| Lodging has always been an important factor affecting the high,stable yield of corn and restricting mechanized harvest.The related traits of maize lodging resistance are morphological,mechanical,chemical and anatomical characteristics of stalk.With the development of sequencing technology,genome-wide association analysis combined with BSA-seq can quickly and simply locate important target trait loci and genes.In this study,natural population was used as test materials,and we established a set of mathematical evaluation model to accurately evaluate the maize lodging resistance inbred lines by using multivariate statistical analysis.The F2 segregating population was constructed with the extreme parental in vascular bundle-related traits.According to the vascular bundle-related traits,extreme individuals in F2 population were divided into two groups to construct two DNA pools for genome re-sequencing.Compared with the genome-wide association analysis,the genes related to maize lodging resistance were located and identified by using BSA-seq.The main results are as follows:1.Comprehensive evaluation of lodging resistance of maize inbred lines was performed using multivariate statistical analysis.The results of the correlation analysis show that 17 characters existed in varying degrees of correlation.The first six principal components explained 79.134%of the phenotypic variation with the contribution rates of 20.768%,18.124%,14.093%,11.173%,8.655%and 6.321%.Five categories were clustered in the maize inbred lines.The result of stepwise discriminant analysis showed that the result of cluster analysis is accurate and reliable.Stalk bending strength,ear height,cellulose content,number of small vascular bundle and cross sectional area were selected and the regression model of lodging resistance of maize inbred line was established by using the ridge regression method.2.Genome-wide association analysis was performed by using 83 057 SNP markers which obtained by GBS genotype analysis and phenotype of the vascular bundle-related traits.A total of 123 association loci were detected by using the BLUP values of five traits.The number of small vascular bundle(NSVB),the number of large vascular bundle(NLVB),average area of single small vascular bundle(ASVB),average area of single large vascular bundle(ALVB)and cross sectional area(CSA)were detected association locus 19,33,11,33 and 27,respectively,and the phenotypic contribution rate of individual loci ranged from 0.00%to 43.86%.The same traits co-localized to 8 co-sites in different environments,and 3 co-locations were co-located among different traits.3.On the B73 AGPV2 reference genome map of the maizeGDB website,candidate genes related to vascular bundle-related traits were found in the range of upstream and downstream 120kb of significant loci.These candidate genes in the confidence interval can be classified into fourteen biological processes,three cellular components,and eight molecular functions.As for the KEGG analysis of the candidate genes,a total of ten pathways were identified.Finally,we found five genes related to vascular development,three genes related to cell wall and two genes related to the mechanical strength of the stalk.4.The BSA-seq method was performed for four samples.We found that Q30 was more than 89%,and the ratio of sample to reference genome was more than 92%.Based on the association algorithm of ED and SNP-index,the intersection interval that a size of 42.89Mb and 9.64Mb were mapped on chromosomes 1 and 3.5.Comparing the results of GWAS and BSA-seq,we found that 8 SNPs were located in the interval range of a single algorithm in F2 population and 3 SNPs were located in the intersection interval of two algorithms in F2 population.At the same time,five candidate genes related to vascular bundle were identified.This study established a mathematical model to accurately evaluate the lodging resistance of maize.Genome-wide association analysis and BSA-seq were used to detect related traits loci and candidate genes which control vascular bundle related traits in maize stem.These results will provide a theoretical basis for the maize lodging resistance genetic improvement and marker-assisted selection breeding of maize. |
PDF Full Text Request