Monitoring Of The Resistanc Isolates To Triadmefon And Analysis On The Virulent Gene Of Blumeria Graminis F.sp Tritici In Shaanxi

To identify the resistance of wheat powdery mildew to triadimefon , 166 isolates of wheat powdery mildew from 19 different towns of Shaanxi.( Puji, Yidian ,Gaodian, Hengqu, Qinghua, Wugong, Gengyu, Yabo, Shoushan, Linping, Laoyu, Shijiaying, Ziwu, Yangjiazhuang, Huaiya, Guo Town, Fengming, Caijiapo, Yangguo) was tested by seed treatment and detached leaf segment methods. The results showed that the mean EC50 of all isolates tested was 34.66mg/L ,and the mean resistance factors (RF) was 16.58. 80.72% of the isolates had the resistance to triadimefon. The isolates with their mean resistance factors 40 flods higher then the susceptible isolates accounted for 9.64%. The isolates with their mean resistance factors as ten to forty flods higher then the susceptible isolates accounted for 37.35%. The resistance of Blumeria graminis f. sp. tritici populations from Puji town in Wugong country. Yidian town in Qishan country and Hengqu town in Mei country is higher then that of other regions. Meanwhile more than 60% of the four regions strains resistant factors is more than 10 times, and the RF is more then 70%. This means the resistance of wheat powdery mildew of these four area is highter.To evaluate the virulent genes of B.graminis f.sp. tritici,103 samples were collected from 19 different towns of Shaanxi.( Puji, Yidian ,Gaodian, Hengqu, Qinghua, Wugong, Gengyu, Yabo, Shoushan, Linping, Laoyu, Shijiaying, Ziwu, Yangjiazhuang, Huaiya, Guo Town, Fengming, Caijiapo, Yangguo) in the middle of June in 2009 when the disease fully developed on wheat in the field under natural infection .Then the virulence frequencies were tested with 32 wheat cultivars whose resistance genes had already been known. The result showed than the virulent frequencies of virulent genes V1,V3b,V3c,V5,V6,V8,V17,V4+8,V1+2+19 and V"Era"were high (all were above 70%) and the virulent frequencies of virulent genes V2,V3a,V3d,V2+Ta were above 60%.indicating that these virulent genes were widely existence in Shaanxi and the corresponding resistance genes Pm1,Pm3b,Pm3c,Pm5,Pm6,Pm8,Pm17,Pm4+8,Pm1+2+19,Pm"Era",Pm2,Pm3a,Pm3d,Pm2+Ta had already lost resistance to powdery mildew. The virulence frequency of V4b,V5(Mli),V19, V21,V2+6,V2+6+?,V4+2+?,V5+6 were between 41.75%～56.31%, it means the corresponding resistance genes Pm4b,Pm5(Mli),Pm19,Pm21,Pm2+6,Pm2+6+?,Pm4+2+?,Pm5+6 Pm4b,Pm5(Mli),Pm19,Pm21,Pm2+6,Pm2+6+?,Pm4+2+?,Pm5+6 were not worth to use lonely. The The virulence frequency of V4a and V7 were 33.98% and 37.86%, it means the corresponding resistance genes Pm 4a and Pm7 is still worth to use. The The virulence frequency of V2+Mld,V4b+Mli,V13,V"XBD"were 22.3% to 30.10%, suggesting that the corresponding resistance genesPm2+Mld,Pm4b+Mli,Pm13,Pm"XBD"were highly resistance to powdery mildew.