| Soybean[Glycine max(L.)Merr.]originates in China,is a main legume crop,which contains protein and oil,which provides all the essential amino acids for human.In order to meet people's demand for protein and oil,the improvement of soybean protein and oil has become the focus of soybean breeding.The yield related traits,such as growth period,plant height and so on,can infect the yield of soybean.Agronomic and quality traits of soybean are all quantitative,thus it is difficult to study the genetics of these traits,so it is very significant to study and apply value to locating these traits.The QTL mapping of soybean quality and agronomic traits is reliable and valuable for maker assisted selection breeding in soybean.In this study,166 recombinant inbred lines derived from Zhonghuang24×Huaxia3 were planted in Guangzhou in 2014 and investigated the growth period traits.248 recombinant inbred lines derived from Guzao1×BRSMG68 were planted in Guangzhou and Zengcheng in two years.Agronomic characters of the RILs were studied and seed from each line was used for Protein and Oil determination by Kjeldahl method,Soxhlet method and NIRs method.We genotyped a recombinant inbred line(RIL)population(Guzao1×BRSMG68)using a restriction-site associated DNA sequencing(RAD-seq)approach.A high-density soybean genetic map was constructed and used to identify several QTLs that were shown to yield-related and quality traits,which could provide reference for soybean molecular marker assisted breeding.The main conclusions are as follows:1.Resequencing of Guizao 1 and BRSMG68 was conducted to finely map the QTLs associated with yield and quality traits.The total reads were 92.24M and 115.51M,and total base were 8.3G and 10.4 G;mapped reads were 83.98 M and 103.41 M,and mapped based were 7.56G and 9.31 G,respectively.The coverage of sequencing were 94.49%and95.62%,and average depth were 7.8×and 9.61×,respectively.Based on 0.2x RAD-seq(restriction-site associated DNA sequencing)of the Guizao1 and BRSMG68 RIL population,90.11 sequence reads were obtained and the average read number was363.34Mb.The coverage of sequencing was 4.41%,with an average depth of 5.06×.According to this data,a total of 56,561 high-quality polymorphic SNP sites were detected for the RILs.All of the SNP sites in the RILs were integrated into a recombination bin unit,and 3715 recombinant bins were obtained.Based on the genotypes of 3715 bins,a high-density bin linkage map was constructed covering 3049.21 cM,and the length and bin number of each linkage group were 120.22 cM-211.37 cM and 147-259,respectively,with an average distance of 0.80 cM between adjacent markers.Therefore,the linkage map constructed with recombination bins resulted in well-distributed linkage distances and has higher resolution than conventional maps.2.The growth period of two parents(Guizao1×BRSMG68)and RILs was investigated in two environments in 2015.The difference of flowering and the mature stage between the two parents were 13 and 35 days,indicated that there were significant differences in the growth period between the two parents,and the Plant Height,Branch Number,Numbers of pods and 100-seed weight were showed the same result.There were significant differences in protein and oil content between Guizao1 and BRSMG68 in different environments with NIRs,Kjeldahl method and Soxhlet extraction method,and the difference between protein and oil content measured by Kjeldahl method and Soxhlet extraction method was even bigger.The RILs had significant differences and genetic variation in quality traits and yield-related traits.3.The correlation analysis showed that most of the yield-related traits were correlated with each other in two environments.Four traits of growth period were positively correlated with Plant Height,Bottom plant height,Number of nodes,Effect pods,2-seed pods,3-seed pods and Seed weight per plant,except for 100-seed weight and Invalid pods were not significant,indicating that these traits were controlled by environmental factors.A highly significant negative correlation was observed between Pro and Oil in different environments with NIRs,Kjeldahl method and Soxhlet extraction method,which are in agreement with some previous studies.4.Based on the genetic map derived from the RILs population of Zhonghuang24×Huaxia3,22 QTLs associated with growth period were identified,the phenotypic effect(R~2)variance explained by the QTLs were 4.47%-42.07%.Based on the genetic map derived from the RILs population of Guzao1×BRSMG68,55 QTLs associated with growth period were identified on seventeen chromosomes,mostly on chromosomes 4,10,12 and 16.18 QTLs was detected on two environments,the phenotypic effect(R~2)variance explained by the QTLs were 0.87%-73.04%.Especially,the locus at the head of the chromosome 4,physical interval between 38506373 and 38596800 bp,were supposed to be a major and stable QTL locus which were responsible for growth period traits.Based on the Williams82 soybean reference genome sequence,the target region contained three putative genes,Glyma04g05260,Glyma04g05280 and Glyma04g05290 may be involved in the growth period in soybean.5.Based on the genetic map derived from the RILs population of Guzao1×Brazil13,100QTLs associated with yield were identified on seventeen chromosomes,mostly on chromosomes 4,10,12 and 19.21 QTLs were detected on two environments,the phenotypic effect(R~2)variance explained by the QTLs were 1.75%-53.58%.Especially,the locus at the head of the chromosome 4,physical interval between 38506373 and 38596800bp,were supposed to be a major and stable QTL locus which were responsible for agronomic traits.The QTL locus was also involved in the growth period.In addition,a QTL which was responsible for flower color on the chromosome 13,physical interval between4718273 and 4801340bp was mapped,and the phenotypic effect(R~2)variance explained by this major QTL was 79.24%.6.A total of 59 QTLs(30 QTLs for protein content and 29 QTLs for oil content)were associated with quality traits on twelve different chromosomes,mostly on chromosomes 5,13,14,17 and 20.Especially,the locus at the lower end of the chromosome 5,physical interval between 38506373 and 38596800 bp and the chromosome 20,physical interval between 31661175 and 32049510 bp,were supposed to be two major and stable QTL loci which were responsible for protein and oil content.In conclusion,We genotyped a RIL population using a restriction-site associated DNA sequencing(RAD-seq)approach.A high-density soybean genetic map was constructed and finely mapped several major QTLs that were shown to influence yield-related and quality traits.Our findings will be helpful for understanding common genetic control mechanisms of co-localized traits and to select cultivars for further analysis to predictably modulate soybean yield and quality simultaneously. |
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