| Endophytes referr to fungi colonizing healthy plant tissues without causing symptom or apparent injury to the host.Reasearch results in recent years show that endophytic fungi can produce some similar physiological active products to the host plant.So studies on the endophytic fungi and their metabolites have been a new way to find medical resources.In this paper,Dendrobium SW.,a chinese valuable medicinal plant,was selected as material. Totally 92 endophytic fungi has been isolated from root,stem,leaf of 8 species Dendrobiums.Two strains of Xylaria from the stem of Dendrobium fimbiratum and the leaf blade of Dendrobium brymerianum were respectively isolated and numbered as LSJ1 and CSY1,and induce them to generate fruiting body.They were identified with morphology and molecular biology method.The results revealed that LSJ1 and CSY1 were Xylaria venosula.The research also determined their fermentation end-point,their contents of polysaccharide and water-soluble protein,as well as the activity of anti-bacteria.β-sitosterol is one of important active constitutents of Dendrobium fimbiratum.12 endophytic fungi of Dendrobium were fermentated on PD liquid medium.The highly performance liquid chromatography(HPLC) was employed to determine the value ofβ-sitosterol of LSJ1, LSJ5,LSY4.The results indicated the mycelium of the 3 strains containβ-sitosterol.The content is 7.94ug/g,0.274ug/g,11.51ug/g respectively.They were identified with morphology and molecular biology method.The results revealed that LSJ1 was Xylaria venosula,LSJ5 was Valsaceae,LSY4 was Colletotrichum gloeosporioides.This paper optimized the method for the total DNA isolation of perennial Dendrobium species.Upgrading filling of extract and improving concentration of CTAB(2.5%) and NaCl(1.4 mol·L-1).0.5V NaCl(5mol/L) was added to water phase after extracted by chloroform/isoamyl alcohol to remove polysaccharide.And adding 2V anhydrous ethanol again to precipitate DNA, the result was satisfactory.
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