Study On Taxonomy Of Orbiliaceae In Four Provinces Of Western China And State Of Georgia In The USA

Orbiliaceous fungus is a kind of small discomycetes which is mostly close to Pezizomycetes and has been proposed to be a single class,single order and single family.The main characteristics of the sexual morph is its waxy and translucent apothecia,ascospores which shows a high morphological diversity among the taxa,as well as the visible spore body when in the vital state.Some species of the family grow in wet habitats and possess the ability to trap nematodes by trapping organs.Most of the species grow in arid habitats and are highly resistant to desiccation.In this study,the resources of Discomycetes fungi in of China and Georgia of USA were systematically investigated.Comprehesive survey on Orbiliaceous fungi were conducted from four provinces of Westen China(Shaanxi,Gansu,Xinjiang,Guangxi)and the state of Georgia in the USA.Three hundred and sixty-two samples were collected from forest park and natural reserves.According to the morphological and molecular data,Nine species of Hyalorbilia and 31 species of Orbilia were identified,in addition to 2 unnamed species,among which there are 3 new species,viz.Orbilia georgina,Orbilia renispora,Orbilia shaanxiensis and 6 are reported as new records from China,viz.H.japonica,O.comma,O.crenatomarginata,O.euonymi,O.fabacearum,while 6 new recods from the USA,viz.H.japonica,O.crenatomarginata,O.eucalypti,O.fabacearum,O.occulta,O.xanthoguttulata.Among these,Orbilia carpoboloides and Orbilia aurantiorubra are xeric-resistance species.Moreover,Keys to all the described species of Hyalorbilia and Orbilia were provided.Eleven anamorphic species of Orbiliaceae were obtained by ascospore-shooting method,they are members of genera of Arthrobotyrs,Dactylella,Dicranidion,Trinacrium and Vermispora.The species belong to Arthrobotyrs trap saprophic nematode with adhesive network.Eleven Teleomorph-anamorph connections have been confirmed.In addition,he anamorph of Orbilia occulta was found and illustrated for the first time,it belongs to genus of Trinacrium.Transmission electron microscope(TEM)was employed to observe the ultrastructure of five species,results were showed as follows.Orbiliaceous fungi own truncatus ascus apex,thin-walled apex or thick wall cell;The ascus wall consisted of two layers:an outer almost uniformly thickened electron-dense layer and an inner less electron-dense amorphous layer.There are electron-light zone(EZ)located between inner wall layer and the plasma membrane.High electron-dense spore body lies in one of the apical of ascospore which is one of the distinctive character of Orbiliaceae.As for it can not be observed under light microscope because of dead status wheras TEM can easily get through when it is not alive,it provides a reference for overcoming the dificiency of optical microscope in observing sporebody in dry specimen.Phylogenetic relationship among species of Orbiliaceae based on internal transcribed spacer regions(ITS,including 5.8 rDNA)and D1-D2 sequences of 28S rDNA as well as sequecnes downloaded from Genbank were combined to construct phylogenetic trees by MEGA 7 and PAUP4.0 programe.Results showed that the phylogenetic trees based on the same gene indicated consistant topological structure,they were divided into seven main groups of Hemiorbilia,Helicoon,Habrostictis,Arthrobotrys,Aurantiorubrae,Orbilia and Hyalorbilia.It revealed that the strains with ability to capture nematodeassembled in the same clade,ascsopores have similar shapes are gathered in one group,eg.strains which have curved ascospores situated in one subgroup.In conclusion,the phylogenetic tree of either single gene or two combined genes manifested the genetic relationship between teleomorph and anamorph of Orbiliaceae,they were classified according to the new concept for genera of Orbiliaece based on the narrow concept that Baral proposed.