Genetic Mapping Of The Powdery Mildew Resistance Gene In Aegilops Tauschii

Wheat powdery mildew resistance directly affects high and stable yield of wheat.It is of great significance to identify new powdery mildew resistant genes in wheat for molecular marker assisted selection breeding of Wheat.Aegilops tauschii is an important gene resource of Wheat.Jia et al(2013)and Luo et al(2014)have released the D genome sequence,laid the foundation fox Ae.tauschii gene discovery.In our lab,we introduced two Ae.tauschii accessions,'20021-2' is from Iran,which is highly resistant to powdery mildew and has bud shaped glumes;'2002I-11' is from Russian Federation's,which is powdery mildew susceptible and has bamboo shaped glumes.For the genetic analysis and location of the powdery mildew resistance genes,a '20021-2' X'20021-11' F2 population was constructed.By SNP chip and molecular marker analysis the gene was preliminary mapped to 2DS by using BSA method.The main results are as follows:1.The phenotype of two Ae.tauschii accessions:'2002I-2' is highly resistant to powdery mildew,has bud shaped glumes;'20021-11' is powdery mildew susceptible,has bamboo shaped glumes.The growth period of '20021-11' is shorter than '2002I-2'.Measuring the thousand grain weight,area,perimeter,length,width and roundness of two lines,result showed that two lines owned significant difference on all grain traits.2.Genetic analysis of powdery mildew resistance using '20021-2' x '20021-11' F2 population:'20021-2' x'20021-11' Fi hybrid and F2 population were evaluated for the powdery mildew resistance using local Blumeria graminis fsp tritici mixture in Jiangsu province.The two parents,a susceptible variety Yangmai 158 and high resistant line 92R137 were used as controls.The results showed that 57 F1 individuals showed different degrees of disease susceptibility(with a infection type as IT 1?4).Among the 338 individuals of the F2 population,71 were resistant(with IT,0-0;)and 267 were susceptible(with IT,1-4).The resistance:susceptible segregation ratio was fit 1:3(x2=2.67,P>0.05).These indicated that the powdery mildew resistance of‘20021-2'was controlled by a single recessive gene.3.Mapping of the the powdery mildew resistance gene:Based on the powdery mildew resistance phenotype of the F2 population,8 extemely resistant and susceptible individuals were pooled for Bulked Segregation Analysis(BSA).Equal amounts of DNA were mixed and used as the disease resistant pool and susceptible pool.Sixty-two co-dominant polymorphic molecular markers covering the seven homoeologous groups were used for linkage analysis.The SSR marker Cfd36,which is located on chromosome 2DS,showed consistent polymorphism between the resistance parent,resistance pool and the susceptible parent,susceptible pool.Twenty molecular markers were further selected from the corresponding 2DS region according to Somers et al(2004).Nine(Barc124?Gwm455?Wmc25?Gwm296?Wmc503?Gwm261?Gwm484?Wmc453 and Gwm102)were polymorphic between the two parents and were used for linkage analysis by amplifying in 179 individuals of the F2 population.By using the Joinmap 4.0,a genetic map was constructed,the gene was located in a region flanked by Cfd36 and Barc124,with genetic distances of 9.2cM and 10.4cM,respectively.The gene was designated as pmAt-2DS.