It was hypothesized that the values of the calculated control show different efficacies when using the AUDPC data compared to those of final severity.

Autores: REIS, E. M.1; ZANATTA, M.2; SILVA, L. H. C. P.3

Trabalho publicado nos Anais do evento e divulgado com a autorização dos autores.

In experiments conducted to identify the best treatments with fungicides, or programs of treatments that result in economic control of Asian soybean rust (ASR), several methods have been used and results published. Analyzing these reports, it can be inferred that sometimes the method of ASR quantification and its effects on the host has been doubled, requiring more time and labor, and with little contribution to data interpretation. Examples include the area under the disease progress curve (AUDPC) that combines multiple observations of disease progress into a single value (Agrios, 2005).

Quantification of disease intensity represents a considerable investment in time and human resources. The AUDPC is determined by measuring the foliolar intensity (incidence or severity) of rust in sequential evaluations at various stages of soybean development. In some of these studies, only the AUCPC values corresponding to each treatment without the control calculation are presented. The reader is disoriented not knowing how to interpret the results. Work with fungicides and fungicide treatment programs aims to identify treatments that achieve economic control, thus requiring the efficacy values.

It was hypothesized that the values of the calculated control show different efficacies when using the AUDPC data compared to those of final severity.

Data from National Cooperative Fungicide Trial conducted in Rio Verde, Goiás, in the 2014/15 growing season were analyzed. ASR severity was taken at four phenological stages, and the AUDPC calculated. Seventeen different fungicides were tested, with only their effects on rust severity. The severity was evaluated on 10 central trifoliate removed from leaves inserted on the main plant stem. AUDPC, calculated with four assessed times, and final severity data were submitted to statistics analysis comparing control for final severity and for AUDPC.

For the 2014/15 growing season, final severity ranged from 5% to 75% (unsprayed) and control from 33% to 94%. The AUDPC ranged from 43 to 532 (unsprayed) units and control from 33% to 92%. General means for final severity control was 66% and for AUDPC 65% with no statistical difference were similar (Table 1).

Table 1. Asian soybean rust control calculated for final severity and for AUDPC data from 2014/15 season.

The analysis showed that the control calculated for the final severity ranged from 25% to 90%, with an overall mean of 66%, and for AUDPC, ranged from 33% to 92%, with an overall mean of 65%. Therefore, similar for both criteria.


Otimize sua lavoura, conheça o curso de manejo de doenças em soja


The use of AUDPC has been recommended mainly to: (i) determine the damage caused by plant diseases (Jesus Jr et al., 2004; Vale et al., 2004); (ii) assess the cultivars reaction (Haynes; Weingatner, 2004; Jeger; Viljanen-Rollinson, 2001); (iii) and compare data obtained in several years, locals or with different disease management tactics (Jesus Junior et al., 2004).

AUDPC data, not expressed in control, are more difficult to interpret than when expressed in control efficacy. It should be kept in mind that > 80% control is required to match the cost of fungicide spraying (Reis et al., 2018).

Therefore, in the case study with the ASR, the control calculated by the final severity (a single evaluation) can be considered similar to that calculated with the AUDPC (four evaluations). There is no justification for the use of AUDPC in work involving the chemical control of soybean rust.

 References

HAYNES, K.G.; WEINGARTNER, D.P. The use of area under the disease progress curve to assess resistance to late blight in potato germplasm. American Journal of Potato Research, New York, v. 81, n. 2, p. 137–141, 2004.

JEGER, M.J.; VILJANEN-ROLLINSON, S.L.H. The use of the area under the diseaseprogress curve (AUDPC) to assess quantitative disease resistance in crop cultivars. Theoretical and Applied Genetics, Wien, v. 102, n.1, p. 32–40, 2001. JESUS JR, W. C.; VALE, F.X.R.; BERGAMIN FILHO, A. Quantificação de danos e perdas. In: VALE, F.X.R.;

JESUS JR, W. C.; ZAMBOLIM, L. (Eds.). Epidemiologia aplicada ao manejo de doenças de plantas. Belo Horizonte: Editora Perfil, 2004. p. 273-297.

REIS, E.M.; ZANATTA, M.; REIS, A.C. Eficiência do controle de doenças para igualar ao custo da aplicação terrestre de fungicida – um exemplo de cálculo com a ferrugem da soja. Summa Phytopathologica, 2018 (In Press).

VALE, F.X.R.; JESUS JR, LIBERATO, J.R.; SOUZA, C.A. Quantificação de doenças e do crescimento do hospedeiro. In: VALE, F.X.R.; JESUS JR, W. C.; ZAMBOLIM, L. (Eds.). Epidemiologia aplicada ao manejo de doenças de plantas. Belo Horizonte: Editora Perfil, 2004. p. 89-123.

Informações dos autores:  

1Programa de pós graduação da Universidade de Buenos Aires;

2Agroservice/Agroresearch Pesquisa e Consultoria Agrícola;

3Agrocarregal, Pesquisa e Proteção de Plantas, Rio Verde, GO.

Disponível em: Anais do VIII Congresso Brasileiro de Soja. Goiânia – GO, Brasil.

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