Rough Mapping And Genetic Analysis Of Cucumber Fruit Shape Related QTLs

Cucumber(Cucumis sativus L.,2n = 14)is one of the economic vegetables widely grown all over the world.Because of its good taste,high nutritional value and economic value,it is popular among people.Fruit shape,as an important appearance characteristic of cucumber,is an important factor affecting the commerciality and yield of cucumber.However,so far,there have been few reports on the location and cloning of cucumber fruit shape-related genes,and the molecular regulatory mechanism of cucumber fruit shape is still unclear.In this study,cucumber chromosome segment substitution lines(CSSLs)was used to preliminarily map cucumber fruit shape-related QTLs\genes,which could provide data support for analyzing the molecular regulation mechanism of cucumber fruit shape.The main findings are as follows:(1)The phenotypic identification of the replacement line CSSL37-84 showed that the fruit shape indexes were 1.714,1.365 and 1.12 of the ovary,commercial fruit and mature fruit,respectively,which were significantly greater than the recurrent parent RNS7.Multi-generational self-breeding of the CSSL37-84 strain,and combined with molecular marker-assisted selection,fruit shape genetic analysis and other methods,single-segment substitution lines CSSL1-16,CSSL5-2,CSSL7-8 and multi-segment substitution lines CSSL11668,CSSL11678,CSSL5268,CSSL6878,CSSL1165268,CSSL1165278,CSSL1166878 were isolated and screened.Ovary length(OVL),ovary fruit diameter(OVD),fruit length(FL),fruit diameter(FD),mature fruit length(MFL),mature fruit diameter(MFD)of the substitution line population were measured respectively,and fruit shape index(OSI,FSI,MSI)of each period was calculated.Cucumber fruit-shaped chromosome substitution lines were used to locate three fruit-shaped QTLs.Three fruit shape related QTLs were identified by using the cucumber fruit chromosome substitution lines,among which FS1.4 was the main effect QTL,FS5.4 and FS7.3 were the minor effect QTLs,and FS1.4 and FS7.3 had positive superposition effect.(2)Comparison of the cell size of the single-segment homozygous replacement line CSSL1-16(main effect QTL FS1.4 locus)with RNS7,it was found that the area of CSSL1-16 cells became larger and cells number decreased;the results of Quantitative Real-time PCR showed that differential expression of key genes in cytokinin,auxin and gibberellin signal transduction pathway;the content of soluble sugar,soluble protein and soluble solids in CSSL1-16 fruit are higher than RNS7,and the content of nitrate are lower than RNS7;Observing the seed characteristics,it was found that the seeds of CSSL1-16 became longer than RNS7.