Taxonomy And Floristic Species Composition Of Erysiphaceae In Southwest China

Erysiphaceae belongs to ascomycota,Leotiomycetes,Helotiales which is a kind of obligate parasitic plant pathogenic fungi widely distributed in the world.It can infect more than ten thousand angiosperms and cause serious harm to crops,horticultural fruits and vegetables,garden flowers and so on.Southwest China is one of the seven major geographical regions in China,with complex and diverse landforms from Sichuan Basin to Qinghai-Tibet Plateau,large altitude span and changeable climate types.The unique geographical location,complex terrain and climate conditions have contributed to the rich biodiversity in Southwest China,and some of the endemic plants in Southwest China may be special species of Erysiphaceae.In order to clarify the species and flora of powdery mildew in Southwest China.A total of 216 specimens were identified,including collected specimens and from Herbarium of Mycology of Jilin Agricultural University.The main research results are as follows:(1)According to the latest international classification system of Erysiphaceae,morphological and molecular systematics(ITS,28 S r DNA,IGS)were used to identify the species of powdery mildews in Southwest China,a total of 53 species in 10 genera parasitized on 100 species of host plants related to 39 families,83 genera were identified by the method of combining morphology and phylogeny.Two new species were proposed: Erysiphe sp.on Chimonanthus praecox and Podosphaera sp.on Photinia serratifolia.An epitype of Erysiphe coriariicola endemic in China,HMJAU-PM92098,was established.The anamorph and molecular sequences of this species were supplemented and clarified the phylogenetic status of E.coriariicola in genus Erysiphe.Two new recorded species in China: Erysiphe ligustri on Ligustrum lucidum and Erysiphe sidae on Sida sp..Three new hosts were recorded in the world:Tarenaya hassleriana parasitized by Erysiphe caricae-papayae,Erythrina crista-galli parasitized by Erysiphe diffusa and Viola arcuata parasitized by Neo(?)rysiphe galeopsidis.The morphological characteristics of the identified species were described in detail,and their taxonomic status was re-evaluated and dicussed.(2)Combined with the results of this study and the previous studies of Erysiphaceae in southwest China,floristic analysis of Erysiphaceae in southwest China was carried out based on the floristic division principle and floristic similarity coefficient.The results showed that Erysiphe was the dominant genus with 108 species,accounting for 60.67% in the total species.Phyllactinia had 27 species,accounting for 15.16% of in the total species.The rest accounted for 16.39%.The analysis of the geographical composition of the species showed that the "endemic species to China elements" was the dominant floristic feature in Southwest China,and the number of these species accounted for 32.02% of the total number of species.The North Temperate type accounted for 18.54%.Eastern Asian type,accounting for 15.73%.Cosmopolitan type accounted for 12.36%.Eastern Asian-North American type accounted for5.06% of the total.The Old World Temperate type accounted for 7.30%.Other types accounted for 8.99%.The results showed that the similarity coefficient between Southwest China and Qinling mountains was the highest,reaching 46.77% and lowest in the Xinjiang Uygur Autonomous Region.