Detection Of Variety Purity By Multiplex PCR And Genetic Analysis Of Fruit Traits In F₂ Generation In Melon

Seed purity is one of the important indicators in the production and sale process,and the purity of seeds directly affects the expression of hybrid vigor in varieties.Establishing a molecular marker-based seed purity identification system is a key step for improving the efficiency of seed purity identification.In Del molecular marker technology has been widely applied in variety purity and authenticity identification.Multiple PCR can overcome the slow rate of traditional single PCR in seed purity identification,and it has characteristics such as good specificity and high accuracy,which are of great significance in determining the purity of melon seeds.The size of fruit,sugar content,and flesh color are important factors influencing consumer choice.The identification of flesh color needs to be done during the fruiting period of the melon,which takes a long time and incurs high costs.Therefore,using molecular markers to assist in selecting melon plants with different flesh colors can accelerate the selection process and achieve the goal of various types of melon flesh colors.In this study,the melon materials“M4-531”、“M4-528”and“M4-533”will be subjected to high-throughput sequencing,and efficient and accurate hybrid seed purity identification will be carried out using In Del markers and multiple PCR.Using the white-fleshed“M4-5-1”as the female parent and the orange-fleshed“M4-633”as the male parent,an F₂segregating population will be created.Similarly,using the green-fleshed“M4-510-1”as the female parent and the white-fleshed“M4-509-1”as the male parent,another F₂ segregating population will be created.Field phenotypic data of the fruit will be collected for these two populations,and the correlation traits of melon fruit will be analyzed using a mixed model of major gene+multiple genes.The developed melon flesh color CAPS molecular markers and SSR molecular markers will be used to validate the F₂ populations of the two combinations.The main research content and results were as follows:（1）The research focused on hybrid seed purity identification.Combinations of SPIⅠ2-1 and SPIⅠ9-1,SPIⅠ3-2 and SPIⅠ9-1,and SPIⅠ3-2 and SPIⅠ9-2 were used to perform multiple PCR amplifications on the melon materials“M4-531”and“M4-528”as well as their hybrid progeny.The results showed that the hybrid seed purity was 82.4%.Similarly,the combination of SPIⅡ5-2and SPIⅡ6-1 was used to perform multiple PCR amplifications on the melon materials“M4-531”and“M4-533”and their hybrid progeny,resulting in a detected hybrid seed purity of 98.1%.（2）The correlation between flesh color and other fruit characters of melon.Flesh color of“M4-5-1-8”was white,while“M4-633”was orange flesh.Flesh color of F₁ generation was orange.In the F₂ segregating population,the chi-square test confirmed a 3:1 ratio between orange-fleshed and non-orange-fleshed fruits.This indicated that the orange flesh trait was controlled by a dominant single gene.On the other hand,“M4-510-1”had green flesh,while“M4-509-1”had white flesh.All the F₁ generation fruits had white flesh.In the F₂ segregating population,the chi-square test confirmed a 3:1 ratio between white-fleshed and green-fleshed fruits.This indicated that the green flesh trait in melons was controlled by a single recessive gene.（3）The single fruit weight of melon is positively correlated with the longitudinal diameter,transverse diameter and pulp thickness of the fruit.The longitudinal diameter of fruit is positively correlated with the transverse diameter,fruit shape index and pulp thickness.The research and analysis on the mixed genetic model of major plus polygenes for melon fruit traits showed that the single fruit weight,fruit longitudinal diameter,fruit shape index,pulp thickness and soluble solids content of melon were all quantitative traits,which were controlled by two pairs of major genes.（4）The F₂ individuals were tested using the orange flesh molecular marker HF,and the molecular detection results showed a 94.4%concordance rate with the field phenotype identification results.Similarly,the F₂ individuals were tested using the green flesh molecular marker FC-W2,and the molecular detection results showed a 98.6%concordance rate with the field phenotype identification results.This indicates that both markers can be used for molecular marker-assisted selection.