A Systematic Study On The Pathogenic Fungi Of Ornamental Orchidaceae In Guizhou

Many species of Orchidaceae have important ornamental value,such as orchid,Paphiopedilum,Cypripedium and so on.However,with the increasing of the area of cultivated orchids,the diseases and insect pests are becoming more and more serious,especially the fungal diseases,such as the coal smoke disease and stem base rot of Phalaenopsis,stem rot,anthrax,leaf spot and so on.Therefore,in view of the influence of orchid plant fungal diseases on industrial development and other issues,this study were carried out on the diseases of ornamental orchid plants caused by fungi in Guizhou,and obtained the following research results.1.Specimen collection: 156 samples of diseased leaves of ornamental Orchids were collected successively from medicinal botanical garden of Guizhou,Nanjiang Grand Canyon of Kaiyang,Maolan National Nature Reserve of Guizhou,Yamugou Nature Reserve of Jiangkou County,Nature Reserve of Meitan County,Institute of horticulture,Guizhou Academy of Agricultural Sciences,Guizhou Botanical Garden,etc.Ninty four samples were obtained after microscopic examination,and 63 pure cultures has gotten by single spore isolation and tissue isolation.2.Molecular systematics analysis: the genes of β-tubulin2(TUB2),glycoldehyde-3-phosphate dehydrogenase(GAPDH),actin(ACT),chitin synthase(CHS-1),and internal transcribed spacers(ITS)and so on,which are commonly used in molecular systematics,were amplified,sequenced,and compared with each other and the sequences with high reliability were downloaded.The molecular system tree was established according to different groups.The comparison analysis results showed that 63 cultures belonged to 11 genera,Colletotrichum,Curvicladiella,Daldinia,physiospora,periconia and Pestalotiopsiss.3.Species identification: eight new species.Three suspected new species belong to Colletotrichum,Curviladiella paphiopedili,Chaetopsina sp.,Chaetotyrina sp.,Parahoma sp.and Pyrenochaetopsis sp.were identified by morphological and molecular phylogenetic analysis.4.Pathogenicity experiment: According to Koch’s law,52 strains were selected and reconnected on the corresponding host,and 15 strains were proved to be pathogens.Among them,1 strain(Curviladiella papiopedili,new species)caused the blight of Paphiopedilum,1 strain(Colletotrichum sp.,suspected new species)caused the Cymbidium disease,and the other one(Nemania,species to be identified)caused Liparis distans C.B.Clarke disease,had only molecular data and did not got the sporulation structure and other morphological characteristics.