Taxonomic And Molecular Systematic Studies Of Ochroconis And Verruconis

Ochroconis and Verruconis belong to the family Sympoventuriaceae,in the order Venturiales(Dothideomycetes,Ascomycota),with wide ecological and geographic distribution,and rich species diversity.Most of these species are saprophytic fungi,and some are important endophytic fungi of plants.In addition,some taxa pose a serious threat to agricultural production,especially to animal and human health,and are of great research value in veterinary and medical fields.However,due to the high similarity of Ochroconis,Verruconis and Scolecobasidium in morphological characteristics,lifestyle,pathogenicity and DNA molecular data,as well as the continuous change of taxonomic status,there are a large number of synonyms in these three similar genera.Among them,there is a significant disagreement amongst mycologists about whether the genus Ochroconis should be established and Scolecobasidium be phased out.Therefore,the taxonomic relationship of this taxa has been controversial for a long time,and the division between genus and species is not clear.Therefore,this study was based on the samples collected from different habitats in Guizhou Province and the strains collected from the Laboratory of Plant Pathology,College of Agriculture,Guizhou University.A systematic study of Ochroconis,Verruconis and Scolecobasidium fungi was carried out in combination with morphology and molecular systematics,to establish a more stable and reliable classification system for these three similar genera with more natural evolution relationship.In this study,24 strains of the fungi were isolated from kinds of specimens by plate dilution method,tissue separation method and single spore separation method,and 12 strains were obtained from the Laboratory of Plant Pathology,College of Agriculture,Guizhou University.Finally,a total of 36 strains of these fungi were collected.On this basis,with the help of some reliable gene sequences in Gen Bank database,use ITS?LSU?SSU?ACT1?TUB2?TEF1-? 6 gene loci to perform multi-gene phylogeny analysis on Ochroconis,Verruconis and Scolecobasidium,evaluate the distinguishing ability of these 6 genes for 3 genera and species,combining with comparative morphological characteristics,analyzing the internal relationship between genotype and phenotype,and discussing the taxonomic relationship of these three similar genera.The results showed that although Scolecobasidium type species S.terreum(CBS 203.27)was now sterile,yet other species of this genus and Ochroconis constitute the same lineage in the phylogenetic tree,and the taxonomic status of this genus is valid according to the International Fungal Nomenclature.Therefore,this study is based on the principle of naming priority and uses Ochroconis as a synonym of Scolecobasidium.Besides,in the phylogenetic tree constructed by multilocus sequence,species with similar morphological characteristics could form independent and closely related clades respectively,but they showed a longer phylogenetic distance.The phenomenon indicated that the molecular and morphological variations of these fungi are great in interspecies and intraspecies.In addition,S.tricladiatum was accommodated in Verruconis as a synonym for V.pseudotricladiata.By analyzing and comparing the recognition degree of each genetic loci to the genera and species level in Scolecobasidium and Verruconis,it is found that LSU and SSU could distinguish Scolecobasidium and Verruconis well,and they were able to gather in different clades respectively.For the assessment of the seven gene loci,LSU and SSU could be used as ideal genes for routine identification in those genera.In the discrimination of interspecific relationship,LSU gene was consistent with the Scolecobasidium phylogenetic tree constructed by combining multiple gene sequences.For Verruconis,the evolutionary relationship formed by TUB2 gene had the best correspondence with the morphological characteristics of each species of this genus.However,although individual single gene data showed good differentiation of intergenus,interspecific and intraspecific relationships,single gene sequences could not fully reflect the phylogenetic relationships among taxa compared with the phylogenetic analysis of multiple gene loci.Based on the new classification system of this group,the 36 strains in this study belonged to 13 species of Scolecobasidium and 2 species of Verruconis,including 3new record species in China: S.phaeophorum?S.globale and V.thailandica,and six new species: S.verrucaria?S.zunyiense?S.camellicola?S.coiledmyces?S.spikemyces and V.cylindricalis.These species are described in detail,and morphological characteristics and DNA molecular data are provided.