| Ophiocordyceps nutans(Pat.)G H.Sung,J.M.Sung,Hywel-Jones&Spatafora is a kind of important fungus resource,it has great application value in medicine and biological control.However,the research of O.nutans is mainly focused on specimen collection,description and identification,it is not clear about the distribution to the suitable area of O.nutans,the existing biosystematics information of O.nutans has also been neither sufficient nor comprehensive,lacks of systematic research.According to the known localities of O.nutans,MaxEnt and ENFA ecological niche models were employed to predict the potential suitable area of O.nutans in the world,and the receiver operating characteristic curve was applied to access the prediction accuracy.The main environmental variables were analyzed by jack-knife approach and niche factor score matrix and cluster analysis.The results showed that the two models were reliable for the prediction of the suitable area of O.nutans and the potential distribution area of O.nutans was far more than its actual distribution area.Except for Antarctica,O.nutans had a wide range of suitable habitat in the world.Among these areas,highly suitable area mainly located in Asia,including China,North Korea,Japan,Korea,Thailand,Vietnam,Myanmar,India,Nepal.Scattered in parts of Australia,African,South America.Temperature and humidity were the main factors influenced the distribution of O.nutans,especially its distribution pattern was impacted by the annual rainfall and average temperature of the most wet season.The morphological and microscopic traits were observated of various hosts in O.nutans.The results showed that the morphological variation of O.nutans was mainly caused by diameter of stroma,length of sclerotium,diameter of sclerotium of the differences of hosts,while the diameter of fertile part was stable with little variation.Among individuals of the same species of insect host,the difference of microscopic traits was mainly result from the length of perithecium and ascus.Among intra-individual or inter-individuals within the same species of insect host,the variation of microscopic traits was mainly resulted from the width of perithecium and ascus.The variation of microscopic traits on intra-individual or inter-individuals within the same species of insect host was much greater than among individuals of the same species of insect host.It was shown that the variation of microscopic traits in O.nutans was mainly caused by the intra-individual or inter-individuals within the same species of insect host.While the length of perithecium was stable,with being little variation.The ITS(the Internal Transcribed Spacer)region sequence of O.nutans were sequenced.Combined with its related sequences from GenBank,analyses for phylogenetic relationship and genetic diversity of O.nutans were conducted.The results showed as follows:(1)62 ITS sequences were sequenced.Combined with 61 ITS sequences of O.nutans from GenBank,a total of 123 ITS sequences were received.The sequence analysis showed that the ITS sequence of the O.nutans from different hosts had a high variation,and base composition has obvious AT bias.(2)The ITS phylogenetic tree was constructed for 123 heads sequence of O.nutans from the different host insects in 4 families of Hemiptera.The results showed that all strains were divided into two groups,and only the strain parasitizing Coreidae had a genetically remote from other strains,and clustered into a separate type ?.The type ?consisted of 107 strains,mainly parasitized other hemipterans,exception of Coreidae,including different species of Pcntatommae,Acanthosomatidae,and Urostylinae.Homology in the sequence of the ITS region between type 1 and type 2 was less than 85%based on a comparison of ungapped alignments.The distance value between types 1 and 2 was very remote(0.275),resulting in the formation of different clades.It was suggested that these two types should be different species.Besides,genetic divergence with the consequences of ecological differences between Coreidae and Pentatomoidea might lead to genetic remoteness between two types of O.nutans.(3)With the exception of Coreidae,the genetic diversity of 107 ITS sequences of O.nutans from the different host insects of 12 genera within Pentatomoidea were analyzed.It was shown that a high haplotype diversity(Hd=0.929)and lower total nucleotide diversity(Pi= 0.0218)at the species leve.There were 54 haplotypes of the ITS sequence of O.nutans,among the 54 haplotypes,the number of private haplotypes was abundant,accounting for 79.6%.Haplotype H22 was the dominant haplotype which had the highest proportion.The second was the haplotype H21,distributed in 2 genera hosts.There were more abundant haplotypes in O.nutans whose hosts belonged to Pentatoma and Acanthosoma.In addition to observing the morphological characteristics of the host,phylogenetic analysis of mitochondrial COI gene sequence was performed.Combined with the method of morphology and molecular systematics,the hosts of O.nutans were identified as Pentatoma armandi Fallou,Pentatoma rufipes(Linnaeus),Pentatoma metallifera(Motshulsky),Amyntor obscurus Dallas,Halyomorpha sp.,Brachyplatys sp,Carbula sp.,Palomena chapana Distant,Acanthosoma sp.,Acanthosoma labiduroides Jakovlev,Sastragala fermata(Walker),Urochela sp.,and Homoeocerus sp..The ergosterol and nucleoside components of six different hosts in O.nutans were determined by high performance liquid chromatography(HPLC).The results showed that the cordycepin were not detected in different hosts of O.nutans,ergosterol and eight nucleoside compounds were tested.Variation of different active components in O.nutans among individuals of the same species of insect was greater than the differences of host.Variation of active components in O.nutans was mainly caused by individuals of the same species of insect.In addition to the difference of adenine was not significant,the other ergosterol and nucleoside components were significantly different. |
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