Progress of Asian soybean rust and airborne urediniospores of Phakopsora pachyrhizi in southern Brazil

Abstract

RESUMOPalavras-chave adicionais: Pakopsora pachyrhizi, epidemiologia, soja.A ferrugem asiática, causada por Phakopsora pachyrhizi, relatada em nível epidêmico em 2003/04, é a principal doença na cultura as soja no Brasil. Este trabalho teve como objetivos estudar o progresso da ferrugem-asiática da soja e quantificar os urediniósporos no ar na região de Campo Mourão no Estado do Paraná, região Sul do Brasil. Três experimentos foram instalados em condições de campo, nas safras 2006/07 e 2007/08. Utilizando-se o método do gradiente de doenças, proporcionado pela aplicação de doses crescentes do fungicida tebuconazole, foram obtidas quatro epidemias em cada experimento com diferentes intensidades de ferrugem asiática. Para quantificar os uredinióporos, foram instalados coletores de esporos tipo catavento durante as duas safras e entressafras. As curvas de progresso da doença Nascimento, J.F.; Vida, J.B.; Tessmann, D.J.; Zambolim, L.; Vieira, R.A. e Oliveira, R.R. Progresso de ferrugem asiática da soja e quantificação de urediósporos de Phakopsora pachyrhizi no ar, na região sul do Brasil. Summa Phytopathologica, v.38, n.4, p.280-287, 2012. das epidemias foram plotadas e estimaram-se a severidade máxima. As curvas foram ajustadas ao modelo logístico por apresentarem maiores coeficientes de determinação e melhor aleatoriedade dos resíduos plotados no tempo. As análises da área abaixo da curva de progresso da doença mostraram que as maiores epidemias ocorreram na safra 2006/07 e as taxas de progresso foram maiores para a severidade, mesmo em plantas protegidas com o fungicida. A quantidade de urediniósporos coletados no ar foi relacionada com a presença de plantas de soja em lavouras cultivadas. A quantidade de urediniósporos também apresentou correlação positiva com a severidade, com a incidência da doença, com a precipitação acumulada e com os dias favoráveis a infecção por P. pachyrhizi. Climate is quite important among the factors that favor the epidemiology of ASR. Climate variations are influenced by macro-, meso-and microclimate. They can affect the different processes of the disease cycle and influence the rate of progress and severity of the epidemics. In soybean fields, rainfall seems to be the most important factor that influences the severity of the disease on a regional scale. In v.38, n.4, p.280-287, 2012. curves were plotted for each epidemic, and maximum severity was estimated. The curves were fit to the logistic model, which provided higher coefficients of determination and more randomly distributed residuals plotted over time. Analyses of the area under the disease progress curve showed that the largest epidemics occurred in the 2007/2008 crop season and that the progress rates were higher for severity, even among plants protected with the fungicide. The number of urediniospores collected in the air was related to the presence of soybean plants in the cultivated crops. The quantity of urediniospores was also positively correlated to the disease severity and incidence, as well as to cumulative ...

Rust fungi and global change

“…Urediniospores are the repeating spores on the telial host. They are produced in vast numbers and represent the spore stage with the highest dispersal potential, generally being considered as the agents of rust epidemics in many crop plants (Nascimento et al ., ). Spore sizes are c .…”

Progresso temporal da ferrugem asiática em função de épocas de semeadura e de cultivares de soja em terras baixas

“…A análise de variância e teste de F, para as três variáveis analisadas: Área Abaixo da (Oliveira et al, 2005;Silva et al, 2007;Nascimento et al, 2012;Rodrigues et al, 2013;Godoy et al, 2016).…”

Hourly and daily changes on airborne urediniospores of Phakopsora pachyrhizi

“…Isard et al (2005) has affirmed the role of environmental factors such as daylight, temperature, and humidity may affect the timing of spore release. Nascimento et al (2012) stated that the number of airborne spores of P. pachyrhizi was related to the presence of soybean field crop, and there were positive correlations among the number of urediniospores, cumulative rainfall, disease intensity and favorable days for Asian rust (SAR). In addition, those authors defined the favorability to epidemic of SAR was associated to 18-26°C and 90-100% relative humidity.…”

“…The most favorable conditions to SAR epidemics reported are: (a) minimum leaf wetness (LW) of 6h per day; (b) optimum LW of 12-14h per day; (c) optimum temperature for spore germination of 18-26 o C; (d) optimum minimum temperature from 20 to 23 o C; (e) optimum maximum temperature inferior to 28 o C; (f) optimum minimum RH from 75 to 80%; (g) constant daily rain for 12-15 days (ALVES et al, 2007;BLUM et al, 2015;DEL PONTE et al, 2006;BONDE et al, 2007;ESKER, 2008;BONDE et al, 2013;DANELLI;REIS, 2016;DUFAULT et al, 2010b;ISARD et al, 2005;MARCHETTI et al, 1976;MELCHING et al, 1979;MELCHING et al, 1989;NASCIMENTO et al, 2012;YANEZ-LOPEZ et al, 2015). Under these conditions, from the urediniospores germination and hyphae penetration to new urediniospores formation, it takes 7-10 days (GARCÉS-FIALLOS, 2011).…”

“…However, studies concerning the quantification of the air dispersed urediniospores of P. pachyrhizi are limited (DEL PONTE et al, 2006;BARNES et al, 2009;ISARD et al, 2011;NASCIMENTO et al, 2012). Iamamoto (2008) using a spore trap in soybean field in central Brazil, stated that was possible to anticipate the chemical control of the soybean Asian rust in 14 to 15 d. This author reported that air weekly collected spores from 100 to 600 could result in a rust outbreak.…”