Variation and probability grading of the main quantitative characteristics of wild Actinidia eriantha germplasm resources

Abstract: 【Objective】There is a special germplasm resource in China,called wild Mao Hua kiwifruit(Actinidia eriantha),which currently has a high utilization value. The main grading standard used for kiwi-fruit is DUS(distinctness,uniformity and stability) testing standards(Actinidia) which were released bythe Agricultural Ministry of China. These standards are used primarily on A. chinensis and A. deliciosa which are the current commercial varieties of kiwifruit. In this study,the main quantitative characteristicsof wild A. eriantha in Jiangxi province are discussed,along with references to the germplasm resourceswhich are proposed. This research could provide references for the specification and data standardizationof kiwifruit germplasm descriptor systems.【Methods】In this research,118 tested materials were obtainedfrom a previous positioning observation site: the Magu mountain nature protection area of Nancheng coun-ty in Jiangxi province(N27° 31′46′′,E116° 32′52′′ to N27° 32′00′′,E116° 32′16′′),where there arethree scattered distribution areas which have a similar habitat surrounding them. The testing took placeduring September to December 2013 and 2014. Testing consisted of performing a germplasm resourcescensus,making the choice and location of the site of the wild A. eriantha during the first year,then posi-tioning,observing and recording the details in the second year. Tested materials were harvested by stages(1st to 10 th in November),the requirement standard for harvesting was when the fruit soluble solids con-tent reached 6.0%. After fruit post-ripening and softening in the laboratory under normal room tempera-ture,all the quantitative character indexes were tested and evaluated when the condition of the fruit wasedible(pulp hardness up to 1.0 kg·cm^-2). The average fruit mass was determined by using an electronic balance,the fruit shape index by using the vernier calipers measurement(including the longitudinal diam-eter of the fruit's longest part,and the transverse diameter of the fruit at the widest part),the soluble sol-ids content by using a hand held saccharometer,the soluble sugar content using the anthrone colorimetricmethod,the titratable acid content using the method of acid-base titration,the vitamin C content usingthe method of 2,6-dichloro indophenol titration,and the dry matter content using the drying method.The quantitative character classification standard was conducted according to the characteristics of the nu-merical frequency distribution. To use the equal distance method,the tested materials are divided into 5levels,level 1 is the lowest level,and level 5 is the highest. For each level,it is necessary to choose twodifferent regions of germplasm as the reference germplasm.【Results】Seven major quantitative traits of thecoefficient of variation were above 10%. The maximum coefficient of variation was the average fruit mass,followed by the soluble sugar content,fruit shape index,vitamin C content,dry matter content,titrat-able acid content and soluble solids content. The average coefficient of variation was 20.77%. Therefore,the major quantitative traits could be used to research and determine the wild A. eriantha ripe fruit traitsgrade. Fruit quality is the main indicator to measure the size of the fruit. The average fruit mass of wild A.eriantha was 12.68 g,and the coefficient of variation was 33.65%. The frequency distribution was a par-tial normal distribution after being checked using a K-S normality test. The group fruit size was given pri-ority to medium and small fruits. According to the frequency distribution,the fruit size covered a rangewhich included extremely small,small,intermediate,big and extremely big. The ratio of fruit length anddiameter was determined using a fruit shape index,which reflected the basic shape of the fruit. The aver-age fruit shape index was 1.62,the coefficient of variation was 22.04%; the frequency distribution was apartial normal distribution. The fruit shapes were primarily composed of cylindrical,which accounted foraround 70% of the total species. According to the frequency distribution the divided fruit shapes consistedof nearly spherical,short cylindrical,middle and long cylindrical and slender. The average dry mattercontent was 16.91%,the coefficient variation was 17.79%; and the frequency distribution was a partialnormal distribution. The maximum was within the scope of the 15.92% to 17.94% distribution frequency,reaching up to 37%. According to the frequency distribution,the dry matter content consisted of veryfew,few,middle,high and very high. The fruit vitamin C content,titratable acidity content,soluble sug-ars content and soluble solids content were important indicators of the quality of the kiwifruit flavor,andthey play important roles in the quality research related to kiwifruit. Through the statistical analysis ob-tained by testing the 118 wild A. eriantha fruit vitamin C content,the titratable acid content,soluble sug-ar content,and soluble solids content,and the coefficients of variation were in the order of 18.77%,15.88%,25.39% and 11.91%; the soluble solids content,soluble sugar and titratable acid frequency dis-tribution were a normal distribution,and the fruit vitamin C content was a partial normal distribution; theaverage fruit vitamin C content was 4.86 g·kg-1,the maximum was within the scope of 3.95 g·kg-1to 4.56g·kg-1and the distribution frequency reaching up to 27%.; the average titratable acid was 1.53%,themaximum distribution frequency was within the scope of 1.45% to 1.61% and the distribution frequencyreaching up to 25%; the average soluble sugar was 7.16%,the maximum was within the scope of 6.56%to 7.78% distribution frequency reaching up to 29%; the average SSC was 12.86%,the maximum waswithin the scope of a 11.33% to 12.35% distribution frequency reaching up to 29%. According to the fre-quency distribution,the flavoring substance content consisted of very low,low,middle,high and veryhigh.【Conclusion】Through the coefficient of variation analysis,we found that there were abundant varia-tions in the main quantitative characteristics,a high level genetic diversity,and a large selection poten-tial from wild A. eriantha fruit germplasm resources. After the main quantitative traits analysis and anevaluation of the 118 resource frequency distribution,the results present a normal distribution,and char-acteristics appear as a multi-directional variation. Five classification standards were put forward,and thedifferent fruit germplasm resources quantitative traits were described. The reference germplasm for wild A. eriantha resources investigation and characteristic descriptions were also provided.