Taxonomy Of Cytospora Species In Northeast China

The genus Cytospora Ehrenberg. can cause trees rot as pathogens. In this study, via microscopical morphology, histopathological and observation of cultural characteristics,149Cytospora specimen on15different hosts collected from23areas in Heilongjiang, Jilin, Liaoning and eastern Inner Mongolia were observed. Combining with the phylogenetic tree construted with rDNA-ITS sequence, Cytospora species in northeast China were analyzed, and the classification basis and the interspecific phylogenetic relationships were discussed. The results are as follows:(1) Morphological observation for Cytospora specimen collected from northeast China shows8asexual species and5sexual groups morphologicaly. The asexual species were identified as Cytospora pruinosa (Fr.) Sacc, C. leucostoma (Pers.) Sacc, C. nivea Fuckel., C. chrysosperma (Pers.) Fr., C. carbonacea Fr. and C. sacculus (Schwein.) Gvrit. Cytospora sp.1(hosts are Ulmus sp.), Cvtospora sp.2,(hosts are Rose davurica); the sexual groups were identified as Leucostoma niveum (Hoffm.) Hohn., Leucostoma persoonii (Nitschke) Hohn., Valsa sp.2(hosts are Rose davurica), Leucostoma sp.(hosts are Ulmus sp.)and Valsa sp.1(hosts are Ulmus sp.).(2) Morphological and phylogenetic analysis of Cytospora shows that the undivided-or multi-locules, the number of ostioles, the size of conidia, and the appeatance of centrum column and black zone line are the basis for classification of Cytospora. While other features such as the form of locules and osticles, stromata morphology and the development degree of entostroma are unstable. The features of maxe-like or rose block-like locules and the shape of ostioles can be various even on the same speciman so that they can not be used for classification. Meanwhile the development degree of entostroma of C. leucostoma can be variant when they resided on different hosts.(3) In the phylogenetic tree, the same Cytospora species gethered in the same clade with effective support rate; the clades of Cytospora species belong to the same sexual genus were togethered closer. There is a good correlationship between morphological species and phylogenetic clades.(4) The specifity of Cytospora species to hosts is not strict. The the same Cytospora fungi can be observed on different hosts, and the differernt Cytospora species can reside on the same host paint.