Analysis Of Aroma Substance And Related Gene Expression Of 'RuiXue' Apple(Malus Domestica Borkh.)

Apple(Malus domestica Borkh.)is one of the most important fruits in the world,with important edible value and economic value.At present,more and more attention is paid to the quality of fruits in the market.Aroma substances are one of the factors that determine the quality of fruits and affect the ultimate acceptance of fruits by consumers.'Rui Xue' is a yellow late-ripening apple variety selected from the cross of 'Qinfu No.1' × 'Cripps Pink'.The experiment mainly used 'Rui Xue' and the representative cultivar 'Fuji' as materials,and carried out experimental research on 'Rui Xue' and 'Fuji' fruits under different developmental stages and bagging treatment with 'Rui Xue' fruits.During the development period,the soluble sugar,titratable acid and aroma substances in the fruit were measured and analyzed.At the same time,the change of ethylene production was also measured,and the key genes in the synthesis process of aroma substances were identified and analyzed.The aim is to provide a theoretical basis for the evaluation of the quality of 'Rixue' apples and the study of the synthesis of apple aroma substances.The main results obtained are as follows:1.With the development of the fruit,the soluble solids and sugar-acid ratio of the two apple fruits of 'Rui Xue' and 'Fuji' gradually increased,but the titratable acid content gradually decreased.There is no significant difference in titratable acid between bagged'Rui Xue' fruit and unbagged 'Rui Xue' fruit,but the content of soluble solids is higher in unbagged fruit than bagged fruit.2.Total of 82 aroma substances were detected in the fruits of two apple cultivars,'Rui Xue' and 'Fuji',mainly including aldehydes,esters,alcohols and olefins.In general,the total amount and types of aroma substances in apple fruit at different development stages of apples are increasing,and at the same time,the process of changing from aldehydes to esters is shown.Total of 68 aroma substances were detected in the 'Rui Xue' cultivars,including 46 species of bagging and 62 species of non-bagging.The aldehyde content of bagged fruits was significantly higher than that of unbagged fruits,and the content of esters and alkenes was significantly lower than that of unbagged fruits.Studies have shown that bagging will delay the conversion of aldehydes to esters and reduce the concentration of total aroma substances.3.Determine the relative expression of genes related to aroma substance synthesis inapple fruit.The results showed that during the ripening of 'Rui Xue' apples,a total of 10 genes were increasing in expression,namely Md AAT2,Md AADC,Md ACPD,Md ADH3,Md Ar AT,Md LOX,Md MCAT,Md PDC2,Md ACP2,Md HPL,but the relative expressions of Md BCAT2 and Md AOS cut back.Comprehensive analysis showed that Md LOX,Md AAT2,and Md ADH3 may be related to fruit aroma synthesis during apple development.Analysis and research of bagging 'Rui Xue' fruits,found that bagging treatment had an effect on genes related to aroma synthesis.In particular,the Md LOX and Md ADH3 genes have the most significant differences,which indicates that bagging treatment will lead to the down-regulation of Md LOX and Md ADH genes in fruits,which will affect the synthesis of aroma substances in fruits,and then change the quality of apple fruits.4.Through the analysis and analysis of the relative expression levels in two apple fruits of 'Rui Xue' and 'Fuji'.The study found that the expression levels of Md ERF,Md ERS2,Md ACS3,Md ACS2,and four ethylene synthesis-related genes have increased in varying degrees during apple fruit development.It shows that during the development of fruit,the increase of ethylene production will promote the synthesis of apple fruit aroma substances.According to the measurement of ethylene production and the relative expression of ethylene synthesis gene Md ERS2 at various stages of bagging treatment of 'Rui Xue' fruit,the ethylene production of bagged fruits was significantly lower than that of non-bagged fruits.At the same time,the quantitative results of Md ERS2 gene also showed that the relative expression was lower in bagged fruits than that in unbagged fruits.Studies have shown that bagging treatment can reduce the production of apple fruit ethylene and negatively regulate the synthesis of apple aroma compounds.