| In order to solve the problems of large quantity of tomato germplasm resources,heavy renewal burden and low breeding efficiency in Ningxia,the coefficient of variation and Shannon Wiener diversity index(H’)genetic diversity of 20 phenotypic traits of 480 tomato germplasm resources was analyzed;Based on the phenotypic data 8 cluster methods and 5 sampling ratios were compared.On this basis,two genetic distances,the top two sampling proportions,three sampling methods and the top two cluster methods were combined to evaluate the representativeness of the core collections.Then,the best method was used to construct core collection.Based on the results of phenotypic clustering,46 representative materials were selected,160 SNP markers were genotyped,and 48 pairs of primers were selected to analyze the genetic diversity of 480 tomato germplasm resources.Finally,the mixed linear model was used to analyze the correlation of important agronomic traits.The main results are as follows:1.The phenotypic traits of the tested materials were rich in genetic diversity.There were 27 variation types in 8 quality traits,and the distribution frequency of variation types was different.The genetic diversity index H’ ranged from 0.43 to 1.81.The coefficient of variation of 12 quantitative characters ranged from 12.36%to 374.51%,in which the coefficient of variation of soluble solid content was the smallest 12.36%,and the rate of malformed fruit was the largest 374.51%.The genetic diversity index H’ ranged from 0.40 to 2.07.The genetic diversity index H’ of malformed fruit rate was 0.40,and the hardness was 2.07.The results of correlation analysis and principal component analysis showed that there were complex relationships among the traits,and the cumulative contribution rate of the first five principal components was 62.901%,which contained most of the information of all the indicators.Based on umpga cluster analysis of phenotypic traits of 480 tomato materials,they were divided into 6 groups when Euclidean distance was 1.25.2.In the strategy research of constructing core collection based on phenotypic data,the sum of squares of deviation and the variable method were the top two systematic clustering methods.15%and 30%were the top two sampling proportions.The combination test finally determined the best construction method:the genetic distance was Mahalanobis distance,the sampling proportion was 15%,the sampling method was deviation sampling method,and the systematic clustering method was the sum of squares of deviation.A total of 72 accessions were successfully constructed with the best method,including 31 accessions of Dahong,20 accessions of Dafen,14 accessions of cherry tomato and 7 accessions of other types.3.Among 160 pairs of primer screening test,135 pairs of SNP primers had good genotyping results,17 pairs had non-specific amplification and could not distinguish the genotypes of samples very well,and 8 pairs had no polymorphism and could not distinguish the genotypes of samples.A total of 192 alleles were generated by genotyping.The frequency of major alleles ranged from 0.352 to 0.946,with an average of 0.686;The heterozygosity ranged from 0 to 0.806,with an average of 0.194;The polymorphism information content(PIC)ranged from 0.101 to 0.630,with an average of 0.363.Based on the analysis of SNP typing results,it can be divided into six groups when the genetic distance is 2.55.The results of population genetic structure analysis and mixed population model calculation showed that when k=5,ΔK reached the maximum value,indicating that 480 tomato germplasm resources collected could be divided into 5 populations.When the genetic distance was 2.55,it could be divided into six groups.4.A total of 1128 SNP combinations were obtained by calculating the linkage disequilibrium between two markers.The R2 values mainly ranged from 0≤R2<0.2,with 856 values.There were 169 in the range of 0.2≤R2<0.4.There are 85 in the range of 0.4≤R2<0.6.0.6≤R2<1,only 18.A total of 27 markers were found to be significantly associated with 17 traits.There were 5 markers related to percentage of abnormal fruit,2 markers related to color of mature fruit,mass per fruit,size of corky area around pedicel scar,suberification size of pedicel scar,lngitudinal diameter and number of fruit per inflorescence,and 1 marker related to transverse diameter,soluble solid content,number of locules,flesh thickness,leaf node below the first inflorescence,inflorescence type,green shoulder,growth potential,fruit cracking and fruit setting.The 27 markers detected involved 15 SNP markers,R2 ranged from 2.2232%to 8.1352%.NDP373 was the most significant marker related to the quality of mass per fruit,size of corky area around pedicel scar,suberification size of pedicel scar,longitudinal diameter,transverse diameter,soluble solid content,number of locules,flesh thickness,inflorescence type,number of fruit per inflorescence and fruit setting.In conclusion,this study is the first time to construct tomato core collection in Ningxia,which lays a foundation for the related research of tomato core collection in Ningxia and provides a theoretical basis for related experiments. |
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