Pathogenicity And Genetic Diversity Of Poplar Rust, Melampsora Larlci-populina

Melampsora larici-populina Kleb.（abbr. MLP） is one of the important pathogensoccurred in the Sect.Tacamachacae, Sect. Aigerios and their hybrids poplars in the world. Therust fungus behaved population differentiation and complex genetic background. Hither to5races of MLP had been reported in Europeen, there also were5races. To further understandthe differerntiation of MLP in china, this dissertation focused on studying the pathogenicitydifferentiation and gentic diversity of the rust fungus. The research results were as follows:（1）Thirty-one isolates of Melampsora larici-populina originating from eight provinces,seventeen cities in China were investigated on the differentiation host reaction type，whichshowed that，the31isolates were grouped separately into4physiological races and4newpathotypes: isolates Tg081and Sb belonged to No.2physiological race （CMLP）2); isolatesHh₀₈₄、Th₀₅4and Gl₀₅₂belonged to No.3physiological race （CMLP₃）; isolates St₁₀₂、St₁₀₄、Wh₀₈₂、Yl₀₇₃and Cj₀₅₂belonged to No.4physiological race （CMLP₄）; isolates Js₁₀₂、Jh₁₀₃、Sz₁₀₁、Sz₁₀₄、Hp₀₉、Hp₁₀₄、Fx₀₉₁and Bq belonged to No.5physiological race （CMLP5）. IsolatesHh₀₉₁、Hh₀₉₂、Hp₀₈₁、Hp₀₈₃、Hp₁₀₃、Yl₀₇₁and Yl08were classified in the first pathotype groupï¼›isolates Jh₁₀₁、Hx₁₁₂、Hx₁₁₅were classified in the second pathotype group; isolates Ts₀₈1andTh₀₈were classified in the third pathotype group; isolates Fx₀₉₂were classified in the fourthpathotype group.（2）The genetic diversity of28isolates of MLP, collected from17locations of eightprovinces in China in2007to2011, was investigated by simple sequence repeat （SSR）analysis. A total of64alleles for five SSR loci were detected from28isolates of MLP, and theeffective number of alleles （Ne） ranged from6.7935to12.6452, with an average of9.0575.The polymorphism information content （PIC） for five loci ranged from0.8418to0.9185, withan average of0.8752. The average values of observed heterozygosity （Ho） and expectedheterozygosity （He） were0.5496and0.8997, respectively, and Shannon’s information index（I） varied from2.0259to2.6972, with an average of2.3212. These results showed that all thetest MLP isolates were very rich in genetic diversity. The coefficient of gene differentiationamong isolate populations （Fst） varied from0.2671to0.4079, with an average of0.3198, andthe average value of gene flow （Nm） was0.5317, which revealed that the genetic diversityappeared mainly within isolate populations （68.02%）, but also showed distinct diff erentiation of genetics among isolate populations （31.98%）. At geographical population level, the averageI and Nei’s gene diversity （Nei’s） were1.0275and0.5965, implying that the genetic diversityamong geographical populations was relative ly lower than that within isolate populations ofMLP. Based on Nei’s genetic distance, ranging from0.7646to3.78.10geographicalpopulations of MLP isolates from different regions in China could be initially grouped intofour clusters: cluster I included isolates Fx、Sb/p、T（Tg,Th,Ts）; cluster II included isolatesCj,Yl,Qh,H（Hh,Hp,Ns） and Ns; cluster III included isolates Hx; and cluster â…£comprisedJh/s,St/z.