Detection Of QTL For Resistance To Brown Spot Disease In Tobacco

Tobacco is one of important economic crops in china.And the leaf is economy organ of tobacco.Leaves with high quality provide raw materials for cigarette processing.Tobacco brown spot disease is one of leaf diseases developing in mature period,which influences the appearance quality and chemical compositions in leaves.There are many measures to mininising the harm of tobacco brown spot,for example,chemical pesticide control,cultivation control,biological control and so on.The research of resistant breeding is an essential way to control brown spot.It provides breeders with theoretical basis to detect resistant quantitative trait locus and markers that tightly associated with resistant gene.In my research,we detected resistant QTLs for brown spot using SNP mapping array in F_2:3originated from jingyehuang×NC82.We analyse the interval regiones associated with brown spot resistance in indifferent environment to ensure a major QTL.A population containing 219 tobacco germplasms was evaluated for validating the major QTL and developping indel markers tightly associated with the major QTL.The results were as follows.1.A total of 443,000 polymorphic SNP locus has been detected in F_2:3 population originated from NC82×jingyehuang.And 36,692 SNP locus showed polymorphism.The result of chi-square test indicated that 7,482 SNP locus have not exhibit distorted segregation at levels the level of P<0.01.And2,462 SNP locus did not exhibit distorted segregation at levels the level of P<0.05.Genetic map will be constructed by these 2,462 SNP markers.2.Finally,30 linkage groups have been constucted.1^th,5^th,8^th,11^th,12^th and 15^th chromosome was divided into two linkage groups respectively.There were one linkage group in each remaining chromosomes.The length of genetic map is 4493.17cM including 2312 SNP markers.Average number of markers is 77.1 in one linkage group.The average distance is 1.94cM between two SNP loci.3.Disease index was analyzed toghter with datas of genotying.A total of 16 QTLs for resistance to brown spot disease were detected.There were a major QTL located in 24^th chromosome.The major QTL were detected in different environments,which explaines 15.07%of phenotypic variation.There were also a QTL located in 18^th chromosome playing an important role in resistance,which explaines9.41%of phenotypic variation.Others play less of a role.4.To validate the major QTL,indel markers were designed in 172^th cM on chr24 linkage.We analyzed the population containing 219 obacco germplasms using association mapping method.Finally,the major QTL was located between indel50 and indel62 covering above 5,340,000 bases.5.Indel53 was tightly associated with the major QTL,which would be used for marker-assisted selection in further studies.