| Phytophthora root rot(PRR)is one of the important diseases of soybean and has been becoming severe gradually in China.Studies have shown that the use of disease resistant varieties is the most economical and effective way to control the disease.This study was carried out in order to use disease resistant resources in soybean breeding programs effectively.The resistance to Phytophthora root rot race 1 was evaluated in cultivated soybeans from Northeast China,and genome wide association study with multiple statistic models were performed to detect QTNs significantly associated with resistance to PRR,At the same time,QTLs related to Phytophthora root rot resistance from published papers at home and abroad were integrated by Meta-analysis and compared with the results of association mapping.In addition,SSR markers were used to analyze the genetic diversity of PRR resistant varieties from Northeast China to further clarify their genetic background and lay the foundation for disease resistant breeding.The main findings are as follows:1.A total of 74 QTLs related to PRR resistance were collected from published papers in China and abroad from 2000 to 2018.Using the mapping function of Biomercator 2.1 software,Through the Meta-analysis of the mapped consensus map,12 ’real’ QTLs related to PRR resistance were obtained,which were distributed on 6 linkage groups such as D1b,C2,A2,F,E and G.The average confidence interval was reduced from 15.1 cM of the original map to 4.18 cM.Among them,5 ’real’QTL maps were less than 1cM,and the minimum map distance was only 0.10c M.2.The hypocotyl wound inoculation method was used to identify resistance to PRR race 1 in 350 soybeans.The results show that in the 349 soybean germplasm resources evaluated,69 accessions were resistant to PRR.Among all provinces,the proportion of disease-resistant types is the highest in Liaoning Province,followed by Jilin Province and the lowest in Heilongjiang Province.3.Six statistic models in mrMLM3.0 and the general linear model(GLM)in TASSEL5.0 were used for genome wide association,the results showed that 6 models in mrMLM detected a total of 13 significant SNPs under the criteria of LOD>2.5,which the LOD score of most significant SNPs were 2.5047 and 5.8779,explained 1.48%and 14.66%of phenotypic variation.By analyzing the annotated genes within 130kb both upstream and downstream of the two SNP loci with the highest contribution,three genes were predicted to be potential candidate genes related to soybean PRR resistance,including glyma.16g193900,glyma.07g033300 and glyma.07g034300.4.The "true" QTL left and right markers obtained after Meta-analysis were compared with the 13 SNP sites detected by association analysis of 6 multi-locus hybrid model methods,and it was found that the two SNP sites ss715583364 and ss715596934 were similar to the two QTLS in the consensus map.5.In order to further clarify the genetic background of soybeans resistant to PRR in northeast China,The genetic diversity of 60 soybeans being resistant to PRR in Northeast China was analyzed by using 35 SSR markers.A total of 189 alleles were detected,with an average of 5.4 alleles per locus.The polymorphism information content index(PIC)varied from 0.1550 to 0.8195 with an average of 0.6636.The genetic similarity coefficient varied from 0.31 to 0.74.The fingerprints of 60 resistant varieties were constructed using 5 SSR markers with high PIC value.The fingerprints could discriminate all 60 resistant genotypes.Clustering analysis were done using NTSYS2.10 based on genetic distance and revealed that sixty resistant genotypes were divided into 7 groups.78.33%of resistant genotypes had a similarity coefficient between 0.45 and 0.74.That indicated a relatively narrow genetic difference among these resistant genotypes.The results of cluster analysis and population genetic structure analysis partially overlap,suggesting the existence of gene penetration and communication events between resistant gentypes from different regions. |
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