| Melon is one of the top ten fruits in the world.Melon has a rich basis for phenotypic and genetic variation,especially fruit traits.For example,fruit shapes,fruit skin color,fruit surface groove,reticulation,wrinkles,cracks,pulp thickness,color,and sugar and acid content,and most of these traits are important agronomic traits.Therefore,genetic improvement of fruit traits has been a common concern of breeding experts.Seed morphological traits are also an important trait in melon.Seeds of different materials have large differences in size,shape,and color.Full and healthy seeds are the basic guarantee for the melon’s robust development at the seedling stage and the later yield and quality.Using the method of population genetics and combining with modern genotyping technology,to detect sites regulating these important traits on the chromosome,and then identify candidate genes,which can not only excavate functional genes that regulate target traits,but also help to analyze the genetics basis of traits and lay a solid foundation for future molecular breeding.In this test,small round fruit melon ZTG005 81 was used as the female parent and snake-shaped long fruit melon ZTG00906 was used as the male parent.F2 and F2:3 populations were constructed as test materials to analyze the characteristics of fruit and seed variation.By resequencing the parents and simplifying the genome sequencing of 140 F2 single plants,a high-density linkage genetic map was constructed,and the phenotypes of fruit and seed traits were combined to genetically map the fruit and seed traits of melon,consistent with previous research results.The results are as follows:(1)Variation analysis of phenotypicStatistical analysis of quantitative traits(fruit weight,fruit length,fruit width,fruit shape index,pulp thickness,1000-seed weight,seed length,seed width,seed shape index)in three environments,finding there are significant differences except for seed shape index parents,and there are significant or very significant differences in other traits.The frequency distribution of quantitative traits indicates that these traits tend to be normally distributed.The Pearson correlation coefficient analysis showed that the fruit weight,fruit length,and fruit shape index were highly correlated(r>0.6;p<0.01)in three environments(F2,two seasons F2:3 population).The seed shape index was moderately correlated(0.3<r<0.6),while the fruit width,flesh thickness,and thousand-seed weight of seeds were less correlated(r<0.3).Genetic analysis of 2 quality traits(peel color,seed coat color)showed that the separation ratio of the two quality traits in the F2 population is 3:1 and the separation ratio in the BC population is 1:1,which is consistent with simple single-gene inheritance.(2)Construction of high-density genetic mapRe-sequencing the parents,the depth of sequencing was 10.36X,29.52X,respectively,the amount of data obtained:6,027,200,032bp,15,903,288,000bp,simplified genome sequencing(ddRAD-seq)of 140 F2 single plants,average sequencing depth 8.05X Data volume:479,421,059,710bp.Through multiple SNP filtering,4654 high-quality SNPs were finally obtained and converted into 1090 bin markers.Using these bin markers,a genetic map with 12 linkage groups and a length of 880.48cM was successfully constructed.The average marker spacing It is 0.81cM.Among them,the first linkage group is the longest(133.14 cM),and the 9th linkage group is the shortest(44.58 cM);the second linkage group has the largest average distance between markers(1.04 cM).The bin haplotype map shows that the genetic map contains most of the recombination events in the F2 population.Collinearity analysis showed that the fitting coefficients of 12 linkage groups were between 0.75 and 0.96,and no segment was in place.(3)QTL mapping of fruit traitsA total of 31 QTLs for fruit-related traits were detected under 3 environments.Five fruit weight QTLs were detected,and the main QTL locus qFw8.1(LOD>9,PVE>21%)was located at LG8,and the physical segment was 194.16Kb.Seven fruit-length QTLs were detected,of which qF12.1(LOD>13,PVE>27%)and qF18.1(LOD>7,PVE>13%)were detected in multiple environments,located on LG2 and LG8,respectively The physical sections are 630.95Kb and 85.37Kb respectively.Six fruit width QTLs were detected,but only in one environment.The main QTL QFd2.1(LOD=7.13,PVE=17.54%)was located at LG2,and the physical segment was 68.75Kb.Seven QTLs were detected,including qFsi2.1(LOD>14,PVE>30%)and qFsi8.1(LOD>4,PVE>8%)were detected in multiple environments,located in LG2 and LG8,respectively Above,the physical sections are 630.95Kb and 85.37Kb respectively.There are two QTL sites for the thickness of the flesh.QPth2.1 and qPth11.1 are located at LG2 and LG 11(LOD>3,PVE>9%).Four QTLs for reticulated traits were detected,of which the main QTL qNw2.1(LOD>26,PVE>54%)was located in LG2,and the physical segment was 351.32Kb.(4)QTL mapping of seed traits.A total of 31 seed-related QTL sites were detected.There are 4 QTLs for the 1000-kernel weight of the seeds,and no repetitive loci are detected.The main QTL locus qSw3.1(LOD=4.19,PVE=10.95%)is located at LG3,and the physical segment is 3989.95bp.The seed length is QTL 14,and its main QTL locus qS13.2(LOD>15,PVE>18%)is located in LG3,and the physical segment is 184.42Kb.Three QTLs of fruit width were detected,qSd4.1(LOD>3,PVE>8%)appeared in both environments,the physical segment was 317.08Kb,and another QTL site qSdll.1(LOD=3.82,PVE=7.96%),the physical segment is 2785.65Kb.The species index has 10 QTL sites,only qSsi6.1(LOD>3,PVE>9%)has been detected in multiple environments,and the physical segment is 231.57Kb.(5)Positioning of quality traits.In this test,the yellow peel gene was initially located at the front end of chromosome 4,with a physical location of 1-3,279,342bp.Previous MEM03C003375 genes have been reported in this section is a candidate genes for controlling yellow/green peel;the white seed coat color gene is located at the position bp 3,863,931-4,235,229bp on chromosome 5.Which is consistent with the previously reported location of the white seed coat on the 5th linkage group. |
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