scholarly journals Archaeophytopathology of Phakopsora pachyrhizi, the Soybean Rust Pathogen

Plant Disease ◽  
2015 ◽  
Vol 99 (5) ◽  
pp. 575-579 ◽  
Author(s):  
James S. Haudenshield ◽  
Glen L. Hartman
Keyword(s):  
Pcr Primers ◽  
Fungal Species ◽  
The Philippines ◽  
Soybean Rust ◽  
Herbarium Specimens ◽  
Phakopsora Pachyrhizi ◽  
The Past ◽  
Rust Pathogen ◽  
Dna Genotyping ◽  
Archival Specimens

Herbarium specimens are useful to compare attributes of the past to attributes of today and predictions into the future. In this study, herbarium specimens from 1887 to 2006 were used to identify Phakopsora pachyrhizi and P. meibomiae, the two known fungal species that cause soybean rust. Historically, these two species differed in geographic distribution, with P. pachyrhizi confined to Asia and Australia, and P. meibomiae confined to the Americas. In our analyses, herbarium specimens were used to determine whether it was possible to extract adequate useful DNA from the fungal structures. If present, quantitative PCR primers specific to P. pachyrhizi, P. meibomiae, or to a third group inclusive of many rust species could be used to speciate the fungus. Of the 38 archival specimens, 11 were positive for P. pachyrhizi, including a 1912 specimen from Japan; 15 were positive for P. meibomiae, including a 1928 specimen from Brazil and two 1923 specimens from the Philippines; and 12 (including all African accessions) were negative for both species. Five specimens were positive in the more inclusive rust assay; all had been labeled as P. pachyrhizi and none were on soybean. These results demonstrate the feasibility of DNA genotyping in archaeophytopathological investigations.

scholarly journals Winter Survival of the Soybean Rust Pathogen, Phakopsora pachyrhizi, in Florida

Plant Disease ◽  
2008 ◽  
Vol 92 (11) ◽  
pp. 1551-1558 ◽  
Author(s):  
Wayne M. Jurick ◽  
Dario F. Narvaez ◽  
Meghan M. Brennan ◽  
Carrie L. Harmon ◽  
James J. Marois ◽  
...  
Keyword(s):  
Relative Humidity ◽  
Spore Germination ◽  
Soybean Rust ◽  
Inoculum Potential ◽  
Phakopsora Pachyrhizi ◽  
Southwest Florida ◽  
Rust Pathogen ◽  
Over Time ◽  
Time Freezing

Soybean rust (SBR) survival and host availability (kudzu, Pueraria spp.) were assessed from November 2006 through April 2007 at six sites from the panhandle to southwest Florida. Micro loggers recorded both temperature and relative humidity hourly at each location. Periods of drought and cumulative hours below 0°C correlated with kudzu defoliation. Inoculum potential from detached kudzu leaves was evaluated in vitro under various temperature and relative humidity levels. Kudzu leaves with SBR kept at 4°C produced viable urediniospores with the highest germination at all moisture levels over time. Freezing temperatures (–4 and –20°C) drastically reduced spore germination. However, when leaves were incubated at low (<35%) relative humidity, inoculum potential was prolonged. Results from this study demonstrate that both temperature and relative humidity impact P. pachyrhizi in the field and in vitro, and that detached kudzu leaves have the potential to serve as an inoculum source in kudzu stands.

scholarly journals First Report of Phakopsora pachyrhizi, the Causal Agent of Asian Soybean Rust, on Florida Beggarweed in the United States

Plant Disease ◽  
2006 ◽  
Vol 90 (7) ◽  
pp. 972-972 ◽  
Author(s):  
L. E. Sconyers ◽  
R. C. Kemerait ◽  
J. H. Brock ◽  
R. D. Gitaitis ◽  
F. H. Sanders ◽  
...  
Keyword(s):  
United States ◽  
Pcr Primers ◽  
The United States ◽  
Soybean Rust ◽  
Phakopsora Pachyrhizi ◽  
Asian Soybean Rust ◽  
Abaxial Leaf Surface ◽  
Humidity Chamber ◽  
Average Size ◽  
Soybean Diseases

Phakopsora pachyrhizi Syd. & P. Syd., which causes Asian soybean rust (SBR), was observed on Florida beggarweed, Desmodium tortuosum (Sw) DC., in Attapulgus, GA during late October and early November 2005. Tan to brown lesions (<1.0 mm in diameter) consistent with symptoms of SBR (2) were observed on older leaves of several plants collected near an SBR-infected soybean trial. Dissection (40 to 60×) and compound microscopy (×200 to 400) revealed conical pustules and ellipsoid, echinulate urediniospores (average size 15 × 20 μm) on the abaxial leaf surface. Polymerase chain reaction (PCR) (primers Ppm1 and Ppa2) (1) was conducted on four samples to confirm identification of P. pachyrhizi or P. meibomiae. Three were positive for P. pachyrhizi, and one was negative for both species. Using morphology and real-time PCR, SBR was confirmed as P. pachyrhizi by the USDA/APHIS in Beltsville, MD. Six noninfected Florida beggarweed plants were transplanted to pots during December 2005 and grown at 22 to 24°C in a greenhouse. On 11 January 2006, a water suspension of urediniospores collected from SBR-infected soybeans (1 × 105 spores per ml) was spray inoculated on all leaves to almost runoff and incubated for 48 h in a plastic humidity chamber. Lesions, pustules, and urediniospores consistent with SBR (2) were observed on 3 February 2006. A PCR assay was conducted on six samples from the infected greenhouse plants and all were positive for P. pachyrhizi. Florida beggarweed is widespread in the southern United States and may serve as an additional overwintering source for P. pachyrhizi and a potential inoculum source for the soybean crop. References: (1) R. D. Fredrick et al. Phytopathology 92:217, 2002. (2) J. B. Sinclair and G. L. Hartman. Soybean rust. Pages 25–26 in: Compendium of Soybean Diseases. 4th ed. G. L. Hartman et al., eds. The American Phytopathological Society, St. Paul, MN, 1999.

scholarly journals Effects of Simplicillium lanosoniveum on Phakopsora pachyrhizi, the Soybean Rust Pathogen, and Its Use as a Biological Control Agent

2012 ◽  
Vol 102 (8) ◽  
pp. 749-760 ◽  
Author(s):  
N. A. Ward ◽  
C. L. Robertson ◽  
A. K. Chanda ◽  
R. W. Schneider
Keyword(s):  
Biological Control Agent ◽  
Signs And Symptoms ◽  
Control Agent ◽  
Soybean Rust ◽  
Phakopsora Pachyrhizi ◽  
Latent Stage ◽  
Leaf Surfaces ◽  
Rust Pathogen ◽  
Soybean Leaf ◽  
Soybean Leaves

The fungus Simplicillium lanosoniveum was isolated from soybean leaves infected with Phakopsora pachyrhizi, the soybean rust pathogen, in Louisiana and Florida. The fungus did not grow or become established on leaf surfaces until uredinia erupted, but when soybean rust signs and symptoms were evident, S. lanosoniveum colonized leaves within 3 days and sporulated within 4 days. Development of new uredinia was suppressed by about fourfold when S. lanosoniveum colonized uredinia. In the presence of S. lanosoniveum, uredinia became increasingly red-brown, and urediniospores turned brown and germinated at very low rates. Assays using quantitative real time polymerase chain reaction revealed that the fungus colonized leaf surfaces when plants were infected with P. pachyrhizi, either in a latent stage of infection or when symptoms were present. However, when plants were inoculated before infection, there was no increase of DNA of S. lanosoniveum, suggesting that the pathogen must be present in order for the antagonist to become established on soybean leaf surfaces. We documented significantly lower amounts of DNA of P. pachyrhizi and lower disease severity when soybean leaves were colonized with S. lanosoniveum. These studies documented the mycophilic and disease-suppressive nature of S. lanosoniveum.

scholarly journals Suppression or Activation of Immune Responses by Predicted Secreted Proteins of the Soybean Rust Pathogen Phakopsora pachyrhizi

2018 ◽  
Vol 31 (1) ◽  
pp. 163-174 ◽  
Author(s):  
Mingsheng Qi ◽  
James P. Grayczyk ◽  
Janina M. Seitz ◽  
Youngsill Lee ◽  
Tobias I. Link ◽  
...  
Keyword(s):  
Immune Responses ◽  
Crop Production ◽  
Rust Fungus ◽  
Functional Characterization ◽  
Rust Fungi ◽  
Effector Proteins ◽  
Soybean Rust ◽  
Phakopsora Pachyrhizi ◽  
Immune Systems ◽  
Rust Pathogen

Rust fungi, such as the soybean rust pathogen Phakopsora pachyrhizi, are major threats to crop production. They form specialized haustoria that are hyphal structures intimately associated with host-plant cell membranes. These haustoria have roles in acquiring nutrients and secreting effector proteins that manipulate host immune systems. Functional characterization of effector proteins of rust fungi is important for understanding mechanisms that underlie their virulence and pathogenicity. Hundreds of candidate effector proteins have been predicted for rust pathogens, but it is not clear how to prioritize these effector candidates for further characterization. There is a need for high-throughput approaches for screening effector candidates to obtain experimental evidence for effector-like functions, such as the manipulation of host immune systems. We have focused on identifying effector candidates with immune-related functions in the soybean rust fungus P. pachyrhizi. To facilitate the screening of many P. pachyrhizi effector candidates (named PpECs), we used heterologous expression systems, including the bacterial type III secretion system, Agrobacterium infiltration, a plant virus, and a yeast strain, to establish an experimental pipeline for identifying PpECs with immune-related functions and establishing their subcellular localizations. Several PpECs were identified that could suppress or activate immune responses in nonhost Nicotiana benthamiana, N. tabacum, Arabidopsis, tomato, or pepper plants.

Documentation of an Extended Latent Infection Period by Phakopsora pachyrhizi, the Soybean Rust Pathogen

2012 ◽  
Vol 13 (1) ◽  
pp. 22
Author(s):  
N. A. Ward ◽  
R. W. Schneider ◽  
C. L. Robertson
Keyword(s):  
Latent Infection ◽  
Late Summer ◽  
Soybean Rust ◽  
Phakopsora Pachyrhizi ◽  
Disease Symptoms ◽  
Infection Period ◽  
Airborne Inoculum ◽  
Rust Pathogen ◽  
Latently Infected ◽  
Soybean Leaves

Phakopsora pachyrhizi, the soybean rust pathogen, overwinters on kudzu in the southern United States. However, even with severely affected kudzu adjacent to soybean fields, disease symptoms do not occur on soybeans until plants are in mid-reproductive stages of growth during mid to late summer. These observations suggested that soybeans are exposed to airborne inoculum of the pathogen long before symptoms occur, and we hypothesized that these plants may be latently infected. This hypothesis was confirmed by using quantitative real-time PCR (qPCR) to detect the rust pathogen in soybean leaves 18 to 60 days before symptoms were observed. Additionally, DNA of P. pachyrhizi increased only slightly until one week before symptoms developed. Results from this study documented that soybeans can become infected by the rust pathogen during early stages of plant growth, but symptoms often develop during the mid-reproductive stages. This extended latent infection period may be an optimum time for fungicide applications. Accepted for publication 12 December 2011. Published 21 March 2012.

Mycoparasitism of Phakopsora pachyrhizi, the soybean rust pathogen, by Simplicillium lanosoniveum

2014 ◽  
Vol 76 ◽  
pp. 87-94 ◽  
Author(s):  
Nicole Ward Gauthier ◽  
Karunakaran Maruthachalam ◽  
Krishna V. Subbarao ◽  
Matthew Brown ◽  
Ying Xiao ◽  
...  
Keyword(s):  
Soybean Rust ◽  
Phakopsora Pachyrhizi ◽  
Rust Pathogen

scholarly journals Occurrence of Telia of Phakopsora pachyrhizi on Kudzu in Texas

Plant Disease ◽  
2008 ◽  
Vol 92 (9) ◽  
pp. 1369-1369 ◽  
Author(s):  
T. Isakeit ◽  
Y. Jo
Keyword(s):  
United States ◽  
Soybean Rust ◽  
Herbarium Specimens ◽  
Subtropical Climate ◽  
Phakopsora Pachyrhizi ◽  
East Texas ◽  
Telial Stage ◽  
Abaxial Leaf Surface ◽  
Hidalgo County ◽  
Soybean Leaves

The first discovery of Asian soybean rust (ASR) caused by Phakopsora pachyrhizi H. Sydow & Sydow in the continental United States was in Louisiana in 2004 (3). In Texas, the uredial stage of this fungus was first found on kudzu (Pueraria lobata) in November 2005 and 3 months later on soybean (Glycine max) (2). The telial stage of P. pachyrhizi was first reported in the continental United States on kudzu in central Florida (1). On January 5, 2008, telia of P. pachyrhizi along with uredia were found on living kudzu leaves at two locations in Polk and Liberty counties of East Texas, where only the uredial stage had been found in September of 2007. The kudzu in both locations had died back more than 99% in January. A single telium or a cluster of telia were found along with uredinia on the abaxial leaf surface. Telia and uredinia (n = 20) were similar in size, 136.3 ± 26.3 and 133.1 ± 16.4 μm in diameter, respectively. Telia were dark brown to black compared with tan colored uredinia. Elongated, oval-shaped teliospores (n = 15) were 18.1 ± 1.7 μm long and 10.6 ± 1.0 μm wide. A reexamination of herbarium specimens from previous ASR collections indicated that telia had been present on kudzu leaves from Liberty County collected in December of 2005 and 2006. In contrast, telia were not found on soybean leaves collected in February of 2006 and 2007 and January of 2008 from Hidalgo County in the Lower Rio Grande Valley (LRGV), an area with a subtropical climate where ASR hosts could survive year round. Kudzu does not occur in the LRGV. Infected kudzu in East Texas can support production of telia over the winter months. However, the hosts that can be infected by basidiospores have not been identified, and so the significance of telia as a source of genetic variation is not known. To our knowledge, this is the first report of the telial stage of P. pachyrhizi in Texas. References: (1) C. L. Harmon et al. Plant Dis. 90:380, 2006. (2) T. Isakeit et al. Plant Dis. 90:971, 2006. (3) R. W. Schneider et al. Plant Dis. 89:774, 2005.

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