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.

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 First Report of Asian Soybean Rust Caused by Phakopsora pachyrhizi on Soybean in Alabama

Plant Disease ◽  
2006 ◽  
Vol 90 (1) ◽  
pp. 112-112 ◽  
Author(s):  
J. M. Mullen ◽  
E. J. Sikora ◽  
J. M. McKemy ◽  
M. E. Palm ◽  
L. Levy ◽  
...  
Keyword(s):  
United States ◽  
The United States ◽  
Soybean Rust ◽  
Phakopsora Pachyrhizi ◽  
Rust Disease ◽  
First Report ◽  
Leaf Spots ◽  
Asian Soybean Rust ◽  
Leaf Surfaces ◽  
Soybean Leaves

On November 4, 2004, soybean leaves (Glycine max (L.) Merr) were submitted to the Auburn University Plant Diagnostic Lab by a State Department of Agriculture and Industries Inspector. Samples were collected from an 80-ha field of soybean plants in a late-reproductive-growth stage in Mobile County, Alabama. Under microscopic examination, leaves showed rust pustules in advanced stages of development with urediniospores and sori characteristic of Phakopsora spp. Uredinia were ostiolate in small, brown, angular leaf spots (2 to 3 mm) on lower leaf surfaces. Urediniospores were pale yellow-to-white, globose or ovate, 20 to 40 × 15 to 25 μm. In a subsequent visit to the field, symptoms and signs of the rust disease were observed on plants bordering the edge of the field since the majority of plants were senescent. Tan lesions on lower leaf surfaces contained small pustules surrounded by a small zone of slightly discolored necrotic tissue. Masses of tan spores covered the lower leaf surface pustules. Leaves were mailed overnight to the USDA National Identification Services (Mycology) Laboratory in Beltsville, MD. The fungal structures were confirmed to be a Phakopsora sp., and the sample was forwarded to the USDA National Plant Germplasm and Biotechnology Laboratory in Beltsville, MD. DNA was extracted from leaf pieces containing sori using the Qiagen DNeasy Plant Mini kit (Qiagen, Valencia, CA). Phakopsora pachyrhizi was detected using a real-time polymerase chain reaction (PCR) protocol (1) performed in a Cepheid SmartCycler (Sunnyvale, CA). The PCR master mix was modified to include OmniMix beads (Cepheid). The field and microscopic suspect diagnosis of P. pachyrhizi was confirmed officially by APHIS on November 18, 2004. This was the fourth USDA official confirmation of Asian soybean rust in the continental United States during 2004, and to our knowledge, this is the first report of the disease in Alabama. This report helps confirm that early occurrences of Asian soybean rust in the United States were present in other areas in addition to the first reported finding in Louisiana (2). References: (1) R. D. Frederick et al. Phytopathology 92:217, 2002. (2) R. W. Schneider et al. Plant Dis. 89:774, 2005.

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 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 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 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 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.

scholarly journals First Report of Soybean Rust Caused by Phakopsora pachyrhizi on Phaseolus spp. in the United States

Plant Disease ◽  
2006 ◽  
Vol 90 (7) ◽  
pp. 970-970 ◽  
Author(s):  
T. N. Lynch ◽  
J. J. Marois ◽  
D. L. Wright ◽  
P. F. Harmon ◽  
C. L. Harmon ◽  
...  
Keyword(s):  
United States ◽  
Phaseolus Vulgaris ◽  
The United States ◽  
Phaseolus Coccineus ◽  
Soybean Rust ◽  
Phaseolus Lunatus ◽  
Phakopsora Pachyrhizi ◽  
Causal Organism ◽  
Chain Reactions ◽  
Soybean Plants

Phakopsora pachyrhizi Syd. & P. Syd., the cause of soybean rust, was first observed in the continental United States in November 2004 (2). During the growing season of 2005, P. pachyrhizi was confirmed on soybean (Glycine max) and/or kudzu (Pueraria montana) in nine states in the southern United States. It is known that P. pachyrhizi has a much larger host range within the Fabaceae family. On 29 September 2005 in Quincy, FL, 45 entries of mostly large-seeded legumes were planted next to soybeans that were infected with P. pachyrhizi. Several seeds of each entry were planted on one hill. Soybean plants growing adjacent to these potential hosts had 15 to 25% of the leaf area affected, 95% incidence, and 73% defoliation on 16 November. On 7 December 2005, all the plants of Phaseolus coccineus L. (scarlet runner bean, PI311827), Phaseolus lunatus L. (lima bean, PI583558), and two Phaseolus vulgaris L. (kidney bean) cvs. Red Hawk and California Early Light Red Kidney (CELRK) were found to have leaves with suspected rust lesions. These plants were at physiological maturity but had not senesced. None of the hosts had been inoculated other than from spores produced by the adjacent rust-infected soybean plants or from unknown locations. On the basis of microscopic examination, suspected infected leaves from plants of the Phaseolus spp. had rust pustules characteristic of P. pachyrhizi uredinia. Uredinia were counted within a randomly selected 2-cm2 area of one leaf of each sample. The mean and range of uredinia per lesion for Phaseolus coccineus was 29 uredinia with a range of 0 to 3 uredinia per lesion, Phaseolus lunatus had 2 uredinia with 0 to 1 uredinium per lesion, Phaseolus vulgaris cv. Red Hawk had 22 uredinia with 0 to 5 uredinia per lesion, and Phaseolus vulgaris cv. CELRK had 43 uredinia with 0 to 4 uredinia per lesion. Polymerase chain reactions using two sets of primers (Ppa1/Ppa2 and Pme1/Pme2) were performed on DNA extracted from leaves of the three species with sporulating rust pustules (1). The results of these tests and further tests conducted by the USDA/APHIS confirmed that P. pachyrhizi was the causal organism for the observed rust. References: (1) P. F. Harmon et al. On-line publication. doi:10.1094/PHP-2005-0613-01-RS. Plant Health Progress, 2005. (2) R. W. Schneider et al. Plant Dis. 89:774, 2005.

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