Identification Of Germplasm And Genome-wide Association Analysis For Chilling Tolerance During Germination And Budding Stage In Maize Backbone Inbred Line

Chilling damages happened on corn production of high frequency and unpredictable natural disaster,has become a typical abiotic stress factors of corn production in our country.Screening and breeding high quality cold resistant maize varieties is the most direct and effective way to reduce cold damage.It is the first task to find and excavate the genes of cold tolerance in breeding the varieties of cold tolerance,and the establishment of an accurate,fast and stable identification and evaluation system of cold tolerance is of great significance for screening and breeding the varieties of high quality and solving the problem of cold damage in production.In the aspect of cold resistance of maize germplasm,with the continuous improvement of molecular marker technology,it can be rapidly explored in depth and improve the efficiency of breeding high-quality varieties.In this study,247 maize diaphysis inbred lines were used as test materials,and low-temperature stress was carried out at germination and bud stages,respectively.Four analytical methods(principal component analysis,regression analysis,cluster analysis,discriminant analysis)were used to comprehensively evaluate the cold tolerance of maize in the germination and bud stages,and the cold tolerance of 247 maize backbones inbred lines was identified and classified according to the strong to weak level.Genome-wide association analysis was carried out using high-throughput genotype data and cold-tolerance phenotype data of 247 maize backbones inbred lines to screen SNPS significantly correlated with cold-tolerance traits.The main research results are as follows:1.The system clustering subdivided 247 maize inbred lines into 4 types,including 14 varieties with strong cold tolerance,31 varieties with moderate cold tolerance,52 varieties with sensitive cold tolerance,and 150 varieties with extremely sensitive cold tolerance.The principal component analysis was carried out on 8 cold tolerance indexes of 247 maize backbones inbred lines under 6? low-temperature stress at the germination stage,and they were synthesized into 2 independent indexes.The accuracy of discriminant analysis of 247 maize inbred lines and their corresponding 8 indexes was 99.0%.2.The survival rate of 247 maize backbones inbred lines at bud stage under 2 ? lowtemperature stress can be divided into 5 grades.There were 10 varieties with strong cold resistance,accounting for 4.05% of the total.There were 19 varieties with strong cold resistance,accounting for 7.69% of the total.There were 43 varieties with moderate cold tolerance,accounting for 17.41% of the total.There were 169 cold-resistant and sensitive varieties,accounting for 68.42% of the total.There were 6 cold-resistant and highly sensitive varieties,accounting for 2.43% of the total.3.According to the genetic diversity and population structure,247 maize backbones inbred lines can be classified into 6 categories.The correlation analysis of cold tolerance of 247 maize backbones inbred lines during germination was conducted using the MLM model.It was found that when P=10-5(-logp =5.0)was set as the threshold,a total of 70 significant SNP sites related to cold tolerance were detected.Except for maize chromosome 4,there are significant loci on all chromosomes,which can be explained by 10% to 20.15% phenotypic variation.The correlation analysis of cold tolerance at bud stage of maize backbones inbred lines revealed that three significant SNP loci were related to stress survival,which was found on chromosome 2,7,and 9 of maize,respectively,and could be explained by the phenotypic variation of 9.88% to 12.20%.