Quantificação de conídios de Pyricularia grisea no plantio direto e convencional de arroz de terras altas

Silva, Gisele B. da; Prabhu, A. S.

doi:10.1590/s0100-41582005000600001

Cited by 5 publications

(3 citation statements)

References 2 publications

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“…The pathogen infects all above ground parts of the wheat plant, but spike infection is of greatest concern because severely bleached spikes do not produce grain. Severe epidemics occur during seasons with Section Editor: Emerson M. Del Ponte extended warm and high humidity (da Silva and Prabhu 2005;Alves and Fernandes 2006). Yield loss due to wheat blast can reach levels as high as 64% and may lead to total crop failure (Goulart et al 2007).…”

Section: Introductionmentioning

confidence: 99%

A weather-based model for predicting early season inoculum build-up and spike infection by the wheat blast pathogen

Fernandes

Nicolau

Pavan

et al. 2017

Trop. plant pathol.

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Wheat blast, caused by the fungus Magnaporthe oryzae Triticum pathotype (MoT), is a serious disease capable of causing severe losses, especially during warm and humid weather conditions. Although the pathogen attacks all aboveground parts, infection of the wheat spikes is of major concern. In this work we developed and evaluated a prediction model based on the analysis of historical epidemics and weather series in the northern Paraná state, Brazil (Apucarana, Maringá and Londrina) and available epidemiological knowledge. The disease and weather datasets (hourly scale) examined encompassed the 2001-2012 period. A specific database management application (agroDb) helped to visualize and identify patterns in weather variables during two major outbreaks (2004 and 2009). Specifically, uncommonly humid and warm weather for most locations during a 60-day period preceding wheat heading during years of major outbreaks were considered key drivers of inoculum build up and airborne spores from regional inoculum sources in the surroundings. An inoculum potential (IP) and a spore cloud (SPOR) variable were estimated from models adapted from literature to predict inoculum build-up and availability. A day favoring infection (DFI) was conditioned to rules relating temperature and relative humidity for the day derived from the epidemic analysis. Successful daily infection (INF) during a DFI was conditioned to IP > 30 and SPOR >0.4. To test the model, a wheat model simulated heading date for 10 planting dates, spaced 5 days apart, within a year, totaling 320 simulations. The model described well epidemic and non-epidemics conditions for the historical dataset, and was able to correctly predict epidemic (2015) and non-epidemic (2016) years not analyzed to build the model. An interactive risk-mapping tool that collects real-time weather data was developed for the target area to warn potential outbreaks.The system can be adapted to other regions where the disease is endemic or to asses the epidemic potential in regions where the disease is not present.

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Section: Introductionmentioning

confidence: 99%

A weather-based model for predicting early season inoculum build-up and spike infection by the wheat blast pathogen

Fernandes

Nicolau

Pavan

et al. 2017

Trop. plant pathol.

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“…It is also plausible that under heavy rain, large raindrops vigorously damage conidiophores, releasing and washing off conidia, thereby reducing the amount of inoculum available for transport from plant to plant, field to field, and across regions. Silva and Prabhu (2005) also reported an inverse relationship between rainfall and trapped P. oryzae conidia. Another important factor for the release of P. oryzae conidia is light (Leach, 1980(Leach, , 1962.…”

Section: Production Release and Aerial Transport Of Inoculummentioning

confidence: 91%

Towards an early warning system for wheat blast: epidemiological basis and model development

Fernandes,

Del Ponte,

Ascari

et al. 2021

Achieving Durable Disease Resistance in Cereals

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“…The amount of spores in the air depends on the environmental conditions. For temperatures between 25°C and 28°C, relative humidity of 76% to 100%, and light rain (< 5 mm) the amount of spore in the air is increased (Leach, 1980;Danelli et al, 2019), and after a period of heavy rains the number of spores decreases (Silva & Prabhu, 2005;Danelli et al, 2019). As to long distance dispersal, infected seeds or grains are the most likely source of inoculum for disease establishment (Tanaka et al, 2009;Gomes et al, 2018).…”

Section: Symptoms Biology and Epidemiologymentioning

confidence: 99%

Sensitivity to fungicides in Pyricularia populations from wheat and signal grass in Minas Gerais

Cazón¹

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Wheat blast, caused by Pyricularia oryzae Triticum pathotype, is a damaging disease of wheat in the Brazilian Cerrado. Fungicides play an important role in management, but their efficacy has been variable. Failures in disease control have been associated with the presence of fungicide resistant populations. To determine if these resistance patterns are also present in Pyricularia populations infecting wheat and signal grass from MG state, we characterized phenotypically and genotypically the resistance of the blast pathogen against seven fungicides belonging to three chemical groups (DMI, QoI and SDHI). The in vitro sensitivity was assessed in 64 isolates obtained from the Triângulo Mineiro and Sul de Minas. For DMIs, the EC 50 was estimated for all isolates. For QoIs and SDHIs, the EC 50 was obtained for 13 isolates prior to determining a discriminatory dose. Control efficacy of each fungicide was also evaluated in vivo upon inoculation of wheat heads with a resistant (R) or a sensitive (S) PoT isolate (determined in vitro) to each fungicide. The presence of mutations in the genes encoding the target proteins of the different groups of fungicides was also evaluated. For the DMIs (TEBU - tebuconazole and EPOX - epoxiconazole), despite showing relatively high EC 50 values for some isolates, the control efficacy on wheat heads was high. We found no association between mutations in the cyp51A region and resistance to DMI. For QoIs, azoxystrobin (AZOX) did not inhibit the in vitro germination of PoT even with an extra dose of 100 µg/ml, and was poorly controlled in vivo (~ 20%). For pyraclostrobin (PYRA), despite the presence of isolates with high leves of spore germination in vitro using a discriminatory dose of 1.3 µg/ml, the control efficacy was also high. The G143A substitution was present in all PoT cytB sequences, even in those of the PYRA sensitive isolates. The non-PoT isolates did not present mutations in the cytB hot spots. For SDHIs, the most fungitoxic in in vitro and in vivo experiments was benzovindiflupyr, followed by bixafen and fluxapyroxad. Molecular analysis of the sdh subunits showed no relationship between mutations and sensitivity to SDHI fungicides. For the seven fungicides tested in this work, the PoT isolates were statistically less sensitive than the isolates from signal grass. Our results demonstrate that PoT populations can be controlled in vivo with at least one fungicide of each of the three chemical groups evaluated. Contrary to previous statements, determining EC 50 values in in vitro experiments was not sufficient to infer loss of efficacy in in vivo experiments. Benzovindiflupyr was the most effective active ingredient evaluated in this work. Conversely, azoxystrobin should not be considered for controlling wheat blast. Keywords: Wheat blast. Fungicide resistance. Epidemiology. Magnaporthe oryzae. Pyricularia oryzae.

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Quantificação de conídios de Pyricularia grisea no plantio direto e convencional de arroz de terras altas

Cited by 5 publications

References 2 publications

A weather-based model for predicting early season inoculum build-up and spike infection by the wheat blast pathogen

A weather-based model for predicting early season inoculum build-up and spike infection by the wheat blast pathogen

Towards an early warning system for wheat blast: epidemiological basis and model development

Sensitivity to fungicides in Pyricularia populations from wheat and signal grass in Minas Gerais

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