Inheritance Analysis Of Powdery Mildew Resistance In Tobacco

Tobacco powdery mildew is a fungal disease in tobacco, which limites the production of thetobacco leaf seriously. In this research, we use the resistant variety taiyan7as the female parent and thesusceptible variety NC89as the male parent to make cross combinations.The cross combinationsinclude six generations: P₁, P₂, F₁, B₁, B₂and F₂.According to that we launched two aspects of theexperimental research, one is the inheritance analysis using the mixed major-gene plus polygeneinheritance model and the other is QTL analysis to the resistance gene of powdery mildew through SSR.The main conclusions are as follows:（1） The inheritance of the resistance to tobacco powdery mildew was fit to a mixed genetic modelof two major genes with additive-dominant-epistatic effects plus polygenes withadditive-dominant-epistatic effects（the E-0model）.The heritability of major gene in B1,B2and F2was88.05%,32.62%and84.43%, respectively. Because of the high heritability of the major gene, theselection of resistant plant could be carried out in the early breeding for disease resistance. Both of thepolygene heritabilities in B1, F₂were0.00%, which showed that the environmental effect should also betaken into consideration for the outbreak of tobacco powdery mildew.（2） Molecular markers closely linked with the resistance genes were explored through the SSRtechnology, which can lay the foundation of molecular assistant selection breeding. Population F2wasconstructed from the resistant variety Taiyan7as the female parent and the susceptible variety NC89asthe male parent. An artificial inoculation method was adopted to test the degree of the resistance toErysiphe cichoracearum DC for the F2family.61polymorphic markers obtained from screening the2317SSR primers in24linkage groups were used to analyze the F₂population. A genetic map wasgenerated with intervarietal cross of Taiyan7×NC89through SSR micro satellite markers.This mapcontains15linkage groups and45SSR markers.The total length of the map is481.8cM, and theaverage distance between the primers is10.7cM. The longest group is64.7cM, and the shortest is5.2cM. QTL analysis of powdery mildew resistance was conducted by WinQTLCart2.5software. OneQTL was located on the14thlinkage group, which tightly linked with the maker52725with the geneticdistance of1.01cM. The additive effect of the QTL is-14.38, and the QTL can explain21.02%of thephenotypic variation.