Construction Of High-Density Genetic Map And Gene Mapping For Fruit Quality Traits In Pear

Pyrus spp.is an important temperate fruit known for its sweet and juicy flavour and its excellent edible,nutritional,medicinal and economic value.In recent years,pear quality breeding has become increasingly important with the improvement of people's living standards and the technological innovation level of fruit trees industry.However,many important quality traits of pears are affected by the combination of multiple genes and environment.It is difficult to genetically improve them,bccause of the pear generation long cycle the complex genetic background and the low efficiency breeding of traditional methods.In this study,150 F1 hybrid progenies of‘Pingguoli'בBayuehong'were used as test materials,and SNP markers were developed by whole genome resequencing technology,and SSR markers were combined to construct a high-density genetic linkage map of pears.At the same time,according to the fruit trait data of the individual progeny of the investigated population,combined with the constructed genetic linkage map and the composite trait mapping method was used to locate the relevant traits.The main results were as follows:1.Using the‘Pingguoli'and‘Bayuehong' that randomly selected F1 populations as the test materials,the original 220 pairs of SSR primers were screened,and the effectively amplified ratio of primers between the parents was 56.4.%,the polymorphism ratio was 42.3%,SSR primers meeting was 22.3% counted for and the total pairs were 49.2.Using the whole genome resequencing method,a total of 3304623 SNP markers with a depth of not less than 4× were detected among the parents,and SNPs were not separated by recombination breakpoints that classified as Bin(Bin considered no recombination event occurred)Finally,Bin was used as a mapping marker to construct a high-density genetic linkage map of pears containing 17 linkage groups with 3116 Bin markers.The total map distance of 17 linkage groups was 1727.98 cM,and the average map distance was 0.55 cM.3.According to the mapping requirements of the amplification results of 49 pairs of progeny,42 pairs of successful SSR primers were integrated as the above Bin map,and mapped to 15 linkage groups with the genetic linkage map,respectively,The increase of 175.65 cM,the length of the linkage group is 64.19 cM(LG14)-187.68 cM(LG2),and the average distance between adjacent markers is 0.47 cM-0.83 cM.The average distance between the markers of LG12 linkage group is the smallest,including 161 markers but the average distance between the LG16 linkage group markers was the largest,with 149 markers.In addition to the LG4 and LG14 linkage groups,there are 1-6 SSR markers on each linkage group.4.Using IBM SPSS Statistics 20 and Excel 2016,the correlation of 14 fruit-related traits in parental in F1 populations and 9 traits(single fruit weight,vertical diameter,transverse diameter,fruit shape index,size of the core,flesh hardness,soluble solid content,titratable acid content,length of pedicel)in the F1 population showed continuous variation;normal or partial normal distribution,quantitative traits,significant correlation among multiple traits and another 5 traits were no obvious continuous variation in the astringency degree,red degree,fruit shape,sepals state and storability,which is characterized by quality traits.The vertical and transverse diameters of the fruit,the weight of single fruit,the hardness of the flesh,the length of pedicel and the shape of the fruit,etc.,were significantly positively correlated with each other.The fruit shape index and soluble solid content,fruit shape,astringency and titratable acid content Etc.,were significantly positively correlated with each other although.The weight of single fruit was negatively correlated with the size of the core and the hardness of the flesh.Moreover,The degree of red was positively correlated with the shape of the fruit,and the traits of the bracts.the degree of astringency,and the hardness of the flesh were a significant negatively correlation.The length of pedicel was also negatively correlated with the hardness of the flesh.5.Using the constructed map and trait phenotypic values,gene mapping analysis was performed in 14 fruit-related traits,and functional annotation of genes in the region.Using the composite interval mapping method,a total of 28 interval sites were obtained: 5 QTL sites(SFW),2 QTL sites(SC),3 QTL sites(FH),6 QTL sites(TD),1 QTL loci(LFP),6 soluble solid content QTL loci(SSC),2 QTL loci(TAC),1 interval locus(SC?RD?FS),276 in the interval and scanned 2266 genes.Among them,the relevant range was not detected in the fruit vertical diameter,fruit shape index,astringency and storability.