Quantitative Trait Loci Mapping For Resistance To Curvularia Leaf Spot In Maize

Maize is the most important food crop in china and have an important ap plictions in food,feed,medical,energy and industry.With the development of living standard and the international competition of maize,it has become an important task in the maize breeding of our country to improve the quality a nd yield of maize.Maize curvularia leaf spot has been a common disease in main maize pro ducing areas such as Northeast and North of China.This disease occurs mainl y in the reproductive stage of maize which inflicts damage to leaves and even causes the whole plant to withered.Therefore the disease has a serious harm to the quality and yield of maize.Although the cultivation of disease-resistant varieties is the most cost and effective measure,we control the disease by che mical measures and field management at present.Many domestic and internatio nal scholars carried on a great deal of research to the pathogenic genes and co rresponding molecular mechanism of curvularia lunata.However,there are few studies on the inheritance of resistance of maize to curvularia.In this study,in bred lines H4074 and Ma664,with significant difference in resistance to this d isease,were used as parents to match the hybrid H4074×Ma664 and futher de velop its F₂ and F_2:3 populations.SSR markers were used to construct the gene tic linkage map and the QTLs of maize related to the resistance to curvularia leaf spot were mapped by Inclusive Composite Interval Mapping?ICIM?.The m ainly results of this paper were as follows:1.Of the 650 SSR markers selected from the MaizeGDB database and dis tributed on 10 maize chromosomes randomly,150 pairs with stable polymorphi c between parents were screened,and the polymorphism was 23%.Genetype a nalysis of the F₂ population showed that 38 of the 150 SSR markers showed s ignificant partial segregation.A genetic linkage map of maize consisted of 112 SSR loci whose segregation rations were 1:2:1 was constructed by the softwar e QTLIcimapping.The linkage map covering 10 chromosomes was 1703.7CM i n length with an average of 15.2CM between markers and the relative position of markers was basically fit with the published linkage map in MaizeGDB.2.Combined with the phenotype of F₂ population in 2015,four QTLs that could totally account for 40.63% of the phenotype variation were detected.A nd the two which located in the chromosome 3 umc2269-bnlg1108 interval and the chromosome 10 mmp121-umc1506 interval could considered as the major QTLs with a higher phenotypic contribution as 14.1% and 14.2% respectively.3.Combined with the phenotype of F_2:3 rep1 population in GongZhuling o f Jiin province in 2016,4 QTLs which were located on Bin1.02,Bin5.07,Bin7.01/7.02 and Bin10.04 respectively were detected by ICIM method,and totally accounted for 31.74% of phenotypic variation.The QTL in the mmp121-umc1506 interval of the chromosome arm Bin10.04 had a large phenotypic contribut ion rate as 11.60%,which could be considered as a major QTL for resistance of maize to Curvularia lunata.4.Combined with the phenotype of F_2:3 rep2 population in ChangChun of Jilin province in 2016,5 QTLs which were localized on Bin2.10,Bin5.03,Bi n6.05,Bin9.01 and Bin10.04 respectively were detected by ICIM method and t otally accounted for 45.46% of phenotype variation.The QTLs in umc1705-bnl g1902 interval of Bin5.03 and mmp121-umc1506 of Bin10.04 were the major QTLs with large phenotype contribution rate as 10.62% and 19.00% respectivel y.In addition,the QTL located in Bin10.04 was common in F₂,F_2:3 rep1 and rep2 populations,flanked by two markers mmp121 and umc1506.Therefore,it i s supposed that it is a stable major QTL responsible for the resistance of maiz e to curvularia lunata.