Asian Soybean Rust Development in 2005: A Perspective from the Southeastern United States.

2006 ◽  
Author(s):  
L.E. Sconyers ◽  
R.C. Kemerait ◽  
J. Brock ◽  
D.V. Phillips
Keyword(s):  
United States ◽  
Southeastern United States ◽  
Soybean Rust ◽  
Asian Soybean Rust

scholarly journals Quantitative Aspects of the Spread of Asian Soybean Rust in the Southeastern United States, 2005 to 2006

2007 ◽  
Vol 97 (11) ◽  
pp. 1428-1433 ◽  
Author(s):  
R. S. C. Christiano ◽  
H. Scherm
Keyword(s):  
United States ◽  
South Carolina ◽  
Average Rate ◽  
Southeastern United States ◽  
Monitoring Program ◽  
Early Summer ◽  
Soybean Rust ◽  
Initial Inoculum ◽  
Disease Progress ◽  
Short Period

The regional dynamics of soybean rust, caused by Phakopsora pachyrhizi, in six southeastern states (Florida, Georgia, Alabama, South Carolina, North Carolina, and Virginia) in 2005 and 2006 were analyzed based on disease records collected as part of U.S. Department of Agriculture's soybean rust surveillance and monitoring program. The season-long rate of temporal disease progress averaged ≈0.5 new cases day–1 and was higher in nonsentinel soybean (Glycine max) plots than in sentinel soybean plots and kudzu (Pueraria lobata) plots. Despite the early detection of rust on kudzu in January and/or February each year (representing the final phase of the previous year's epidemic), the disease developed slowly during the spring and early summer on this host species and did not enter its exponential phase until late August, more than 1 month after it did so on soybean. On soybean, cases occurred very sporadically before the beginning of July, after which their number increased rapidly. Thus, while kudzu likely provides the initial inoculum for epidemics on soybean, the rapid increase in disease prevalence on kudzu toward the end of the season appears to be driven by inoculum produced on soybean. Of 112 soybean cases with growth stage data, only one occurred during vegetative crop development while ≈75% occurred at stage R6 (full seed) or higher. The median nearest-neighbor distance of spread among cases was ≈70 km in both years, with 10% of the distances each being below ≈30 km and above ≈200 km. Considering only the epidemic on soybean, the disease expanded at an average rate of 8.8 and 10.4 km day–1 in 2005 and 2006, respectively. These rates are at the lower range of those reported for the annual spread of tobacco blue mold from the Caribbean Basin through the southeastern United States. Regional spread of soybean rust may be limited by the slow disease progress on kudzu during the first half of the year combined with the short period available for disease establishment on soybean during the vulnerable phase of host reproductive development, although low inoculum availability in 2005 and dry conditions in 2006 also may have reduced epidemic potential.

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 Epidemiology of Soybean Rust in Soybean Sentinel Plots in Florida

Plant Disease ◽  
2011 ◽  
Vol 95 (6) ◽  
pp. 744-750 ◽  
Author(s):  
Heather M. Young ◽  
James J. Marois ◽  
David L. Wright ◽  
Dario F. Narváez ◽  
G. Kelly O'Brien
Keyword(s):  
United States ◽  
Growth Stage ◽  
Disease Incidence ◽  
Southeastern United States ◽  
Tropical Storm ◽  
Environmental Data ◽  
Soybean Rust ◽  
Phakopsora Pachyrhizi ◽  
Maturity Group ◽  
Rain Events

Since its discovery in the southeastern United States in 2004, soybean rust (SBR) has been variable from year to year. Caused by Phakopsora pachyrhizi, SBR epidemics in Florida are important to understand, as they may serve as an inoculum source for other areas of the country. This study examined the first disease detection date, incidence, and severity of SBR in relation to environmental data, growth stage, and maturity group (MG3, MG5, MG7) in soybean sentinel plots (225 m2) across north Florida from 2005 through 2008. The majority (91%) of the initial infections were observed in MG5 and MG7 soybeans, with plots not becoming infected until growth stage R4 or later. Precipitation was the principle factor affecting disease progress, where disease increased rapidly after rain events and was suppressed during dry periods. On average, plots became infected 30 days earlier in 2008 than 2005. In 2008, there was a significant increase in disease incidence and severity associated with the occurrence of Tropical Storm Fay, which deposited up to 380 mm of rainfall in north Florida. The results of this study indicate that climatic and environmental factors are important in determining the development of SBR in north Florida.

scholarly journals Comparative Susceptibility of Kudzu Accessions from the Southeastern United States to Infection by Phakopsora pachyrhizi

Plant Disease ◽  
2009 ◽  
Vol 93 (6) ◽  
pp. 593-598 ◽  
Author(s):  
M. R. Bonde ◽  
S. E. Nester ◽  
W. F. Moore ◽  
T. W. Allen
Keyword(s):  
United States ◽  
Southeastern United States ◽  
Average Diameter ◽  
Economic Loss ◽  
The United States ◽  
Soybean Rust ◽  
Phakopsora Pachyrhizi ◽  
Wide Range ◽  
The Individual ◽  
A Site

Soybean rust, caused by Phakopsora pachyrhizi, was first discovered in the continental United States in the fall of 2004. The potential for economic loss in the United States hinges largely on whether or not the pathogen can survive winters in the absence of soybean. Kudzu (Pueraria lobata) is known to be a host for P. pachyrhizi in Asia and South America and is widely distributed in the southern United States. This study examined reactions of kudzu collected from several areas of the southeastern United States to three isolates of P. pachyrhizi, one each from Alabama, Louisiana, and Brazil. Susceptible tan (TAN) lesions, resistant reddish-brown (RB) lesions, and immune (IM) response, previously described on soybean, were produced on kudzu based on the evaluation of 125 plants. However, in contrast to soybean, the RB response on kudzu was common, with approximately 50% frequency. IM responses to at least one isolate were observed on five individual plants, and two plants were immune to all three pathogen isolates used in the test. TAN lesions averaged 3.2 uredinia per lesion with an average diameter per uredinium of 121 μm. In contrast, RB lesions had an average of 0.3 uredinia per lesion with an average uredinial diameter of 77 μm. In 25 of 39 (64%) instances in which multiple plants were tested from a site, each reacted the same to the individual pathogen isolates. This suggested a tendency for plants at specific sites to be genetically identical with respect to rust reaction. Only 19 of 125 (15%) individual plants produced a different reaction to one isolate than to the other two isolates. When four kudzu plants previously shown to produce only TAN lesions to P. pachyrhizi isolates Alabama 04-1, Brazil 01-1, and Louisiana 04-1 were inoculated with eight additional isolates from several areas of the world, all 11 isolates produced only TAN lesions. Likewise, when five other plants previously shown to produce only RB lesions when inoculated with the three isolates were inoculated with the 11 isolates, all produced only RB lesions. These results suggest that susceptibility or resistance to P. pachyrhizi in individual kudzu plants often is broad, extending over a wide range of P. pachyrhizi isolates.

scholarly journals Effects of Daily Temperature Highs on Development of Phakopsora pachyrhizi on Soybean

2012 ◽  
Vol 102 (8) ◽  
pp. 761-768 ◽  
Author(s):  
M. R. Bonde ◽  
S. E. Nester ◽  
D. K. Berner
Keyword(s):  
United States ◽  
Southeastern United States ◽  
The United States ◽  
Daily Temperature ◽  
Soybean Rust ◽  
Limiting Factor ◽  
Climatic Data ◽  
Phakopsora Pachyrhizi ◽  
Diurnal Temperature ◽  
National Climatic Data Center

Although considerable information exists regarding the importance of moisture in the development of soybean rust, little is known about the influence of temperature. The purpose of our study was to determine whether temperature might be a significant limiting factor in the development of soybean rust in the southeastern United States. Soybean plants infected with Phakopsora pachyrhizi were incubated in temperature-controlled growth chambers simulating day and night diurnal temperature patterns representative of the southeastern United States during the growing season. At 3-day intervals beginning 12 days after inoculation, urediniospores were collected from each plant and counted. The highest numbers of urediniospores were produced when day temperatures peaked at 21 or 25°C and night temperatures dipped to 8 or 12°C. When day temperatures peaked at 29, 33, or 37°C for a minimum of 1 h/day, urediniospore production was reduced to 36, 19, and 0%, respectively, compared with urediniospore production at the optimum diurnal temperature conditions. Essentially, no lesions developed when the daily temperature high was 37°C or above. Temperature data obtained from the National Climatic Data Center showed that temperature highs during July and August in several southeastern states were too high for significant urediniospore production on 55 to 77% of days. The inhibition of temperature highs on soybean rust development in southeastern states not only limits disease locally but also has implications pertaining to spread of soybean rust into and development of disease in the major soybean-producing regions of the Midwestern and northern states. We concluded from our results that temperature highs common to southeastern states are a factor in the delay or absence of soybean rust in much of the United States.

scholarly journals Introduction of Asian Soybean Rust Urediniospores into the Midwestern United States—A Case Study

Plant Disease ◽  
2006 ◽  
Vol 90 (9) ◽  
pp. 1254-1259 ◽  
Author(s):  
Sagar Krupa ◽  
Van Bowersox ◽  
Roger Claybrooke ◽  
Charles W. Barnes ◽  
Les Szabo ◽  
...  
Keyword(s):  
United States ◽  
Mixed Boundary ◽  
Quantitative Polymerase Chain Reaction ◽  
Sampling Site ◽  
Geographic Origin ◽  
Soybean Rust ◽  
Rain Event ◽  
Back Trajectories ◽  
Source Areas ◽  
Asian Soybean Rust

In 2005, weekly rain samples collected at 124 National Atmospheric Deposition Program/National Trends Network (NADP/NTN) sites in the eastern and central United States were screened for Asian soybean rust (ASR; Phakopsora pachyrhizi) urediniospores. Application of a quantitative polymerase chain reaction method detected P. pachyrhizi DNA in the filter residue of rain samples collected during the week of 19 to 26 July 2005 in Minnesota, Missouri, and South Dakota. To determine the geographic origin of ASR urediniospores in those weekly composite samples, back air trajectories of the lifted condensation and mixed boundary layers were calculated for each rain event within the week, by sampling site. The calculations, based on the hybrid single-particle lagrangian integrated trajectory model, pointed to source areas in eastern and southern Texas. In a separate case, DNA of P. pachyrhizi was detected in a 28 June to 5 July 2005 rain sample from an eastern Texas site. Back trajectories pointed to southern Texas and the Yucatan Peninsula in Mexico as potential source areas of ASR urediniospores. Vertical motions of those back trajectories indicated a ventilation of the boundary layer in the upwind areas, suggesting the possible injection of urediniospores into the free troposphere where they can be transported for long distances before wet deposition.

scholarly journals Effects of Frequency of “Extreme” Temperature Highs on Development of Soybean Rust

2013 ◽  
Vol 103 (7) ◽  
pp. 708-716 ◽  
Author(s):  
M. R. Bonde ◽  
S. E. Nester ◽  
D. K. Berner
Keyword(s):  
United States ◽  
Southeastern United States ◽  
Extreme Temperature ◽  
The United States ◽  
Major Effect ◽  
Soybean Rust ◽  
Temperature Pattern ◽  
Extreme Temperatures ◽  
Diurnal Temperature ◽  
Soybean Industry

Previously, we hypothesized that summer “extreme” diurnal temperature highs in the southeastern United States were responsible for the yearly absence or delay of soybean rust development until fall. Utilizing temperature-controlled growth chambers, a diurnal temperature pattern of 33°C high and 20°C low reduced urediniospore production by 81%. However, that study did not consider the influence of frequency of extreme temperatures on soybean rust. We now report that a temperature high of 35°C for 1 h on three consecutive days, initiated 15 days after inoculation, when lesions had formed, reduced urediniospore production by 50% and required 9 to 12 days for sporulation to resume once the extreme temperature highs ceased. Furthermore, three consecutive days in which the temperature high was 37°C, beginning immediately after inoculation and subsequent dew period, reduced lesion numbers by 60%. The combined effects of reduced numbers of lesions and urediniospores per lesion caused by extreme temperature highs can account for observed absence or delay of soybean rust development in the southeastern United States until fall. A comparison of frequency of extreme temperature highs with numbers of counties reporting presence of soybean rust from 2005 to 2012 verified that extreme temperature highs may be largely responsible for absence or delay of soybean rust development. This is the first report showing the effect of frequency of extreme temperature highs on development of soybean rust. Because the south-to-north progression of soybean rust is required for the disease to occur in the major soybean-production regions of the United States, temperatures in the southeastern United States have a major effect on the entire U.S. soybean industry.

scholarly journals Effectiveness of Fungicide on Soybean Rust in the Southeastern United States: A Meta-Analysis

2018 ◽  
Vol 10 (6) ◽  
pp. 1784 ◽  
Author(s):  
Mary Delaney ◽  
Althea ArchMiller ◽  
Dennis Delaney ◽  
Alan Wilson ◽  
Edward Sikora
Keyword(s):  
United States ◽  
Meta Analysis ◽  
Southeastern United States ◽  
Soybean Rust

scholarly journals Novel Phakopsora pachyrhizi Extracellular Proteins Are Ideal Targets for Immunological Diagnostic Assays

2012 ◽  
Vol 78 (11) ◽  
pp. 3890-3895 ◽  
Author(s):  
Douglas G. Luster ◽  
Michael B. McMahon ◽  
H. Herb Edwards ◽  
Britney L. Boerma ◽  
Melanie L. Lewis Ivey ◽  
...  
Keyword(s):  
United States ◽  
Monoclonal Antibodies ◽  
The United States ◽  
Extracellular Proteins ◽  
Sentinel Surveillance ◽  
Soybean Rust ◽  
Phakopsora Pachyrhizi ◽  
Content Type ◽  
Diagnostic Assays ◽  
Asian Soybean Rust

ABSTRACTPhakopsora pachyrhizi, the causal agent of Asian soybean rust (ASR), continues to spread across the southeast and midsouth regions of the United States, necessitating the use of fungicides by producers. Our objective in this research was to identify ASR proteins expressed early during infection for the development of immunodiagnostic assays. We have identified and partially characterized a small gene family encoding extracellular proteins in theP. pachyrhiziurediniospore wall, termed PHEPs (forPhakopsoraextracellularprotein). Two highly expressed protein family members, PHEP 107 and PHEP 369, were selected as ideal immunodiagnostic targets for antibody development, after we detected PHEPs in plants as early as 3 days postinfection (dpi). Monoclonal antibodies (MAbs; 2E8E5-1 and 3G6H7-3) generated against recombinant PHEP 369 were tested for sensitivity against the recombinant protein and extracts from ASR-infected plants and for specificity against a set of common soybean pathogens. These antibodies should prove applicable in immunodiagnostic assays to detect infected soybeans and to identify ASR spores from sentinel surveillance plots.

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