Pachyrhizi Syd Research Articles

(2688) Proposal to conserve the name Phakopsora (Basidiomycota, Pucciniales) with a conserved type

(2688) Phakopsora Dietel in Ber. Deutsch. Bot. Ges. 13: 333. 28 Aug 1895, nom. cons. prop. Typus: P. pachyrhizi Syd. & P. Syd. in Ann. Mycol. 12: 108. 15 Mai 1914, typ. cons. prop. The generic name Phakopsora has been widely used for species of rust fungi that occur on soybeans and other members of the Fabaceae such as P. pachyrhizi Syd. & P. Syd. causing Asian soybean rust and P. meibomiae (Arthur) Arthur causing Latin American soybean rust (Ono & al. in Mycol. Res. 96: 825. 1992). In addition, this genus includes a complex of species that cause serious leaf rust diseases on grapevine and other vitaceous plants such as P. ampelopsidis Dietel & P. Syd., P. euvitis Y. Ono, and P. vitis P. Syd. (Chatasiri & Ono in Mycoscience 49: 66. 2008; Okane & Ono in Mycoscience 59: 99. 2018), on cotton such as P. gossypii (Lagerh.) Hirats. (Gjaerum in Mycotaxon 24: 243. 1985) and on eucalypts such as P. myrtacearum McTaggart & al. (Maier & al. in Pl. Pathol. 65: 189. 2016). The original type of Phakopsora is a little-known species, P. punctiformis (Barclay & Dietel) Dietel (in Hedwigia 37: 217. 1898), which was initially described as Melampsora punctiformis Barclay & Dietel (in Hedwigia 29: 267. 1890) on Galium aparine in India. Although this name was the only species name mentioned in the protologue of the generic name (Dietel in Ber. Deutsch. Bot. Ges. 13: 333. 1895) and is thus the obligate type, it was not transferred to Phakopsora until Dietel (l.c. 1898) created the new combination P. punctiformis. The taxonomic placement of P. punctiformis is uncertain in that it has rarely been reported and is known only from China, India, Nepal and Russia (Farr & Rossman, Fungal Databases, U.S. National Fungus Collections [https://nt.ars-grin.gov/fungaldatabases/]. 2018). Almost no literature deals with P. punctiformis (Google Scholar [GS] exact phrase search: “Melampsora punctiformis” = 9, “Phakopsora punctiformis” = 12), and no DNA sequences exist for this species. In addition, this species lacks the uredinial paraphyses characteristic of most current species of Phakopsora (Sydow & Sydow, Monogr. Urediniearum: 3. 1915; Cummins & Hiratsuka, Ill. Gen. Rust Fungi, ed. 3. 2003) and is thus not representative of most of the species now considered to belong in the genus Phakopsora. As mentioned, Phakopsora pachyrhizi causes Asian soybean rust, a fungus of plant quarantine importance that is widely studied and well known (GS exact phrase search = 9180). Although reported for decades from Asia, the recent introduction of this fungus into the Western Hemisphere has resulted in considerable concern because of its virulence on the important soybean crop (Frederick in Phytopathology 92: 217. 2002). Recent molecular phylogenetic studies show that P. pachyrhizi and the closely related P. meibomiae cluster in a monophyletic clade with other economically important species of Phakopsora, such as P. myrtacearum (Beenken in Mycol. Progr. 13: 791. 2014; Maier & al., l.c.), as well as P. ampelopsidis and P. euvitis causing leaf rust of grapevine (Chatasiri & Ono, l.c.; Okane & Ono, l.c.). To bring the definition of the generic name Phakopsora in line with its current usage, we propose to conserve Phakopsora with a new type, P. pachyrhizi, the cause of the globally important disease Asian soybean rust. MCA, https://orcid.org/0000-0001-8742-6685; AYR, https://orcid.org/0000-0002-8191-2663; YO, https://orcid.org/0000-0002-8247-7245; LAC, https://orcid.org/0000-0002-6131-7736 We appreciate the assistance of Paul Kirk, CABI, in determining the correct place and date of the publication of Phakopsora punctiformis. USDA is an equal opportunity provider and employer.

Phakopsora pachyrhizi, the causal agent of Asian soybean rust

The plant pathogenic basidiomycete fungi Phakopsora pachyrhizi and Phakopsora meibomiae cause rust disease in soybean plants. Phakopsora pachyrhizi originated in Asia-Australia, whereas the less aggressive P. meibomiae originated in Latin America. In the New World, P. pachyrhizi was first reported in the 1990s to have spread to Hawaii and, since 2001, it has been found in South America. In 2004, the pathogen entered continental USA. This review provides detailed information on the taxonomy and molecular biology of the pathogen, and summarizes strategies to combat the threat of this devastating disease. Phakopsora pachyrhizi Syd. & P. Syd; uredial anamorph: Malupa sojae (syn. Uredo sojae); Domain Eukaryota; Kingdom Fungi; Phylum Basidiomycota; Order Uredinales; Class Urediniomycetes; Family Phakopsoraceae; Genus Phakopsora (http://www.indexfungorum.org). The nomenclature of rust spores and spore-producing structures used within this review follows Agrios GN (2005) Plant Pathology, 5th edn. London: Elsevier/Academic Press. In the field, P. pachyrhizi infects leaf tissue from a broad range (at least 31 species in 17 genera) of leguminous plants. Infection of an additional 60 species in other genera has been achieved under laboratory conditions. At the beginning of the disease, small, tan-coloured lesions, restricted by leaf veins, can be observed on infected soybean leaves. Lesions enlarge and, 5-8 days after initial infection, rust pustules (uredia, syn. uredinia) become visible. Uredia develop more frequently in lesions on the lower surface of the leaf than on the upper surface. The uredia open with a round ostiole through which uredospores are released.

Evaluation of Australian Native Species ofGlycinefor Resistance to Soybean Rust

sprayed with distilled water, covered with ABSTRACT plastic film, and incubated at 24 C in a BURDON,J.J.,and D. R. MARSHALL. 1981. Evaluationof Australian native species of Glycine growth cabinet lit at 70 Wm2 for 16 for resistance to soybean rust. Plant Disease 65:44-45. hr/day. Leaves of soybean cultivar Extensive screening of six Australian native species of Glycine uncovered variation in reaction to Dare were included in all cases as Phakopsora pachyrhizi, the causal agent of leaf rust of soybeans. Some of these native species control. represent a potentially valuable source of resistance genes for soybean rust resistance breeding For all accessions four epidemiprograms. ologically related characters were assessed: incubation period (sensu [15]; the number of days from inoculation to Soybeans are affected by a wide range to promote germination and planted in visible symptoms such as flecking), latent of pests and diseases (1,4,11). The most individual pots in a heated glasshouse. period (number of days from inoculation important in the eastern hemisphere Eight weeks after emergence, plants were until the first pustule [uredium] erupted), (2,12) is leaf rust caused by Phakopsora screened for resistance to P. pachyrhizi. number of active pustules 5 days after the pachyrhizi Syd. In years favoring Because this survey was designed to first pustule erupted, and intensity of development and spread of this pathogen, determine the extent of resistance in the pustule development 5 days after the first the total soybean production of individual six species, only one plant was tested per pustule erupted (scale of 0, no southeast Asian countries has been accession. development, to 3, large, highly productive reduced by as much as 30%, and losses up Levels of disease resistance were pustules). to 90% have been reported in individual determined by using a detached leaf Accessions were then categorized as fields (2,6,10). This pathogen was technique (16). Ten newly expanded highly resistant, intermediate, or highly recently discovered in Puerto Rico leaves from each plant were placed, susceptible. In highly resistant plants, (13,14) and seriously threatens soybean abaxial surface up, on a 0.4% water agar disease failed to develop beyond visible production in the United States and support medium containing 5 ppm flecking. Plants in the intermediate and South America. gibberellic acid. Leaves were inoculated highly susceptible categories showed a The vulnerability of the American in a 1.2-m Perspex settling tower by continuum in response to infection by P. soybean crop to this pathogen is compressed air injection of 6 mg of P. pachyrhizi as measured by the three illustrated by a lack of resistance to the pachyrhizi spores through a modified characters of the latent period, the virulent and highly aggressive races surgical syringe into the top of the tower. number of pustules per square centimeter, found in Asia. Of 215 cultivars listed by For 5 min spores were allowed to settle, and pustule intensity. Although many Hymowitz et al (5) for which rust and then each agar gel was removed from values differed significantly (Table 1), resistance has been assessed, 205 (95.4%) the tower. Inoculated leaves were then categorization of intermediate accessions are highly susceptible, 8 (3.7%) are susceptible, and only 2 (0.9%) show intermediate resistance. Some resistance is . .. a mediapparen istat hogen risolates fm Table 1. Range of responses of six Australian native species of Glycinea to infection by Phakopsora apparent to pathogen isolates from pachyrhizi Puerto Rico (3). This vulnerability is also true in Asia where extensive disease Species Incubation period Latent period Pustules screening tests have demonstrated only Accessionb (days) (days) (no./ct) Intensity