Studies On The Metabolites Of Two Endoparasitic Nematophagous Fungi

Plant-parasitic nematodes cause serious damage to crops.Biological control is one of the effective ways to control nematodes.Endoparasitic nematophagous fungi are a kind of important biocontrol fungi,which can cause disease or kill nematodes by producing various spores,and have certain potential in controlling plant-parasitic nematodes.In this paper,the secondary metabolites and their biologhical activities of two endoparasitic fungi,Drechmeria coniospora YMF1.01759 and Hirsutella rhossiliensis YMF1.01353 were firstly studied,to investigate the possible role of secondary metabolites in the process of nematode infection by endoparasitic fungi.The specific contents were as follows:The endoparasitic activities against nematode of 34 endoparasitic fungal strains were tested,and they belonged to Catenaria,Cylindrocarpon,Drechmeria,Harposporium,Hirsutella,Idriella,Nematoctonus and Verticillium respectively.The strains Drechmeria coniospora YMF1.01759 and Hirsutella rhossiliensis YMF1.01353 had high infection efficiency against Caenorhabditis elegans,and the infection rate was more than 90% in 72 hours.The process of infecting C.elegans by the two endoparasitic fungi was observed under electron microscope.The culture media of D.coniospora YMF1.01759 were screened.The SDAY solid medium was selected by detecting extract and assaying nematocidal activity.Fourteen metabolites were isolated and identified from the fermentation products.They were2-acetylnaphthalene（wmd-2）,（9Z,11E）-octadecadienoic acid methyl ester（wmd-3）,（3β,5?,8?,22E）-5,8-epidioxy-ergosta-6,22-dien-3-ol（wmd-7）,methylparaben（wmd-8）,1-formyl-2,6-dimethoxy-anthracene（wmd-9）,7β,8β,11-drimanetriol（wmd-11）,4-hydroxy-benzaldehyde（wmd-12）,3-carboxaldehyde-indole（wmd-15）,4-hydroxy-benzoic acid（wmd-16）,4-hydroxy-benzene acetic acid methyl ester（wmd-18）,4-hydroxy-benzene acetic acid（wmd-22）,drechcon acid（wmd-28）,3β,5α,9α-trihydroxy-（22E,24R）-ergosta-7,22-dien-6-one（wmd-29）and adenosine（wmd-32）.Among them,drechcon acid（wmd-28）was a new compound.H.rhossiliensis YMF1.01353 was fermented on PGA solid medium,six compounds were obtained from the fermentation products,including 2-oleoyl-glycerol（wh-1）,ergosterol peroxide（wh-6）,22E-7?-methoxy-5?,6?-epoxyergosta-8（14）,22-dien-3β-ol（wh-8）,6-O-methylcerevisterol（wh-10）,5-hydroxymethyl-furfural（wh-11）and cerevisterin（wh-16）.The metabolites from the two strains were tested for their nematocidal activity against Meloidogyne incognita.The results showed that drechcon acid（wmd-28）from D.coniospora could kill 80.1% M.incognita at 100 μg/m L for 48 h,wmd-28 inhibits the hatching activity of eggs of M.incognita at 50 μg/m L.the mortality of M.incognita by 5-hydroxymethylfurfural（wh-11）from H.rhossiliensis YMF1.01353 reached 80.3% at 50 μg/m L for 48 h,wh-11 inhibits the hatching activity of eggs of M.incognita at 50 μg/m L.These results indicated that endoparasitic fungi could not only infect nematodes by producing spores,but also produce active metabolites kill nematodes.The biological control potential of endoparasitic fungi against nematodes was further expounded.