Genetic Architecture Analysis Of Root Traits Of American Maize Germplasm Introgression DH Lines At Seedling Stage

Maize is an important food and feed crop in the world.Maize root system is the key organ of plant morphology,and the function of root system is one of the important influencing factors of maize yield formation.The absorption of nutrients by maize roots is the main physiological function of roots.In addition,maize roots are effective organs to improve maize stress,and play an important role in lodging resistance and drought resistance.Researchs of genetic mechanism of maize root system have been taken in order to search the excellent alleles of root morphogenesis and improve the root traits of existing varieties by molecular breeding,as a result,the nutrient utilization efficiency and stress resistance of maize were improved,therefore these research could increase the yeild of unit area and economic benefit.This research was processed with the BC₃DH population derived from PHZ51 and PHB47,measuring the root traits in maize seedling stage incubated by paper roll and testing the seedling root traits of kernels under hormones(BR/GA)inhibitor treated.After corrected of high-density GBS markers,154601 GBS makers were used for analysis population structure,LD decay distance,genetic diversity and the similarity of among all lines.53823 high-quality and no-repeat genetic distance GBS markers were involved in the correlation analysis in the GLM,MLM and FarmCPU model and processed GWAS for candidate genes.This research could fundamentally provide genetic mechanism and molecular markers for future maize root system research,the main achievements will be listed as below:1.28 seedling root traits of introgression lines were identified and testing by manual measurement and analysis by WinRhizo and ARIA,the seedling root traits included:Primary Root Length(PRL),Seminal Root Length(SEL),Total Root Length(TRL),Total Number of Root(TNR),and Total Surface Area(TSA)et al.Phenotype analysis indicated that abundant diversity presented in other traits except PRL.After three measurements between root traits and genetic correlation coefficient,the measurements from WinRhizo and ARIA is totally correlated,however PRL from manual measurement was significantly correlated with the ARIA analysis result of 0.93.The correlation coefficient between the TRL measured by hand and WinRhizo and ARIA was 0.57 and 0.59,respectively.The phenotypic heritability measured by the three methods was also close,indicating that the ARIA software can be quickly and accurate analysis of the root traits in the seedling stage.This research focused on seedling root traits of three groups:with BR inhibitor(Pcz),with GA inhibitor(Ucz)and blank control with water.The phenotype from these three group indicated that these three treatment would product significant different among introgression lines,PHZ51 derived population and PHB47 derived population.And Ucz show greatest inhibition on these three populations and PHB47 derived population show the lowest average values of root traits among those three populations.Mesocotyl length show the most sensitive to Ucz and 10 highly sensitive and lowest sensitive lines were picked up from introgression lines respectively.Near-isogenic lines with significant differences in mesoderm sensitivity were screened.2.The monomorphic loci in high-density GBS markers were corrected.The results showed that the proportion of recurrent parents and the number of recombination events were significantly decreased by correction.The distribution of recurrent parents was uneven among different chromosomes and lines,and the number of recombination events was different among different chromosomes and different parent populations.The results of 154601 corrected GBS markers showed that the introgression lines was clearly divided into two derived populations,PHZ51 and PHB47,which were consistent with the classification of maize heterosis populations.The genetic diversity and PIC value of PHB47 derived populations were higher than those of PHZ51 derived populations,and there were differences in the regions with high diversity,and there were significant differences between the two subgroups on chromosomes 5 and 9.The LD decay distance of the whole population was 1.5-2 Mb(r²=0.4),and the LD decay distance of the PHZ51 derived population was the largest.The similarity between families in different regions was identified.Among the 10 families with the highest similarity with PHB47 derived populations,8 regions similarity with PHB47 less than 0.3 were identified.Among the 10 families with the highest similarity to PHZ51 derived populations,9 regions similarity with PHZ51 less than 0.3 were identified,which laid the foundation for further analysis of candidate gene segments.3.In this study,GLM model,MLM model and FarmCPU model were used to conduct genome-wide association analysis of all seedling-related traits based on high-quality 53823 GBS markers.4891significant association SNPs were identified in total.Among them,4487 were identified in the GLM model,171 were identified in the MLM model,and 233 were identified in the FarmCPU model.The three models detected more significant SNPs in the morphologically related traits of hormone suppression.1876significant SNP sites were also detected using the PHZ51-derived population.The GO functional enrichment analysis of 196 and seedling root related candidate genes indicated that the candidate genes are mainly involved in biological processes such as cell formation,signal transduction and physiological metabolism.The GO functional enrichment analysis of 196 and seedling root related candidate genes indicated that the candidate genes are mainly involved in biological processes such as cell formation,signal transduction and physiological metabolism.