scholarly journals Spray volume deposits and fungicide efficacy on soybean rust (Phakopsora pachyrhizi)

2019 ◽  
pp. 1698-1705
Author(s):  
Evandro Pereira Prado ◽  
Carlos Gilberto Raetano ◽  
Mario Henrique Ferreira do Amaral Dal Pogetto ◽  
Rafael de Souza Christovam ◽  
Paulo Renato Matos Lopes ◽  
...  
Keyword(s):  
Disease Severity ◽  
Field Experiments ◽  
Soybean Rust ◽  
Phakopsora Pachyrhizi ◽  
Control Efficacy ◽  
Application Techniques ◽  
Application Methods ◽  
Spray Volume ◽  
Soybean Leaves ◽  
Thousand Seed Weight

Soybean rust (SBR), caused by Phakopsora pachyrhizi, is one of the most destructive fungal diseases affecting soybean yields in many countries. Fungicide application methods that provide better SBR control efficacy may reduce soybean losses due to this disease. We investigated the effects of spray volumes applying the fungicide pyraclostrobin plus epoxiconazol at 133 + 50 g a.i. ha-1 by a conventional sprayer (CS) and an air-assisted sprayer (AAS). Field experiments were conducted comparing the effects of spray volumes of 110, 160, and 210 L ha-1 and two application techniques (CS and AAS) on spray deposits and SBR control. Fungicide efficacies were measured by disease severity, thousand seed weight, and yield. Correlations between disease severity and yield were also assessed. All treatments were applied with an Advance 2000 AM18 sprayer. In general, SBR disease and yield did not differ significantly when fungicide applications were applied with AAS compared to CS. Increasing the spray volume from 110 to 210 L ha-1 did not increase spray deposit coverage on soybean leaves. Low disease severity was obtained by fungicide applications using a spray volume of 210 L ha-1. Safe recommendations of ground spray volumes for SBR control should be between 160 and 210 L ha-1, using hydraulic nozzles.

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.

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 Gene Expression in Leaves of Susceptible Glycine max during Infection with Phakopsora pachyrhizi Using Next Generation Sequencing

Sequencing ◽  
2011 ◽  
Vol 2011 ◽  
pp. 1-14 ◽  
Author(s):  
Arianne Tremblay ◽  
Parsa Hosseini ◽  
Nadim W. Alkharouf ◽  
Shuxian Li ◽  
Benjamin F. Matthews
Keyword(s):  
Soybean Rust ◽  
Cdna Libraries ◽  
Phakopsora Pachyrhizi ◽  
Rust Disease ◽  
Illumina Platform ◽  
Molecular Events ◽  
Genes Encoding ◽  
Exotic Pathogen ◽  
Soybean Leaves ◽  
Host Genes

Soybean rust is caused by the obligate biotrophic fungus Phakopsora pachyrhizi, an exotic pathogen causing important yield losses in soybean production. We used an mRNA-Seq strategy to analyze the expression pattern of soybean genes and better understand molecular events occurring in soybean following the infection. cDNA libraries were constructed from RNA isolated from whole infected soybean leaves 10 days after inoculation with P. pachyrhizi and sequenced using an Illumina platform to identify soybean genes that are affected by pathogen growth. We obtained 15 million sequences corresponding to soybean genes. Forty-two percent of the genes were downregulated including genes encoding proteins involved in amino acid metabolism, carbohydrate metabolism, and transport facilitation; 31% were upregulated including genes encoding proteins involved in lipid metabolism, glycan biosynthesis, and signal transduction. Candidate host genes identified in this study will be manipulated to assay their potential to control soybean rust disease.

scholarly journals Adult Plant Evaluation of Soybean Accessions for Resistance to Phakopsora pachyrhizi in the Field and Greenhouse in Paraguay

Plant Disease ◽  
2008 ◽  
Vol 92 (1) ◽  
pp. 96-105 ◽  
Author(s):  
M. R. Miles ◽  
W. Morel ◽  
J. D. Ray ◽  
J. R. Smith ◽  
R. D. Frederick ◽  
...  
Keyword(s):  
Field Trial ◽  
Field Experiments ◽  
Field Evaluation ◽  
Soybean Rust ◽  
Adult Plant ◽  
Phakopsora Pachyrhizi ◽  
Sources Of Resistance ◽  
Plant Evaluation ◽  
Maturity Groups

Five hundred thirty soybean accessions from maturity groups (MG) III through IX were evaluated for resistance to Phakopsora pachyrhizi in a replicated field trial at Centro Regional de Investigación Agrícola in Capitán Miranda, Itapúa, Paraguay during the 2005–06 season. Soybean rust severities of individual accessions ranged from 0% (resistant) to 30.0% (susceptible). In MG III and IV, the most resistant accessions were PI 506863, PI 567341, and PI 567351B, with severities less than 1.2%. In MG V, the most resistant accessions were PI 181456, PI 398288, PI 404134B, and PI 507305, with severities less than 0.3%. In MG VI, the most resistant accessions were PI 587886, PI 587880A, and PI 587880B, with severities less than 0.3%. In MG VII and VIII, the most resistant were PI 587905 and PI 605779E, with severities less than 1.0%. In MG IX, the most resistant accessions were PI 594754, PI 605833, PI 576102B, and PI 567104B, with severities less than 1.0%. The resistance in 10 selected accessions from MG VI, VII, VIII, and XI was confirmed in subsequent greenhouse and field experiments where severities of 0.4% or less and reddish-brown lesions with sporulation levels less than 3.0 were observed. These accessions, with low severities in the adult plant field evaluation, may be new sources of resistance to P. pachyrhizi.

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 Simulation of Apparent Infection Rate to Predict Severity of Soybean Rust Using a Fuzzy Logic System

2005 ◽  
Vol 95 (10) ◽  
pp. 1122-1131 ◽  
Author(s):  
K. S. Kim ◽  
T. C. Wang ◽  
X. B. Yang
Keyword(s):  
Fuzzy Logic ◽  
Disease Severity ◽  
Infection Rate ◽  
Field Experiments ◽  
Fuzzy Logic System ◽  
Soybean Rust ◽  
Weather Data ◽  
Epidemic Period ◽  
Apparent Infection Rate ◽  
Logic System

Few biologically based models to assess the risk of soybean rust have been developed because of difficulty in estimating variables related to infection rate of the disease. A fuzzy logic system, however, can estimate apparent infection rate by combining meteorological variables and biological criteria pertinent to soybean rust severity. In this study, a fuzzy logic apparent infection rate (FLAIR) model was developed to simulate severity of soybean rust and validated using data from field experiments on two soybean cultivars, TK 5 and G 8587. The FLAIR model estimated daily apparent infection rate of soybean rust and simulated disease severity based on population dynamics. In weekly simulation, the FLAIR model explained >85% of variation in disease severity. In simulation of an entire epidemic period, the FLAIR model was able to predict disease severity accurately once initial values of disease severity were predicted accurately. Our results suggest that a model could be developed to determine apparent infection rate and an initial value of disease severity in advance using forecasted weather data, which would provide accurate prediction of severity of soybean rust before the start of a season.

scholarly journals Reduced Asian Soybean Rust Control by Commercial Fungicides Co-formulations in the 2018-2019 Growing Season in Southern Brazil

2021 ◽  
Vol 13 (4) ◽  
pp. 113
Author(s):  
Erlei Melo Reis ◽  
Mateus Zanatta ◽  
Andrea Camargo Reis
Keyword(s):  
Block Design ◽  
Soybean Rust ◽  
Growth Stages ◽  
Phakopsora Pachyrhizi ◽  
Southern Brazil ◽  
Control Efficacy ◽  
Growing Seasons ◽  
Asian Soybean Rust ◽  
Randomized Block Design ◽  
Commercial Fungicide

It has been a growers concen the reduction of Asian soybean rust (ASR) control by commercial fungicide co-formulations in the last growing seasons in southern Brazil. The objective of this work was to assess the ASR control efficacy by the most used co-formulations in the 2018/19 season. In a field experiment, 19 fungicides in commercial formulations to control soybean rust caused by Phakopsora pachyrhizi, were evaluated. Chemicals at their recommended doses were sprayed at four soybean growth stages. The first application was performed with 1.82% leaflet incidence and coinciding with R1 phenological stage. The others were performed at 14-18 days intervals. At stage R6, end of the epidemic and coinciding with half of the defoliation in the control plots, the leaf severity was appraised. The experiment was conducted with Ativa soybean cultivar, in 3 &times; 6 m plots, four replications and randomized block design. The harvest was made with a plot combine and the yield expressed in grains kg/ha. The means were compared by the Scott-Knott test. The disease control efficacy by 17 fungicide co-formulation showed control less than 57%, one with 78% and none with &ge; 80%. The unsprayed treatment severity was 81% and the greatest control of 78% resulted in 3,876 kg/ha yield. Therefore, the hypothesis raised in this work was accepted showing that the site-specific fungicides co-formulations are showing efficacy reduction season after season.

scholarly journals Effects of Simplicillium lanosoniveum on Phakopsora pachyrhizi, the Soybean Rust Pathogen, and Its Use as a Biological Control Agent

2012 ◽  
Vol 102 (8) ◽  
pp. 749-760 ◽  
Author(s):  
N. A. Ward ◽  
C. L. Robertson ◽  
A. K. Chanda ◽  
R. W. Schneider
Keyword(s):  
Biological Control Agent ◽  
Signs And Symptoms ◽  
Control Agent ◽  
Soybean Rust ◽  
Phakopsora Pachyrhizi ◽  
Latent Stage ◽  
Leaf Surfaces ◽  
Rust Pathogen ◽  
Soybean Leaf ◽  
Soybean Leaves

The fungus Simplicillium lanosoniveum was isolated from soybean leaves infected with Phakopsora pachyrhizi, the soybean rust pathogen, in Louisiana and Florida. The fungus did not grow or become established on leaf surfaces until uredinia erupted, but when soybean rust signs and symptoms were evident, S. lanosoniveum colonized leaves within 3 days and sporulated within 4 days. Development of new uredinia was suppressed by about fourfold when S. lanosoniveum colonized uredinia. In the presence of S. lanosoniveum, uredinia became increasingly red-brown, and urediniospores turned brown and germinated at very low rates. Assays using quantitative real time polymerase chain reaction revealed that the fungus colonized leaf surfaces when plants were infected with P. pachyrhizi, either in a latent stage of infection or when symptoms were present. However, when plants were inoculated before infection, there was no increase of DNA of S. lanosoniveum, suggesting that the pathogen must be present in order for the antagonist to become established on soybean leaf surfaces. We documented significantly lower amounts of DNA of P. pachyrhizi and lower disease severity when soybean leaves were colonized with S. lanosoniveum. These studies documented the mycophilic and disease-suppressive nature of S. lanosoniveum.

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