QTL Mapping And Genome-wide Association Analysis Of Nitrate Reductase Activity In Maize

Maize is a major crop in China.The increase in its output has a profound effect on solving the food problem in China.Nitrogen,as an essential nutrient for plant growth,is one of the most vulnerable elements in soil.The utilization efficiency of corn nitrogen is low.At the same time,excessive application of nitrogen fertilizer results in the loss of large amounts of nutrients into the environment,causing serious environmental problems.Nitrate reductase is a key enzyme in the assimilation of plant nitrogen,which plays an important role in the efficient use of plant nitrogen.In this study,139 natural populations and 150 recombinant inbred lines?RIL?from the Xu178×K12 cross combination were used as materials.SNP and SSR markers were combined with QTL mapping and correlation analysis.Reductase activity was genetically analyzed.The key SNP loci affecting nitrate reductase activity in maize and highly efficient candidate genes for nitrogen were explored,which laid a solid theoretical foundation for molecular breeding of maize nitrogen.The results are as follows:1.Analysis of nitrate reductase activity in RIL populations and natural populations showed that the maternal Xu178 nitrate reductase activity was significantly higher than that of paternal parent K12,and RIL populations had super-parental isolation;Nitrate content will affect the nitrate reductase activity,higher nitrate content can increase nitrate reductase activity.2.The QTL mapping of nitrate reductase activity in the RIL population revealed that 15 QTLs were detected at the two nitrogen levels and distributed on chromosomes other than chromosomes 9 and 10.Most of the QTLs were detected in a single environment,indicating that the activity of nitrate reductase is mainly controlled by minor genes;qLNRA₁-1?qHNRA₁-1?and qHNRA₆-1?qHNRA₆-2?located on chromosomes 1 and 6 were detected under two treatments and were the main studies.QTL.Located on chromosome 1qLNRA₁-1?qHNRA₁-1?,the marker interval is umc2151-umc1335,the contribution rate is between 7.47-14.56%,and the synergic allele is from the female parent Xu178.qHNRA₆-1?qHNRA₆-2?located on chromosome 6 has a marker interval of umc2068-bnlg391 with a contribution rate of 16.32–18.65%.The synergic allele is also derived from the parent Xu178.3.Genome-wide association analysis of natural population nitrate reductase activity was performed using TASSEL software.A total of 19 SNP markers significantly associated withnitrate reductase were detected in the E3 environment;A total of 21 SNP markers significantly associated with nitrate reductase were detected in the E2 environment;a total of 8 SNP markers significantly associated with nitrate reductase were detected using BLUP values.Almost all SNPs were detected.The spots were detected in a single environment.The above results all indicate that the nitrate reductase activity is mainly controlled by minor genes.4.Comparing the QTL mapping results with the genome-wide association analysis results,the SNP marker AX-86258733 was found to fall within the marker interval umc2068-bnlg391 of the qHNRA₆-1?qHNRA₆-2?sites,which was detected by QTL mapping.This site is associated with the gene Zm00001d035050,which encodes a protein kinase superfamily protein with a contribution rate of 12.69%.After further analysis,it was found that the linkage between the locus and other loci was low and there were genotypes AA and GG.Analysis of genotypes and phenotypes revealed a positive correlation between genotype AA and phenotypic values.It is beneficial to the improvement of nitrate reductase activity.