Marcelo Giovanetti Canteri

Efeitos Protetor, Curativo e Erradicante de Fungicidas no Controle da Ferrugem da Soja Causada por Phakopsora pachyrhizi, em Casa de Vegetação

Protective, curative and eradicative effects of fungicides to control soybean rust caused by Phakopsora pachyrhizi, in greenhouse Protective, curative and eradicative effects of systemic fungicides (azoxystrobin 50 g a.i./ha + nimbus 0,5%, carbendazin 250 g a.i./ha, tebuconazole 100 g a.i./ha, difenoconazole 50 g a.i./ha e epoxiconazole 25 g a.i./ha + pyraclostrobin 66,5 g a.i./ha) were evaluated in soybean (Glycine max) plants inoculated with a urediniosporal suspension of Phakopsora pachyrhizi, in greenhouse. To evaluate the protective effect plants were treated with fungicides and inoculated four, eight and 14 days after the treatment. To evaluate the curative and eradicative effects, the plants were inoculated with a urediniosporal suspension of P. pachyrhizi and treated with fungicides after two, four and eight days. Disease severity was assessed 16 days after each inoculation. With the exception of the fungicide carbendazin, all of the fungicides inhibited over 90% of urediniosporal germination until eight days after the treatment. Plants inoculated 16 days after the treatment with carbendazin presented severity statistically similar to unsprayed plants, while plants treated with fungicides of ergosterol biosynthesis inhibitors and strobilurin groups showed over 60% germination control. None of the tested fungicides provided an eradicative effect when applied before symptoms developed. However, all treatments reduced disease severity and urediniosporal viability. With the exception of carbendazin, all fungicides inhibited over 60% of urediniosporal germination until eight days after inoculation, in the incubation period of the disease.

Diagrammatic scale for assessment of grapevine rust

A diagrammatic scale with six levels of disease severity (1, 5, 12, 25, 50 and 75%) was developed to assess grapevine (Vitis spp.) rust severity, caused by the fungus Phakopsora euvitis. Two versions of the scale, in black-and-white and in color, were validated by seven raters without previous experience with grapevine rust, who estimated the severity of 30 grapevine leaves showing rust symptoms, with and without the use of the scales. Precision and accuracy were determined by linear regression, relating the assessments using the scales to actual severity. Actual severity was assessed with the software ASSESS®. Using the diagrammatic scales, some raters were able to improve precision and accuracy. The color scale provided slightly more precise and accurate estimates than the black-and-white scale.

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

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.

Sensitivity of Corynespora cassiicola from soybean to carbendazim and prothioconazole

The incidence of target spot disease on soybean has increased in recent years in Brazil even with intensive use of fungicides, and fungal resistance has been reported in recent studies. The objective of this study was to determine the fungicide sensitivity to carbendazim and prothioconazole in a sample of 24 isolates of Corynespora cassiicola from soybean collected from 1996 to 2011 in the states of Parana, Mato Grosso and Sao Paulo ( Brazil) and Corpus Christi (Paraguay). The 50% effective concentration (EC50) values were estimated by the relative mycelium growth reduction on fungicide-amended medium with the doses of 0, 0.5, 1, 10, 100 and 1000 µg of active ingredient/ mL. For carbendazim, four highly resistant isolates (EC50>50 µg/mL) were observed from samples collected from Mato Grosso in 2008 and from Parana and Mato Grosso in 2011. The EC50 values for prothioconazole ranged from 0.47 µg/mL to 26.44 µg/mL (mean: 5.02 µg/ ml). The results reinforce the occurrence of C. cassiicola resistance to benzimidazole in Parana and Mato Grosso states.

Quantificação de danos e relações entre severidade, medidas de refletância e produtividade no patossistema ferrugem asiática da soja

Os objetivos deste trabalho foram obter funcoes de dano para o patossistema ferrugem asiatica da soja e verificar o potencial de uso de medidas de refletância para quantificar os danos causados pela doenca. Experimentos foram conduzidos no municipio de Londrina, PR, nas safras 2005/06 e 2006/07. Ensaios foram repetidos em diferentes epocas de semeadura, a fim de obter intensidade variavel da doenca em diferentes estadios fenologicos. O delineamento experimental foi em blocos ao acaso, com quatro repeticoes. Para obter gradiente de doenca foram utilizadas diferentes epocas para aplicacoes de fungicida nas cultivares BRS 133 e Coodetec 217. A severidade da doenca foi estimada em intervalos semanais e utilizada para calcular a area abaixo da curva de progresso da doenca (AACPD). Medicoes da porcentagem de luz solar refletida pelo dossel foram obtidas com um radiometro portatil de multiplo espectro. O indice vegetativo da diferenca normalizada (IVDN) foi calculado utilizando os comprimentos de onda na faixa do vermelho (660 nm) e do infravermelho proximo (810 nm). As variaveis AACPD e IVDN apresentaram alta correlacao com a produtividade, com R2 medio de 91,5% e 86,7%, respectivamente. Variacoes na severidade da doenca entre as safras afetaram a relacao AACPD x produtividade. Medidas de refletância podem ter sofrido a interferencia da epoca de cultivo e das cultivares diferentes utilizadas nos experimentos.

Análise multivariada dos componentes da resistência à ferrugem-asiática em genótipos de soja

The objective of this study was to detail the infection cycles of Phakopsora pachyrhizi Syd. & P. Syd. in soybean genotypes, in order to establish a group of the most promising genotypes for use as sources of resistance to Asian soybean rust. The infection cycle components were quantifi ed in 48 genotypes. The assessments consisted of: type of lesion, intensity of sporulation, severity, number of lesions and uredinias, and productivity of urediniospores. The cluster analysis formed four groups: A - developed the highest amount of disease; B - developed the lowest amount of disease; C - low initial resistance; and D - high initial resistance. All the genotypes of groups B, C and D had RB (redish-brown) lesions and varied for initial resistance, delayed resistance, intensity of sporulation, stability of the qualitative response, productivity of urediniospores, and number of days to reach 50% of the maximum severity. Qualitative responses and disease severity evaluations refl ect the combined effects of resistance on all the infection components and show practical importance in genotypes differentiation, regarding disease resistance. The genotypes of groups B, C and D presented qualitative and quantitative resistance, in different degrees, and they are promising genotypes as sources of resistance to Asian soybean rust.

Infectividade natural por Xylella fastidiosa Wells et al. de cicadelíneos (Hemiptera: Cicadellidae) de lavouras cafeeiras do Paraná

Xylella fastidiosa Wells et al., a gram-negative and xylem limited bacterium, causes significative economic on several crops, such as the leaf scorch in coffee. It is transmitted by xylem feeding insects and four sharpshooters species have been reported as vectors of X. fastidiosa in coffee. The objective of this study was to determine the natural infectivity of X. fastidiosa in five species of sharpshooters from coffee trees: Acrogonia citrina Marucci & Cavichioli, Bucephalogonia xanthophis (Berg), Dilobopterus costalimai Young, Oncometopia facialis (Signoret) and Sonesimia grossa (Signoret). Samples were collected from coffee plantations in five counties of the North and Northwest regions of the State of Parana, Brazil, from October 1998 through November 2001. A total of 806 samples containing three to five insects were examined for the presence of X. fastidiosa by using PCR and nested PCR tests. X. fastidiosa was present in samples of all five species of sharpshooters collected in the two coffee regions. The average level of natural infectivity potential was 30.4%. However, this natural infectivity ranged from 2.2% for O. facialis to 68.8% for A. citrina. Sharpshooters collected in the spring tended to have lower natural infectivity of X. fastidiosa as compared to those collected in other seasons. The results obtained showed the high potential of dissemination of X. fastidiosa by different insect vectors in coffee trees in Parana.

Escala diagramática para avaliação da severidade da mancha branca em milho

The Dia grammatic scales are important tools to standardize the severity assessments of pla nt disea ses. T he objective of this work was to develop a nd to va lida te a dia gra mma tic sca le for severity assessment of lea ves spot Ph ae osph ae ria on ma ize. T he proposed scale had the levels of 1; 3; 6; 13, 25; 43; 63 and 79% of severity in the third medium part of the maize leaf. Scale validation was performed by ten raters (five inexperienced and five experienced), who estimated the severity disease in 50 maize leafs showing Pha eosp haeria leaf spot symptoms, with a nd without the u se of the sca le. Ana lyses of Sachs, P.J.D.; Neves, C.C.S.V.J.; Canteri, M.G.; Sachs, L.G. Diagrammatic scale for assesment of the phaeosphaeria leaf spot severity in maize. Summa Phytopathologica, v.37, n.4, p.202-204, 2011. regression wa s used to eva lu ate the precision and accuracy of the estimates. The evaluation of the accuracy indicated that without the use of the scale seven raters had presented systematic shunting lines in the estimates, whereas with the use of the scale they was only two ra ters. T he precision represented for coefficient of determina tion (r 2) of the regressions, varied of 0.86 the 0.95 for the inexperienced ra ters withou t sca le a nd 0 .9 1 the 0 .9 8 with sca le. T he proposa l dia gra mma tic sca le improved the precision a nd a ccu ra cy of the estimates, independent of the experience of the ra ters.

Validação de escala diagramática para estimativa de desfolha provocada pela ferrugemasiática em soja

This study aimed to evaluate the precision and accuracy of evaluators using diagrammatic scale to estimate defoliation caused by diseases in soybean. The scale had six levels of severity of defoliation (5, 15, 45, 65, 85 and 100%). The images used for evaluation were obtained in plots attacked by Asian soybean rust (Phakopsora pachyrhizi), presenting different levels of defoliation. The validation was performed by ten evaluators, comparing estimated data with the actual data of the area coverage leaf, obtained by processing images in Paint Shop Pro 4 software, and Adobe Photoshop 7.0. The evaluators presented tendency to underestimate the defoliation in the lower levels of severity and overestimate the defoliation in high levels of severity, when the scale was not used. The accuracy and precision of the evaluators increased with the use of the scale diagrammatic.

Germinação de uredósporos de Puccinia kuehnii submetidos a diferentes temperaturas e tempos de incubação

ABSTRACT The orange rust caused by Puccinia kuehnii , is currently oneof the most important diseases of sugarcane due to the potentialdamage to susceptible varieties. This study evaluated the effectof temperature on germination of uredospores. Uredospores werecollected in the commercial field of sugarcane, variety SP 891115in the city of Andira (PR). After being removed from leaves, theuredospores underwent separation of impurities and placed in asolution of distilled water with Tween-20. The spores suspensionwas calibrated using a Neubauer chamber and plated an aliquot of0.1 ml on the agar-water (1.5%). The plates were placed in BOD,at temperatures: 10, 15, 20, 25 and 30 ° C in six incubation Minchio, C. A.; Canteri, M.G.; Rocha, J.A. Germination of uredospores of Puccinia kuehnii subjected to different temperatures and incubationtimes. Summa Phytopathologica, v.37, n.4, p.211-214, 2011. periods: 1, 3, 6, 12, 18, 24 hours, totaling 30 treatments withfive replications. At the end of each period, germination wasstopped by adding 0.1 ml of lactophenol. Each plate was dividedinto four fields and 50 spores were assessed in each field. Data ongermination percentage were subjected to analysis of variance ina factorial 5x6 with the unfolding of interaction in orthogonalpolynomials. By adjustment of mathematical model, the maximumgermination occurred for the period of 12h at a temperature of21°C (R2 = 82%). For the incubation periods, the model estimatedthat in the curve of temperature 20°C were required 14 hours (R2= 65%) to reach maximum germination.