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 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 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 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 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.

scholarly journals Prediction of Short-Distance Aerial Movement of Phakopsora pachyrhizi Urediniospores Using Machine Learning

2017 ◽  
Vol 107 (10) ◽  
pp. 1187-1198 ◽  
Author(s):  
L. Wen ◽  
C. R. Bowen ◽  
G. L. Hartman
Keyword(s):  
Machine Learning ◽  
Random Forest ◽  
Short Distance ◽  
Soybean Rust ◽  
Machine Learning Techniques ◽  
Phakopsora Pachyrhizi ◽  
Primary Means ◽  
Soybean Plants ◽  
Selection Operator ◽  
Active Trap

Dispersal of urediniospores by wind is the primary means of spread for Phakopsora pachyrhizi, the cause of soybean rust. Our research focused on the short-distance movement of urediniospores from within the soybean canopy and up to 61 m from field-grown rust-infected soybean plants. Environmental variables were used to develop and compare models including the least absolute shrinkage and selection operator regression, zero-inflated Poisson/regular Poisson regression, random forest, and neural network to describe deposition of urediniospores collected in passive and active traps. All four models identified distance of trap from source, humidity, temperature, wind direction, and wind speed as the five most important variables influencing short-distance movement of urediniospores. The random forest model provided the best predictions, explaining 76.1 and 86.8% of the total variation in the passive- and active-trap datasets, respectively. The prediction accuracy based on the correlation coefficient (r) between predicted values and the true values were 0.83 (P < 0.0001) and 0.94 (P < 0.0001) for the passive and active trap datasets, respectively. Overall, multiple machine learning techniques identified the most important variables to make the most accurate predictions of movement of P. pachyrhizi urediniospores short-distance.

scholarly journals Transcriptome analyses and virus induced gene silencing identify genes in the Rpp4-mediated Asian soybean rust resistance pathway

2013 ◽  
Vol 40 (10) ◽  
pp. 1029 ◽  
Author(s):  
Aguida M. A. P. Morales ◽  
Jamie A. O'Rourke ◽  
Martijn van de Mortel ◽  
Katherine T. Scheider ◽  
Timothy J. Bancroft ◽  
...  
Keyword(s):  
Gene Expression ◽  
Transcription Factors ◽  
Gene Silencing ◽  
Differentially Expressed ◽  
Soybean Rust ◽  
Phakopsora Pachyrhizi ◽  
R Gene ◽  
Virus Induced Gene Silencing ◽  
Asian Soybean Rust ◽  
Defence Responses

Rpp4 (Resistance to Phakopsora pachyrhizi 4) confers resistance to Phakopsora pachyrhizi Sydow, the causal agent of Asian soybean rust (ASR). By combining expression profiling and virus induced gene silencing (VIGS), we are developing a genetic framework for Rpp4-mediated resistance. We measured gene expression in mock-inoculated and P. pachyrhizi-infected leaves of resistant soybean accession PI459025B (Rpp4) and the susceptible cultivar (Williams 82) across a 12-day time course. Unexpectedly, two biphasic responses were identified. In the incompatible reaction, genes induced at 12 h after infection (hai) were not differentially expressed at 24 hai, but were induced at 72 hai. In contrast, genes repressed at 12 hai were not differentially expressed from 24 to 144 hai, but were repressed 216 hai and later. To differentiate between basal and resistance-gene (R-gene) mediated defence responses, we compared gene expression in Rpp4-silenced and empty vector-treated PI459025B plants 14 days after infection (dai) with P. pachyrhizi. This identified genes, including transcription factors, whose differential expression is dependent upon Rpp4. To identify differentially expressed genes conserved across multiple P. pachyrhizi resistance pathways, Rpp4 expression datasets were compared with microarray data previously generated for Rpp2 and Rpp3-mediated defence responses. Fourteen transcription factors common to all resistant and susceptible responses were identified, as well as fourteen transcription factors unique to R-gene-mediated resistance responses. These genes are targets for future P. pachyrhizi resistance research.

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