Genetic Diversity Of Barley Powdery Mildew Populations Investigated In Jiangsu And Zhejiang

A systematic investigation of pathotypes of barley powdery mildew(Blumeria graminis f.sp.hordei)populations collected from Jiangsu and Zhejiang was conducted by using 'Pallas' near iso-genic lines and two other varieties as differential Lines.Different virulence gene frequencies of the two populations were investigated based on the hypothesis of "gene for gene".The DNA fingerprinting based on AFLP(amplified fragment length polymorphism)for the 26 isolates selected from the population was also performed for the first time in China.The main results obtained in this study were as follows:1.One hundred isolates of Blumeria graminis f.sp.hordei,sixty-five of them from Jiaxing,Zhejiang and thirty-five from Yancheng,Jiangshu,were collected.Nine pathotypes,two identified from the isolates collected from Jiaxing,six from Yancheng, and one in common for both places,were determined.2.Virulence gene frequencies of virulent genes Va8,VBw,V22,(Vra,Va8),(VRu2, Va8),Vnn and Vch are 100%,implying that these genes are pre-dominant in these two areas.Accordingly their corresponding resistant genes Mla8,MlBw,Ml22,(Mlra, Mla),(MlRu2,Mla8),Mlnn and Mlch have no breeding values in the area.The frequencies of virulent genes Vg,(Vla,Va8),Vh are ranged between 66.3%～55.7%,the breeding values of the corresponding resistant genes are rather small.The frequencies of virulent gene Va23 is 44.3%,thus the breeding value of the corresponding resistant gene is quite high.The frequencies of virulent genes(Val,Va),Va3,(Va6,Val4), (Va7,Vk),(Va7,Va),Va7,(Va9,Vk),(Va10,VDu2),(Va12,Va),(Va13,Va), (Vkl,Va8),Vpl,Vat,V05 and Va9 are ranged between 0～1.45%,indicating the very high values of the corresponding resistant genes for barley breeding in these areas.3.Ten AFLP primer pairs producing more polymorphic bands with better quality were selected from 112 primer pairs for DNA finger-printing.A total of 404 among 510 bands generated from 26 isolates were found polymorphic,giving the rate of polymorphism as 79.2%.4.Similarity coefficients of the twenty-six isolates are ranged between 0.96～0.58 and all these isolates fell into five genetic lineages when similarity coefficient is 0.81.The isolates collected from the same area or the same hosts are not always in the samegenetic lineage and the isolates showing the same pathotype are presented in different genetic lineages,suggesting that DNA fingerprinting data generated from molecular marker are not necessarily associated with pathotypes identified from the isolates under investigation.