Exploration And Genetic Mapping Of Gene Governing Resistance To Powdery Mildew In A Wheat Landrace Hongyoumai

Wheat is the most important crop in the world,and is one of China’s three major grain crops.Powdery mildew(Blumeria graminis f.sp.Tritici)seriously impact on yields and quality in wheat.Practice shows that deployment of resistant varieties is the most environmental friendly and cost-effectively fundamental measures to control the disease.Wheat landrace is the nature product of farmer through long-term selection.There is a rich genetic variation in it.Exploring resistance genes have a great role in enriching the wheat genetic resource.Hongyoumai,a wheat landrace,shows a high resistance to powdery mildew in the whole growth period.In this study,Hongyoumai was crossed to the susceptible varieties Huixianhong to develop the F2 segregating population.Genetics of resistance to powdery mildew in Hongyoumai was studied and resistant gene was preliminarily mapped by using SSR markers and BSA method.And the resistant gene was re-mapped by developing new molecular markers.The physical location of the resistance gene was confirmed by using a set of Chinese Spring aneuploidies.The main results are as followings:(1)Powdery mildew resistance was evaluated in resistant and susceptible parents,F1,F2 and F2:3 families by using isolate B02 of powdery mildew physiological race.Hongyoumai showed highly resistant,while Huixianhong and F1showed highly susceptible,F2 population segregated as 68 resistant,and 151 susceptible,fitting the 1:3 ratio,F2:3 family test confirmed the segregation of 68 homozygous resistant,96heterozygous susceptible,and 51 homozygous susceptible,fitting the 1:2:1 ratio by chi-square test.By combiningF1,F2 and F2:3 identification results we concluded that there was a single recessive gene governing powdery mildew resistance in Hongyoumai,and tentatively named it as pmHYM(2)Five markers,Xwmc232,Xgwm611,Xgwm577,Xgpw1144 and Xwmc581,showed consistent polymorphism between parents and resistant-susceptible bulks by the method of BSA analysis and significantly correlated with resistance to powdery mildew in the F2 population.The gene was initially mapped on the chromosome 7BL.Through the development of new molecular markers,the pmHYM was assigned between Xmp925 and Xgwm577.Genetic distances were 7.5cM and 14.4cM,respectively.(3)Physical location of the target gene pmHYM was conducted by using Chinese Spring(CS)nulli-tetrasomic lines of the homologous group Ⅶ.The result showed that the markersXgwm577,Xgwm611,and Xwmc581 could amplify the target bands on CSN7A-T7D、CSN7D-T7B and CS-Dt7BL and could not amplify the target bands on CSN7B-T7B and CS-Dt7SL.Therefore,the pmHYM was physically located on chromosome 7BL.(4)Analysis of resistant spectrum showed that Hongyoumai resisted 11 of 12 isolates while other Pm5 gene carriers only resisted a few of the 12 isolates of powdery mildew.It indicates that pmHYM is different from Pm5 gene alleles and might be a new gene for resistance to powdery mildew.