Título: DETECTION OF FUNGICIDE RESISTANT ISOLATES OF CORYNESPORA CASSIICOLA IN ARKANSAS SOYBEAN FIELDS

Autoria de: Rafael Zaia

Orientação de: Fernanda Carvalho Lopes de Medeiros

Coorientação de: Alejandro Rojas

Presidente da banca: Fernanda Carvalho Lopes de Medeiros

Primeiro membro da banca: Alejandro Rojas

Segundo membro da banca: Marcos Paulo da Silva

Palavras-chaves: fungicides, azoxystrobin, Corynespora cassiicola, fungicide resistance, soybean

Data da defesa: 18/04/2022

Semestre letivo da defesa: 2021-2

Data da versão final: 03/05/2022

Data da publicação: 03/05/2022

Referência: Zaia, R. DETECTION OF FUNGICIDE RESISTANT ISOLATES OF CORYNESPORA CASSIICOLA IN ARKANSAS SOYBEAN FIELDS . 2022. 30 p. Trabalho de Conclusão de Curso (Graduação em Agronomia Bacharelado)-Universidade Federal de Lavras, Lavras, 2022.

Resumo: Fungicide application is the main tool used to control foliar diseases of soybean. Depending on the mode of action, fungicides are considered to have a moderate to high risk for resistance development. Fungicide resistance is defined as the naturally occurring ability of an individual in a pathogen population to survive a fungicide treatment that would normally have effective control. This study aimed to screen populations of Corynespora cassiicola to monitor the emergence of fungicide resistance in Arkansas soybean fields. Symptomatic leaves with target spot were sampled from fields in six Arkansas counties. Leaf tissue was disinfected using 70 ethanol for 3 min and plated on acidified potato dextrose agar (APDA) summing 24 isolates of C. cassiicola. The collection of C. cassiicola isolates was used for an in vitro evaluation for fungicide resistance using poison plate method. For In vitro fungicide testing, clean isolates were cultured on potato dextrose agar (PDA) and maintained in an incubator at 26????C for seven days. A mycelium growth assay was used to calculate EC50 values (the effective concentration of fungicide that reduces mycelial growth by 50) to the commercial-grade of azoxystrobin (22.9 a.i. Syngenta) with doses ranging from 0 to 10 mgL. Salicyhydroxamic acid (SHAM) was added in all doses to inhibit the alternative oxidase pathway. A 3.7mm plug was transferred to the center of the Petri plate (mycelium side down) with a specific fungicide concentration. Tests were conducted in an incubator with the temperature at 26????C in dark. The plates were completely randomized and designed with three replicates for each fungicide concentration. Each plate was an experimental unit, and plates were evaluated after five days. The colony diameters were averaged together, and the mean colony diameter was calculated. Analysis of the average colony diameter was analyzed with a log-logistic model in R (R version 4.1.0) using the Dose-Response Curve (DRC) program. All isolates had uniform reductions in mycelial growth, but no isolates were severely inhibited. The effective concentration for reducing 50 of the mycelium growth ranged from ???????? 0.001 to 10.0 mgL (X???? 1.88 mgL, median 0.85 mgL) Based on the results, C. cassiicola isolates show lower sensitivity to QoI. All isolates were sequenced using specific primers for the cytb gene to detect the potential mutations associated with reduced sensitivity. Eighteen out of twenty-four isolates showed a mutation in the codon G143A changing the amino acid from glycine to alanine coffering resistance to QoI. Ongoing monitoring of fungicide resistance will aid the development of a resistance management program in Arkansas, which could help to address production challenges in the future.

URI: sip.prg.ufla.br/publico/trabalhos_conclusao_curso/acessar_tcc_por_curso/
agronomia/20212201720163

URI alternaviva: repositorio.ufla.br/handle/1/54923

Curso: G001 - AGRONOMIA (BACHARELADO)

Nome da editora: Universidade Federal de Lavras

Sigla da editora: UFLA

País da editora: Brasil

Gênero textual: Trabalho de Conclusão de Curso

Nome da língua do conteúdo: Inglês

Código da língua do conteúdo: eng

Licença de acesso: Acesso aberto

Nome da licença: Licença do Repositório Institucional da Universidade Federal de Lavras

URI da licença: repositorio.ufla.br

Termos da licença: Acesso aos termos da licença em repositorio.ufla.br

Detentores dos direitos autorais: Rafael Zaia e Universidade Federal de Lavras

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