EFFICIENCY LOSS OF RECORDED FUNGICIDES FOR THE CONTROL OF ASIAN SOYBEAN RUST IN CENTRAL REGION OF BRAZIL

Due to grower allege of low efficiency of triazole fungicides in recent years in Central Brazil on the control of Asian soybean rust (Phakopsora pachyrhizi), this study was undertaken to demonstrate the efficiency loss of products registered for rust and applied alone and to evaluate the efficiency of fungicides mixtures. The trials were carried out in five locations in Brazil, in the 2009/10 growing season. The experimental design was completely randomized blocks with four replications. Ten mixtures of triazole + strobilurin and two applications of pure triazoles were evaluated and the control without application. The application of fungicides started in the R1/R2 stage or in any vegetative stage if infections occurred early. The mixtures of fungicides were effective in controlling Asian soybean rust. Application of sole triazole fungicides was less effective in controlling the rust than the mixtures of triazoles + strobilurins. The use of commercial mixtures of triazole with strobilurin for rust control is recommended.

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Morphologic and Pathometric Characterization of the Asian Soybean Rust (Phakopsora pachyrhizi) in Santa Fe Province, Argentina

Plant Disease ◽

10.1094/pd-89-0684b ◽

2005 ◽

Vol 89 (6) ◽

pp. 684-684 ◽

Cited By ~ 1

Author(s):

R. N. Pioli ◽

M. V. Cambursano ◽

E. N. Morandi

Keyword(s):

Growing Season ◽

Brown Spot ◽

Soybean Rust ◽

Disease Spread ◽

Phakopsora Pachyrhizi ◽

Santa Fe ◽

Asian Soybean Rust ◽

Soybean Plants ◽

Soybean Leaves

The Asian soybean rust caused by the fungus Phakopsora pachyrhizi was cited for the first time in Argentina during the 2002-2003 growing season (3). During 2003-2004, the disease spread to other northern provinces and was also observed in north-central Santa Fe, the main producing soybean province of the country. Because the disease appeared at the end of the crop growing season (late March to early April) it had little or no impact on crop yields. The objectives of this study were to characterize morphologically and pathometrically the disease on soybean and check the presence of P. pachyrhizi on volunteer soybean plants that could eventually carry the disease to the next growing season. The study was conducted in the San Justo Department, Santa Fe Province (between 30 and 31°S latitude), where the presence of the soybean rust was molecularly confirmed by Sistema Nacional Vigilancia y Monitoreo (on-line publication at www.sinavimo.gov.ar ). Three field locations were sampled and identified as M1, M2, and M3. Transversal cuts of soybean leaves through rust lesions and histo-pathological staining were used for micromor-phologic characterization of the developmental stages of P. pachyrhizi. The disease incidence was estimated as the proportion of affected soybean plants and leaves. Average severity, expressed as the percentage of leaf area affected, including chlorosis, was measured on the terminal leaflet of leaves sampled from the lower one-third of the canopy. Three replicates of 10 plants, randomly chosen, were used. The number of uredinia per square centimeter and per lesion (symptomatic foliar area showing chlorosis and necrosis caused by the fungus) was measured on the undersides of the sampled leaflets at ×40 magnification (1). Typical signs and symptoms of P. pachyrhizi coexisted on soybean leaves with brown spot (Septoria glycines), downy mildew (Peronospora manshurica), anthracnose (Colletotrichum truncatum), and blight and leaf spot (Cercospora kikuchii) and also with bacteria (Pseudomonas and Xanthomonas spp.). Uredinia and telia of the P. pachyrhizi cycle were observed. Uredinia were also observed on soybean petioles. The average size of urediniospores (n = 60) was 23.3 × 16.6 μm. Telia were located adjacent to the uredinia. These telia were dark and crusty with four stacked layers of teliospores. Rust incidence in plants was 100% for the three fields, while the incidence in leaves was 100% for M1 and M2 and 60% for M3. Average disease severity was 50.3, 25.6, and 14.8% for M1, M2, and M3, respectively. The mean number of uredinia per square centimeter was 327, 179, and 177, for M1, M2, and M3, respectively. The number of uredinia per lesion ranged from 1 to 6. P. pachyrhizi was also found on volunteer soybean plants that emerged shortly after harvest. On 40 leaflets, the foliar incidence was 25%, showing one to two lesions with one to two uredinios per leaflet (2). The volunteer soybean plants could constitute a potential early source of inoculum. References: (1) M. Marcchetti et al. Phytopathology. 66:461, 1976. (2) R. Pioli et al. La roya asiática en Santa. Fe, Arg. XII Cong. AAPRESID, II Sem. Internac. Soja, Arg. 283–290, 2004. (3) R. L. Rossi. Plant Dis. 87:102, 2003.

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Overwinter and Survival of Asian Soybean Rust Caused by Phakopsora pachyrhizi in Volunteer Soybean Plants in Entre Ríos Province, Argentina

Plant Disease ◽

10.1094/pd-90-0826b ◽

2006 ◽

Vol 90 (6) ◽

pp. 826-826 ◽

Cited By ~ 1

Author(s):

A. N. Formento ◽

J. de Souza

Keyword(s):

Growing Season ◽

Soybean Rust ◽

Limiting Factor ◽

Research Station ◽

Phakopsora Pachyrhizi ◽

Asian Soybean Rust ◽

On Line ◽

Freezing Temperatures ◽

Soybean Plants ◽

Entre Rios

Asian soybean rust (ASR) caused by Phakopsora pachyrhizi was initially reported in the Province of Entre Ríos, Argentina in April 2004 (1). During the 2004-2005 growing season, ASR was observed in the main soybean-producing (Glycine max) region of the country (4) and it was observed on kudzu (Pueraria lobata) in Misiones and Santa Fe provinces (2). Of the environmental factors affecting rust survival over the winter, temperature is probably the most important one with no germination occurring below 7°C (3). The objectives of this study were to analyze the subfreezing daily air temperatures in the presence of new erumpent uredinia and the germination of P. pachyrhizi urediniospores. Ten sites with volunteer plants close to the meteorological station were found in the Paraná Research Station (31°51′S, 60°31′W). Weekly, from June 2004 through December 2005, sites were randomly sampled for volunteer plants (n = 15). The presence of the ASR was confirmed with a polymerase chain reaction (PCR) assay by SINAVIMO (4). The ASR incidence (ASRI) and erumpent uredinia incidence (EUI) was estimated as the proportion of affected plants. Uredinia were classified as: new erumpent with colorless spores; mature cinnamon with pale cinnamon-brown spores; and dead, empty, and dark without spores. The disease density was estimated as an average of the diseased leaflets according to the following scale: light (number of lesions 1 to 100), moderate (101 to 500), and heavy (>500). The ability of urediniospores from the erumpent pustules to germinate was tested during July 2004 and September 2005 on 1.5% of water agar and kept at 25 ± 2°C for 2 days. The subfreezing daily air (0.05 m height) temperature was registered. During the complete evaluation period, surviving plants from the Vc to R6 stages were observed. However, plants with ASR were only observed from June to July 2004 and May to September 2005. Locally, first planting dates begin in October. New uredinia were observed close to mature and dead uredinia on unifoliate and trifoliate leaflets, and petiols and stems in plants from the V2 to R5 stages. There were 13 days with below freezing temperatures from 1 June to 31 July 2004 (-0.1 to -7.4°C), and ASRI and EUI was 100%. The ASR mean density was light. The coldest temperature was -7.4°C on 11 July 2004, and thereafter, no uredinia were observed until the next growing season. From 25 April to 16 September 2005 there were 20 days with below freezing temperatures (-0.1 to -4.9°C). The ASRI and the EUI were 92.3 (76.9), 75.0 (58.3), 59.1 (32.6), 50.0 (40.9), and 36.7 (23.3)% in May, June, July, August, and September, respectively. The incidence of plants with a moderate to heavy disease level was 50.0, 41.7, 28.6, 29.5, and 10% respectively. Germination rate of urediniospores collected in July 2004 was 11% and 28% in September 2005. Low temperatures do not seem to be a limiting factor for the survival of P. pachyrhizi, and urediniospores could survive on volunteer plants until new soybean plants grow. Since another host is rare or absent in the region, volunteer soybean plants may provide a reservoir of inoculum for the next season. References: (1) A. N. Formento. Roya de la soja en Entre Ríos. INTA-EEA Paraná. On-line publication. INTA, 2004. (2) A. N. Formento and J. de Souza. INTA-EEA Paraná. Serie Extensión No. 32, 2004. (3) M. Marchetti et al. Phytopathology 66:461, 1975. (4) SINAVIMO. Sistema Nacional Argentino de Vigilancia y Monitoreo de Plagas, Roya de la soja. On-line publication. SENASA, 2004.

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Performance of chlorothalonil levels and spraying intervals on Asian rust control and soybean grain yield

Summa Phytopathologica ◽

10.1590/0100-5405/204867 ◽

2019 ◽

Vol 45 (3) ◽

pp. 261-264

Author(s):

Erlei Melo Reis ◽

Mateus Zanatta ◽

Andrea Camargo Reis

Keyword(s):

Grain Yield ◽

Analysis Of Variance ◽

Growing Season ◽

Soybean Cultivar ◽

Soybean Rust ◽

Phakopsora Pachyrhizi ◽

Fungicide Application ◽

Resistance Strategies ◽

Asian Soybean Rust ◽

Rust Severity

ABSTRACT In an experiment conducted in the field, during the 2017/18 growing season, with the soybean cultivar Syn 1561 IPRO, the interaction of chlorothalonil levels with application intervals was evaluated for the control of Asian soybean rust, caused by Phakopsora pachyrhizi. The first fungicide application was performed in V8 stage, 44 days after emergence, with 1.85% rust leaflet incidence. The experiment consisted of a factorial arrangement with five fungicide levels (1.0, 1.5, 2.0, 2.5 and 3.0 L/ha) applied at 8, 12 and 16-day intervals, using randomized block treatments and four replicates. A self-propelled sprayer with 16 bars, XR11001VS nozzles and 150 L/ha volume was employed. Leaflet rust severity in R5.4 stage and grain yield were evaluated. Data were subjected to analysis of variance, and means were compared according to Tukey’s test. At eight-day intervals (six sprayings), control ranged from 75% to 93%; at 12-day intervals (four sprayings), it ranged from 35 to 63%, and at 16-day intervals (three sprayings), control ranged from 15 to 29% according to the sprayed levels. The longer the interval between applications, the lower the response of the used level for rust control and soybean grain yield. Chlorothalonil showed fungitoxicity to integrate a program of anti-resistance strategies to control soybean rust.

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Transcriptome analyses and virus induced gene silencing identify genes in the Rpp4-mediated Asian soybean rust resistance pathway

Functional Plant Biology ◽

10.1071/fp12296 ◽

2013 ◽

Vol 40 (10) ◽

pp. 1029 ◽

Cited By ~ 30

Author(s):

Aguida M. A. P. Morales ◽

Jamie A. O'Rourke ◽

Martijn van de Mortel ◽

Katherine T. Scheider ◽

Timothy J. Bancroft ◽

...

Keyword(s):

Gene Expression ◽

Transcription Factors ◽

Gene Silencing ◽

Differentially Expressed ◽

Soybean Rust ◽

Phakopsora Pachyrhizi ◽

R Gene ◽

Virus Induced Gene Silencing ◽

Asian Soybean Rust ◽

Defence Responses

Rpp4 (Resistance to Phakopsora pachyrhizi 4) confers resistance to Phakopsora pachyrhizi Sydow, the causal agent of Asian soybean rust (ASR). By combining expression profiling and virus induced gene silencing (VIGS), we are developing a genetic framework for Rpp4-mediated resistance. We measured gene expression in mock-inoculated and P. pachyrhizi-infected leaves of resistant soybean accession PI459025B (Rpp4) and the susceptible cultivar (Williams 82) across a 12-day time course. Unexpectedly, two biphasic responses were identified. In the incompatible reaction, genes induced at 12 h after infection (hai) were not differentially expressed at 24 hai, but were induced at 72 hai. In contrast, genes repressed at 12 hai were not differentially expressed from 24 to 144 hai, but were repressed 216 hai and later. To differentiate between basal and resistance-gene (R-gene) mediated defence responses, we compared gene expression in Rpp4-silenced and empty vector-treated PI459025B plants 14 days after infection (dai) with P. pachyrhizi. This identified genes, including transcription factors, whose differential expression is dependent upon Rpp4. To identify differentially expressed genes conserved across multiple P. pachyrhizi resistance pathways, Rpp4 expression datasets were compared with microarray data previously generated for Rpp2 and Rpp3-mediated defence responses. Fourteen transcription factors common to all resistant and susceptible responses were identified, as well as fourteen transcription factors unique to R-gene-mediated resistance responses. These genes are targets for future P. pachyrhizi resistance research.

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Resistance to Asian soybean rust in soybean lines with the pyramided three Rpp genes

Cropp Breeding and Applied Biotechnology ◽

10.1590/s1984-70332013000100009 ◽

2013 ◽

Vol 13 (1) ◽

pp. 75-82 ◽

Cited By ~ 28

Author(s):

Naoki Yamanaka ◽

Noelle G Lemos ◽

Miori Uno ◽

Hajime Akamatsu ◽

Yuichi Yamaoka ◽

...

Keyword(s):

Genetic Background ◽

Susceptible Variety ◽

Soybean Rust ◽

Phakopsora Pachyrhizi ◽

Soybean Line ◽

Pathogen Population ◽

Resistance Level ◽

Asian Soybean Rust ◽

High Level

In this study, the influence of genetic background on the resistance level of a soybean line carrying Rpp2, Rpp4, and Rpp5 was evaluated by backcrossing it with a susceptible variety. It was also evaluated eight lines which carry these Rpp genes against five Asian soybean rust (ASR) isolates, in order to determine the likely range of resistance against ASR isolates differing in pathogenicity. The results indicated that a high level of resistance against various ASR isolates could be retained in lines carrying the three Rpp genes in susceptible genetic backgrounds, although minor influences of plant genetic background and ASR pathogenicity to the ASR resistance could occur. Thus, lines with the pyramided three Rpp genes should be effective against a complex pathogen population consisting of diverse Phakopsora pachyrhizi isolates.

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Characterization of three soybean landraces resistant to Asian soybean rust disease

Molecular Breeding ◽

10.1007/s11032-020-01132-w ◽

2020 ◽

Vol 40 (6) ◽

Author(s):

Luciano Nobuhiro Aoyagi ◽

Yukie Muraki ◽

Naoki Yamanaka

Keyword(s):

Susceptible Variety ◽

Soybean Rust ◽

Resistance Locus ◽

Chromosome 6 ◽

Phakopsora Pachyrhizi ◽

Rust Disease ◽

Asian Soybean Rust ◽

The World ◽

Trait Locus

Abstract Phakopsora pachyrhizi is an obligatory biotrophic fungus that causes Asian soybean rust (ASR) disease. ASR control primarily involves chemical control and the use of resistant soybean cultivars carrying an Rpp (resistance to P. pachyrhizi) gene. This study aimed to characterize the ASR resistance of three soybean Asian landraces. By screening the world core collection (WC) of soybean, which consists of 80 varieties, three landraces were identified in Southeast Asia as resistant to ASR. Genetic mapping using the F2 population derived from a cross with an ASR-susceptible variety, BRS 184, indicated that KS 1034 (WC2) has ASR resistance conferred by a single dominant resistance gene, mapped on chromosome 18, in the same region where Rpp1 was mapped previously. The BRS 184 × WC61 (COL/THAI/1986/THAI-80) F2 population, on the other hand, showed an ASR resistance locus mapped by quantitative trait locus analysis on chromosome 6, in the region where the resistance conferred by PI 416764 Rpp3 resides, with a logarithm of the odds score peak at the same position as the marker, Satt079, while the BRS 184 × WC51 (HM 39) population showed the resistance to ASR allocated between Satt079 and Sat_263 markers, also in the region where Rpp3 was mapped previously. Both WC51 and WC61 have the same infection profile as FT-2 and PI 462312 when tested against the same ASR isolate panel. These three WCs can be used in MAS programs for introgression of Rpp1 and Rpp3 and the development of ASR-resistant cultivars in the breeding program.

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Models and applications for risk assessment and prediction of Asian soybean rust epidemics

Fitopatologia Brasileira ◽

10.1590/s0100-41582006000600001 ◽

2006 ◽

Vol 31 (6) ◽

pp. 533-544 ◽

Cited By ~ 10

Author(s):

Emerson M. Del Ponte ◽

Cláudia V. Godoy ◽

Marcelo G. Canteri ◽

Erlei M. Reis ◽

X.B. Yang

Keyword(s):

Disease Modeling ◽

Weather Conditions ◽

Epidemiological Studies ◽

Soybean Rust ◽

Phakopsora Pachyrhizi ◽

Spatial And Temporal Scales ◽

Asian Soybean Rust ◽

New Development ◽

Glycine Max L ◽

Favorable Weather

Asian rust of soybean [Glycine max (L.) Merril] is one of the most important fungal diseases of this crop worldwide. The recent introduction of Phakopsora pachyrhizi Syd. & P. Syd in the Americas represents a major threat to soybean production in the main growing regions, and significant losses have already been reported. P. pachyrhizi is extremely aggressive under favorable weather conditions, causing rapid plant defoliation. Epidemiological studies, under both controlled and natural environmental conditions, have been done for several decades with the aim of elucidating factors that affect the disease cycle as a basis for disease modeling. The recent spread of Asian soybean rust to major production regions in the world has promoted new development, testing and application of mathematical models to assess the risk and predict the disease. These efforts have included the integration of new data, epidemiological knowledge, statistical methods, and advances in computer simulation to develop models and systems with different spatial and temporal scales, objectives and audience. In this review, we present a comprehensive discussion on the models and systems that have been tested to predict and assess the risk of Asian soybean rust. Limitations, uncertainties and challenges for modelers are also discussed.

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