| Wheat flour and flour products are the most important staple food for residents in the north of China.Flour color is the main factor affecting wheat quality.Superoxide dismutase（SOD）can bleach flour color and improve the rheological properties of dough.The higher SOD activity,the higher whiteness of flour.Therefore,it is of great significance for wheat quality improvement to detect SOD activity in wheat grains,screen cultivars（lines）with high SOD activity,excavate SOD active sites and predict candidate genes.In this study,using natural populations and RIL populations as materials,212 winter wheat varieties（lines）in3 environments and RIL populations（309 families）constructed by“Berkut×Worrakatta”in 4 environments were tested for SOD activity.Using wheat 90 K and 50 K SNP chips,the SOD activity of 212 winter wheat varieties（lines）and the SOD activity of 309 families constructed by“Berkut×Worrakatta”were used for genome-wide association analysis and linkage analysis.The main results are as follows:1.The extreme values of SOD activity in 212 winter wheat varieties（lines）under different environments were 1.5 times different,the coefficient of variation was 4.34%-5.23%,and the heritability was 0.79.The SOD activity in each environment showed a normal distribution,and the average SOD activity of different wheat varieties（lines）was as follows:northern winter wheat region(1801.74 U·g-1)>foreign varieties(1788.26 U·g-1)>southwest winter wheat region(1787.21 U·g-1)>huanghuai winter wheat region(1771.19 U·g-1)>middle/lower reaches of the Yangtze River winter wheat region(1759.67U·g-1).The selected five varieties,including Jing dong 22,Zhou mai 12 and Zhong 892,provided basic materials for further stress resistance breeding and ear germination gene mining.The population structure analysis divided the test materials into 3 subgroups.Using Tassel 5.0 software,the SOD activity of 212winter wheat varieties（lines）was combined with the 16705 high-quality SNP markers of the 90 K chip for genome-wide association analysis.Using the Q+K mixed linear model,a total of 29 significant markers（P≤0.001）were detected on chromosomes 1A,1B,2A,2B,2D,3B,3D,4B,4D,5A,5B,5D,6A,6B and7B of wheat.A single locus could explain 5.47%-32.43%of the phenotypic variation.The candidate genes of the significant associated locus of stable inheritance were excavated,and a total of 7 SOD active genes and 2 SOD active genes were screened out.Related candidate genes.2.The extremum of SOD activity in 309 RIL populations under different environments varied 1.8times,the coefficient of variation ranged from 3.88-7.07,and the heritability was 0.75.The phenotypic mean of Berkut(1828.14 U·g-1)was higher than that of Worrakatta(1707.23 U·g-1),and the maximum phenotypic variation in 2016 was 1248.07 U·g-1-2237.51 U·g-1.SOD activity was significantly positively related to different environment,the correlation coefficient is 0.38-0.85（P<0.001）,the RIL population 309family material SOD activity in combination with 50 k SNPS gene chip,with complete drawing interval method（ICIM）for QTL mapping,QTL were detected 7 SOD activity and distribution in 1BL、4DS、5AL、5BL and 5DL,contribution rate of 2.20%to 7.39%.Two QTLs were detected on chromosome 5A and 5D respectively,which accounted for 2.20%-7.39%of the phenotypic variation.The SOD activity enhancing alleles were distributed between the two parents.Except for the loci on chromosome 4DS,5BL and 5DL,the synergic alleles were from worrakata,the other loci were from berkut.Three SOD active genes and two candidate genes related to SOD activity were found by gene mining for the detected QTL loci.3.The physical location of the SOD activity-related sites located by the genome-wide association analysis and linkage analysis was compared,and 4 pairs of similar sites were found by integration,which are located on chromosome 1B,the sites BS00022411＿51 and QSOD.xjau-1BL that are significantly associated with SOD activity;Located at the association sites Kukri＿c14889＿1086 and QSOD.xjau-5AL.1on the 5A chromosome;at the association sites RAC875＿c33791＿320 and QSOD.xjau-5BL on the 5B chromosome;at the association sites RAC875＿c49940＿385 and QSOD.xjau-5DL.1 on the 5D chromosome.There are similar sites on the fifth homologous staining,which can be used as hot spots for future research.Candidate genes were mined at 4 pairs of similar sites,and 3 SOD genes were found,which are located on chromosomes 5A and 5D. |
