| Nitrogen is one of the indispensable nutrient elements for Maize,which plays a very important role in regulating crop growth and improving photosynthetic productivity.Insufficient nitrogen would affect the growth of corn.Excessive application of nitrogen fertilizer would increases the production costs,but also causes environmental pollution.Therefore,it is important to release varieties with high nitrogen usage efficiency for maize,which can reduce the application of nitrogen fertilizer in the field.In addition,leaf architecture related traits can affect the planting density and light utilization efficiency directly,which can affect the yield finally.Reports showed that,nitrogen nutrition always showed an important effect on leaf architecture related traits.Therefore,in-depth analysis of the molecular genetic mechanism of nitrogen response to leaf architecture related traits,which can provide theoretical support for maize cultivars with high nitrogen efficiency and plant architecture breeding.In this study,an association mapping panel(AMP)containing226 maize inbred lines and a single segment substitution population(SSSLs)containing 145 lines were used as materials to be treated with different nitrogen levels.Then,leaf architecture related traits under different nitrogen were evaluated.Genotypes of these lines were evaluated by using maize SNP50 chip and GBS method for AMP and SSSLs,respectively.Data were analyzed by jointing Linkage and GWAS method.The aim was to provide scientific support for further revealing the physiological mechanism of maize plant architecture variation and nitrogen efficient utilization.The main research results are as follows:(1)Phenotypic analysis results: Under the three nitrogen levels(LL?LW?LA),the mean,standard deviation and coefficient of variation of the three leaf architecture related traits related traits were significantly different,which indicated that nitrogen and environment had a great influence on the leaf architecture related traits related traits.At the same time,the absolute values of kurtosis and skewness of the three leaf architecture related traits were all less than 1,indicating that the leaf architecture related traits showed to be normal distribution.In addition,the genotype and environmental of the three leaf architecture related traits in the linked population were extremely significant(P < 0.01)correlation,but interation between genotype and environment did not reach the significant level.The genotype,environmental and interation between genotype and environment of the three leaf architecture related traits related traits in the association mapping panel were extremely significant(P <0.01)correlation,indicating significant genetic variation and significant environmental impact.(2)QTL mapping showed that,24 QTLs controlling leaf architecture related traits were detected.Among them,7,9 and 8 QTLs were detected under low,medium and high nitrogen treatments,respectively.A total of 261 candidate genes were involved,and 256 of them had functional annotations,whose main functions included nitrogen-promoting proteins,signal transduction,protein transport,abiotic stress and growth and development processes.(3)GWAS showed that,126 QTNs controlling leaf architecture related traits related traits were detected.Among them,41,30 and 55 QTNs were detected under low,medium and high nitrogen treatments,respectively.A total of 208 candidate genes were involved,and 153 of them had functional annotations,Its main functions include DNA polymerization,plant hormone regulation,photomorphogenesis,protein synthesis,energy metabolism,stress response and stress response.In addition,five consistent SNP markers were detected under different nitrogen levels and different environments(PZE-101106818 ? PZE-103169160 ? SYN492 ? SYN24008 ?PZE-105049073).(4)Common analysis showed that,SNP markers PZE-105127132 and PZE-107023268 were detected in the associated population,which just fell on the SSSL population marker interval S177717463-S185776595 and S25980542-S37281704.Both regions were located on chromosome 5,and there were a total of 21 candidate genes with functional annotations.Its main functions include stress response,signal transduction and growth and development.In addition,the specific nitrogen efficiency candidate gene ZM00001D016468 detected at low nitrogen levels encodes high affinity nitrate transporter 2(NRT2).NRT2 is involved in nitrate uptake and reuse under nitrogen stress.It was speculated that this gene could improve the ability of nitrogen uptake at low nitrogen level and was an important candidate gene for controlling nitrogen use efficiency in maize. |
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