scholarly journals Pathogenic Variation of South American Phakopsora pachyrhizi Populations Isolated from Soybeans from 2010 to 2015

2017 ◽  
Vol 51 (3) ◽  
pp. 221-232 ◽  
Author(s):  
Hajime AKAMATSU ◽  
Naoki YAMANAKA ◽  
Rafael Moreira SOARES ◽  
Antonio Juan Gerardo IVANCOVICH ◽  
Miguel Angel LAVILLA ◽  
...  
Keyword(s):  
South American ◽  
Phakopsora Pachyrhizi ◽  
Pathogenic Variation

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 Differential Pathogenicity of Xanthomonas campestris pv. phaseoli and X. fuscans subsp. fuscans Strains on Bean Genotypes with Common Blight Resistance

Plant Disease ◽  
2008 ◽  
Vol 92 (4) ◽  
pp. 546-554 ◽  
Author(s):  
N. Mutlu ◽  
A. K. Vidaver ◽  
D. P. Coyne ◽  
J. R. Steadman ◽  
P. A. Lambrecht ◽  
...  
Keyword(s):  
Common Bean ◽  
Bacterial Blight ◽  
Xanthomonas Campestris ◽  
South American ◽  
Bacterial Strains ◽  
Genetic Changes ◽  
Germplasm Screening ◽  
Lack Of Information ◽  
Pathogenic Variation ◽  
The Common

Both the common bacterial blight (CBB) pathogen (Xanthomonas campestris pv. phaseoli) and X. fuscans subsp. fuscans, agent of fuscous blight, cause indistinguishable symptoms in common bean, Phaseolus vulgaris. Yield losses can exceed 40%. Lack of information about the specificity between X. campestris pv. phaseoli strains and major quantitative trait loci (QTL) or alleles conferring resistance makes the task of identifying genetic changes in host–pathogen interactions and the grouping of bacterial strains difficult. This, in turn, affects the choice of pathogen isolates used for germplasm screening and complicates breeding for CBB resistance. Common bean host genotypes carrying various sources and levels of resistance to CBB were screened with 69 X. campestris pv. phaseoli and 15 X. fuscans subsp. fuscans strains from around the world. Differential pathogenicity of the CBB pathogen was identified on the 12 selected bean genotypes. The X. fuscans subsp. fuscans strains showed greater pathogenicity than X. campestris pv. phaseoli strains having the same origin. African strains were most pathogenic. The largest variation in pathogenicity came from X. campestris pv. phaseoli strains that originated in Caribbean and South American countries. Pathogenic variation was greater within X. campestris pv. phaseoli than within X. fuscans subsp. fuscans strains. Implications for breeding for CBB resistance are discussed.

scholarly journals Virulence diversity of Phakopsora pachyrhizi in Mexico

2021 ◽  
Author(s):  
Julio César García-Rodríguez ◽  
Zeferino Vicente-Hernández ◽  
Manuel Grajales-Solís ◽  
Naoki Yamanaka
Keyword(s):  
Comparative Analysis ◽  
South America ◽  
Geographic Variation ◽  
Soybean Rust ◽  
South American ◽  
Phakopsora Pachyrhizi ◽  
Common Trend ◽  
Asian Soybean Rust ◽  
Production Knowledge ◽  
Virulence Diversity

Asian soybean rust (ASR), caused by the pathogen Phakopsora pachyrhizi, is the main disease of soybean in Mexico and worldwide, threatening its production. Knowledge about the virulence of Mexican rust populations (MRPs) is crucial in order to develop or introduce soybean cultivars with resistance to this disease. This study investigated the geographic variation on the virulence of 19 MRPs collected in two states of Mexico: Tamaulipas and Chiapas, using a set of 12 differential soybean varieties. The inoculation of MRPs showed that there was no large difference in virulence to differentials carrying Rpp4 or Rpp5 between MRPs from the two states. However, a contrasting phenotype was observed on Rpp1, Rpp1-b, Rpp2, and Rpp3. In the comparative analysis of virulence profiles with 157 and 20 P. pachyrhizi samples from South America and Asia, respectively, the MRPs from Chiapas form an isolated cluster, including the Tamaulipas state. The MRPs from Tamaulipas clustered with South American samples because of common characteristics, such as virulence to Rpp1 and avirulence to Rpp1-b. However, opposite reactions on Rpp1 and Rpp1-b that have been reported in major USA pathogen were also observed in Chiapas samples. A common trend between Chiapas and major USA pathogen was also observed in Rpp3. As the main conclusion of the present study, the 1,000 km distance between these two states in Mexico makes a big difference in the virulence of ASR.

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.

scholarly journals Pathogenic Variation of Phakopsora pachyrhizi Infecting Soybean in Nigeria

2009 ◽  
Vol 99 (4) ◽  
pp. 353-361 ◽  
Author(s):  
M. Twizeyimana ◽  
P. S. Ojiambo ◽  
K. Sonder ◽  
T. Ikotun ◽  
G. L. Hartman ◽  
...  
Keyword(s):  
Disease Severity ◽  
Leaf Tissue ◽  
Principal Component ◽  
Exponential Model ◽  
Soybean Rust ◽  
Phakopsora Pachyrhizi ◽  
Guinea Savanna ◽  
Pathogenic Variation ◽  
Rust Severity ◽  
Soybean Leaves

Soybean rust, caused by Phakopsora pachyrhizi, is an important disease in Nigeria and many other soybean-producing countries worldwide. To determine the geographical distribution of soybean rust in Nigeria, soybean fields were surveyed in the Derived Savanna (DS), Northern Guinea Savanna (NGS), and Southern Guinea Savanna (SGS) agroecological zones in Nigeria between 2004 and 2006. Disease severity in each zone was determined and analyzed using geostatistics. Prevalence of infected fields and disease severity in surveyed fields were significantly (P < 0.05) different between geographical zones with both variables being higher in the DS zone than in either NGS or SGS zones. Geostatistical analysis indicated that the spatial influence of disease severity at one location on severity at other locations was between 75 and 120 km. An exponential model best described the relationship between semivariance and lag distance when rust severity was high. Spatial interpolation of rust severity showed that locations in the DS zone were more conducive for the rust epidemic compared to areas in the NGS zone. In the 2005 survey, 116 purified isolates were established in culture on detached soybean leaves. To establish the nature of pathogenic variation in P. pachyrhizi, a set of four soybean accessions with Rpp1, Rpp2, Rpp3, and Rpp4 resistance genes, two highly resistant and two highly susceptible genotypes were inoculated with single uredinial isolates. Principal component analysis on the number of uredinia per square centimeter of leaf tissue for 116 isolates indicated that an adequate summary of pathogenic variation was obtained using only four genotypes. Of these four, PI 459025B (with Rpp4 gene) and TG× 1485-1D had the lowest and highest number of uredinia per square centimeter, respectively. Based on cluster analysis of the number of uredinia per square centimeter, seven pathotype clusters were determined. Isolates in cluster III were the most virulent, while those in cluster IV were the least virulent. Shannon's index (H) revealed a more diverse pathogen population in the DS zone (H = 1.21) compared to the rust population in SGS and NGS with H values of 1.08 and 0.91, respectively. This work will be useful in breeding and management of soybean rust by facilitating identification of resistant genotypes and targeting cultivars with specific resistance to match prevailing P. pachyrhizi pathotypes in a given geographical zone.

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