Difference Comparison And Analysis Of Antioxidant Substance And Antioxidant Capability In Different Kiwifruit Genotypes

Kiwifruit is a kind of deciduous fruit tree belong to genus Actinidia Lindl,and its fruit rich in vitamin C.Vitamin C also known as ascorbic acid(AsA),which is an effective antioxidant commonly found in living organisms.In recent years,the rapid development of kiwifruit industry in China had emerged as many new cultivars.There were significant differences in the antioxidant substances and antioxidant capacity of different varieties,but no detailed reports have been reported.The study determined the Vc contents,related enzyme activities and the correlation with antioxidant capacity of 22 kiwifruit varieties.In addition,the contents of AsA,related enzyme activities and the genes involved in AsA synthesis and recycling were studied by using eriantha、latifolia ‘Hongyang’ and ‘Hort16A’ as materials to analyze the reason for the large difference in AsA between kiwifruit fruits,which provided a reference for the evaluation and breeding of kiwifruit nutrients.The main research results were as follows:1.The comparative analysis of the AsA contents of 22 kiwifruit materials showed that the difference of AsA contents in different kiwi fruits were huge.Among them,the contents of AsA in latifolia and eriantha were the highest,above 28.2umol/g;the AsA contents of arguta,deliciosa and melanandra were 9.6-16.3umol/g;and the AsA contents of the others were lowest,below 6.8 umol/g.Among 12 cultivars,the AsA contents in ‘Hayward’,‘Wuzhi3’,‘Fengyue’,‘Guihai4’ and ‘Kuimi’ were relatively higher.The AsA contents of ’Hongyang’ and ’Hort16A’ were the lowest.2.During fruits development,the changes of AsA contents in eriantha、latifolia ‘Hongyang’ and ‘Hort16A’ were consistent,that was,AsA had a higher accumulation in the young fruits but decreased with the ripening of kiwi fruits.The AsA contents of latifolia and eriantha is 7 and 4.5 times that of ‘Hongyang’ and ‘Hort16A’.3.The expression analysis of AsA synthesis-related genes found that the L-galactose pathway is the main pathway for the AsA synthesis in kiwi fruits.The relative expression levels of GMP1,GME1,GGP2,GPP1 and GPP2 are consistent with the changes of AsA levels,indicating that they played the important roles in AsA synthesis of kiwifruit.4.The expression analysis of D-galacturonic pathway and inositol pathway related genes revealed that five D-GalUR and two MIOX genes were expressed during fruit development.Among them,the relative expression of MIOX2 and D-GalUR1 in latifolia weres significantly higher than that in ‘Hongyang’ and ‘Hort16A’;while the relative expression of MIOX2 and D-GalUR5 in eriantha was significantly higher than that of ‘Hongyang’ and ‘Hort16A’,speculate that the D-galacturonic pathway and the inositol pathway were the main causes of high AsA levels in latifolia and eriantha.5.The relative enzyme activities and gene expression analysis of AsA cycle pathway showed that the relative expression of APX2,APX5,APX6,APX7,MDHAR4 in latifolia were significantly higher than that of ‘Hongyang’ and ‘Hort16A’.The enzyme activities of APX and MDHAR in latifolia were laso significantly higher than that of ‘Hongyang’ and ‘Hort16A’.Therefore,the regeneration of AsA were also the main cause of the high AsA level of latifolia and eriantha.