Analysis Of Genetic Diversity And Genetic Characteristics Of Sugar And Acid Quality In Apple Germplasm With Red-Flesh

Red flesh apples are rich in antioxidant substances such as flavonoids and are more resistant to adversity,and have become the main direction and important germplasm material for the selection and breeding of new apple varieties in recent years.However,the current germplasm material of red flesh apples generally exhibits low sugar-to-acid ratio and heavy astringency,which makes the selection and breeding of new high-quality red flesh apple varieties difficult.It is important to investigate the genetic diversity of red flesh apples and the genetic characteristics of their quality traits for breeding new red flesh apple varieties.In this thesis,we first explored the genetic diversity and relatedness between 51 red flesh apples,7 cultivated apples and 59 Xinjiang wild apples using 17 reported SSR primer pairs,and analyzed the genetic diversity of fruit quality traits by measuring 16 fruit quality indexes;meanwhile,we analyzed the genetic diversity of 61 ’Red Flesh HM’ × The genetic analysis of 16 fruit quality indicators of 61 ’Red Flesh HM’ × ’ Nagafu 2’ hybrid was also conducted to pro vide theoretical support for the utilization of red flesh apple germplasm resources and the selection and breeding of new varieties.The main research results are as follows:1.Seventeen pairs of primers with good polymorphism were screened based on the reported SSR primer information,and PCR amplification was performed using the total leaf DNA of 117 apple germplasm resources as the template,and the amplification results were analyzed for genetic diversity and population structure.The results showed that a total of 105 polymorphic loci were detected in the 117 test materials,and the observed number of alleles(Na)per SSR locus ranged from 3 to 10,with an average of 6.18 alleles per pair;the effective number of alleles(Ne)ranged from 1.38 to 6.76,with an average value of 4.32;the observed heterozygosity(Ho)ranged from 0.01 to 0.87 These apple materials were divided into three subgroups,and red flesh apples were mainly located in subgroup I,accounting for 68.18% of subgroup I.They were more closely related to cultivated apples and some Xinjiang wild apples(3-33),four red-fleshed apples were classified into subgroup II,and the remaining 17 red-fleshed apples were classified into subgroup III.2.The ’Red Flesh HM’ × ’ Nagafu 2’ hybrid population had abundant genetic characteristics for fruit quality.The coefficients of variation ranged from 10.58% to 83.76%,showing moderate variation,with the highest coefficient of variation being total anthocyanin and the lowest being soluble solids;solub le sugar and total flavonoid content showed a continuous normal distribution;the cumulative contribution of five principal components in the principal component analysis was 71.24%,and Z112,Z71 and Z86 had the highest comprehensive evaluation In the cor relation analysis,total anthocyanin,soluble solids and a*,T-As A and L*,total phenols and total flavonoids showed highly significant positive correlation,soluble solids and L*,b*,As A and a*showed highly significant negative correlation;sugar-acid ratio and total anthocyanin content were lower than the middle parental value and tended to be low parental inheritance.