Sensitivity of Fusarium graminearum causing head blight of wheat in Brazil to tebuconazole and metconazole fungicides

Abstract

Fusarium head blight (FHB) of wheat, is caused by fungal populations belonging to the Fusarium graminearum species complex. Although triazole fungicides are widely used in FHB management, information about the sensitivity of F. graminearum populations to such fungicides is scarce, particularly in Brazil. This work aimed at determining the sensitivity of pathogenic populations of F. graminearum to metconazole and tebuconazole. Fungal isolates were obtained from diseased wheat heads collected in commercial fields at the northern region of Rio Grande do Sul state, Brazil, along the 2009 and 2010 growing seasons. Fifty isolates obtained from eleven locations were grown in media amended with increasing fungicide dosages and the effective concentration reducing mycelial growth to 50% (EC 50 ) was determined. The median of the EC 50 values was 0.001 mg/L (<0.001-0.152 mg/L) and 0.037 mg/L (<0.001-0.324), for tebuconazole and metconazole, respectively. Cross-resistance was detected based on significance of correlation analysis (r s = 0.46; P < 0.0001) between the log-transformed EC 50 of the two triazoles. The mean EC 50 for a group of ten isolates classified as "more sensitive" differed statistically from the ten isolates representing the "less sensitive" group. Nevertheless, these groups did not differ in terms of mycelial growth on PDA in the absence of fungicides. It was concluded that pathogenic populations of F. graminearum are sensitive to the triazoles at various levels due to the intrinsic characteristics of the isolates or to selection pressure by the increasing fungicide use.

Agressividade diferencial de espécies do complexo Fusarium graminearum em interação com o fungicida tebuconazole na redução do rendimento de trigo

“…As médias de esporulação total, taxa de germinação e CE 50 do fungicida tebuconazole foram as mais altas nos isolados Fgss (P≤0,016). Na média, a CE 50 de Fgss foi 4,5 vezes superior à CE 50 de Fmer ratifi cando resultados anteriores (SPOLTI et al, 2012b). Não foi possível discriminar as duas espécies quanto ao progresso da doença, tanto pela incidência como pela severidade (P≥0,0829) (Tabela 1).…”

“…Cada isolado foi caracterizado quanto à esporulação total, germinação e sensibilidade ao tebuconazole, inferida pela concentração efetiva, que reduz 50% do crescimento micelial (CE 50 ), conforme descrito previamente (SPOLTI et al, 2012b). A agressividade foi avaliada por inoculação por aspersão em espigas no momento da antese plena com uma suspensão de esporos (10 ).…”

In vitro sensitivity reduction of Fusarium graminearum to DMI and QoI fungicides

“…This task can be accomplished by in vitro assays as reported by Spolti et al (26) and Avozani et al (2).…”

Imidazolium salts with antifungal potential for the control of head blight of wheat caused by Fusarium graminearum

“…Nevertheless, previous studies with F. graminearum isolates from Brazil showed median EC 50 value of 0·001 μ g ml −1 (<0·001–0·152) in a sample of 50 isolates, agreeing with our findings (Spolti et al . ). On the other hand, MIC values determined based on conidial germination were similar between these two compounds.…”