Genetic Analysis Of Major Agronomic Traits And Drought Tolerance In Different Maize Populations

Maize is an important food crop in the world,and it is also a model plant for academic research.Yield is an eternal core issue in maize breeding,while plant architecture directly affects the plant density and production of maize.Therefore,it is of great importance for high and stable yield to choose materials with the ideal plant architecture.Drought is the most important abiotic stress affecting the growth and development of maize,which heavily restrict the production of maize.In this study,a number of excellent inbred lines with drought tolerance and breeding values were screened through the identification of drought tolerance at seedling stage and the phenotyping of agronomic traits at adult stage in multi-parent population,natural population,maize-teosinte distant hybridization populations,respectively.Genome-wide association study and linkage analysis were carried out to traits of maize populations with high-quality genotypes.Many QTLs and candidate genes related to the plant architecture and yield at adult stage and drought tolerance at seedling stage were identified,which lay the foundation of molecular marker-assisted selection breeding for maize ideal plant architecture and drought tolerance.The main results of this research are as follows:1.The identification of drought tolerance to five maize populations at seedling stage under the conditions of normal watering and drought stress were carried out.As a result,the similar trend of the coefficient of variation was identified that the coefficient of variation of root diameter was the smallest,while the root branch number was the largest.High correlations were found for most of these maize root traits,except root diameter.According to the drought tolerance index(DTI)to all five maize populations,the longest root length is the largest and greater than the value of 1,which indicated that drought stress will accelerate root elongation lengthways.A total of 65 maize inbred lines with tolerance to drought were screened according to the average DTI value of all traits in each population,including 27 lines from multiple parental population,8 from natural population,12 from BD population,9 from BP population,and 9 from ZP population,respectively.2.According to the statistics and analysis of plant architectures and yield-related traits at the adult stage of five maize populations,it was found that the coefficient of variation of yield is the largest,while the leaf length and width of ear leaf,row numbers of ear are all the smallest.High correlation coefficient,with the value above 0.6,were found between plant height and ear height,and between the yield per ear and the number of rows per ear,the number of grains per row or the weight of 100 grains.Analysis of variance showed that the differences among these traits were mainly caused by genotype differences.Through a comprehensive comparative analysis of plant type traits and yield traits,A total of 11 lines with breeding potential were selected in three maize-teosinte distant hybridization populations according to the comprehensive analysis on traits of plant architecture and yield.Among which,six of them were from the BD population,two from the BP population,and three from the ZP population.3.Genome-wide association study and linkage analysis were carried out to drought related traits at seedling stage for multi-parent population,natural population and BD population,respectively.As a result,in both multi-parent population and natural population,a total of 26 significantly associated SNPs were identified,and candidate genes GRMZM2G020040,GRMZM2G074267,and GRMZM2G122999 were found to be related to drought tolerance in maize seedlings.In BD population,there were 38,49 and 10 QTLs related to 20 traits were identified under the conditions of drought stress,normal watering and the ratio of drought stress to normal watering,respectively.In addition,two major QTLs(m QTLs)were found under the condition of drought stress.The phenotypic variation explained(PVE)of these two m QTLs,q BS＿SLL2.2 and q ES＿SFW1.2,were 10.34% and10.83%,respectively.It was inferred that functional genes in this two m QTLs interval may related to drought tolerance in maize seedlings.4.Genome-wide association study and linkage analysis were carried out to agronomic traits at adult stage for multi-parent population,natural population and BD population,respectively.As a result,a total of 7 and 89 candidate genes related to eight traits in multiparent population and 15 traits in natural population,respectively.In BD population,a total of 17 m QTLs related to eight agronomic traits were identified.Among which,six QTLs related to the plant architecture were found and five of them with positive effects were from teosinte,and 11 QTLs related to yield and yield related traits were found and all of them with positive effects were from maize,which meet the anticipation.In summary,teosinte has an important application value for the improvement of drought tolerance to maize.Many QTLs and candidate genes related to the plant architecture and drought tolerance were identified,which will lay the foundation of molecular markerassisted selection breeding for maize ideal plant architecture and drought tolerance.