Quality analysis and comprehensive evaluation of 35 Actinidia argute accessions

Abstract：【Objective】The fruit quality of Actinidia argute was evaluated comprehensively, and a fruit quality evaluation system was established for selecting excellent resources of A. argute.【Methods】 Fruits of 35 A. argute were used as the test materials for determining the fruit appearance quality and 21 other quality indexes. The appearance quality indexes included fruit shape, fruit color, shoulder shape and fruit tip shape, and the 21 quality indexes included single fruit mass, transverse diameter, longitudinal diameter, fruit shape index, fruit color values (L^* , a^* , b^* and c^* ), soluble solids content(SSC), titratable acids (TA), solid to acid ratio, soluble sugars, vitamin C, soluble proteins, juice yield, pH, reducing sugars, tannins, soluble pectin, protopectin and pectin. Systematic description, correlation analysis, principal component analysis and factor analysis were used to analyze and evaluate the fruit appearance quality and nutrient composition.【Results】The single fruit quality of SH1, SH5 and A130701 was significantly higher than that of most of the materials by significance difference analysis. The transverse diameters of SH5, A100101, SH1, and T060203 were the highest and in the range of 2.90 to 3.12 cm and had no significant difference. The longitudinal diameter of SH1, A130701, SH5 and A140301 was significantly higher than that of the other accessions. The fruit shape index of A130701, SH1 and SH2 was the highest, and there was no significant difference. The L^* of SH5 and SH2 was significantly higherthan that of the other materials, indicating that the fruits of SH5 and SH2 were whiter and brighter. The a* values of A191002 and B080401 were higher, while their b* and c* values were lower, indicating that the fruit color of these two accessions was more greenish and the color saturation was lower. The internal fruit quality of different A. argute is also different. SH5, SH3 and SH1 had the highest soluble solids in the range of 16.50%-17.73%. Titratable acid content of B070101 and B080701 was the highest but had no significant difference compared with the other accessions, whose TA was 1.59%-1.51%. The solid to acid ratio of SH5 was the highest, reaching 54.77, which was significantly higher than the other materials. The soluble sugar content of B080701 was significantly higher than that of the other materials, reaching 13.97% . The vitamin C content of A100703 and B080401 was the highest reaching 102.61 mg·100 g^-1 and 101.92 mg·100 g^-1 , respectively, but had no significant difference with the other materials. The soluble protein content of A020203 was 0.43 mg·g^-1 , significantly higher than that of the other materials. The juice recovery of A040103 was the highest, up to 74.30%, which was significantly higher than that of the other materials. The pH of fruit ranged from 3.54 to 4.24. The highest pH was found in A170303 and T060203, and the lowest in SH1 and SH2. Reducing sugar content varied in a range of 0.41%-7.52%. That in SH1 was significantly higher than in the other materials. The tannin content in B070101 was the highest, reaching 0.80 g ·L^-1 , which was significantly higher than in the other materials. The soluble pectin and pectin contents in A140101 were the highest (0.92%-1.82%) and significantly higher than in the other materials. The protopectin content in SH5 was significantly higher than in the other materials. The correlation analysis showed that the appearance index of single fruit weight, transverse diameter and longitudinal diameter had an extremely significant correlation with fruit shape index. Color indexes L^* , a^* , b^* and c^* were significantly correlated with each other. L* was significantly correlated with flavor indexes including SSC, TA and solid to acid ratio, and a* was significantly positively correlated with vitamin C. SSC was negatively correlated with TA and positively with solid to acid ratio; TA was negatively correlated with solid to acid ratio and positively with soluble sugar; tannin was negatively correlated with SSC and solid to acid ratio and positively with TA. Soluble protein was positively correlated with SSC and solid acid ratio, and negatively correlated with TA and protopectin. The functional component vitamin C was positively correlated with a* and TA. The juice yield was negatively correlated with L^* , b^* , SSC and solid to acid ratio, and positively correlated with TA and soluble pectin. The soluble pectin, protopectin and pectin were positively correlated with each other. According to the principle that the characteristic value was greater than 1, five principal components were extracted, and the cumulative variance contribution rate reached 76.782%. Most of the information of the 13 quality indexes were integrated. The contribution rate of principal component 1 was 25.288%, which mainly represented solid to acid ratio, TA, tannin, juice yield and soluble solid, reflecting flavor and processing quality. The  L^* , a^* and b* , reflecting fruit color. The contribution rate of principal component 3 was 14.535%, which mainly represented single fruit quality and fruit shape index, reflecting fruit size. The contribution rate of principal component 4 was 10.177%, which mainly represented soluble sugar and soluble protein, reflecting nutritional quality. The contribution rate of the fifth principal components was 9.828%, which mainly represented vitamin C and a* , reflecting functional components.【Conclusion】TA, SSC, juice yield, tannin, a* , fruit weight, soluble sugar and vitamin C were selected as the core indexes of fruit quality evaluation by coefficient of variation, correlation analysis and principal component analysis. SH5, SH1, SH3, SH4 and B080701 were selected as the top 5 excellent A. argute lines according to factor analysis.