Taxonomic And Phylogenetic Study Of A Rust Genus Coleosporium In China

Pine needle rusts caused by Coleosporium Lev. (Coleosporiaceae, Basidiomycetes) are among the damaging diseases of young pines in plantations and natural forests worldwide, retarding growth by causing premature defoliation and contributing to tree death. Among the approximately one hundred and thirteen Coleosporium species described worldwide, fifty nine species have been reported in China. The uredinial and telial states of Coleosporium occur on 16 various families of Angiospermae. Species delimitation in Coleosporium remains difficult and confusing. The traditional identifications are mainly based on their telial host plant genera. However, the host plants often tend to overlap in related species, and the teliospore morphological characteristics are very similar. The taxonomy and phylogenetic relationship of Coleosporium species in China are also challenging.A total of 876 uredinio-telial specimens, from 21 provinces, were used for light microscopy, scanning electron microscopy and molecular phylogenetic investigation. The association between the morphological characters of Coleosporium species and the telial host families were summarized, then phylogenetic trees were constructed from the 28S region of nuclear large subunit rDNA, and the internal transcribed spacers regions, respectively. We aimed to define the relations between the phylogenetic group and morphological characteristics, and to evaluate the taxonomic the morphological similar species of Coleosporium. Main results are as follows:1. The total number of valid Coleosporium species in China is 56. The valid names of species are given together with synmonyms, new descriptions for each spore stages, revised or original descriptions, specimens examined, distribution, and remarks. Also the Classification table of Coleosporium species is listed. The following specific names in brackets are reduced to synonyms of the former namers:C.horianum (syn. C.campanumoea), C.cimicifugatum (syn. C.actaea), and a new Coleosporium species is described, named as Coleosporium zhuangii C.M. Tian & C.J. You (Type on Ligularia fischeri). Two wrong recorded Coleosporium species, including Coleosporium pseudocampanulae and Coleosporium elongatum, are moved.2. The surface structure of urediniospores, and the morphological characters of teliospores have been proved to be more reliable taxonomic characters for the delimitation and circumscription of Coleosporium species.3. The circumscription and identification of the following morphologically similar species have been demonstrated to be clear based on morphological characters and phylogenetic study. C. plectranthi and C.perillae, C.clematidis and C.clematidis-apiifolia, C.campanulae and C.lycopi, C.pulsatillae and C. anemones, C.ligulariae, C. saussureae and C. pedunculatum, C. pedicularil and C. euphrasiae.4. Sequence data were obtained from 28S region of nuclear large subunit rDNA, and from internal transcribed spacers. Then, phylogenetic trees were constructed from the 28S and ITS regions, repectively. Those Coleosporium species were separated into seven groups by MP trees in 28s region, however, the analyses of ITS trees clearly distinguished six groups. The relations between the phylogenetic groups and morphological characteristics were investigated, and the results showed that the urediniospore surface-structure and the morphological characters reflected the phylogeny, the germ pore arrangement of urediniospores and the shape, size of urediniospores and teliospores did not correspond to the phylogeny.