Effects Of 1-MCP And Ethephon On Degradation Of Jackfruit Fruit Starch

Jackfruit?Artocarpus heterophyllus Lam?is rich in starch during harvest.During its ripening process,the rapid degradation of pulp starch is the key to the rapid softening of the fruit texture and the formation of flavor quality.Post-harvest starch degradation is a complicated process.Although there have been studies on starch in banana and kiwi fruit,there is little research on starch degradation during jackfruit ripening,and there are many unknowns.Amylase is an important hydrolytic enzyme in starch degradation.In this study,'haida-2'jackfruit was used as the material and treated with 0.5 mg/L 1-mcp and 1000 mg/L ETH to study the effects of ETH and1-MCP treatment on the changes of pulp cell microstructure,fruit quality,AMY activity,BAM activity,starch degradation,Ahe AMY1/2/3 and Ahe BAM1/3/6/8expression and their correlation in the post-ripening process of jackfruit.The results are as follows:1.During the softening process of jackfruit,the starch granules gradually disappeared,the cells became loose,the cell gap increased,the number of Primary orifice field increased,and the cell wall gradually thinned to crack at later stages.ETH treatment accelerated the softening process of jackfruit and had no obvious effect on cell structure and other aspects.1-MCP treatment slowed the softening process of jackfruit,and there were still a few starch granules in the cells in the late storage period.2.Jackfruit is a starch-converted fruit and sucrose-accumulating fruit.The total starch content in immature jackfruit pulp is as high as 159.4 mg/g,of which amylopectin is about 2.65 times that of amylose.Sucrose accounted for 74.3%of the total in fully ripe fruit.ETH treatment accelerated the softening of jackfruit,promoted the increase of TSS and sugar content,and made the jackfruit mature 2 d earlier.The1-MCP treatment reduced the fruit softening rate,inhibited the rising rate of TSS and sugar content,and extended the shelf life of fruit for 7 d.3.In this experiment,Ahe AMY1/2/3 and Ahe BAM1/3/6/8 were cloned into 7full-length amylase genes with lengths of 1269 bp,1212 bp,2718 bp,1791 bp,1608bp,1683 bp and 2019 bp.The encoded proteins are all hydrophobic proteins.The secondary structure is composed of random coils,extended chains and?-helices.Its three-dimensional structure is relatively similar.They are composed of hydrogen bonds,?-helices,corners and?-sheets.They contain a typical??/??₈barrel core4.The activity of beta-amylase in normal post-ripening fruits was peak-like and reached a peak at 3 d.Both ETH and 1-MCP treatment reduced the activity of?-amylase and improved the activity of?-amylase.ETH treatment accelerated the degradation rate of amylopectin and amylose,and advanced the appearance of the peaks of?-amylase and?-amylase activity by 2 d.The 1-MCP treatment significantly delayed the degradation of the two starches and inhibited the increase of the two amylase activities.5.The expression levels of Ahe AMY1/2/3 and Ahe BAM3 were high during the post-ripening process of jackfruit.The ETH treatment advanced the expression peaks of Ahe AMY1/2/3 and Ahe BAM3,and maintained the high expression levels for a long time.The 1-MCP treatment inhibited the expression of Ahe AMY1/2/3 and Ahe BAM3in the early stage of storage,and increased the expression of Ahe AMY1/2/3 and Ahe BAM3 in the later stage of storage.In CK and ETH treatment,the expression level of Ahe BAM 1/6/8 was low,but the 1-MCP treatment up-regulated the expression of these three genes and delayed the peak time.6.The correlation analysis showed that the hardness of the fruit was significantly correlated with the content of amylopectin and amylose,and negatively correlated with the content of fructose,sucrose and glucose.There was a significant correlation between the activity of?-amylase and the content of starch.1-MCP treatment reduced the correlation between the two,while ETH treatment had no effect.There was a significant correlation between Ahe AMY1/2/3 and the expression of Ahe BAM3,and ETH treatment reduced their correlation.The expression of Ahe AMY1/2/3 and Ahe BAM3 was significantly correlated with the activity of?-amylase,and the correlation was reduced by 1-MCP treatment.To sum up:starch content is an important factor that affects the hardness of jackfruit.The degradation of starch during fruit ripening is an important reason for its hardness decrease.?-amylase is a key hydrolytic enzyme for starch degradation,and Ahe BAM3 gene is also an important gene encoding?-amylase.It may have some synergy with Ahe AMY1/2/3 gene during fruit ripening.