Genetic Analysis And Gene Mapping Of Yellow-Brown Fruit Skin In Cucumber

Cucumber（Cucumis sativus L.）is one of the main vegetable crops widely cultivated in China,which is high nutritional value and deeply loved by consumers.Peel color is an important quality trait of cucumber.Research on color traits of cucumber peel is of great significance to guide cucumber quality breeding.In this study,four generations of genetic population（P1,P2,F1,F2）were constructed using the cucumber inbred line PW with yellow-brown mature peel and the cucumber inbred line Gy2 with green mature peel as parents,and the yellow-brown（yb）gene controlling the color of cucumber mature peel was studied by genetic analysis and gene mapping.The main research results are as follows:1.The field phenotypic statistics of four generations of PW and Gy2 were carried out,and the color of mature fruit peel of cucumber was analyzed genetically.The results showed that the mature peel of Fi plant was yellow-brown,and F2 plant was yellow-brown.The isolation ratio of plants with mature yellow-brown peel and green peel was 3:1 by the squared test,so it was inferred that the yellow-brown peel trait of cucumber mature fruit was a quality trait controlled by a pair of genes,and the yellow-brown peel of mature fruit was dominant to green.2.Using extreme single plant pool（BSA）combined with high-throughput sequencing technology（Mutmap）,the yb gene was initially located in the range of 0～4.12Mb of chromosome 4.The genetic map of molecular markers was drawn using 239 strains of F2 generation mapping population constructed from cucumber materials PW and Gy2,and the yb gene was successfully mapped between InDel₁66394 and SSR22231（Chr4:166,394～1,065,156）.3.According to the preliminary mapping results,through further screening of recombinant strains and encryption markers in the interval,the yb gene was finely mapped to the range of～17kb（Chr4:499,872～516,951）,and the wings on both sides were labeled SNP₄99872 and SNP₅16951,Three candidate genes were predicted using FGENESH software,and all encoded epoxide hydrolase.4.Gene cloning and sequence alignment of three candidate genes between parents revealed that CsGy4G000840 gene had a single base mutation in Gy2 material,and the mutation site was at the end of the second intron of the parent Gy2,resulting in a change in gene splicing,and the remaining two gene sequences were completely identical.The expression of CsGy4G000840 gene in cucumber fruits at different developmental stages was analyzed.The results showed that the expression of this gene was significantly different between the two parents,and the expression of this gene in PW peel was significantly higher than that in Gy2 on the 24th day of fruit development.5.A CAPS marker（SNP01）was developed based on the base site of CsGy4G000840 in parents and validated in Cucumber natural population.The results showed that the genotype of this SNP locus had a high coincidence of 86.8%with the color of mature peel,which could be used for marker-assisted selection.