| Maize is the most important food crop in the world,and it involves development and application in the economic industry,feed industry and new energy industry.Its demand,especially in developing countries,will increase.It is expected to double by 2050.Maize ranks first in my country's cultivated area and total output,and drought is the main factor restricting its output.Seedling stage is the primary stage of the development of various organs of maize.Drought will cause weak seedlings and low survival rate,which will affect the future growth state of seedlings and strong seedlings,and finally affect corn yield.According to reports,except for 2016,a large area of spring drought has occurred in Northeast my country in the past five years.Therefore,the use of genetics and genetic engineering methods to carry out genetic breeding of maize and to cultivate maize varieties with drought resistance,especially at the seedling stage,is of great scientific significance for improving the drought resistance of maize and even increasing the yield of maize,in order to satisfy people's demand for maize.In this paper,326 maize inbred lines with wide variation were selected and 20% PEG6000 solution was used to simulate drought stress in the maize seedling stage to obtain the plant height,root length,shoot fresh weight,root fresh weight,shoot dry weight,root dry weight and root shoot ratio data that 7 morphological indicators were used to calculate the drought resistance index,and BLUP analysis was carried out.Combined with the population genotype,a genome-wide association analysis(GWAS)was performed to locate and screen out independent significant single nucleotide polymorphisms(SNP)related to the drought resistance phenotype.According to the SNP loci,the candidate genes for drought resistance that can regulate maize traits were selected.Drought resistance membership function method was used to compare two maize materials with different drought resistance sensitivities,and the expression levels of five genes related to drought tolerance selected from candidate genes under maize seedling leaf drought stress were analyzed(q RT-PCR)to verify the results of GWAS analysis and lay the foundation for the isolation of drought resistance related genes.The results of this experiment are as follows:(1)The data of the 7 drought resistance indexes measured in this test were normally distributed,and the heritability analysis results all presented medium and high heritability.The maximum heritability level of the indicator plant fresh weight was 0.89,and the medium heritability level of the indicator plant height was 0.52.The results show that drought tolerance is controlled by genetic factors and the experimental results are reliable.The results of correlation analysis among traits indicated that except for the irrelevance between root length,root fresh weight and root shoot ratio,there were significant positive or negative correlations among other traits,which might be caused by the root dry weight is not easy to measure make number cut down.Which in addition to the plant height,shoot fresh weight,shoot dry weight and root shoot ratio showed a significant negative correlation,between the rest of the indicators were very significant positive correlation,negative correlation between the corresponding Pearson coefficient of-0.26,-0.24 and-0.32 respectively,the positive correlation coefficient of Pearson range 0.19-0.72,corresponding index of plant height and root length,shoot fresh weight and the correlation between shoot dry weight.(2)The test of 7 drought index data in statistical analysis found that between different subgroup,index of plant height and root cap ratio affected by population structure showed significant difference,other indicators in no obvious difference between different subsets distribution,observation analysis found that all index of drought sensitive show the biggest influence in the source of temperate maize,and the ground part of the index of drought sensitivity is affected by group underground part is big,so the root-shoot ratio group appeared significant difference effect,effect result is inversely proportional to the ground part of the trend.(3)The experiment through drought resistance index of seven corn seedling drought characters as phenotypic data with group genotypes GWAS analysis,locate and select total of 53 independent significant SNP loci,the drought index to predict 193 candidate genes associated area,the gene functional annotation and way to classification,can be divided into 10 types:There were 38 signal transduction pathways,31 metabolic pathways,21 transcriptional regulatory pathways,16 cell transport pathways,12 protein editing pathways,8 redox reaction pathways,8 RNA editing pathways,6 translation regulatory pathways,2 DNA editing pathways and 51 genes without functional annotation information.(4)In this experiment,53 core genes in corresponding regions were screened by the physical location of independent and significant SNP sites.According to the functional annotation of these genes,16 candidate genes were found to be related to drought resistance.GRMZM5G858197,GRMZM2G142932,GRMZM5G838098,GRMZM2G060114,GRMZM2G341621,GRMZM2G086992,GRMZM2G355679,GRMZM2G382632,GRMZM2G046816,GRMZM2G130348,GRMZM2G009368,GRMZM2G179147,GRMZM2G168375,GRMZM2G323830,GRMZM2G129357 and GRMZM2G034572,these genes can be isolated from arabidopsis thaliana,rice,wheat and other plants.A large number of studies have proved that these genes are related to plant biological and abiotic stress,and are important candidate genes for future studies on drought resistance and other stress mechanisms.(5)The drought resistance membership function method was used to calculate the membership value of the drought resistance index of 7 drought resistance traits in maize seedling stage.The average 7 index membership values were used to evaluate the drought resistance of each corn line.7884-4Ht and 975-12 were used as gene expression analysis materials.Selected from the candidate genes of five representative to drought resistance gene(Trpp6 b ZIP NCED1 CPD20 and TIFY)are expressed in the corn seedling leaves under drought stress analysis,the results showed that the five genes are involved in the stress response,the amount of differentially expressed different induction model as a result,illustrates the five genes are important genetic resistance related plants.By analyzing the correlation between the expression levels of these five genes and drought resistance indexes,it was found that root length was positively correlated with Trpp6,NCED1 and CPD20 genes,plant fresh weight and b ZIP gene,root crown ratio and TIFY gene. |
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