The Race Differentiation And Genetic Diversity Of Melampsora Larici-populina

Melampsora larici-populina Kleb. is one of the most important rust fungus on the Sect. Tacamachacae,Sect. Aigerios and their hybrids poplars. The rust fungus behaved population differentiation and strong variability. Based on the previous researches, this study focused on studying the pathogenicity differentiation and gentic diversity of the rust fungus with SSR molecular marker and capillary electrophoresis technology.The results were as follows:25 isolates of M.larici-populina in China were investigated based on the reaction types of differentiation host,which showed that the 25 isolates were grouped separately into 5physiological races and 3 new pathogenic groups: the isolate Th₀₅₃ belonged to No.1physiological race（CMLP₁）; Ts and Yl₀₇₁ belonged to No.2 physiological race（CMLP₂）;isolates Nm, Fx₀₉₁, Gd₀₈ and Gf₀₈₁ belonged to No.3 physiological race（CMLP₃）; Cj₀₅₂, Cj₍111_,Ns₁₁₄, Sb₁₁₃, Sp₁₁₂ and Yl₀₇₃ belonged to No.4 physiological race（CMLP₄）;isolates Bq, Tg₀₈₁,Wh₀₃, Yl₀₃₅ and l₀₈ belonged to No.5 physiological race（CMLP₅）;isolates Qh₁₁₁ and Wh₀₈₂ were classified in the first new pathogenic group;isolates Jh₁₀₁ and Js₁₀₂ were classified in the second new pathogenic group;isolates Sz₁₀₃, St₁₁₂ and Hx₁₁₂ were classified in the third new pathogenic group.39 MLP strains were analyzed by SSR molecular marker to study the genetic diversity and population genetic structure. A total of 53 alleles were detected through 7 SSR primers selected for DNA amplification, with an average number of alleles（Na） was 7.5714, and the effective number of alleles（Ne） ranged from 1.7052 to 7.8168, with an average of 3.5359.The polymorphism information content（PIC） for 7 loci ranged from 0.87 to 0.98, with an average of 0.95, were greater than 0.5.,and the Shannon’s information index（I） varied from0.9244 to 2.1969, with an average of 1.3494, which showed that 39 isolates behaved high genetic diversity. The mean observed heterozygosity（Obs_Het） was 0.6317, and the average expected heterozygosity（Exp_Het） was 0.6335.The coefficient of gene differentiation among isolate populations（Fst） varied from 0.1400 to 0.6066, with an average of 0.3519, and the average value of gene flow（Nm） was 0.4605（<1）, which revealed that the genetic diversity appeared mainly within isolate populations（64.81%）. The average value of Shannon’s information index（I） and Nei’s gene diversity（Nei’s） were 0.6404 and 0.4495, respectively,implying that the genetic diversity among geographical populations was relatively lower.Based on Nei’s genetic distance, 17 geographical populations of MLP isolates from different regions in China could be initially grouped into six clusters: cluster I included isolates By and Sb; cluster II included isolates Fx, Yl, Gd, Cj, Hb; cluster III included isolates H, Nm and Tt;cluster IV included T, Wh, Gl and Qh; cluster V included St/Sz and Js; and cluster VI only included comprised Hx.