DNA barcoding in the rust genusChrysomyxaand its implications for the phylogeny of the genus

Abstract

Chrysomyxa rusts are fungal pathogens widely present in the boreal forest. Taxonomic delimitation and precise species identification are difficult within this genus because several species display similar morphological features. We applied a DNA barcode system based on the ribosomal internal transcribed spacer region (ITS), large subunit (28S) ribosomal RNA gene, mitochondrial cytochrome oxidase 1 (CO1) and mitochondrial NADH dehydrogenase subunit 6 (NAD6) in 86 strains from 16 different Chrysomyxa species, including members of the Chrysomyxa ledi species complex. The nuclear ITS and 28S loci revealed higher resolving power than the mitochondrial genes. Amplification of the full CO1 barcode region failed due to the presence of introns limiting the dataset obtained with this barcode. In most cases the ITS barcodes were in agreement with taxonomic species based on phenotypic characters. Nevertheless we observed genetically distinct (different DNA barcodes) lineages within Chrysomyxa pyrolae and Chrysomyxa rhododendri, providing some evidence for allopatric speciation within these morphologically defined species. This finding, together with the observed pattern of host specificities of the studied rust fungi, suggest that species diversification within the C. ledi species complex might be governed by a set of factors such as specialisation to certain Ericaceae species as telial hosts and to a lesser extent specialization to different spruce species as aecial hosts. Moreover allopatric speciation by geographic disruption of species also seems to take place. When our data were integrated into a broader phylogenetic framework the Chrysomyxa genus unexpectedly was not resolved as a monophyletic group. Indeed the spruce cone rusts C. pyrolae and C. monesis coalesced with the pine needle rusts belonging to the genus Coleosporium, whereas the microcyclic species Chrysomyxa weirii was embedded within a clade comprising the genus Melampsora.

Two new Chrysomyxa rust species on the endemic plant, Picea asperata in western China, and expanded description of C. succinea

“…Detailed descriptions of the morphology of the two species are given in the taxonomy section. Morphology of the two rust fungi was compared with descriptions of other known Chrysomyxa species in taxonomic references (Pethybridge 1918, Takahashi & Saho 1985, Crane 2001, 2003, 2005b, Tillman-Sutela et al 2004, Kaitera et al 2010, Feau et al 2011. The two rust fungi differed from other Chrysomyxa species in aeciospore surface ornamentation and aecial peridium.…”

“…PCR products were purified and cloned for sequencing (TSINGKE, Beijing, China). Chrysomyxa weirii obtained from BOLD was used as an outgroup (Feau et al 2011).…”

“…Most species are heteroecious, and macrocyclic producing spermogonia and aecia on needles and cones of Pinaceae hosts, mainly on Picea (Cummins & Hiratsuka 2003), and uredinia and telia on Ericaceae and Pyrolaceae, mainly on Rhododendron, Ledum, Chamaedaphne, Vaccinium, Moneses and Pyrola (Crane 2001, Feau et al 2011.Others species are microcyclic, producing only telia on the conifer host, or demicyclic, having all spore states except uredinia (Crane 2005b, Feau et al 2011. Of the eight Chrysomyxa species reported on needles of Picea spp.…”

“…Gross morphology of the aecia and aecial perdium may be useful taxonomical characters for several species, but the morphology of teliospores and basidiospores are fairly consistent within a species. Taxonomic studies and DNA barcoding of Chrysomyxa species have been conducted in Europe, Japan and North America (Pethybridge 1918, Takahashi & Saho 1985, Crane 2001, 2003, 2005a, 2005b, Tillman-Sutela et al 2004, Kaitera et al 2010, Feau et al 2011, but morphological taxonomy at the species level is confusing due to overlapping features. Therefore, comprehensive taxonomic studies including molecular data are required.…”

A new rust species of Diaphanopellis on Rhododendron oreodoxa from Southern China

“…We compiled two datasets for phylogenetic analyses: (A) an rDNA ITS dataset that consisted of sequence data obtained from this study, and rust species of Coleosporiaceae from BOLD (Feau et al 2011) and GenBank (Table 1), and (B) a rDNA ITS dataset, which included the related rust genera with Chrysomyxa, representing major lineages of Pucciniaceae, Pucciniastraceae, Coleosporiaceae, Cronartiaceae and Melampsoraceae (Table 3). Phylogenetic trees obtained from analyses (A) and (B) were rooted with Melampsora epitea (AY471646) and Puccinia melampodii (EU659697) respectively.…”