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 Pathogenic Variation of Phakopsora pachyrhizi Isolates on Soybean in the United States from 2006 to 2009

Plant Disease ◽  
2012 ◽  
Vol 96 (1) ◽  
pp. 75-81 ◽  
Author(s):  
M. Twizeyimana ◽  
G. L. Hartman
Keyword(s):  
United States ◽  
Resistance Genes ◽  
The United States ◽  
Soybean Rust ◽  
Phakopsora Pachyrhizi ◽  
Soybean Genotype ◽  
Pathogenic Variation ◽  
Differential Set ◽  
Soybean Genotypes ◽  
Soybean Leaves

The introduction of Phakopsora pachyrhizi, the cause of soybean rust, into the United States is a classic case of a pathogen introduction that became established in a new geographical region overwintering on a perennial host (kudzu, Pueraria lobata). The objective of our study was to classify the pathogenic variation of P. pachyrhizi isolates collected in the United States, and to determine the spatial and temporal associations. In total, 72 isolates of P. pachyrhizi collected from infected kudzu and soybean leaves in the United States were purified, then established and increased on detached soybean leaves. These isolates were tested for virulence and aggressiveness on a differential set of soybean genotypes that included six genotypes with known resistance genes (Rpp), one resistant genotype without any known characterized resistance gene, and a susceptible genotype. Three pathotypes were identified among the 72 U.S. P. pachyrhizi isolates based on the virulence of these isolates on the genotypes in the differential set. Six aggressiveness groups were established based on sporulating-uredinia production recorded for each isolate on each soybean genotype. All three pathotypes and all six aggressiveness groups were found in isolates collected from the southern region and from both hosts (kudzu or soybean) in 2008. Shannon's index based on the number of pathotypes indicated that isolates from the South region were more diverse (H = 0.83) compared with the isolates collected in other regions. This study establishes a baseline of pathogenic variation of P. pachyrhizi in the United States that can be further compared with variation reported in other regions of the world and in future studies that monitor P. pachyrhizi virulence in association to deployment of rust resistance genes.

scholarly journals Sources: Oil: A Cultural and Geographic Encyclopedia of Black Gold

2015 ◽  
Vol 54 (4) ◽  
pp. 83
Author(s):  
Paul MacLennan
Keyword(s):  
United States ◽  
International Relations ◽  
The United States ◽  
Monetary Value ◽  
Wide Range ◽  
To Come ◽  
The Individual ◽  
As Effects

In the winter of 2015, as this review is being written, the price of gasoline is plummeting in the United States and what this will mean for the individual, community, and country for the immediate future but also in years to come is unknown. There are a wide range of implications in politics, economics, and international relations as well as effects on what the individual pays for everyday groceries. It is therefore important that libraries provide their communities with the resources that include information and discussion on how energy and its monetary value interact with society.

scholarly journals First Report of Soybean Rust Caused by Phakopsora pachyrhizi on Pachyrhizus erosus in the United States

Plant Disease ◽  
2011 ◽  
Vol 95 (8) ◽  
pp. 1034-1034
Author(s):  
M. A. Delaney ◽  
E. J. Sikora ◽  
D. P. Delaney ◽  
M. E. Palm ◽  
J. Roscoe ◽  
...  
Keyword(s):  
United States ◽  
Ribosomal Rna ◽  
Agricultural Research ◽  
The United States ◽  
University Teaching ◽  
Soybean Rust ◽  
Infected Leaf ◽  
Phakopsora Pachyrhizi ◽  
First Report ◽  
Pachyrhizus Erosus

Soybean rust, caused by the fungus Phakopsora pachyrhizi, was detected on jicama (Pachyrhizus erosus L. Urban) for the first time in the United States in November 2009. The pathogen was observed on leaves of a single, potted jicama plant grown outdoors in a residential area and on leaves of all plants in a 12-m2 demonstration plot located at the Auburn University Teaching Garden in Auburn, AL. Symptoms on the upper leaf surfaces were isolated chlorotic areas near the leaf edges in the lower part of the canopy. The abaxial surface was first observed to exhibit brown lesions and subsequently produced volcano-shaped uredinia. These symptoms are consistent with a rust previously described on jicama in Mexico (1). Representative symptomatic plant tissue was sent to the USDA National Identification Services (Mycology) Laboratory in Beltsville, MD for diagnostic confirmation at both the Urbana, IL lab and the USDA National Plant Germplasm and Biotechnology Laboratory for DNA testing. From an infected leaf, samples of approximately 5 mm2 were excised from a microscopically observed rust lesion and an apparently noninfected area. Total DNA was purified with the FastDNA Spin Kit (MP Biomedicals, Solon, OH) followed by the E.Z.N.A. MicroElute DNA Clean-Up Kit (Omega Bio-tek, Inc, Doraville, GA) per manufacturer's instructions. Detection of P. pachyrhizi and P. meibomiae DNA was achieved by quantitative PCR using the method of Frederick et al. (2) and a DNA standard of previously prepared P. pachyrhizi spores. The observed rust pustule was found to contain P. pachyrhizi DNA in excess of 28,000 genomes, while no P. pachyrhizi DNA was observed from the asymptomatic sample. Both samples were negative for P. meibomiae. The fungal structures present were confirmed to be Phakopsora spp. DNA was extracted from sori aseptically removed from leaves with a Qiagen (Valencia, CA) DNeasy Plant Mini Kit and amplified with primers Ppa1 and NL4. The resulting partial ITS2 and 28S ribosomal RNA sequences were 100% identical to GenBank entry DQ354537 P. pachyrhizi internal transcribed spacer 2 and 28S ribosomal RNA gene, partial sequence. Sequences from jicama from Alabama were deposited in GenBank. Voucher specimens were deposited in the USDA Agricultural Research Service, National Fungus Collection (BPI). To our knowledge, this is the first report of the disease on jicama in the United States. References: (1) A. Cárcamo Rodriguez et al. Plant Dis. 90:1260, 2006. (2) R. D. Frederick et al. Phytopathology 92:217, 2002.

scholarly journals Assessment of Epidemic Potential of Soybean Rust in the United States

Plant Disease ◽  
2005 ◽  
Vol 89 (6) ◽  
pp. 678-682 ◽  
Author(s):  
S. Pivonia ◽  
X. B. Yang ◽  
Z. Pan
Keyword(s):  
United States ◽  
The United States ◽  
Soybean Rust ◽  
Phakopsora Pachyrhizi ◽  
Long Distance Dispersal ◽  
Long Distance ◽  
Climate Conditions ◽  
Soybean Production ◽  
Critical Components ◽  
Production Areas

This article assesses the epidemic potential of soybean rust (Phakopsora pachyrhizi) in the United States. In the assessment, there are three critical components of uncertainty: (i) suitability of climate conditions in production areas for soybean rust epidemics; (ii) likelihood of establishment of the fungus in North America; and (iii) the seasonal dispersal potential of the pathogen from overwintering regions to major soybean production regions. Assessments on the first and second components suggest soybean rust epidemics are likely in the United States, and the certainty of the third component is yet to be determined. Comparison of epidemiological factors for soybean rust in soybean production regions between China and the United States shows a complicated picture with the United States having factors that both increase and decrease risk. Future investigation of risk components—incipience in the field and long-distance dispersal—is needed.

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 New Legume Hosts of Phakopsora pachyrhizi Based on Greenhouse Evaluations

Plant Disease ◽  
2008 ◽  
Vol 92 (5) ◽  
pp. 767-771 ◽  
Author(s):  
T. L. Slaminko ◽  
M. R. Miles ◽  
R. D. Frederick ◽  
M. R. Bonde ◽  
G. L. Hartman
Keyword(s):  
United States ◽  
New Species ◽  
The United States ◽  
Soybean Rust ◽  
Southern United States ◽  
Phakopsora Pachyrhizi ◽  
Legume Species ◽  
Causal Organism ◽  
Immunological Assay ◽  
Phaseolus Species

Phakopsora pachyrhizi, the causal organism of soybean rust, was first found in the continental United States in 2004 and has been found on soybean, kudzu, Florida beggarweed, and three Phaseolus species in the field. The pathogen has been reported to occur on more than 90 legume species worldwide and it is likely to infect native and introduced legume species in the United States. The objective of this study was to determine if 176 species representing 57 genera of legumes, the majority of which are either native or naturalized to soybean-growing areas of the United States, could be hosts of P. pachyrhizi. Between one and three accessions of each species, a total of 264 accessions, were inoculated with a mixture of four isolates of P. pachyrhizi. Severity and sporulation were rated on a 1-to-5 scale at 14 and 28 days after inoculation. P. pachyrhizi was confirmed by the presence of sporulating uredinia and/or immunological assay on 65 new species in 25 genera; 12 of these genera have not been reported previously as hosts. Many of the newly identified hosts grow in the southern United States, and like kudzu, could serve as overwintering hosts for P. pachyrhizi.

scholarly journals First Report of Phakopsora pachyrhizi Telia on Kudzu in the United States

Plant Disease ◽  
2006 ◽  
Vol 90 (3) ◽  
pp. 380-380 ◽  
Author(s):  
C. L. Harmon ◽  
P. F. Harmon ◽  
T. A. Mueller ◽  
J. J. Marois ◽  
G. L. Hartman
Keyword(s):  
United States ◽  
South Carolina ◽  
Leaf Surface ◽  
The United States ◽  
Visual Observation ◽  
Soybean Rust ◽  
Hypodermic Needle ◽  
Phakopsora Pachyrhizi ◽  
First Report ◽  
Telial Stage

Soybean rust caused by Phakopsora pachyrhizi H. Sydow & Sydow was first reported in the continental United States during 2004 (2). By 10 November 2005, the disease was confirmed in eight southern states (Florida, Georgia, Alabama, Mississippi, South Carolina, North Carolina, Louisiana, and Texas). Diagnoses have been based on visual observation of uredinia and urediniospores of the pathogen followed by polymerase chain reaction confirmation. On 10 November 2005, uredinia and telia were identified on leaves of kudzu (Pueraria lobata) in central Florida. Telia first were noted as dark brown-to-black flecks on the abaxial leaf surface intermingled with abundant tan-to-light brown uredinia. Of 200 leaves examined, 143 (72%) had telia. The number of telia ranged from a few (1/cm2) that were scattered to many (73/cm2). Telia were approximately the same diameter as uredinia, but were appressed to the leaf surface and pigmented. Twenty telia were excised from host tissue with the aid of a dissecting microscope and a 20 gauge hypodermic needle. Telia averaged 89 × 100 μm (n = 20, σ = 17 and 16 μm, respectively). Four telia were crushed and five teliospores from each averaged 4.3 × 8.3 μm (n = 20, σ = 0.5 and 0.9 μm, respectively). Pale yellowish brown-to-hyaline teliospores were similar in color to urediniospores. Observations matched descriptions by Ono et al. (1). To our knowledge, this is the first report of the telial stage of P. pachyrhizi in the United States. References: (1) Y. Ono et al. Mycol. Res. 96:825, 1992. (2) R. W. Schneider et al. Plant Dis. 89:774, 2005.

scholarly journals Soybean Rust Caused by Phakopsora pachyrhizi Detected in the State of Campeche on the Yucatan Peninsula, Mexico

Plant Disease ◽  
2009 ◽  
Vol 93 (8) ◽  
pp. 847-847 ◽  
Author(s):  
Ma. de Jesús Yáñez Morales ◽  
I. Alanis Martínez ◽  
J. Manuel Soto Rocha ◽  
D. K. Malvick ◽  
J. E. Kurle ◽  
...  
Keyword(s):  
United States ◽  
Yucatan Peninsula ◽  
The United States ◽  
The State ◽  
Soybean Rust ◽  
Phakopsora Pachyrhizi ◽  
Pcr Assay ◽  
Long Distance ◽  
Southern Mexico ◽  
Yucatán Peninsula

Soybean rust caused by Phakopsora pachyrhizi Syd. & P. Syd is a destructive foliar disease of soybean (Glycine max L), which was first confirmed in North America in Louisiana during 2004 (4). Soybean rust (SBR) has also been reported late in the growing season as far north as Illinois, Indiana, and Iowa. SBR was first confirmed in Mexico in 2005 in the state of San Luis Potosi on soybean (3) and subsequently reported in the states of Tamaulipas, Veracruz, and the southwestern coast of Chiapas. Symptoms of SBR were observed on leaves of multiple, nearly mature soybean plants near the city of Campeche (19.72796°N, 90.0771°W) on the Gulf Coast of the Yucatan Peninsula during November 2008. Angular and irregular chlorotic lesions on leaves contained necrotic spots and pale brown, erumpent, cone-like uredinia with a central opening. Ellipsoid to obovoid, echinulate, light tan urediniospores (10 to 13 × 16 to 18 μm) were observed microscopically. DNA was extracted from leaf tissue containing uredinia and from asymptomatic tissue with the DNeasy Plant Mini Kit (Qiagen, Valencia, CA). P. pachyrhizi was confirmed in the symptomatic leaves by a PCR assay with Ppm1/Ppa2 primers, but not from the asymptomatic leaves (1). Subsequently, the DNA extracted from symptomatic and asymptomatic leaf tissues was tested again in another laboratory by a specific quantitative PCR assay (1), and positive results for the presence of soybean rust were obtained only from the symptomatic tissue. As a final confirmatory step, amplified DNA from the PCR assay was sequenced, and the results matched P. pachyrhizi sequences in the GenBank database. To our knowledge, these observations confirm for the first time the presence of P. pachyrhizi in the state of Campeche of southern Mexico. Although it was confirmed on soybean during 2008, it is not known how long the pathogen has been present or which other hosts may be infected there. The presence of SBR on the Yucatan Peninsula is significant because of its potential effects on local plant hosts. In addition, the climate allows possible year-round survival of the pathogen and long-distance transport of urediniospores to the United States. Potential transport of SBR spores from this part of Mexico to the United States has been reported through the application of NOAA's HYSPLIT (Hybrid Single Particle Lagrangian Integrated Transport) model and atmospheric back-trajectory analysis (2). References: (1) R. D. Frederick et al. Phytopathology 92:217, 2002. (2) S. V. Krupa et al. Plant Dis. 90:1254, 2006. (3) A. C. Rodriguez et al. Plant Dis. 90:1260, 2006. (4) R. W. Schneider et al. Plant Dis. 89:774, 2005.

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