and all showed a downward trend;Viscosity and hardness showed a very significant negative correlation,and showed an upward trend during storage.Different concentrations of calcium chloride treatment can effectively delay the hardness of papaya fruit and the color of the peel to turn yellow,reduce the rate of ethylene release and respiratory intensity and delay the appearance of ethylene release peaks and respiratory peaks,delay the hydrolysis of original pectin and soluble pectin Increase,inhibit the activity of fruit softening related polygalacturonase(PG)and β-galactosidase(β-Gal),inhibit the activity of ACS and ACO,the key enzymes of ethylene synthesis,and reduce the ACC content of ethylene synthesis substrate This delays the post-harvest fruit ripening and aging process,which is beneficial to delay the softening of papaya fruit and prolong the storage life.Among them,the preservation effect of 3% calcium chloride treatment concentration is the best,and the preservation treatment of papaya with 1% and 5% calcium chloride treatment concentration There is no significant difference in effect.2.Screened and obtained the gene family members related to papaya fruit ripening and softening.Using the papaya RNA-Seq database,4 differentially expressed genes for pectin degradation and 7 ethylene synthesis were screened and named CpPG125.9,CpPG250.6;Cpβ-Gal25.57,Cpβ-Gal93.34;CpACS1.CpACS2;CpACO1,CpACO2,CpACO3,CpACO4,CpACO5.The gene expression responded differently to calcium chloride.Among them,the expressions of CpPG125.9,CpPG250.6 and Cpβ-Gal93.34 were inhibited by different concentrations of calcium chloride treatment,including 3% concentration The effect was most significant.The expression of Cpβ-Gal25.75 was inhibited or delayed by treatment with different concentrations of calcium chloride,of which 1% and 5% concentrations of calcium chloride treatment delayed the arrival of peak expression,while 3% treatment concentration of papaya gene expression Significantly suppressed.The expressions of CpPG and Cpβ-Gal were positively correlated with papaya fruit softening,and the inhibitory effect of 3% calcium chloride treatment concentration was the most significant.Among the 7 ethylene synthesis genes,the gene expression of CpACS1 at 4 days decreased by 38.2%,59.8%,and 67.64% compared with the control,which was significantly lower than that of the control group;the gene expression of CpACS2 at8 d was comparable to that of the control.Compared with the control group,the decline rates were 39.5%,84.8%,and 43%,respectively,which were significantly lower than those of the control group;the gene expression levels of CpACO1 at 4days were 59.7%,88.6%,and 76.2%,respectively,which were extremely low Compared with the control group;the gene expression of CpACO2 at 4 days decreased by 85%,86.3%,and 75.9% compared with the control,which was significantly lower than the control group;the gene expression of CpACO3 at 4 days decreased by 4% 59.8%,81.1%,and 72.8%,respectively,which was significantly lower than that of the control group;the gene expression levels of CpACO4 at 4 days decreased by 90.8%,95.2%,and 89.7% compared with the control group,which was significantly lower than that of the control group;Compared with the control,the gene expression value of CpACO5 at 8 days decreased by 30.1%,78.3%,and 67.7%,which was significantly lower than that of the control group;the expression levels of the above seven groups of ethylene synthesis-related genes were inhibited by calcium chloride,Where the treatment concentration of 3% has the most inhibitory effect Significant,but the best effect CpACS1 gene 5% calcium chloride was slightly better than the group treated group 3% calcium chloride.In summary,this study found that treatment with different concentrations of calcium chloride can effectively delay the post-harvest softening and quality deterioration of papaya fruits,and 3% calcium chloride treatment has the best effect.