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1-3 Melampsora nujiangensis on Populus yunnanensis (TSH-R20042, holotype). 1 Hypophyllous telia and teliospores. 2 Globoid urediniospores with thin walls. 3 Uniformly echinulate urediniospores. 4-6 M. abieti-populi on P. wilsonii (HMAS-55410). 4 Hypophyllous telia and teliospores. 5 Ellipsoid urediniospores. 6 Uniformly echinulate urediniospores. Bars 20 µm
Source publication
Melampsora nujiangensis, a rust fungus found on Populus yunnanensis in China, is described as a new species. Light and scanning electron microscopy with herbarium specimens of the rust fungus
show that the shape of its urediniospores differs from that of other known species of Melampsora, and its urediniospore walls are thinner than the other speci...
Context in source publication
Context 1
... round or ellipsoid, 0.2-0.8 mm, orange-yellow or pale yellow, initially covered by epidermis, later erumpent, pulverulent; urediniospores mostly globoid or rarely ovoid, 17.0-26.8 × 18.2-22.8 µm (average, 21.3 × 19.7 µm); walls uniformly thick, 0.9-1.9 µm (average, 1.3 µm; Fig. 2), echinulate, distance between spines 1.1-2.0 µm (average, 1.5 µm; Fig. 3 ...
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Citations
... Poplar rust is one of the most serious diseases affecting the development of the poplar industry. The fungus was introduced into Australia in the 1970s, which had a devastating impact on the local poplar production, with the volume loss reaching more than 80% (Brown, 1984).In China, leaf rust frequently breaks out and spreads due to the large planting area and single stand of Populus deltoides (Liang et al., 2006). In May and June, the first onset of leaf rust occurs, and injured leaves showed flaky orange-yellow spots the affected leaves show flaky-orange spots. ...
... The main pathogen of poplar leaf rust is Melampsora, and 32 species have been found (Vankraay et al., 1974), most of which are allogeneic (Bagyanarana et al., 1984;Shang et al., 1990a;Liang et al., 2006), most of which need further separation and identification. In the existing reports, the color, shape and size of the spores of rusts, the number of bud holes germinated, the arrangement of bud holes and the presence or absence of bald spots were mostly preliminarily identified (Arthur, 1934;Wang et al., 1983;Cao et al., 2000), leading to inaccurate identification of some rust fungi. ...
... by other pathogens, thus causing harm to its growth. It was found that there were 9 species of phyllostachys parasitizing on Chinese poplar (Shang and Pei, 1984;Yuan, 1984;Liang et al., 2006), among which 5 species are the most common: M. medusae, M. abietis-Canadensis, M. aecidioides, M. laricisi-Populina and M. Allii-populina. However, their morphological characteristics are similar without obvious differences, and they are only judged to have certain risks according to their morphological characteristics. ...
... To date, over 20 Melampsora species have been described worldwide from different Euphorbia species of which the most common are M. euphorbiae, M. helioscopiae and M. gelmii (Farr and Rossman 2016). In earlier literature, several forms of M. euphorbiae have been described (e.g., gerardanae, helioscopiae, euphorbiae, dulcis, pepli, exiguae and cyparissiae) (Wilson and Henderson 1966;Kuprevich and Tranzsehel 1957). However, the study of Bagyanarayana (1999) separated the forms of Melampsora infecting Euphorbia into distinct species on the basis of morphological characters, such as the apical thickness of teliospores. ...
... In the past, Melampsora rusts on Euphorbia have been mostly identified as M. euphorbiae. While many hostspecies-based forms of this species have been described (e.g., M. euphorbiae-gerardianae), these were later all synonymized with M. euphorbiae (Wilson andHenderson 1966, Kuprevich andTranzsehel 1957) along with several species previously considered separate like M. ricini and M. helioscopiae (Farr and Rossman 2016;Bagyanarayana 1999). Therefore, it is difficult to evaluate the species richness of Euphorbia rusts without further study of the original collections. ...
A rust fungus was found on the leaves of Euphorbia helioscopia during a field study in Pakistan. Previously, Melampsora euphorbiae, M. euphorbiae-gerardianae and M. helioscopiae have been reported on E. helioscopia, the first two of which are also known from Pakistan. Morphological observations of the newly collected rust samples detected some differences from the previously described Melampsora species on E. helioscopia. The molecular analysis of the ITS and LSU sequences also detected that the rust is different from the previously reported rusts described from E. helioscopia. Based on both morphological comparisons and sequence analysis, the rust is described here as M. pakistanica sp. nov. This species could have potential as a bio-control agent against its host plant—E. helioscopia—which is a weed of wheat fields in Pakistan and elsewhere in the world.
... Recently, a combined genomic and transcriptomic approach led to the discovery of a very large repertoire of candidate M. larici-populina effectors (Duplessis et al. 2009Hacquard et al. 2011). Despite considerable efforts by breeders to generate resistant hybrid poplars, rapid breakdown of resistance was generally observed because of the continuous development of new rust pathogens (Shang et al. 1986;Newcombe et al. 2000;Liang et al. 2006). Thus, the sustainability of newly selected resistance-types requires better understanding of the interactions between Populus and M. larici-populina. ...
The uredinial stage in the life cycle of Melampsora larici-populina on poplar leaves is the most important pathogenic phase. We captured partial phases of uredinial infection in the wild, aiming to reconstruct the process of uredinial ontogeny by using scanning and transmission electron microscope. At the initial infection stage, germ tubes germinated from the echinulate urediniospores. Germ tubes were frequently seen to merge with the leaf surface and cuticle breakage was observed, indicating direct hyphal penetration. Stomata penetration occurred commonly, sometimes with more than one germ tube penetrating the same stoma. Melampsora larici-populina did not form appressoria in the infection process, implying that infectious behavior of this pathogen may differ from the other rust pathogens. In general, germ tubes branched randomly, and no distinct evidence indicated that stoma could induce or orient germ tube branches. However, oriented germ tube growth has been occasionally observed in other studies. The urediniospores collapsed and finally wizened when they became nutrient stressed. At the last stage of infection, the uredinia erupted from the leaf epidermis and appeared as orange pustules on the leaf surface.
... (). A few illustrated taxonomic keys to recognize and identify Melampsora species on poplar have been published but solely at the level of individual countries or specific geographical regions ( Cummins 1943 Cummins , 1950 Ziller 1955; Kuprevich and Tranzschel 1957; Arthur and Cummins 1962; Hiratsuka and Sato 1982; Shang et al. 1986; Shain 1988; Cellerino 1999; Frey et al. 2005; Sharma 2005; Liang et al. 2006). As no previous study or review has considered all described Melampsora poplar rust species together, a summary is presented in the next section. ...
... A global effort to morphologically and molecularly characterize Melampsora rusts occurring on poplars in China was attempted (). Based on the ITS regions, compared morphological/taxonomic groups with the molecular phylogenetic clades and suggested the following taxonomic changes: i) recognition of a new species M. nujiangensis, based on its phylogenetically distinct profile ( Liang et al. 2006); and ii) the probable synonymy between M. aecidioides, M. magnusiana and M. rostrupii (). However, that study only included specimens from Populus spp. ...
We present a review of previous taxonomic treatments of the Melampsora species occurring on poplar and describe the features associated with each spore stage in a typical poplar rust life cycle. The morphological, biological and ecological characters traditionally used for taxonomy are summarized for all Melampsora taxa, including 17 accepted species, 2 formae speciales and 2 hybrids, currently listed in the literature as pathogenic on Populus spp. We discuss the historical taxonomic decisions that led to nomenclatural and classification complications for this group of rusts, and highlight the lack of type material for three species known only from the original collections: M. cumminsii, M. multa, and M. osmaniensis. Even when all the traditional features are considered, the taxonomy of Melampsora poplar rust species remains uncertain and incomplete. An overview of recent molecular studies suggests the need for a comprehensive revision of species concepts, based on phylogenetic relationships. To that end, we propose a polyphasic approach, including the Genealogical Concordance Phylogenetic Species Recogni-tion method, be used to build robust and meaningful systematic framework for the Melampsora poplar rusts.
... Similarly, identification of strains from pines with similar DNA sequences will allow irrevocably the diagnostic of M. pinitorqua. Given the risks associated with the introduction of this fungus on North American pines (at less five potentially susceptible pine species), the availability of reference DNA barcodes for M. pinitorqua should now avoid Tsuga canadensis M. populnea (Pei et al. 2005) M. laricis (= M. larici-tremulae) (Liang et al. 2006) Melampsora sp. (Tian et al. 2004) M. magnusiana (Liang et al. 2006) Initial identification (reference) Taxon ID DNA barcode identification GenBank Accession No. erroneous diagnostic and drastic phytosanitary advices which could arose. ...
... Given the risks associated with the introduction of this fungus on North American pines (at less five potentially susceptible pine species), the availability of reference DNA barcodes for M. pinitorqua should now avoid Tsuga canadensis M. populnea (Pei et al. 2005) M. laricis (= M. larici-tremulae) (Liang et al. 2006) Melampsora sp. (Tian et al. 2004) M. magnusiana (Liang et al. 2006) Initial identification (reference) Taxon ID DNA barcode identification GenBank Accession No. erroneous diagnostic and drastic phytosanitary advices which could arose. Microscopic investigations led us to believe that the leaf rust strains we obtained from Populus alba in Canada exhibited traits of Melampsora aecidioides (Arthur 1962). ...
... These strains were collected on P. alba, P. alba var. pyramidalis, and Populus tomentosa in China, and deposited in the Mycological Herbarium of the College of Forestry at the Northwest Sci-Tech University of Agriculture and Forestry in China (HMNWFC), and in the Mycological Herbarium of the Institute of Agriculture and Forestry at the University of Tsukuba in Japan (TSH) (Liang et al. 2006;Tian et al. 2004). The urediniospore morphologies and sizes described for these M. magnusiana isolates in Tian et al. (2004) (Arthur 1962;Pinon 1973). ...
Wide variation and overlap in morphological characters have led to confusion in species identification within the fungal rust genus Melampsora. The Melampsora species with uredinial-telial stages on white poplar and aspens are especially prone to misidentification. This group includes the Melampsora populnea species complex and the highly destructive pine twisting rust, Melampsora pinitorqua, which alternates between hosts in Populus section Populus and Pinus. Our objective was to compare morphologically based identification to genetic material extracted from Melampsora species pathogenic to aspen and white poplar. We compared morphometric traits and DNA barcodes obtained from internal transcribed spacer (ITS), large ribosomal RNA subunit (28S), and mitochondrial cytochrome oxidase 1 (CO1) sequences to delimit within this taxonomically difficult group. Eight different Melampsora species were initially defined based on host specificity and morphometric data. DNA barcodes were then overlaid on these initial species definitions. The DNA barcodes, specifically those defined on ITS and 28S sequences, provided a highly accurate means of identifying and resolving Melampsora taxa. We highlighted species misidentification in specimens from Canadian herbaria related to either Melampsora medusae f. sp. tremuloidae or Melampsora aecidioides. Finally, we evidenced that the north-American species found on Populus alba, M. aecidioides is closely related but distinct from the four species of the M. populnea complex (Melampsora larici-tremulae, Melampsora magnusiana, Melampsora pinitorqua, and Melampsora rostrupii) found in Eurasia.
Rust diseases of Abies and Populus caused by Melampsora abietis-populi are observed in the forests of northeastern Asia. However, the life cycle and distribution of this species are not sufficiently clarified in China. The heteroecious life cycle alternating between spermogonial and aecial stages on A. holophylla and uredinial and telial stages on Populus pseudosimonii is confirmed for the first time in China by inoculations and phylogenetic analyses. The identity of these stages with M. abietis-populi is also confirmed by comparative morphology with specimens from Japan and phylogenetic analyses. These plants are new hosts for this species. Host plants and distribution of this species in China are described based on specimens obtained from the field and from inoculations. The phylogenetic position of this species within Melampsora is clarified for the first time. Based on morphological similarities and phylogenetic analyses, M. nujiangensis reported on Populus yunnanensis is treated as a synonym of M. abietis-populi.
