Fungi Resistance to Multissite Fungicides

Multisite fungicides have been used for many years in fruit and vegetable crops worldwide. Cases of the fungi resistance development to these fungicides have been rare. From the 2002 season onwards, with the outbreak of Asian soybean rust in Brazil, caused by Phakopsora pachyrhizi, site-specific fungicides became the main weapon for its control. From 2002 to 2011, penetrant mobile site-specific fungicides were used and until today in double (DMI + QoI) or triple (DMI + QoI + SDHI) co-formulatoons in an area of more than 30 million hectares and with three sprays per area. This resulted, as expected, in the fungus sensitivity reduction, today with cross and multiple resistance to those site-specific fungicides. From the 2011 season in an attempt to recover control that for some chemicals and mixtures reached < 30%, research was started with site-specific + multi-site mixtures, taking as example Phytophthora infestans resistance development to metalaxyl in Europe showinig long-lasting solution found by the addition of multisite mancozeb. It is expected that the effective life of site-specific + multi-site mixtures may be as long in controlling soybean rust as it has been for potato, tomato and grape downy mildews. This review presents the concepts involved in the sensitivity reduction to fungicides. Some fungal species and fungicides involved are listed. Considering the P. pachyrhizi sporulation potential, the great soybean area sprayed and the number of sprays per area mainly with site-specific co-formulations and the reduced area sprayed with multisites, we discuss the need for annual monitoring of P. pachyrhizi sensitivity to the these chemicals.

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

Summa Phytopathologica ◽

10.1590/0100-5405/190162 ◽

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.

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In vivo sensitivity of Phakopsora pachyrhizi to fungicides

Ciência Rural ◽

10.1590/0103-8478cr20190593 ◽

2020 ◽

Vol 50 (1) ◽

Author(s):

Amanda Chechi ◽

Valéria Cecília Ghissi-Mazetti ◽

Elias Zuchelli ◽

Carolina Cardoso Deuner ◽

Carlos Alberto Forcelini ◽

...

Keyword(s):

Soybean Rust ◽

Phakopsora Pachyrhizi ◽

Copper Oxychloride ◽

Toxic Activity ◽

Site Specific ◽

Fungicide Application ◽

Asian Soybean Rust ◽

Randomized Design ◽

Completely Randomized Design

ABSTRACT: Asian soybean rust is one of the most destructive diseases that can be found in this crop. It can be largely controlled by fungicide application. The objective was to assess the sensitivity of P. pachyrhizi isolates to fungicides. The tests were performed in a completely randomized design, with six replicates. The sensitivity of twelve isolates to site-specific and multisite fungicides at concentrations of 0.1; 1.0; 10.0, and 100.0 mg L-1, plus a control with absence of fungicide (0.0 mg L-1) was assessed. Soybean leaflets were immersed in the appropriate fungicide solutions, disposed in wet chambers in plastic boxes, and inoculated using each uredinia suspension of P. pachyhrizi (5.0 x 104 uredospores mL-1), separately. Boxes were incubated for 20 days at a temperature of 23°C and a 12-hour photoperiod. Next, the number of uredinia per cm2 on the abaxial face of each leaflet was evaluated. The active ingredients prothioconazole, trifloxystrobin, fluxapiroxade, trifloxystrobin + prothioconazole, trifloxystrobin + bixafen + prothioconazole, azoxystrobin + benzovindiflupyr, and azoxystrobin + benzovindiflupyr + diphenoconazole were highly fungitoxic for the majority of the isolates, with EC50 lower than 1.0 mg L-1. Diphenoconazole, azoxystrobin, and fenpropimorph were considered moderately fungitoxic for nine of the twelve isolates, with EC50 between 1 and 10 mg L-1. The multisites mancozeb and copper oxychloride presented EC50 responses classified as low toxic for the twelve isolates and eight for chlorothalonil (EC50 between 10 mg L-1 and 50 mg L-1). Site-specific fungicides showed high-to-moderate fungitoxicity to P. pachyrhizi isolates, even as the multisites presented moderate-to-less toxic activity.

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Addition of Mancozeb to DMI + QoI, and SDHI + QoI Co-formulations Improving Control of Asian Soybean Rust

Journal of Agricultural Science ◽

10.5539/jas.v13n1p195 ◽

2020 ◽

Vol 13 (1) ◽

pp. 195

Author(s):

Erlei Melo Reis ◽

Mateus Zanatta ◽

Andrea Camargo Reis

Keyword(s):

Chlorophyll Content ◽

Growth Stage ◽

Soybean Rust ◽

Growth Stages ◽

Phakopsora Pachyrhizi ◽

Site Specific ◽

Asian Soybean Rust ◽

Rust Severity ◽

The Mean ◽

Actual Control

The reduced sensitivity of Phakopsora pachyrhizi to site-specific fungicides used to control Asian soybean rust by the current co-formulations needs investigation. To improve the rust control the performance of cyproconazole + picoxystrobin, tebuconazole + picoxystrobin, cyproconazole + azoxystrobin, epoxyconazole + pyraclostrobin, fluxapyroxade + pyraclostrobin, benzovindiflupyr + azoxystrobin, prothioconazole + trifloxystrobin and cyproconazole + trifloxystrobin mixtures added by five doses of the multisite mancozeb were evaluated. The fungicides were sprayed at four growth stages the first performed at R1 growth stage and the others with 15-18 days intervals. The rust severity was quantified, the control was calculated, the percentage of chlorophyll and the yield of soybean were determined. The mean of rust control by the mixtures without addition of the multi-site fungicide was 46% (21 to 71%). There was an increase in control efficiency due to addition and mancozeb doses in all treatments. Control over 80% was obtained with tebuconazole + picoxystrobin, fluxapyroxade + pyraclostrobin, benzovindiflupyr + azoxystrobin, and prothioconazole + trifloxystrobin added at least of 2.0 kg/ha mancozeb. In unsprayed plots the maximum 78% severity corresponded to 59% damage. There was an increase in chlorophyll content and soybean yield as a function of the mancozebe increased doses: 2,019 kg/ha in the unsprayed control and in the best treatment 5,132 kg/ha. Actual control reduction due to fungal decrease in sensitivity can be improved by the multi-site fungicide addition.

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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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