Analysis Of The Genetic Basis Of The Aerial Root Occurrence Time And Penetrometer Resistance In Maize By GWAS

Zea Mays,as an important food and feed crop in the world,is critical to the stability of its total output.With the progress of agricultural technology,mechanized harvesting has become a trend of development.One of the main factors affecting the mechanized harvesting of corn is lodging.The main effect of maize aerial root on plant is to support the plant and reduce the lodging rate of the plant,which is suitable for the mechanical harvesting to increase the total yield.Therefore,the formation of aerial roots of corn is crucial to ensure total production.The occurrence time and puncture resistance of maize aerial root are closely related to lodging resistance.The accurate measurement of occurrence time and mild puncture resistance can effectively evaluate the lodging resistance characteristics of maize.The genetic basis for its influence so far is not clear.This study analyzed the relationship between the aerial root occurrence time and the penetrometer resistance to lodging,and predicted the candidate genes of maize root formation based on Genome-wide association study.The experiment was based on 508 related groups with extensive polymorphism and was planted in Shenyang,Liaoning,in 2016 and 2017.Firstly,accurately investigate the occurrence time of aerial roots and the puncture-resistance intensity of rooting in 30 days and 50 days,and conduct correlation analysis on the survey data.The analysis results are compared with the genotype data completed by the National Maize Improvement Center of China Agricultural University and the time and resistance to aerial rooting.Genome-wide association analysis of puncture intensity was performed to predict candidate genes that regulate the formation of aerial root formation.The results of the study are as follows:1.In the experiment,the phenotypic values of the occurrence time of aerial rooting and30-day and 50-day puncture resistance in 2016 and 2017 were respectively determined.The amplitude of the aerial rooting occurrence time was 51.8-68.33 T,and the variation of the puncture resistance intensity of the 30-day rooting was change in the penetration resistance of2.03-42.68 N and 50 days was 6.27-49.53 N.The rooting time of aerial roots and the puncture resistance of 30 days and 50 days all accorded with the normal distribution law,belonging to quantitative genetic traits;The puncture resistance at 30 and 50 days after silking showed a correlation,indicating that the root penetration resistance of aerial roots was consistent with the growth and development of aerial roots.To sum up that aerial root traits belong to quantitative genetic traits.2.508 inbred lines were divided into 3 subgroups by genetic relationship: SS subgroup,NSS subgroup,and TST subgroup.No clear classification was recorded as MIXED subgroup.The analysis results showed that the mean and amplitude of the aerial roots occurrence time in the TST subgroup compared with the SS and NSS subgroups were both increased.The 30-day and 50-day aerial roots penetrometer resistance was changed in the NSS subgroup and the SS subgroup and the TST subgroup decreased.It shows that the population structure affects the shape of aerial roots.The variation mainly comes from genetic factors;3.Genome-wide association analysis was conducted on the aerial root occurrence time and 30 day,50 day aerial roots penetrometer resistance.The heritability of three traits was0.73,0.49 and 0.33,respectively.The threshold was set to 5,and 21 independent SNP sites associated with the aerial root were detected by removing the relationship and the influence of the population structure.A gene scan was performed within ±50 kb of the physical location of all significant relevant SNP loci,for a total of 97 relevant loci(see Appendix).Through function search,a total of 11 candidate genes that directly or indirectly regulate aerial root morphogenesis were screened out.Among the 11 candidate genes,the gene GRMZM2G135808 induces root growth and participates in the response to auxin stimulation and the formation of lateral roots.When the phenotypic contribution rate was 13.51%,the gene was directly related to the shape of aerial roots.4.97 candidate genes were divided into 8 functional types,of which 4 genes(4%)belonged to metabolic pathways,17 genes(18%)were transcriptional regulatory pathways,and 9 genes(9%)were signal transduction pathways.There are 8 genes(8%)in the cell transport pathway,2 genes in the secretory pathway(2%),10 genes in the oxidation-reduction reaction(11%),5 genes in RNA editing(5%),and 42 other genes.Gene has no functional annotation information(43%)...