scholarly journals Comparisons of Visual Rust Assessments and DNA Levels of Phakopsora pachyrhizi in Soybean Genotypes Varying in Rust Resistance

Plant Disease ◽  
2011 ◽  
Vol 95 (8) ◽  
pp. 1007-1012 ◽  
Author(s):  
C. Paul ◽  
C. B. Hill ◽  
G. L. Hartman
Keyword(s):  
Quantitative Polymerase Chain Reaction ◽  
Single Gene ◽  
The Other ◽  
Soybean Rust ◽  
Disease Assessment ◽  
Fungal Colonization ◽  
Phakopsora Pachyrhizi ◽  
Breeding Populations ◽  
Soybean Genotypes ◽  
Infection Types

Soybean resistance to Phakopsora pachyrhizi, the cause of soybean rust, has been characterized by the following three infection types: (i) immune response (IM; complete resistance) with no visible lesions, (ii) resistant reaction with reddish brown (RB) lesions (incomplete resistance), and (iii) susceptible reaction with tan-colored (TAN) lesions. Based on visual assessments of these phenotypes, single gene resistance in soybean to P. pachyrhizi has been documented, but colonization within infected tissues based on fungal DNA (FDNA) levels in different soybean genotypes had not been analyzed. The research used a quantitative polymerase chain reaction (Q-PCR) assay to compare visual disease assessment to FDNA in controlled inoculation experiments using two isolates of P. pachyrhizi. The objective of the first experiment was to compare data from digital visual disease assessment to FDNA from Q-PCR assays using digital visual disease assessment using five resistant soybean genotypes (one IM and four RB) and five susceptible genotypes (TAN). The objective of the second experiment was to quantify FDNA using Q-PCR at different time points after inoculation to determine if levels of fungal colonization differed in five soybean genotypes with different levels of resistance (one IM, two RB, and two TAN). For experiment 1, the numbers of uredinia and uredinia per lesion on four of the five resistant soybean genotypes were lower (P < 0.05) than the other six genotypes. Significant differences (P < 0.05) in FDNA concentrations were found among soybean genotypes with TAN lesions and among soybean genotypes with RB lesions. Soybean cultivar UG5 (IM phenotype) had significantly less (P < 0.05) FDNA than all of the other genotypes. Some genotypes that produced TAN lesions had significantly lower (P < 0.05) or non-significantly different FDNA concentrations compared to those genotypes that produced RB lesions. For experiment 2, the regression of FDNA on days after inoculation was significant (P < 0.01) with positive slopes for all genotypes except for UG5, in which FDNA declined over time, indicating a reduction of fungal colonization. The results of this Q-PCR FDNA screening technique demonstrates its use to distinguish different types of resistance, and could be used to facilitate the evaluation of soybean breeding populations, where precise quantification of incomplete and/or partial resistance is needed to identify and map quantitative trait loci.

scholarly journals Characterizing Resistance to Phakopsora pachyrhizi in Soybean

Plant Disease ◽  
2011 ◽  
Vol 95 (5) ◽  
pp. 577-581 ◽  
Author(s):  
M. R. Miles ◽  
M. R. Bonde ◽  
S. E. Nester ◽  
D. K. Berner ◽  
R. D. Frederick ◽  
...  
Keyword(s):  
Immune Response ◽  
Partial Resistance ◽  
Single Gene ◽  
Plant Introduction ◽  
The Other ◽  
Soybean Rust ◽  
Phakopsora Pachyrhizi ◽  
Progress Curve ◽  
Lesion Type ◽  
Incomplete Resistance

Resistance in soybean to Phakopsora pachyrhizi, the cause of soybean rust, is characterized by either reddish-brown (RB) lesions or an immune response. The RB type of resistance can be incomplete, as evidenced by the presence of sporulating uredinia within lesions. Susceptibility, on the other hand, is exemplified by tan-colored (TAN) lesions, and can be expressed in gradations of susceptibility or partial resistance that are less well defined. This study evaluated traits associated with incomplete or partial resistance to P. pachyrhizi in soybean by comparing 34 soybean accessions inoculated with four P. pachyrhizi isolates. Six accessions produced RB lesions to all four isolates, while 19 accessions produced TAN lesions, including plant introduction (PI) 200492 (Rpp1) and the susceptible check ‘Williams’. Williams had among the largest area under the disease progress curve (AUDPC) values and area under the sporulating uredinia progress curve (AUSUPC) values, while eight accessions had lower AUSUPC values. Of the known sources of single-gene resistance, only PI 230970 (Rpp2), PI 459025B (Rpp4), and PI 594538A (Rpp1b) had lower AUDPC and AUSUPC values than Williams. PI 594538A and PI 561356 had RB lesions and had the lowest AUDPC and AUSUPC values. Of the known sources of single-gene resistance, only PI 230970 (Rpp2) and PI 594538A (Rpp1b) produced fewer and smaller-diameter uredinia than Williams. This study characterized reactions to P. pachyrhizi in 34 accessions based on lesion type and sporulation, and defined incomplete resistance and partial resistance in the soybean–P. pachyrhizi interaction.

scholarly journals Variation in the Internal Transcribed Spacer Region of Phakopsora pachyrhizi and Implications for Molecular Diagnostic Assays

Plant Disease ◽  
2019 ◽  
Vol 103 (9) ◽  
pp. 2237-2245 ◽  
Author(s):  
Tomás Allen Rush ◽  
Jacob Golan ◽  
Alistair McTaggart ◽  
Cade Kane ◽  
R. W. Schneider ◽  
...  
Keyword(s):  
Internal Transcribed Spacer ◽  
Quantitative Polymerase Chain Reaction ◽  
Single Gene ◽  
False Negative ◽  
Soybean Rust ◽  
Disease Spread ◽  
Molecular Diagnostic ◽  
Phakopsora Pachyrhizi ◽  
Internal Transcribed Spacer Region ◽  
Diagnostic Assays

Phakopsora pachyrhizi, the causal agent of soybean rust (SBR), is a global threat to soybean production. Since the discovery of SBR in the continental United States, quantitative polymerase chain reaction assays based on the internal transcribed spacer (ITS) ribosomal DNA locus were established for its rapid detection. However, insufficient data were initially available to test assays against factors that could give rise to misidentification. This study aimed to reevaluate current assays for (i) the potential for false-positive detection caused by nontarget Phakopsora species and (ii) the potential for false-negative detection caused by intraspecific variation within the ITS locus of P. pachyrhizi. A large amount of intraspecific and intragenomic variation in ITS was detected, including the presence of polymorphic ITS copies within single leaf samples and within single rust sori. The diagnostic assays were not affected by polymorphisms in the ITS region; however, current assays are at risk of false positives when screened against other species of Phakopsora. This study raises caveats to the use of multicopy genes (e.g., ITS) in single-gene detection assays and discusses the pitfalls of inferences concerning the aerobiological pathways of disease spread made in the absence of an evaluation of intragenomic ITS heterogeneity.

scholarly journals Characterization and Quantification of Fungal Colonization of Phakopsora pachyrhizi in Soybean Genotypes

2014 ◽  
Vol 104 (1) ◽  
pp. 86-94 ◽  
Author(s):  
R. Vittal ◽  
C. Paul ◽  
C. B. Hill ◽  
G. L. Hartman
Keyword(s):  
Mesophyll Cell ◽  
Visual Assessment ◽  
Soybean Rust ◽  
Fungal Colonization ◽  
Phakopsora Pachyrhizi ◽  
Mesophyll Cells ◽  
Soybean Genotype ◽  
Interaction Sites ◽  
Soybean Genotypes ◽  
Incomplete Resistance

Soybean rust, caused by the fungus Phakopsora pachyrhizi, is an economically important disease of soybean with potential to cause severe epidemics resulting in significant yield losses. Host resistance is one of the management tools to control this disease. This study compared soybean genotypes exhibiting immunity, complete and incomplete resistance, and susceptibility to an isolate of P. pachyrhizi based on visual assessment of reaction type, other visual traits such as sporulation, quantitative measurements of the amount of fungal DNA (FDNA) present in leaf tissues, and data on infection and colonization levels. Soybean genotype UG5 (immune), and plant introduction (PI) 567102B and PI 567104B (complete resistance) had lower quantities of uredinia and FDNA than four other genotypes with incomplete resistance. Based on microscopic observations, early events of spore germination, appressorium formation, and fungal penetration of the epidermis occurred within 24 h postinoculation and were similar among the tested soybean genotypes. Differences in infection among the genotypes were evident once the hyphae penetrated into the intercellular spaces between the mesophyll cells. At 2 days after inoculation (dai), soybean genotype Williams 82 had a significantly (P < 0.05) higher percentage of hyphae in the mesophyll tissue than other soybean genotypes, with UG5 having significantly (P < 0.05) lower percentages than all of the other soybean genotypes at 3, 4, and 5 dai. The percentage of interaction sites with mesophyll cell death was significantly (P < 0.05) higher in UG5 than other genotypes at 3, 4, and 5 dai. There was a significant positive correlation (r = 0.30, P < 0.001) between quantities of hyphae in the mesophyll cells and FDNA. These results demonstrated that incompatible soybean–P. pachyrhizi interaction results in restricted hyphal development in mesophyll cell tissue, likely due to hypersensitive apoptosis.

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 Proteomic Analysis of Soybean Leaves in a Compatible and an Incompatible Interaction with Phakopsora Pachyrhizi

2014 ◽  
Vol 1 (1) ◽  
Author(s):  
Mateus Rodrigues Pereira ◽  
Bianca Castro Gouvêa ◽  
Francismar Corrêa Marcelino-Guimarães ◽  
Humberto Josué de Oliveira Ramos ◽  
Maurilio Alves Moreira ◽  
...  
Keyword(s):  
Control Measure ◽  
Production Costs ◽  
Soybean Rust ◽  
Phakopsora Pachyrhizi ◽  
Fructose Bisphosphate ◽  
Soybean Genotypes ◽  
Fructose Bisphosphate Aldolase ◽  
Soybean Leaves ◽  
Dimensional Electrophoresis ◽  
Carbonic Anhydrase 1

AbstractAsian soybean rust (ASR), which is incited by the fungus Phakopsora pachyrhizi, is considered one of the most aggressive diseases to the soybean culture. There are no commercial cultivars immune to the pathogen and the control measure currently used is the application of fungicides that harms the environment and increases production costs. For a better understanding of the host’s response to the pathogen at the molecular level, two soybean genotypes were analyzed (PI561356, resistant to ASR and Embrapa 48, susceptible) at 72 hours and 192 hours after inoculation with spores of P. pachyrhizi. Leaf protein profiles of the plants were compared by two-dimensional electrophoresis associated with mass spectrometry (MS). Twenty-two protein spots presented different levels when the two treatments were compared (inoculated vs. non-inoculated). From those, twelve proteins were identified by MS analysis. Some of them are involved in metabolic pathways related to plant defense against pathogens, as in the case of carbonic anhydrase, 1-deoxy-D-xylulose- 5-phosphate reductoisomerase, fructose-bisphosphate aldolase and glutamine synthetase. The possible biochemical-physiological meanings of our findings are discussed.

scholarly journals The Importance of Phenolic Metabolism to Limit the Growth of Phakopsora pachyrhizi

2009 ◽  
Vol 99 (12) ◽  
pp. 1412-1420 ◽  
Author(s):  
Anatoliy V. Lygin ◽  
Shuxian Li ◽  
Ramya Vittal ◽  
Jack M. Widholm ◽  
Glen L. Hartman ◽  
...  
Keyword(s):  
Protective Role ◽  
Soybean Rust ◽  
Phakopsora Pachyrhizi ◽  
Phenolic Metabolism ◽  
Rust Infection ◽  
Resistant Lines ◽  
Significant Difference ◽  
Soybean Genotypes ◽  
Soybean Leaves

Understanding the metabolic responses of the plant to a devastating foliar disease, soybean rust, caused by Phakopsora pachyrhizi, will assist in development of cultivars resistant to soybean rust. In this study, differences in phenolic metabolism were analyzed between inoculated and noninoculated plants using two susceptible and three resistant soybean genotypes with known resistance genes. Rust infection resulted in increased accumulation of isoflavonoids and flavonoids in leaves of all soybean genotypes tested. Although the soybean phytoalexin glyceollin was not detected in leaves of uninfected plants, accumulation of this compound at marked levels occurred in rust-infected leaves, being substantially higher in genotypes with a red-brown resistant reaction. In addition, there was inhibition of P. pachyrhizi spore germination by glyceollin, formononetin, quercetin, and kaempferol. However, there was no correlation between concentrations of flavonoids quercetin and kaempferol and rust-induced isoflavonoid formononetin in soybean leaves and rust resistance. Lignin synthesis also increased in all inoculated soybean genotypes whereas there was no significant difference in all noninoculated soybean genotypes. Cell wall lignification was markedly higher in inoculated resistant lines compared with inoculated susceptible lines, indicating a possible protective role of lignin in rust infection development.

scholarly journals Performance of prothioconazole solo or added to mancozeb in the control of Asian soybean rust

2020 ◽  
Vol 46 (4) ◽  
pp. 345-347
Author(s):  
Erlei Melo Reis ◽  
Mateus Zanatta ◽  
Andrea Camargo Reis
Keyword(s):  
Field Experiment ◽  
Grain Yield ◽  
Factorial Design ◽  
The Other ◽  
Soybean Rust ◽  
Phakopsora Pachyrhizi ◽  
Site Specific ◽  
Asian Soybean Rust ◽  
Rust Severity

ABSTRACT The evolution of the reduction in Asian soybean rust (caused by Phakopsora pachyrhizi) control by site-specific fungicides has been reported season after season. In a field experiment, the effect of prothioconazole solo and added to multisite mancozeb was evaluated for rust control. Treatments were evaluated in a factorial design of four prothioconazole doses and three mancozeb doses. In a set of treatments, three applications were performed in one soybean cycle and four applications in another one. The first applications were performed at GS V8, 11 days before rust detection, with 2.56% leaflet incidence, while the other applications were at 12 to 14-day interval. Rust severity was quantified, control was calculated in relation to the unsprayed treatment, and soybean grain yield was estimated as kg/ha. Fifty-one to 61% control was obtained with three sprayings and 68% to 70% control with four sprayings of prothioconazole alone. Over 80% control was obtained with at least 0.3 L/ha prothioconazole + 2.0 kg/ha mancozeb, corresponding to 75 g a.i./ha prothioconazole + 1500 g a.i./ha mancozeb. Reduction in P. pachyrhizi control by the use of the site-specific fungicide alone was confirmed, while the addition of mancozeb can recover the efficacy of the site-specific fungicide.

scholarly journals Differential Response of Common Bean Cultivars to Phakopsora pachyrhizi

Plant Disease ◽  
2007 ◽  
Vol 91 (6) ◽  
pp. 698-704 ◽  
Author(s):  
M. R. Miles ◽  
M. A. Pastor-Corrales ◽  
G. L. Hartman ◽  
R. D. Frederick
Keyword(s):  
Common Bean ◽  
Single Gene ◽  
The United States ◽  
Differential Response ◽  
Soybean Rust ◽  
Phakopsora Pachyrhizi ◽  
Bean Rust ◽  
Lesion Type ◽  
Lower Severity ◽  
The Common

Soybean rust (Phakopsora pachyrhizi) has been reported on common bean (Phaseolus vulgaris) in Asia, South Africa, and the United States. However, there is little information on the interaction of individual isolates of Phakopsora pachyrhizi with common bean germplasm. A set of 16 common bean cultivars with known genes for resistance to Uromyces appendiculatus, the causal agent of common bean rust, three soybean accessions that were sources of the single gene resistance to P. pachyrhizi, and the moderately susceptible soybean ‘Ina’ were evaluated using seedlings inoculated with six isolates of P. pachyrhizi. Among the common bean cultivars, Aurora, Compuesto Negro Chimaltenango, and Pinto 114, were the most resistant to all six P. pachyrhizi isolates, with lower severity, less sporulation, and consistent reddish-brown (RB) lesions associated with resistance in soybean. A differential response was observed among the common bean cultivars, with a cultivar-isolate interaction for both severity and sporulation levels, as well as the presence or absence of the RB lesion type. This differential response was independent of the known genes that condition resistance to U. appendiculatus, suggesting that resistance to P. pachyrhizi was independent of resistance to U. appendiculatus.

scholarly journals First Report of Soybean Rust Caused by Phakopsora pachyrhizi on Kudzu (Pueraria montana var. lobata) in Illinois

Plant Disease ◽  
2010 ◽  
Vol 94 (4) ◽  
pp. 477-477 ◽  
Author(s):  
C. A. Bradley ◽  
R. A. Hines ◽  
N. R. Pataky ◽  
J. S. Haudenshield ◽  
G. L. Hartman
Keyword(s):  
United States ◽  
The State ◽  
The Other ◽  
Soybean Rust ◽  
Southern United States ◽  
Phakopsora Pachyrhizi ◽  
Southern Illinois ◽  
Glycine Max L ◽  
Health Progress ◽  
Pueraria Montana

Soybean rust, caused by Phakopsora pachyrhizi Syd., first was observed in the continental United States during 2004 on soybean (Glycine max (L.) Merr.) in Louisiana (4), and on kudzu (Pueraria montana (Lour.) Merr. var. lobata (Willd.) Maesen & Almeida) in Florida (2). Kudzu is a leguminous weed that is prevalent in the southern United States with its range extending northward into other states including Illinois. In October 2009, a kudzu patch located in Pulaski County in southern Illinois was investigated for the presence of soybean rust. Twenty-five leaflets were collected, and the abaxial sides of leaflets were evaluated visually for the presence of uredinia with a dissecting microscope. Uredinia and urediniospores were found on two leaflets. When viewed with a compound microscope, urediniospores were hyaline, echinulate, and measured 20 × 25 μm. On the basis of uredinia and urediniospores, the disease tentatively was identified as soybean rust caused by P. pachyrhizi. To confirm the identification, one leaflet with pustules was assayed with a Soybean Rust QuickStix Diagnostic Kit (Envirologix, Portland, ME). For the other leaflet, the area of the pustule was excised (approximately 28 mm2) and an area of the leaflet at the margin on the opposite half of the leaflet with no visible pustule (approximately 54 mm2) was excised. DNA was extracted from the excised areas of the leaflet for confirmation by quantitative PCR (Q-PCR) using primers and probe specific to P. pachyrhizi and P. meibomiae (Arthur) Arthur (1). Both the QuickStix Diagnostic Kit and the Q-PCR confirmed the diagnosis as soybean rust caused by P. pachyrhizi. Q-PCR also suggested the presence of a nonsporulating latent rust infection on the same kudzu leaflet at the margin on the opposite side of the midrib. Soybean rust first was confirmed on soybean in Illinois in 2006 (3), but to our knowledge, this is the first observation of the disease on kudzu in the state. This report confirms that at least some kudzu plants in Illinois are susceptible to soybean rust and that latent kudzu infection may exist without outward signs of the fungus. Currently, this is the most northern observation of soybean rust on kudzu in North America. It is unknown what role, if any, Illinois kudzu will play in the epidemiology of soybean rust in the state. Since kudzu tops die after the first frost, there is no expectation of P. pachyrhizi to overwinter in Illinois on kudzu as it does in some states adjacent to the Gulf of Mexico. References: (1) R. D. Frederick et al. Phytopathology 92:217, 2002. (2) P. F. Harmon et al. Online publication. doi:10.1094/PHP-2005-0613-01-RS. Plant Health Progress, 2005. (3) G. L. Hartman et al. Plant Dis. 91:466, 2007. (4) R. W. Schneider et al. Plant Dis. 89:774, 2005.

scholarly journals Comparison of Pathogenic Variation among Phakopsora pachyrhizi Isolates Collected from the United States and International Locations, and Identification of Soybean Genotypes Resistant to the U.S. Isolates

Plant Disease ◽  
2015 ◽  
Vol 99 (8) ◽  
pp. 1059-1069 ◽  
Author(s):  
C. Paul ◽  
R. D. Frederick ◽  
C. B. Hill ◽  
G. L. Hartman ◽  
D. R. Walker
Keyword(s):  
Principal Component ◽  
The United States ◽  
Soybean Rust ◽  
Phakopsora Pachyrhizi ◽  
Pathogenic Variation ◽  
Virulence Pattern ◽  
Soybean Genotypes ◽  
Rust Severity ◽  
Two Measures ◽  
The U.S

A major constraint in breeding for resistance to soybean rust has been the virulence diversity in Phakopsora pachyrhizi populations. In greenhouse experiments, reactions of 18 soybean genotypes to 24 U.S. isolates from 2007 and 2008 and 4 foreign isolates were compared. Reactions of four differentials (Rpp1 to Rpp4) to these U.S. isolates were also compared with reactions to nine foreign isolates and three U.S. isolates from 2004. Principal component analysis (PCA) of the reaction types grouped the U.S. isolates into a single virulence group, whereas each of the foreign isolates had a unique virulence pattern. In another experiment, reactions of 11 differentials to the 24 U.S. isolates were compared and significant interactions (P < 0.001) were found between the isolates and host genotypes for rust severity and uredinia densities. PCA of these two measures of disease placed the 24 isolates into seven or six aggressiveness groups, respectively. In a third experiment, evaluation of 20 soybean genotypes for resistance to the previously established aggressive groups identified 10 genotypes resistant to isolates representing most of the groups. This study confirmed the pathogenic diversity in P. pachyrhizi populations and identified soybean germplasm with resistance to representative U.S. isolates that can be used in breeding.

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