Phragmidium Species Research Articles

First report of Phragmidium rubi‐oldhami causing rust disease on Rubus pungens in Korea

Rubus pungens (‘Korean creeping raspberry’; Rosaceae) is a deciduous, broad-leaved tree native to East Asia. Its edible fruit is consumed fresh or used as a medicinal ingredient for diabetes and asthma (Moon, 1991). In May 2021, symptoms of a rust disease were observed on Rubus pungens in the Korea National Arboretum, Pocheon, Korea, with a disease incidence of 50% amongst the 30 plants surveyed. Bright yellow-orange rust pustules of the uredinial stages were found on both sides of the infected leaves. The pustules were often erumpent and 1 to 3 mm in diameter (Figure 1). The infected leaves were examined under a light microscope. Uredinia (Figure 2; n = 20) were erumpent, round, yellow to pale yellow, mostly scattered, rarely grouped and 200–536 µm in diameter (Figure 2). Urediniospores (= 50) were hyaline, globose to sub-globose and (16.0–)18.4–21.2(–23.6) × (12.6–)15.3–18.5(–19.7) µm (mean 19.8 × 16.9 µm), with an echinulate wall of 1.0 µm thick (Figures 3, 4). Paraphyses (n = 30) were hyaline, oblong or curved, and 56.2–11.1 µm, with a thin wall of 0.5–1.0 µm, occasionally slightly thickened at apex, 1.2–2.5 µm (Figure 5). The telial stage was not found. Based on morphological characteristics, the rust fungus was identified as Phragmidium rubi-oldhami Togashi & Y. Maki (Hiratsuka, 1934). To confirm the identification of the rust, genomic DNA was extracted from a representative specimen (KSNUH1322). Two ribosomal DNA regions were amplified, the internal transcribed spacer (ITS) with primers ITS5u and ITS4rust (Pfunder & Schürch, 2001) and the large subunit (LSU) with primers LRust1R and LRust3 (Beenken et al., 2012). The resulting sequences were deposited in GenBank (Accession Nos. ON180674 for ITS and ON170371 for LSU). A BLASTn search revealed that the Korean isolate had 99.43% identity in the LSU region to the only P. rubi-oldhami sequence in Genbank, which was obtained from Rubus pungens in China (MG669116). Close identities were found with other Phragmidium species when analysing the ITS sequences, however, there is no ITS reference sequence in GenBank for P. rubi-oldhami. In a maximum likelihood phylogenetic analysis using ITS (Figure 6) and LSU (Figure 7) sequences, the Korean isolate grouped with the reference sequence of P. rubi-oldhami in the LSU tree and formed a distinct branch among other Phragmidium species in the ITS tree. Phragmidium rubi-oldhami was originally described as a rust on Rubus oldhami in Japan (Togashi & Maki, 1934) and has since been recorded on R. amabilis, R. pungens and R, thibetanus in China and Japan (Farr & Rossman, 2022; Liu et al., 2018; Zhuang & Wei, 2009). To our knowledge, this is the first report of P. rubi-oldhami and of the rust disease on R. pungens in Korea. Given that urediniospores can easily disperse long distances by wind, this can pose a potential risk of rust disease on other Rubus species in Korea. This work was supported by the Korea National Arboretum grant (KNA3-1-10, 21–4) from the Korea Forest Service, Korea.

Taxonomic revision of species of Kuehneola and Phragmidium on Rosa, including two new species from China

ABSTRACT Kuehneola japonica and K. warburgiana are the only species of genus Kuehneola that parasitize plants belonging to genus Rosa (Rosaceae). Systematic revision of the genus Phragmidium and related genera by molecular phylogenetic analyses using nuc rDNA internal transcribed spacer (5.8S-ITS2 = ITS2) and nuc rDNA 28S (28S) sequences indicated that K. japonica and K. warburgiana belong to a group of Phragmidium species that also occur on Rosa. Morphological and molecular phylogenetic analyses revealed that these Kuehneola species were transferred to Phragmidium and renamed as P. japonicum and P. warburgianum. Two new Phragmidium species were also discovered on Rosa from China that could be distinguished from other species in the genus based on aeciospore or urediniospore morphology and phylogenetic placement. The first species, P. jiangxiense, is characterized by a urediniospore surface structure with stout spines that are basally embedded in the wrinkled spore wall. The second species, P. leucoaecium, is characterized by an aeciospore surface structure with irregularly elongated verrucae. Taxonomic descriptions and illustrations are provided.

<p><strong>Taxonomy and phylogenetic position of <em>Phragmidium altaicum</em>, a newly described rust fungus on <em>Rosa</em>, based on molecular and morphological data</strong></p>

Phragmidium altaicum, a new causal fungus of a rose rust disease, is described and illustrated. The species, collected in Xinjiang Province, northwestern China, is well distinguished by its morphology and rDNA LSU and ITS sequences from the other Phragmidium species on Rosa. The new rust species is characterized primarily by 4–7-celled teliospores, bearing robust verrucae on the surface, aeciospore-surface structure of ‘Echinulate type 4,’ and urediniospore surface completely covered with echinulae with inapparent mushroom-shaped base. The sequence analysis showed that this species is closely allied to P. tuberculatum, but they differ in their morphological characteristics.

Phragmidium species parasitizing species of Rosaceae in Tibet, China, with descriptions of three new species

Phragmidum spp. are rust fungi that are serious pathogens of plants in the Rosaceae. We characterized 15 Phragmidium species from Tibet, including 12 previously described and 3 new species. All the taxa, including the three new species (Ph. chayuensis, Ph. cibanum, Ph. zangdongii) are described and illustrated based on morphological characteristics. These taxa have multi-celled teliospores with firm pedicels. Phragmidium chayuensis is characterized by (5)7–9-celled teliospores with short papillae. Phragmidium cibanum is characterized by smooth teliospores that are distinctly constricted at the septa. Phragmidium zangdongii is characterized by large uredinia and 11–13-celled teliospores. Five types of urediniospore-surface structures were identified based on the gross shape of ornamentations and their distribution on the urediniospore wall. Molecular sequence data from the LSU rDNA analysis showed that the new taxa formed distinct clades independent from previously recorded species represented by LSU rDNA sequence data. The phylogenetic tree indicated that Phragmidium species are highly host specific.

Two new Phragmidium species identified on Rosa plants native to China

Two new Phragmidium species, Phragmidium zhouquensis and Ph. longissima, were identified on two native plants, Rosa omeiensis and R. lichiangensis respectively, during an investigation of the occurrence of rust fungi in western China. Phragmidium zhouquensis is mainly characterized by 3–9-celled teliospores bearing minute verrucae on the surface. Phragmidium longissima differs from other Phragmidium species in that it possesses echinulate urediniospores with a pore membrane at the germ pore. Phylogenetic analyses based on 28S rRNA partial gene sequences revealed that specimens of Ph. zhouquensis and Ph. longissima formed two distinct lineages. Phragmidium longissima is the first Phragmidium species to be identified on R. lichiangensis.

Different evolutionary histories of two Phragmidium species infecting the same dog rose hosts

Rust fungi in the genus Phragmidium are frequent pathogens of both wild and cultivated roses. We investigated the occurrence and relationships of rusts on dog roses, Rosa sect. Caninae (Rosa canina, R. corymbifera and R. rubiginosa) in Germany. Two Phragmidium species, P. mucronatum and P. tuberculatum, were able to infect each of the three dog rose species examined. However, the overall infection of R. rubiginosa was significantly lower, which could be important for rose breeding. Despite overlapping host ranges, the evolutionary background of P. tuberculatum and P. mucronatum is quite distinct. Phylogenetic analyses of the D1/D2 region of the LSU rDNA suggest that P. mucronatum shares a common ancestor with other rose rusts, whereas P. tuberculatum evolved from a Rubus-Sanguisorba rust clade and must have undergone a host shift to Rosa spp.

Aeciospore-surface structures of Phragmidium species parasitic on roses

Aeciospore-surface structures of Phragmidium species parasitic on roses were investigated by scanning electron microscopy. Seven kinds of structures were distinguished according to gross shape of ornamentations and their distribution on the aeciospore wall. The seven different structures were categorized into three major types: echinulate, annulate, and verrucose. The echinulate type was further classified into five types and designated in a numerical series, echinulate types 1–5. Application of the aeciospore-surface structures in the classification of Phragmidium species is discussed.

Morphological analyses of urediniospores and teliospores in seven Phragmidium species parasitic on ornamental roses

Ornamental roses worldwide harbor 10Phragmidium species. Among theseP. americanum, P. fusiforme, P. montivagum, P. mucronatum, P. rosae-pimpinellifoliae, P. rosae-rugosae andP. tuberculatum are frequently reported; however, these species are morphologically similar and difficult to distinguish. For better circumscription and correct identification of the species, this study examined morphological features in urediniospores and teliospores of the sevenPhragmidium species collected on ornamental rose cultivars and wild species. The results indicated that some host-specific groups could be well circumscribed by the morphological properties of urediniospores and teliospores. However, without the precise identification of hosts, these morphological properties were not effective key characters for the identification of the species.

The Inability of Phragmidium Species to Infect Species of Agropyron

The Inability of <i>Phragmidium</i> Species to Infect Species of <i>Agropyron</i>

The Inability of Phragmidium Species to Infect Species of Agropyron

"The Inability of Phragmidium Species to Infect Species of Agropyron." Mycologia, 74(6), p. 1020Key Words: PhragmidiumAgropyronrust fungi

Phragmidium Species of North America: Differential Teliospore and Aecial Characters

Differential teliospore characters of the nineteen species of Phragmidium in North America are used herein as a basis for arranging the species occurring on the three host tribes, Potentilleae, Rubeae and Roseae, under the two sections of the genus Phragmidium, Earlea, characterized by firm non-hygroscopic teliospore pedicels, and Euphragmidium, characterized by hygroscopic teliospore pedicels. Aecial characters and teliospore char? acters are used as bases for keys to the species on each of the three host tribes. For host range and geographic distribution of each species the reader is referred to the North American Flora (3). Measurements are included where they are useful and when pertaining to teliospores do not include the pedicels. The first comprehensive study of the rust genus Phragmidium was published by Dietel (4) in 1904. In this paper he recognized seventeen species in North America and of this number thirteen are accepted as valid today. Arthur (1), in 1906, erected the genus Earlea to provide for those species which lacked uredinia in the life-cycle and in 1912 followed the same arrangement in the North American Flora (3). In subsequent works by Sydow (6) and Dietel (5) this separation into two genera was not accepted.

Phragmidium Species of North America: Differential Teliospore and Aecial Characters

Summary1. Segregation of the nineteen North American species of Phragmidium based on the character of the teliospore pedicel gives two sections, Earlea, including the six species whose pedicels are non-hygroscopic, and Euphragmidium, which includes the thirteen species with hygroscopic pedicels.2. The species are arranged according to three tribes of the host-family Rosaceae, six species occurring on Potentilleae, five on Rubeae, and eight on Roseae.3. The shape and size of the teliospores, the length and shape of the pedicels, the color and degree of marking of the wall, and the presence or absence of an apiculus are used as differential characters of the individual species within the sections Earlea and Euphragmidium on each of the three host tribes.4. On the basis of aeciospore marking the species are discussed under two types as follows: five species have aeciospores which are verrucose with irregular warts and twelve species have aeciospores which are verrucose with regular papillae. In addition one species has strongly echinulate aeciospores, and in one species aecia are unknown.5. The presence or absence of the aecial paraphyses and their characters are pointed out where characteristic of species.6. The value of aeciospore size, shape, and wall thickness in the determination of species is discussed and the advantage of using both aeciospore and teliospore characters is emphasized.7. The effect of different host species on teliospore morphology is shown in certain species.8. Keys to the North American species of Phragmidium, based on aecial characters and teliospore characters, are included.