Species Delimitation Of Four Quarantine Basidiomycetous Taxa Based On Morphological And Molecular Evidences

Preventing the invasion of alien species is crucial to ensure sustainable development of China’s agriculture and forestry and the maintenance of national ecological security.There are130 species of fungi in the "List of Imported Quarantine Pests of the People’s Republic of China",and most of them are tiny and difficult to identify based simply on morphological characteristics.Consequently,detection,prevention,and control of these pests have been a difficult task for a long time.So far,only 35 fungal species have been intercepted at ports,leaving the majority undetected and presenting long-term challenges.This situation mainly results from insufficient type specimens,strains,and reliable reference sequences for most species,as well as unclear phylogenetic relationships and interspecific relationships with closely-related species.These factors not only hinder the development of detection methods for quarantine fungi at ports but also impede prevention and control of harmful plant pathogenic fungi.This study focues on four quarantine-significant basidiomycota species that have not yet been intercepted and reported.Based on literature reviews,numbers of specimens of quarantine species and closely related species were loaned from herbaria worldwide.Species were delimitated based on morphological and molecular data,host range,geographical distribution,DNA barcoding sequences,phylogenetic status,typical disease symptom,etc.which were further confirmed.To date,The main findings are as following:(1)The lectotype and epitype speimens of Urocystis cepulae were designated due to the lack of type specimens.Through morphological and phylogenetic studies,the species boundary between U.cepulae and U.magica is clarified,highlighting the importance of morphological characteristics of spore ball,spore and sterile cell.Microscopic and ultramicroscopic morphologies,DNA barcode sequences,host range and geographical distribution of this species were also confirmed.In addition,species-specific primers of Urocystis spp.were designed and multiple sequences of Urocystis spp.were added.(2)The phylogenetic relationships between Tilletia controversa and other species within genus Tilletia,especially T.caries,T.laevis were clarified by using ITS,rpb2 and tef.Combining with morphological characterisitcs,the main criteria for identifying T.controversa include not only reticulate ornamentation,thickness of gelatinous sheath and spore size,but also include host range and geographic distribution.(3)The phylogenetic relationships between Chrysomyxa arctostaphyli and other Chrysomyxa spp.were clarified and an epitype was designated.Morphology of different stages in the whole life cycle,DNA barcode sequences,host range and distribution were also confirmed.(4)The species boundary of Melampsora medusae was clarified,and its phylogenetic relationship with other rust fungi was determined through a multi-gene systematic phylogenetic analysis.Additionally,the host range,alternate hosts,and geographic distribution of the species were updated.