| Isaria fumosorosea is an important entomopathogenic fungus which has been a microbial insecticide and plays an important role in biological control with high pathogenicity and wide range of host.It is widely distributed all over the world.Different strains in the same species have genetic polymorphism.The study of genetic polymorphism can reveal the origin,variation and evolution of species diversity.Genetic polymorphism of I.fumosorosea was studied in biological characteristics,pathogenicity and molecular level.These results will not only have academic and practical significance for collecting and isolating,breeding and production or quality monitoring of high property strains,but also provide the utilization of the fungi for biological control of pests to provide scientific theory basis in the future.The main results were as follows: 1.Biological characteristics of I.fumosoroseaMacroscopic culture characteristics of I.fumosorosea have a great variability under the different lighting conditions,especially they have a greater difference on PDA media.Strain H3 has synnemata.In addition,microscopic features of conidiophore,phialides,conidia,the sporulation and spore germinate rate have great differences.The spore quantity of strain H5 was the most and the spore germinate rate of strain H4 was the highest.2.The pathogenicity of I.fumosorosea strains against Tetranychus urticaeI.fumosorosea strains have pathogenicity against Tetranychus urticae,different strains for the same kind of pest showed different pathogenicity in the same concentration.Strain of H4 showed the short time of pathogenicity and high fatality rate.The conidial quantity was up to 1.08×107/ml.Strains of H8,H9 and H11 in spore quantity and pathogenicity were relatively better and the LT50 were also shorter.The spore quantities were 0.958×107/ml,0.82×107/ml and 0.762×107/ml respectively.The pathogenicity was significantly correlated to the sporulation.3.Gene sequence analysis and its correlation analysis with the biological characteristics and pathogenicity of I.fumosorosea strainsThe phylogenetic analysis based on ITS sequence of different I.fumosorosea strains showed that I.fumosorosea strains were separated into two completely separated clades,one of which was clustered into clade I-1 with 98% bootstrap value,the other was into clade II-2 with 81% bootstrap value.For determining the true taxonomic status of both clades,polymorphism of I.fumosorosea strains and I.javanica strains were analyzed.The results revealed that there were seven haplotypes,the details were as follows,monophyletic diversity Hd = 0.605,nucleotide diversity Pi= 0.04,coefficient of genetic differentiation Fst = 0.78,gene flow Nm = 0.07 and existed two different conserved DNA regions and so on.In conclusion,there was large genetic diversity at the species level or assumed populations among I.fumosorosea,which indicated that the differences were beyond species boundaries of I.fumosorosea,the strains in clade I-1 was true I.fumosorosea,and those in clade II-1 might be I.javanica.Analysis phylogenetic tree of different strains of I.fumosorosea based on multi-gene sequences showed that they have differences.The strains in Clade I was from the same geographical origin;Most members of the Clade II have extremely thick colonies,dense aerial hyphae and lower conidium germination rates on PDA;The pathogenicity of the strains H2,H5 and H7 against T.urticae was weak.However,the strains in Clade III produced synnemata.Except strain H6,the rest conidial germination rates were higher and the pathogenicity was better.The strains H3 and H9 with the similar pathogenicity were clustered with 100% bootstrap value.Therefore,the pathogenicity of I.fumosorosea against T.urticae was correlated to the molecular data to some extend.The strains H1 & H4 clustering in a separated branch have great differences not only in the morphological characteristics but also in the spore germinate rate. |
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