Fruit Intrinsic Quality Substances Genetic Analysis Of ’Nagafu 2’ × ’P6’ Hybrid Population

Apple is deciduous tree,belongs to rose family,of which fruits are of abundant antioxidant substances,taste unique with excellent flavor and are favored by vast number of consumers.The fruit intrinsic quality is important part of consumer evaluation,the intrinsic quality substances of apple fruit mainly include soluble sugar,organic acid,ascorbic acid,and tannin.In this study,the hybrid progenies of‘Nagafu2’בP6（progeny of Malus sieversii）’was used as the material,the content of fruit intrinsic quality substances（sugar,acid,ascorbic acid,and tannin）of 102 hybrid F₁strain were determined and the genetic variation analysis was conducted.The progenies’genetic structure of existing marker genes that mainly affect sugar and acid content and their correlation with phenotypic traits were clarified,the preliminary screening of sugar acid regulatory genes was finished,which aim to lay foundation for further usage of this population analyzing the genetic regulation mechanism of the phenotype related to fruit intrinsic quality content.The main results are as follows:1.The fruit quality components content genetic variation analysis of‘Nagafu 2’בP6’hybrid population.Using the hybrid progeny of‘Nagafu 2’בP6’as material,the fructose（Fru）,glucose（Glc）,sucrose（Suc）,sorbitol（Sor）,galactose（Gal）,malate（Mal）,total ascorbic acid（TAs A）,ascorbic acid（As A）,and tanin content of mature fruits were analyzed.The results indicated that 9 phenotypic traits were widely separated in the F₁population,the coefficient of variation ranges from 27.32%to 58.50%,Sor had the biggest coefficient of variation,which meant it had major selection potential.Fru,Glc,Gal and Mal tended to be lower parental inheritance,tanin tended to be mid-parental inheritance,Suc,Sor,TAs A and As A tended to be higher parental inheritance,the content of TASA and As A was of significantly positive heterosis.The analysis of phenotypic data indicated that the content of Fru,Suc and TAs A showed normal distribution,Glc and Gal were significantly positive correlated,Suc and tanin were significantly negative correlated.2.The correlation analysis between fruit sugar and acid content of‘Nagafu 2’בP6’hybrid population and related marker genes’variation.With previous studies integrated,7 genes with different mutation types and relevant to sugar and acid content have been screened,including Md SWEET15a（MD16G1125300）,Md PP2CH（MDP0000141481）,Md SAU37（MDP0000153382）,Mdcy MDH1（MD13G1214000）,Md MYB44（MDP0000463846）,Md Ma1（MDP0000252114）,and Md MYB123（MD02G1087900）.Cloning all the above regulatory genes fragments with different mutation types,taking advantage of DNA sequencing or CAPS technology to analyze the genotype and genetic structure of the parents and progeny populations,doing correlation analysis between fruit sugar and acid content of progenies and marker genes by analysis of variance.The results showed that only Mdcy MDH1 has same homozygous genotype between‘Nagafu 2’בP6’.The genotype and phenotype of Md SWEET15a,Md PP2CH,Md SAU37,Md MYB44 and Md MYB123 were synergistic separated but not correlated in the progenies.The genotype and phenotype of Md Ma1 were synergistic separated,the gene frequency changed with phenotype and the malate content were significantly different among different genotype populations,indicating this gene was associated with malate content in this population.